Savings Account

Industrial demand from China will have impact on silver price

China is now largest energy consumer. For over a century it US consumed most energy. China and its people are getting richer. They have high savings rate which enables them to invest in production and buy gold, silver and other commodities. As Chinese people getting richer they will want to increase their standards of living. They will create demand for electronics and other consumer goods. As we know it’s impossible to make iphone or TV without silver. Silver is the best electricity conductor. There is a lot of potential for high silver demand. Around 20% of Earth population lives in China.

Alex Jones Tv 1/5: Alex Takes Calls on Bank Holiday

Update: Citigroup Says Feds Ordered 7 Day Restriction On Bank Withdrawals Announcement stokes fears of old fashioned bank runs if economy takes a turn for the worse Paul Joseph Watson Prison Planet.com Monday, February 22, 2010 A new advisory being sent by Americas third largest bank to its account holders has stoked fears that major financial institutions could be preparing for old fashioned bank runs if the economy takes a turn for the worse. Originally reported by John Carney over at the Business Insider website, Citigroup is sending the following information to customers along with their bank statements. Effective April 1, 2010, we reserve the right to require (7) days advance notice before permitting a withdrawal from all checking accounts. While we do not currently exercise this right and have not exercised it in the past, we are required by law to notify you of this change. An almost identical advisory to the one being sent out can be read on page 22 of Citbanks Client Manual effective January 1, 2010, which can be read here from Citibanks own website. We reserve the right to require seven (7) days advance notice before permitting a withdrawal from all checking, savings and money market accounts. We currently do not exercise this right and have not exercised it in the past, states the manual. According to the Future of Capitalism blog, Citigroup originally claimed that the warning was only sent nationwide as a result of a mistake, but that the measures do apply to …
Video Rating: 4 / 5

Update: Citigroup Says Feds Ordered 7 Day Restriction On Bank Withdrawals Announcement stokes fears of old fashioned bank runs if economy takes a turn for the worse Paul Joseph Watson Prison Planet.com Monday, February 22, 2010 A new advisory being sent by Americas third largest bank to its account holders has stoked fears that major financial institutions could be preparing for old fashioned bank runs if the economy takes a turn for the worse. Originally reported by John Carney over at the Business Insider website, Citigroup is sending the following information to customers along with their bank statements. Effective April 1, 2010, we reserve the right to require (7) days advance notice before permitting a withdrawal from all checking accounts. While we do not currently exercise this right and have not exercised it in the past, we are required by law to notify you of this change. An almost identical advisory to the one being sent out can be read on page 22 of Citbanks Client Manual effective January 1, 2010, which can be read here from Citibanks own website. We reserve the right to require seven (7) days advance notice before permitting a withdrawal from all checking, savings and money market accounts. We currently do not exercise this right and have not exercised it in the past, states the manual. According to the Future of Capitalism blog, Citigroup originally claimed that the warning was only sent nationwide as a result of a mistake, but that the measures do apply to …
Video Rating: 4 / 5

8. High Credit Card Interest Rates

There are reasons which make credit card interest rates so high. High credit card interest rates make having this kind of debt a bad idea especially if it compounds very quickly after we bought things that quickly lose their value.
Video Rating: 4 / 5

Restaurant Cleaning Outsourcing

A few nice money market saving account images I found:

Restaurant Cleaning Outsourcing


Image by Frederick Md Publicity
>Commercial Buildings Maintenance satisfies cleaning and maintenance requirements for a variety of commercial, industrial and residential environments.

Janitorial services seem similar but they are separated by; powerful management tools, efficient cleaning solutions, years of experience, number of buildings with commercial cleaning and maintenance services, efficiency of cleaning, eco-friendly chemicals; chemical mixing centers; vacuum filtration systems; light weight, maneuverable equipment; and ongoing equipment investment , experience in multiple commercial, institutional, high tech and retail industries, best; lowest cost commercial cleaning service supplies and equipment ; stringent hiring and selection processes; company values, competitive compensation, performance-based recognition, extensive training, and advancement opportunities result in greater service and longer customer relationships, regional coverage and experience in many, commercial and institutional to high tech and retail industries.

GIMME SOME OF THAT GOOD ‘OLE OBAMA DOUBLESPEAK


Image by SS&SS
**IN REALITY FOLKS, HE’S SPENDING YOU, ME, EVERY AMERICAN MAN WOMAN AND CHILD INTO A FREEFALL SPIN OF BANKRUPTCY, DEBT, AND SECOND OR THIRD WORLD STANDARDS OF LIVING AND HE’S DOING IT RAPIDLY**

AND THE U.S. DEBT CLOCK KEEPS RUNNING
www.usdebtclock.org/
FACT CHECK:

In Barack Obama’s State of the Union Address he mentioned the word invest or investments 11 times at a rough count and in fairness a couple of those keywords were used in relation to other countries investments.

The rest of those mentions were talk of spending more tax payer money when out debt is at trillion already. In fairness again, he did mention once in relation to investments the words "paid for".

With that said, contradicting headlines today show one specific portion of the SOTU speech to be completely intellectually dishonest.

We are living with a legacy of deficit-spending that began almost a decade ago. And in the wake of the financial crisis, some of that was necessary to keep credit flowing, save jobs, and put money in people’s pockets.

But now that the worst of the recession is over, we have to confront the fact that our government spends more than it takes in. That is not sustainable. Every day, families sacrifice to live within their means. They deserve a government that does the same.

Let us start with the fact that over the last two years Barack Obama and a Democratically controlled House of Representatives and Democratically controlled Senate has raised our national debt from approximately .6 trillion to trillion.

Make no mistake, Bush started Tarp and signed the initial bailouts, so he should take his fair share of the blame when it comes to spending like a drunken sailor and rasing out national debt.

The 2009 Budget is on Bush and the Democratically controlled House and Senate, the 2010 Budget and the 2011 Budget are all on Obama.

Obama has expanded the problem with massive spending on more bailouts, a trillion dollar healthcare law, a stimulus program, earmarks and countless other spending when we were already debt ridden and did not and do not have the money to spend, so Obama borrowed more, spent more and this has continued and still is continuing.

Yet he says he wants to invest more aka spend more while out of the other side of his mouth he proposes a "freeze annual domestic spending for the next five years."

Obama said and I quote "we have to confront the fact that our government spends more than it takes in. That is not sustainable. Every day, families sacrifice to live within their means. They deserve a government that does the same."

Has that not been the point conservatives have been making over the last two years as Obama, Pelosi and Reid merrily went on a spending spree using American taxpayers as their own personal credit cards or atm machines?

Obama also claimed "worst of the recession is over."

Then I see today’s headlines:

Outside D.C., a grim housing market originally titled "Home prices fall in nearly all major cities, heightening fears of double dip."

In that Wapo piece we see the following information.

- housing prices, compared year-over-year, have declined nationally for six consecutive months.

-nine major cities have dipped to new lows, the report shows. They are Atlanta, Charlotte, Chicago, Detroit, Las Vegas, Miami, Portland, Ore., Seattle and Tampa.

-On a year-over-year basis,the 20-city price index fell 1.6 percent in November.

The next headline is from the Hill, with even more disturbing news:

CBO: Deficit widened to .5 trillion this year

The nonpartisan Congressional Budget Office made it official on Wednesday morning: America’s free fall into debt is accelerating.

The budget deficit is now estimated to have widened this year to .5 trillion, the CBO said. That compares to a budget deficit of .3 trillion for the fiscal year that ended Sept. 30.

The increase in the deficit would bring it to 9.8 percent of gross domestic product, the CBO said, following deficits of 10 percent and 8.9 percent during the previous two years. The CBO notes those are the largest deficit levels since the end of World War II.

The CBO’s projections assume that current laws remain unchanged. If the nation continues on its current path, the CBO said, the total national debt will rise from 40 percent of GDP in 2008 to 70 percent by the end of 2011, reaching 77 percent of GDP by 2021.

You can see a summary at the CBO’s Director’s blog and you can see the entire report from the CBO, with graphs and explanations at the Congressional Budget Office’s website.

It is not pretty and it belies Obama’s words completely.

The Associated Press has also done some fact checking on Obama’s speech and where I chose one small portion to start with, Calvin Woodard from the AP, delves into other aspects and comments by Obama during his SOTU address.

FACT CHECK: Obama and his imbalanced ledger

That article deals with Obama’s statements on healthcare savings, earmarks, medical malpractice reform, high speed rail transportation, the recommendations by the bipartisan Fiscal Commission, Social Security,and Iran.

After quoting each of Obama’s statements from the SOTU address, the AP goes on to provide the facts instead of the Obama spin.

Read the entire thing to see how Obama truly spoke out of both sides of his mouth on each topic listed above.

I do not know what reality Barack Obama lives in, but it is not the same one that every day Americans live in, which is part of the reason the focus group came down so hard on him immediately after his speech.

====================================================================
ADDENDUM: (FOR YOU LIBERAL VIEWERS, something that is or has been added)
**READ WHAT ONE ECONOMIST SAYS ARE THE REAL NUMBERS
AND THE REAL STORY **

Neil Reynolds
The scary actual U.S. government debt
NEIL REYNOLDS OTTAWA— From Wednesday’s Globe and Mail

Economist Laurence Kotlikoff says U.S. government debt is not .5-trillion (U.S.), which is 60 per cent of current gross domestic product, as global investors and American taxpayers think, but rather 14-fold higher: 0-trillion – 840 per cent of current GDP. “Let’s get real,” Prof. Kotlikoff says. “The U.S. is bankrupt.”

Writing in the September issue of Finance and Development, a journal of the International Monetary Fund, Prof. Kotlikoff says the IMF itself has quietly confirmed that the U.S. is in terrible fiscal trouble – far worse than the Washington-based lender of last resort has previously acknowledged. “The U.S. fiscal gap is huge,” the IMF asserted in a June report. “Closing the fiscal gap requires a permanent annual fiscal adjustment equal to about 14 per cent of U.S. GDP.”

This sum is equal to all current U.S. federal taxes combined. The consequences of the IMF’s fiscal fix, a doubling of federal taxes in perpetuity, would be appalling – and possibly worse than appalling.

Prof. Kotlikoff says: “The IMF is saying that, to close this fiscal gap [by taxation], would require an immediate and permanent doubling of our personal income taxes, our corporate taxes and all other federal taxes.

“America’s fiscal gap is enormous – so massive that closing it appears impossible without immediate and radical reforms to its health care, tax and Social Security systems – as well as military and other discretionary spending cuts.”

He cites earlier calculations by the Congressional Budget Office (CBO) that concluded that the United States would need to increase tax revenue by 12 percentage points of GDP to bring revenue into line with spending commitments. But the CBO calculations assumed that the growth of government programs (including Medicare) would be cut by one-third in the short term and by two-thirds in the long term. This assumption, Prof. Kotlikoff notes, is politically implausible – if not politically impossible.

One way or another, the fiscal gap must be closed. If not, the country’s spending will forever exceed its revenue growth, and no one’s real debt can increase faster than his real income forever.

Prof. Kotlikoff uses “fiscal gap,” not the accumulation of deficits, to define public debt. The fiscal gap is the difference between a government’s projected revenue (expressed in today’s dollar value) and its projected spending (also expressed in today’s dollar value). By this measure, the United States is in worse shape than Greece.

Prof. Kotlikoff is a noted economist. He is a research associate at the U.S. National Bureau of Economic Research. He is a former senior economist with then-president Ronald Reagan’s Council of Economic Advisers. He has served as a consultant with governments around the world. He is the author (or co-author) of 14 books: Jimmy Stewart Is Dead (2010), his most recent book, explains his recommendations for reform.

He says the U.S. cannot end its fiscal crisis by increasing taxes. He opposes further stimulus spending because it will simply increase the debt. But he does suggest reforms that would help – most of which would require a significant withering away of the state. He proposes that the government give every person an annual voucher for health care, provided that the total cost not exceed 10 per cent of GDP. (U.S. health care now consumes 16 per cent of GDP.) He suggests the replacement of all current federal taxes with a single consumption tax of 18 per cent. He calls for government-sponsored personal retirement accounts, with the government making contributions only for the poor, the unemployed and people with disabilities.

Without drastic reform, Prof. Kotlikoff says, the only alternative would be a massive printing of money by the U.S. Treasury – and hyperinflation.

As former president Bill Clinton once prematurely said, the era of big government is over. In the coming years, the U.S. will almost certainly be compelled to deconstruct its welfare state.

Prof. Kotlikoff doesn’t trust government accounting, or government regulation. The official vocabulary (deficit, debt, transfer payment, tax, borrowing), he says, is vulnerable to official manipulation and off-the-books deceit. He calls it “Enron accounting.” He also calls it a lie. Here is an economist who speaks plainly, as the legendary straight-shooting film star Jimmy Stewart did for an earlier generation.

But Prof. Kotlikoff’s economic genre isn’t the Western. It’s the horror story – “and scarier,” one reviewer of his book suggests, than Stephen King.

Cool Money Market Saving Account images

A few nice money market saving account images I found:

Imaginary Money Graveyard


Image by Eifachfilm Vacirca
Imaginary Money Graveyard by d-oo-b.cc

A graveyard for all this money that died end of the year 2008.
Beware of the zombie bills they might take all your money.

The movie:
d-oo-b.cc/ImaginearyMoneyGraveyard.mov

uqbar-mediaartculture.ning.com/video/video/show?id=224051…

marcominghetti.nova100.ilsole24ore.com/2009/02/imaginary-…

The secondlife Landmark:
slurl.com/secondlife/Switzerland/78/162/34

Read the news paper article here:

only in german but nice foto of eif and jazz

www.kunstnet.ch/doob/displayimage.php?pos=-2748

Tv documentary movie:

eifachfilm.ch/SF_me.htm

Short movie incinemas rigth now:
(subtitled in 11 languages)

video.google.com/videoplay?docid=-1797618522240273307

The fotos and more:
www.kunstnet.ch/doob/displayimage.php?pos=-2743
www.youtube.com/watch?v=9PRNnOjGOq4
www.kunstnet.de/werk/115874-imaginary-money-graveyard/
eifachfilm.ch/bm/detail.php?c=1&i=436f3a9fa66e647ad0a…
flickr.com/photos/arcorosca/sets/72157608868260247/show/w…
www.flickr.com/photos/roxelo/3020310910

A graveyard for all this money that died end of the year 2008.
Beware of the zombie bills they might take all your money.

Europe was caught out by the financial crisis and did not see recession looming, the head of the Eurogroup of nations conceded today, amid estimates that the EU has plunged into a downturn. OCt 08

‘Recession awaits us, and we didn’t think that recession lay in waiting,’ euro zone chairman Jean-Claude Juncker told members of the European Parliament in Brussels. Oct 08

‘We were badly mistaken with the different sequences of this crisis,’ said Juncker, who is also the premier and finance minister of Luxembourg. Oct 08

The European Commission in early November 2008 warned that the worst financial crisis for generations has driven the EU economy into recession and that economic growth would come close to a standstill next year.

"Increasingly, the signs point to a deep and synchronised global recession that began last quarter and has gathered momentum," said Bruce Kasman, an economist at JPMorgan Chase in New York. November 08

The eurozone’s second-biggest economy will grow by just 0.2-0.5 percent next year instead of the 1 percent previously predicted, Economy and Finance Minister Christine Lagarde told the Senate.
The minister said the growth forecast for next year 2009 was “the lowest ever by a government in France” but that it was realistic.

“The international economic outlook has deteriorated much more than was expected, which will impact growth in Switzerland over the next several quarters,” the Swiss National Bank said in a statement in October 08

The sharp falls came after the Dow Jones index slid 5.05 percent on Wall Street November 7th 08 as investors braced for a gloomy economic ride after the euphoria of Obama’s election victory faded.
“Now that the event is over, investors are sobering up and looking at the economic gloom,” said Mizuho Investors Securities broker Masatoshi Sato.

Billionaire philanthropist George Soros conceded in OCtober 08 that US influence was waning: "It has already declined. For the past 25 years, we have been running a constant current account deficit. The Chinese and the oil-producing countries have been running a surplus. We have consumed more than we produced. While we have run up debt, they have acquired wealth with their savings. Increasingly, the Chinese will own a lot more of the world because they will be converting their dollar reserves and US government bonds into real assets."

Japan
By James Kirkup and Julian Ryall in Tokyo
Last Updated: 4:00PM BST 16 Oct 2008
Telegraph.co.uk
"To cope with the current crisis, further steps may be needed," Mr Aso told members of the Japanese parliament. "However, I still believe this package will be effective to a certain degree."
Mr Aso’s budget package will be mean direct financial support for farmers and fishermen paying higher fuel bills, and for Japanese consumers.
The emergency budget is part of a wider 11.7-trillion-yen package announced in August.
The Bank of Japan also made another 300 billion-yen of emergency loans to Japanese banks, hoping to unblock the Tokyo money markets. The central bank has been offering extra liquidity on an almost daily basis for a month.

euro
Author: ČTK
www.ceskenoviny.cz/news/index_view.php?id=338324
Prague – The current situation on financial markets will affect the agenda of Czech EU presidency in the first half of 2009, deputy prime minister for EU affairs Alexandr Vondra said.
The financial crisis has become a new priority of the European Union, Vondra said.
"When you are making preparations for a football match, you sometimes base your tactics more on offensive while another time you are more defensive. It is evident that in the economic situation in which Europe will be finding itself next year, emphasis will be rather placed on the protection and defence of what has already been attained," Vondra said.

Posted by Kevin Anderson Sunday October 12 2008 06.50 BST

Homelessness, the economic crisis and voting
Homelessness is on the rise in the US, and the newly homeless could find their votes challenged.
In Reno Nevada, joblessness has jumped 60% and a tent city of 170 people grew. Reno is trying to shut down the tent city and move people to newly opened shelters. CBS News has reported tent cities in Seattle, Portland, Fresno, Columbus, and Chattanooga. There are also reports of encampments in Seattle, San Diego, and Columbus, Ohio, Santa Barbara and Fresno California.
The wave of foreclosures, which in some areas of the country disproportionately affect black voters, could also come into play. The Republican Party of Macomb County Michigan, one of three counties that make up Detroit, is planning to use list of foreclosed homes to challenge people who try to vote using those addresses.
Republicans claim that they are trying to prevent voter fraud. Homeless and voting rights advocates are trying to make sure that people don’t lose their homes and their right to vote.

USA
As veteran curator of that realm of American national power upon which all others ultimately depend, Greenspan has inspired remarkable deference. He long ago tamed the legislature, to the point that, instead of exercising oversight over his tenure, Congress has ritually idolized rather than interrogated him. Greenspan’s aura has extended even to presidents of the United States. Bill Clinton went so far as to ask Greenspan in 2000 if he would like to be appointed to a fourth term as chairman, or whether he’d prefer to "go out now on top." The then 73-year-old replied: "Oh, no. This is the greatest job in the world. It’s like eating peanuts. You keep doing it, keep doing it, and you never get tired."
BY PETER HARTCHER
American Interests www.the-american-interest.com
Winter Issue

“Those of us who have looked to the self-interest of lending institutions to protect shareholders’ equity, myself included, are in a state of shocked disbelief,” he told the House Committee on Oversight and Government Reform.

Mr. Greenspan conceded: “Yes, I’ve found a flaw. I don’t know how significant or permanent it is. But I’ve been very distressed by that fact.”

Mr. Greenspan said that he had publicly warned about the “underpricing of risk” in 2005 but that he had never expected the crisis that began to sweep the entire financial system in 2007.

“This crisis,” he told lawmakers, “has turned out to be much broader than anything I could have imagined. It has morphed from one gripped by liquidity restraints to one in which fears of insolvency are now paramount.”
NEW YORK TIMES (US)

Greenspan’s sins return to haunt us
By David Blake
Published: September 18 2008 18:39 | Last updated: September 18 2008 18:39

Back in 2002, when his reputation as “The Man Who Saved the World” was at its peak, Alan Greenspan, former chairman of the Federal Reserve, came to Britain to pick up his knighthood. His biggest fan, Gordon Brown, now the UK prime minister, had ensured that the citation said it was being awarded for promoting “economic stability”.
Even as things went completely wild, Mr Greenspan dismissed those who warned that a new bubble was emerging. It was just a case of a little “froth” in a few areas. Later, after waiting until 2007, two years after he left office, he conceded that “froth” had been his euphemism for “bubble”. “All the froth bubbles add up to an aggregate bubble,” he told the Financial Times……
Mr Greenspan realises that something big has happened and describes it as a “once in a hundred years” event. But then, you do not get Alan Greenspans coming along every day.
Finincial Times (UK) Copyright The Financial Times Limited 2008

Neoliberalism, White (Male) Privilege & the Current Financial Crisis
by Jessie on Sep 30, 2008 at 11:29 am
Make no mistake, all the available evidence suggests that the American political economy is headed for a major crash. Some are even speculating that this is the end of American economic dominance in the world’s financial market. But don’t be deceived by the blame-the-victim rationalizing that’s being floated now. Let’s be clear about what policies and which people are behind the current financial crisis: neoliberal policies and the overwhelmingly majority of economically privileged white men (photo from same link) who created, implemented and benefited from those policies.
Neoliberalism refers to a set of policies that encourage “less government” and unfettered (and unregulated) capitalism. The key elements of neoliberalism include: 1) the rule of the market, 2) reducing government expenditures on social services, 3) deregulation, 4) privatization, and 5) gutting the notion of “the public good.”
The end result of neoliberal policies is that while a handful of people get very, very rich, these policies simultaneously exacerbate the suffering of just about everyone else and increase domestic and international instability. So, what we’re seeing now is just the logical, perhaps inevitable, result of these policies.

Focus on and take control of your retirement


Image by s_falkow

China likely Winner of the Information Age Ecommerce Supply Chain by maintaining peace and corporate property rights


Image by Wonderlane
The Report
China is a likely winner of the information age supply chain through ecommerce by sticking with its successful strategy of continued steady growth, coupled with continuing (the appearance of) a transparent society (where currently major decisions are made by top government and business officials behind closed doors) which manipulate and manage economies at large. In order to be considered a great global leader China should maintain peace and respect for corporate property rights. They need to immediately focus on their serious environment pollution problems to survive.

Caption: "The sign that says you’re welcome in Shanghai" – Johnny Vulkan www.flickr.com/photos/johnnyvulkan/1856903750/

The evidence is clear: China has McDonalds restaurants, and with extensive factories they make Dell and other computers. Bill Gates is eagerly pursuing business with China, and the Chinese government has given Microsoft the right to grant post-doctorial fellowships. Key companies invested in technology are willing to go to court to keep the most important Chinese corporate leaders. Kai-Fu Lee, once a vice-president at Microsoft is now Google’s manager in China. Mr. Lee was the person at the center of twin lawsuits (suit and countersuit), a battle over which of the two companies would win him to work for them – he may be the ultimate in ‘intellectual property.’

Caption ”On the Shanghai subway, rather than advertising computers for sale, Dell promotes job openings.” Danburg Murmur www.flickr.com/photos/danburgmurmur/247299162/

What is at issue are personably identifiable information (PII) and intellectual property rights (patents and copyrights) which are legislated and widely respected in the West.

Personal information is the feeder fish at the bottom of the information age food chain. China does not believe people have a right to privacy because of how communism is structured; this is true of members of their society until that person is wealthy and thus powerful enough to opt out of it, and even then the appearance of opting in must be kept.

Even in the West Intellectual property rights are eroding, which is as it should be, as it is not the same as owning a house, and can be damaging to others on a massive scale such as medical patents for aids, cancer, and other life saving drugs.

The Chinese style of governance comes with a 5 thousand year old administrative history of ordering a society consisting of large numbers of people. Because most people in American and the West do not speak their language nor write it, much of China remains a society closed to the English speaking countries. Due to communication barriers the West does not have the very healthy level of respect for China that it should.

Even the Chinese written language may give China advantages with online screens unknown in the West with their thousands of dense glifts, pictographs, and phonetic parts. Currently it is estimated more than 1 billion people use some form of Chinese as their native language.

It can be said that he who owns the resources wins; especially true when supply chains are consistent and reliable. This applies to personally identifiable information in the information age as it relates to sales, because personal information is a building block in the information supply chain. Creating mass marketing campaigns targeting not just individuals but large groups of people is based on creating desire , an example is Steve Jobs and the Apple iPod. This is in addition to knowing what people want, not just what they need.

Meeting the needs of all people in the world is still a goal some people are working towards, while many more others try to capture wealth only for themselves and their investors. From the point of view that in the long run we’re all dead, many investors do not view themselves as breaking any moral or other rules, just trying to get ahead, or make a profit on their investment, which they want right now. This uninformed short sighted view is killing people, and eroding the middle class of nations. Any country that has a middle class will miss it when it is gone; most countries are trying to build their middle class.

Business to Business (B2B) resource supply chains control wealth. Only the wealthy have a reason to protect privacy of information, because the poor and the very poor have much more immediate concerns. Hopefully the Chinese will learn as other countries like Malaysia did, that including diverse ethnic types is not just a ethical ideal, it is a strategy for long term success.

This lesson continues to be a painful and costly lesson to the US, which in many ways is exclusionary. Viewing the poor as beggars while subsidizing production with huge remedies is one of the inadequacies that may be overturned as international growth is managed at a global level because it can not be justified as anything other than corrupt practices. By all accounts I read, generosity in international relationships is mythical and with the digital age has only grown worse . Does it matter what you wear while you ask for money or how well educated you are? Apparently it does.

One size fits all privacy will never suit everyone because it has a biological basis and the need increases with education, and its cousin, wealth. Increasingly to have the opt out choice in terms of privacy you need wealth. That too will change subtly because as ecommerce becomes pervasive, some system or sets of systems will always know that someone is there in some detectable way.

The patent and copyright systems can be damaging to others on a global scale by shutting down creativity, and unfairly favoring their protection even against life, due to medical patents for aids, cancer, and other life saving drugs being so expensive to produce or purchase that people are allowed to die as a result. Calls to action for multinational drug companies to reduce these costs, have changed little or nothing in the developing world. This has been featured so well in the headlines and news stories lately that it can hardly be a surprise to anyone that it is a problem – youth know because Digital Rights Management (DRM) is dead.

Ecommerce is a tool and can be used in many ways. Trading is already a cold transaction and to remove it from human context makes it even more so. In accounting they discuss "arms length transactions" – with ecommerce those arms get pretty long.

So we can expect that the human repercussions of global ecommerce, driven by the integration of B2B procurement systems, could stabilize and destabilize entire populations unless the planning is very good. That means everyone must hold the keys in some way, and be open to transparency at some level which runs counter to special interest groups . Transparency in action does exactly what it need to do, but which, for example, is not a match for existing culture in China.

Real transparency in global governance with a goal to meet the basic needs of all people living sounds like a science fiction plot, but that is what makes it exciting. Transparent governance may only become possible due to radically unexpected causes, like education, religious idealism, or a shared social solution of the young through organizations such as www.one.org.

Ironically one of the religions likely to have a positive effect in China, and likely to benefit from it, is Tibetan Buddhism, long repressed by the current Chinese government.

Ecommerce will not cause peace in the world, educated people working with strong idealism in transparent cultures will. Still my conclusion remains that China is a likely winner of the information age supply chain through ecommerce.

We should invest in China.

Quicken Rental Property Manager 2011 – [Old Version]

Quicken Rental Property Manager 2011 – [Old Version]

• Quicken Rental Property Manager 2011 helps you manage your personal, business, and rental property finances in one place
• Identifies tax-deductible rental property expenses; tracks income and expenses by property; lets you know which rents have been paid
• Shows you where your money is going: automatically categorizes your personal and home business expenses
• Lets you view your profit and loss at a glance, so you always know how your home-based business is doing
• Helps you choose the right investments to reach your goals, and identifies ways to minimize taxes on your investments

Organizes your personal and rental property finances, all in one place. Identifies tax-deductible rental property expenses. Tracks income and expenses by property. Creates Schedule E report to save time on taxes. Quicken Rental Property Manager 2011 includes all of the features found in Quicken Home & Business, plus smart tools for managing your rental properties. Always know how your home-based business is doing. Helps maximize deductions and simplify your taxes. Ma

List Price: $ 149.99

Price:

HP C4193A Toner Cartridge (Magenta/Red)

HP C4193A Toner Cartridge (Magenta/Red)

• Optimum magenta (red) color output
• Chemically grown color toner particles
• Reduces waste
• Requires less interaction
• Genuine HP toner for HP Color LaserJet 4500/4550 printers

Genuine HP LaserJet printing supplies are always the right choice. They deliver exceptional print quality and hassle-free operation, page after page, because they’re specifically designed to work with HP printers. Did you know that 70% of a LaserJet printer’s imaging system is based on HP’s LaserJet print cartridges? The technology of the print cartridge is any printing system’s most critical component, so if you’re not using HP supplies, you’re not getting HP printing. With genuine HP LaserJet

List Price: $ 212.33

Price:

More High Yield Online Savings Accounts Products

HP 12C Platinum Financial Calculator

HP 12C Platinum Financial Calculator

• Robust and versatile financial calculator
• Over 120 built-in functions for business, finance, mathematics, and statistics, including date calculations
• Efficient data entry using RPN
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Concrete


Image by Joost J. Bakker IJmuiden
Concrete
Concrete is a composite construction material, composed of cement (commonly Portland cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravel or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water, and chemical admixtures.

The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a robust stone-like material. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick/block walls and footings for gates, fences and poles.

Concrete is used more than any other man-made material in the world. As of 2006, about 7.5 cubic kilometres of concrete are made each year—more than one cubic metre for every person on Earth.

Concrete powers a US billion industry, employing more than two million workers in the United States alone.[citation needed] More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days.

History

Concrete has been used for construction in various ancient structures. An analysis of ancient Egyptian pyramids has shown that concrete may have been employed in their construction, although its composition would have differed from modern concrete.

During the Roman Empire, Roman concrete (or opus caementicium) was made from quicklime, pozzolana, and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick material and allowed for revolutionary new designs in terms of both structural complexity and dimension.

Hadrian’s Pantheon in Rome is an example of Roman concrete construction.Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that trouble the builders of similar structures in stone or brick.

Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (ca. 200 kg/cm2). However, due to the absence of steel reinforcement, its tensile strength was far lower and its mode of application was also different:

Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.

The widespread use of concrete in many Roman structures has ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges have masonry cladding on a concrete core, as does the dome of the Pantheon.

Some have stated that the secret of concrete was lost for 13 centuries until 1756, when the British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate. However, the Canal du Midi was built using concrete in 1670.[11] Likewise there are concrete structures in Finland that date back to the 16th century. Portland cement was first used in concrete in the early 1840s.

Additives

Concrete additives have been used since Roman and Egyptian times, when it was discovered that adding volcanic ash to the mix allowed it to set under water. Similarly, the Romans knew that adding horse hair made concrete less liable to crack while it hardened, and adding blood made it more frost-resistant.

Recently the use of recycled materials as concrete ingredients has been gaining popularity because of increasingly stringent environmental legislation. The most conspicuous of these is fly ash, a byproduct of coal-fired power plants. This use reduces the amount of quarrying and landfill space required, and, as the ash acts as a cement replacement, reduces the amount of cement required.

In modern times, researchers have experimented with the addition of other materials to create concrete with improved properties, such as higher strength or electrical conductivity. Marconite is one example.

Composition

There are many types of concrete available, created by varying the proportions of the main ingredients below. In this way or by substitution for the cemetitious and aggregate phases, the finished product can be tailored to its application with varying strength, density, or chemical and thermal resistance properties.

The mix design depends on the type of structure being built, how the concrete will be mixed and delivered, and how it will be placed to form this structure.

Cement
Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar, and plaster. English masonry worker Joseph Aspdin patented Portland cement in 1824; it was named because of its similarity in colour to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. It consists of a mixture of oxides of calcium, silicon and aluminium. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay, and grinding this product (called clinker) with a source of sulfate (most commonly gypsum).

Water

Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and allows it to flow more freely.

Less water in the cement paste will yield a stronger, more durable concrete; more water will give an freer-flowing concrete with a higher slump. Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure.

Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles, and other components of the concrete, to form a solid mass.

Reaction:

Cement chemist notation: C3S + H → C-S-H + CH
Standard notation: Ca3SiO5 + H2O → (CaO)·(SiO2)·(H2O)(gel) + Ca(OH)2
Balanced: 2Ca3SiO5 + 7H2O → 3(CaO)·2(SiO2)·4(H2O)(gel) + 3Ca(OH)2

Aggregates

Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition and excavation waste) are increasingly used as partial replacements of natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.

Decorative stones such as quartzite, small river stones or crushed glass are sometimes added to the surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers.

The presence of aggregate greatly increases the robustness of concrete above that of cement, which otherwise is a brittle material, and thus concrete is a true composite material.

Redistribution of aggregates after compaction often creates inhomogeneity due to the influence of vibration. This can lead to strength gradients.

Reinforcement

Concrete is strong in compression, as the aggregate efficiently carries the compression load. However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete solves these problems by adding either steel reinforcing bars, steel fibers, glass fiber, or plastic fiber to carry tensile loads. Thereafter the concrete is reinforced to withstand the tensile loads upon it.
Chemical admixtures

Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement, and are added to the concrete at the time of batching/mixing. The common types of admixtures are as follows.

Accelerators speed up the hydration (hardening) of the concrete. Typical materials used are CaCl2, Ca(NO3)2 and NaNO3. However, use of chlorides may cause corrosion in steel reinforcing and is prohibited in some countries, so that nitrates may be favored.
Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable. Typical polyol retarders are sugar, sucrose, sodium gluconate, glucose, citric acid, and tartaric acid.
Air entrainments add and entrain tiny air bubbles in the concrete, which will reduce damage during freeze-thaw cycles, thereby increasing the concrete’s durability. However, entrained air entails a tradeoff with strength, as each 1% of air may result in 5% decrease in compressive strength.
Plasticizers increase the workability of plastic or "fresh" concrete, allowing it be placed more easily, with less consolidating effort. A typical plasticizer is lignosulfonate. Plasticizers can be used to reduce the water content of a concrete while maintaining workability, and are sometimes called water-reducers due to this use. Such treatment improves its strength and durability characteristics. Superplasticizers (also called high-range water-reducers) are a class of plasticizers that have fewer deleterious effects, and can be used to increase workability more than is practical with traditional plasticizers. Compounds used as superplasticizers include sulfonated naphthalene formaldehyde condensate, sulfonated melamine formaldehyde condensate, acetone formaldehyde condensate, and polycarboxylate ethers.
Pigments can be used to change the color of concrete, for aesthetics.
Corrosion inhibitors are used to minimize the corrosion of steel and steel bars in concrete.
Bonding agents are used to create a bond between old and new concrete.
Pumping aids improve pumpability, thicken the paste, and reduce separation and bleeding.

Mineral admixtures and blended cements

There are inorganic materials that also have pozzolanic or latent hydraulic properties. These very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures), or as a replacement for Portland cement (blended cements).

Fly ash: A by product of coalfired electric generating plants, it is used to partially replace Portland cement (by up to 60% by mass). The properties of fly ash depend on the type of coal burnt. In general, siliceous fly ash is pozzolanic, while calcareous fly ash has latent hydraulic properties.
Ground granulated blast furnace slag (GGBFS or GGBS): A by-product of steel production is used to partially replace Portland cement (by up to 80% by mass). It has latent hydraulic properties.[18]
Silica fume: A by-product of the production of silicon and ferrosilicon alloys. Silica fume is similar to fly ash, but has a particle size 100 times smaller. This results in a higher surface to volume ratio and a much faster pozzolanic reaction. Silica fume is used to increase strength and durability of concrete, but generally requires the use of superplasticizers for workability.[19]
High reactivity Metakaolin (HRM): Metakaolin produces concrete with strength and durability similar to concrete made with silica fume. While silica fume is usually dark gray or black in color, high-reactivity metakaolin is usually bright white in color, making it the preferred choice for architectural concrete where appearance is important.
Concrete production

The processes used vary dramatically, from hand tools to heavy industry, but result in the concrete being placed where it cures into a final form. Wide range of technological factors may occur during production of concrete elements and their influence to basic characteristics may vary

When initially mixed together, Portland cement and water rapidly form a gel, formed of tangled chains of interlocking crystals. These continue to react over time, with the initially fluid gel often aiding in placement by improving workability. As the concrete sets, the chains of crystals join and form a rigid structure, gluing the aggregate particles in place. During curing, more of the cement reacts with the residual water (hydration).

This curing process develops physical and chemical properties. Among these qualities are mechanical strength, low moisture permeability, and chemical and volumetric stability

Mixing concrete

Thorough mixing is essential for the production of uniform, high quality concrete. For this reason equipment and methods should be capable of effectively mixing concrete materials containing the largest specified aggregate to produce uniform mixtures of the lowest slump practical for the work.

Separate paste mixing has shown that the mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete.[21] The paste is generally mixed in a high-speed, shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, plasticizers, pigments, or silica fume. The premixed paste is then blended with aggregates and any remaining batch water, and final mixing is completed in conventional concrete mixing equipment.

High-energy mixed (HEM) concrete is produced by means of high-speed mixing of cement, water, and sand with net specific energy consumption of at least 5 kilojoules per kilogram of the mix. A plasticizer or a superplasticizer is then added to the activated mixture, which can later be mixed with aggregates in a conventional concrete mixer. In this process, sand provides dissipation of energy and creates high shear conditions on the surface of cement particles. This results in the full volume of water interacting with cement. The liquid activated mixture can be used by itself or foamed (expanded) for lightweight concrete. HEM concrete hardens in low and subzero temperature conditions and possesses an increased volume of gel, which drastically reduces capillarity in solid and porous materials.
Workability

Main article: Concrete slump test
Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (vibration) and without reducing the concrete’s quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration), and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures will increase concrete workability. Excessive water will lead to increased bleeding (surface water) and/or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. The use of an aggregate with an undesirable gradation can result in a very harsh mix design with a very low slump, which cannot be readily made more workable by addition of reasonable amounts of water.

Workability can be measured by the concrete slump test, a simplistic measure of the plasticity of a fresh batch of concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod in order to consolidate the layer. When the cone is carefully lifted off, the enclosed material will slump a certain amount due to gravity. A relatively dry sample will slump very little, having a slump value of one or two inches (25 or 50 mm). A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by using the Flow table test.

Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio. Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.

High-flow concrete, like self-consolidating concrete, is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.

After mixing, concrete is a fluid and can be pumped to the location where needed.

Curing

In all but the least critical applications, care needs to be taken to properly cure concrete, to achieve best strength and hardness. This happens after the concrete has been placed. Cement requires a moist, controlled environment to gain strength and harden fully. The cement paste hardens over time, initially setting and becoming rigid though very weak, and gaining in strength in the weeks following. In around 3 weeks, typically over 90% of the final strength is reached, though strengthening may continue for decades. The conversion of calcium hydroxide in the concrete into calcium carbonate from absorption of CO2 over several decades further strengthen the concrete and making it more resilient to damage. However, this reaction, called carbonation, lowers the pH of the cement pore solution and can cause the reinforcement bars to corrode.

Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. Strength of concrete changes (increases) up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation.

During this period concrete needs to be kept under controlled temperature and humid atmosphere. In practice, this is achieved by spraying or ponding the concrete surface with water, thereby protecting the concrete mass from ill effects of ambient conditions. The pictures to the right show two of many ways to achieve this, ponding – submerging setting concrete in water, and wrapping in plastic to contain the water in the mix.

Properly curing concrete leads to increased strength and lower permeability, and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing, or overheating due to the exothermic setting of cement (the Hoover Dam used pipes carrying coolant during setting to avoid damaging overheating). Improper curing can cause scaling, reduced strength, poor abrasion resistance, and cracking.

Properties

Main article: Properties of concrete
Concrete has relatively high compressive strength, but much lower tensile strength, and for this reason is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion, and shrinks as it matures. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.

Tests can be made to ensure the properties of concrete correspond to specifications for the application.
Environmental concerns

Carbon dioxide emissions and climate change

The cement industry is one of two primary producers of carbon dioxide (CO2), creating up to 5% of worldwide man-made emissions of this gas, of which 50% is from the chemical process, and 40% from burning fuel. The embodied carbon dioxide (ECO2) of one tonne of concrete is around 100 kg/tonne. The CO2 emission from the concrete production is directly proportional to the cement content used in the concrete mix. Indeed, 900 kg of CO2 are emitted for the fabrication of every ton of cement. Cement manufacture contributes greenhouse gases both directly through the production of carbon dioxide when calcium carbonate is thermally decomposed, producing lime and carbon dioxide, and also through the use of energy, particularly from the combustion of fossil fuels. However, some companies have recognized the problem and are envisaging solutions to counter their CO2 emissions. The principle of carbon capture and storage consists of directly capturing the CO2 at the outlet of the cement kiln in order to transport it and to store the captured CO2 in an adequate and deep geological formation.

Surface runoff

Surface runoff, when water runs off impervious surfaces, such as non-porous concrete, can cause heavy soil erosion. Urban runoff tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants from sidewalks, roadways and parking lots. The impervious cover in a typical urban area limits groundwater percolation and causes five times the amount of runoff generated by a typical woodland of the same size. A 2008 report by the United States National Research Council identified urban runoff as a leading source of water quality problems.

Urban heat

Both concrete and asphalt are the primary contributors to what is known as the urban heat island effect.
Using light-colored concrete has proven effective in reflecting up to 50% more light than asphalt and reducing ambient temperature. A low albedo value, characteristic of black asphalt, absorbs a large percentage of solar heat and contributes to the warming of cities. By paving with light colored concrete, in addition to replacing asphalt with light-colored concrete, communities can lower their average temperature.

In many U.S. cities, pavement covers about 30-40% of the surface area. This directly affects the temperature of the city, and contributes to the urban heat island effect. Paving with light-colored concrete would lower temperatures of paved areas and improve nighttime visibility. The potential of energy saving within an area is also high. With lower temperatures, the demand for air conditioning decreases, saving energy.

Atlanta has tried to mitigate the heat-island effect. City officials noted that when using heat-reflecting concrete, their average city temperature decreased by 6 °F The Design Trust for Public Space found that by slightly raising the albedo value in in New York City, beneficial effects such as energy savings could be achieved.[citation needed] It was concluded that this could be accomplished by the replacement of black asphalt with light-colored concrete.

However, in winter this may be a disadvantage as ice will form more easily and remain longer on the light colored surfaces as they will be colder due to less energy absorbed from the reduced amount of sunlight in winter.

Concrete dust

Building demolition and natural disasters such as earthquakes often release a large amount of concrete dust into the local atmosphere. Concrete dust was concluded to be the major source of dangerous air pollution following the Great Hanshin earthquake

Health concerns

The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns. Natural radioactive elements (K, U and Th) can be present in various concentration in concrete dwellings, depending on the source of the raw materials used. Toxic substances may also be added to the mixture for making concrete by unscrupulous makers. Dust from rubble or broken concrete upon demolition or crumbling may cause serious health concerns depending also on what had been incorporated in the concrete.

Concrete handling/safety precautions

Handling of wet concrete must always be done with proper protective equipment. Contact with wet concrete can cause skin chemical burns due to the caustic nature of the mixture of cement and water. Indeed, the pH of fresh cement water is highly alkaline due to the presence of free potassium and sodium hydroxides in solution (pH ~ 13.5). Eyes, hands and feet must be correctly protected to avoid any direct contact with wet concrete and washed without delay if necessary.
Damage modes

Main article: Concrete degradation

Concrete spalling caused by the corrosion of reinforcement bars after that carbonation of cement decreased the pH below the passivation threshold for steel.Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonation, chlorides, sulfates and distillate water)

Concrete repair

Concrete pavement preservation (CPP) and concrete pavement restoration (CPR) are techniques used to manage the rate of pavement deterioration on concrete streets, highways and airports. Without changing concrete grade, this non-overlay method is used to repair isolated areas of distress. CPP and CPR techniques include slab stabilization, full- and partial-depth repair, dowel bar retrofit, cross stitching longitudinal cracks or joints, diamond grinding and joint and crack resealing. CPR methods, developed over the last 40 years, are utilized in lieu of short-lived asphalt overlays and bituminous patches to repair roads. These methods are often less expensive[citation needed]than an asphalt overlay but last three times longer and provide a greener solution.[38]

CPR techniques can be used to address specific problems or bring a pavement back to its original quality. When repairing a road, design data, construction data, traffic data, environmental data, previous CPR activities and pavement condition, must all be taken into account. Pavements repaired using CPR methods usually last 15 years. The methods are described below.

Slab stabilization restores support to concrete slabs by filling small voids that develop underneath the concrete slab at joints, cracks or the pavement edge.
Full-depth repairs fixes cracked slabs and joint deterioration by removing at least a portion of the existing slab and replacing it with new concrete.
Partial-depth repairs corrects surface distress and joint-crack deterioration in the upper third of the concrete slab. Placing a partial-depth repair involves removing the deteriorated concrete, cleaning the patch area and placing new concrete.
Dowel bar retrofit consists of cutting slots in the pavement across the joint or crack, cleaning the slots, placing the dowel bars and backfilling the slots with new concrete. Dowel bar retrofits link slabs together at transverse cracks and joints so that the load is evenly distributed across the crack or joint.
Cross-stitching longitudinal cracks or joints repairs low-severity longitudinal cracks. This method adds reinforcing steel to hold the crack together tightly.
Diamond grinding, by removing faulting, slab warping, studded tire wear and unevenness resulting from patches, diamond grinding creates a smooth, uniform pavement profile. Diamond grinding reduces road noise by providing a longitudinal texture, which is quieter than transverse textures. The longitudinal texture also enhances surface texture and skid resistance in polished pavements.
Joint and crack sealing minimizes the infiltration of surface water and incompressible material into the joint system. Minimizing water entering the joint reduces sub-grade softening, slows pumping and erosion of the sub-base fines, and may limit dowel-bar corrosion caused by de-icing chemicals
Concrete recycling

Concrete recycling is an increasingly common method of disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws, and economic benefits.

Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and put through a crushing machine, often along with asphalt, bricks, and rocks.

Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On March 3, 1983, a government funded research team (the VIRL research.codep) approximated that almost 17% of worldwide landfill was by-products of concrete based waste.

Recycling concrete provides environmental benefits, conserving landfill space and use as aggregate reduces the need for gravel mining.

World records

The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 16 million cubic meters over 17 years. The previous record was 3.2 million cubic meters held by Itaipu hydropower station in Brazil.

Concrete pumping

The world record was set at on 7 August 2009 during the construction of the Parbati Hydroelectric Project, near the village of Suind, Himachal Pradesh, India, when the concrete mix was pumped through a vertical height of 715 m (2,346 ft).
Continuous pours

The world record for largest continuously poured concrete raft was achieved in August 2007 in Abu Dhabi by contracting firm Al Habtoor-CCC Joint Venture. The pour (a part of the foundation for the Abu Dhabi’s Landmark Tower) was 16,000 cubic meters of concrete poured within a two day period.[44] The previous record (close to 10,500 cubic meters) was held by Dubai Contracting Company and achieved March 23, 2007.

The world record for largest continuously poured concrete floor was completed November 8, 1997, in Louisville, Kentucky by design-build firm EXXCEL Project Management. The monolithic placement consisted of 225,000 square feet (20,900 m2) of concrete placed within a 30 hour period, finished to a flatness tolerance of FF 54.60 and a levelness tolerance of FL 43.83. This surpassed the previous record by 50% in total volume and 7.5% in total area.

The record for the largest continuously placed underwater concrete pour was completed October 18, 2010, in New Orleans, Louisiana by contractor C. J. Mahan Construction Company, LLC of Grove City, Ohio. The placement consisted of 10,224 cubic yards of concrete placed in a 58 hour period using two concrete pumps and two dedicated concrete batch plants. Upon curing, this placement will allow the 50,180-square-foot (4,662 m2) cofferdam to be dewatered approximately 26 feet (7.9 m) below sea level to allow the construction of the IHNC GIWW Sill & Monolith Project to be completed in the dry

Use of concrete in infrastructure

Mass concrete structures

These include gravity dams such as the Hoover Dam, the Itaipu Dam, and the Three Gorges Dam and large breakwaters. Concrete that is poured all at once in one block (so that there are no weak points where the concrete is "welded" together) is used for tornado shelters.

Reinforced concrete structures

Reinforced concrete contains steel reinforcing that is designed and placed in the structure at specific positions to cater for all the stress conditions that the structure is required to accommodate.
Prestressed concrete structures

Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those found when in use. This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement. For example a horizontal beam will tend to sag down. If the reinforcement along the bottom of the beam is prestressed, it can counteract this.

In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.

Concrete textures

When one thinks of concrete, the image of a dull, gray concrete wall often comes to mind. With the use of form liner, concrete can be cast and molded into different textures and used for decorative concrete applications. Sound/retaining walls, bridges, office buildings and more serve as the optimal canvases for concrete art. For example, the Pima Freeway/Loop 101 retaining and sound walls in Scottsdale, Arizona, feature desert flora and fauna, a 67-foot (20 m) lizard and 40-foot (12 m) cacti along the 8-mile (13 km) stretch. The project, titled "The Path Most Traveled," is one example of how concrete can be shaped using elastomeric form liner.

Building with concrete

Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction, can gain strength over time. Structures made of concrete can have a long service life. Concrete is the most widely used construction material in the world with annual consumption estimated at between 21 and 31 billion tonnes
Environmentally sustainable

With its 100-year service life, concrete conserves resources by reducing the need for reconstruction. Its ingredients are cement and readily available natural materials: water, aggregate (sand and gravel or crushed stone). Concrete does not require any CO2 absorbing trees to be cut down. The land required to extract the materials needed to make concrete is only a fraction of that used to harvest forests for lumber.

The Baths of Caracalla, Rome, Italy, in 2003.Concrete absorbs CO2 throughout its lifetime through carbonation, helping reduce its carbon footprint. A recent study [48] indicates that in countries with the most favorable recycling practices, it is realistic to assume that approximately 86% of the concrete is carbonated after 100 years. During this time, the concrete will absorb approximately 57% of the CO2 emitted during the original calcination. About 50% of the CO2 is absorbed within a short time after concrete is crushed during recycling operations.

Concrete consists of between 7% and 15% cement, its only energy-intensive ingredient. A study [49] comparing the CO2 emissions of several different building materials for construction of residential and commercial buildings found that concrete accounted for 147 kg of CO2 per 1000 kg used, metals accounted for 3000 kg of CO2 and wood accounted for 127 kg of CO2. The quantity of CO2 generated during the cement manufacturing process can be reduced by changing the raw materials used in its manufacture.

A new environmentally friendly blend of cement known as Portland-limestone cement (PLC) is gaining ground all over the world. It contains up to 15% limestone, rather than the 5% in regular Portland cement and results in 10% less CO2 emissions from production with no impact on product performance. Concrete made with PLC performs similarly to concrete made with regular cement and thus PLC-based concrete can be widely used as a replacement. In Europe, PLC-based concrete has replaced about 40% of general use concrete. In Canada, PLC will be included in the National Building Code in 2010. The approval of PLC is still under consideration in the United States
Energy efficiency

Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Once in place, concrete offers significant energy efficiency over the lifetime of a building.[50] Concrete walls leak air far less than those made of wood-frames. Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete’s thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs. While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both insulation and thermal mass to create an energy-efficient building. Insulating Concrete Forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

Concrete


Image by Joost J. Bakker IJmuiden
Concrete
Concrete is a composite construction material, composed of cement (commonly Portland cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravel or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water, and chemical admixtures.

The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a robust stone-like material. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick/block walls and footings for gates, fences and poles.

Concrete is used more than any other man-made material in the world. As of 2006, about 7.5 cubic kilometres of concrete are made each year—more than one cubic metre for every person on Earth.

Concrete powers a US billion industry, employing more than two million workers in the United States alone.[citation needed] More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days.

History

Concrete has been used for construction in various ancient structures. An analysis of ancient Egyptian pyramids has shown that concrete may have been employed in their construction, although its composition would have differed from modern concrete.

During the Roman Empire, Roman concrete (or opus caementicium) was made from quicklime, pozzolana, and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick material and allowed for revolutionary new designs in terms of both structural complexity and dimension.

Hadrian’s Pantheon in Rome is an example of Roman concrete construction.Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that trouble the builders of similar structures in stone or brick.

Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (ca. 200 kg/cm2). However, due to the absence of steel reinforcement, its tensile strength was far lower and its mode of application was also different:

Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.

The widespread use of concrete in many Roman structures has ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges have masonry cladding on a concrete core, as does the dome of the Pantheon.

Some have stated that the secret of concrete was lost for 13 centuries until 1756, when the British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate. However, the Canal du Midi was built using concrete in 1670.[11] Likewise there are concrete structures in Finland that date back to the 16th century. Portland cement was first used in concrete in the early 1840s.

Additives

Concrete additives have been used since Roman and Egyptian times, when it was discovered that adding volcanic ash to the mix allowed it to set under water. Similarly, the Romans knew that adding horse hair made concrete less liable to crack while it hardened, and adding blood made it more frost-resistant.

Recently the use of recycled materials as concrete ingredients has been gaining popularity because of increasingly stringent environmental legislation. The most conspicuous of these is fly ash, a byproduct of coal-fired power plants. This use reduces the amount of quarrying and landfill space required, and, as the ash acts as a cement replacement, reduces the amount of cement required.

In modern times, researchers have experimented with the addition of other materials to create concrete with improved properties, such as higher strength or electrical conductivity. Marconite is one example.

Composition

There are many types of concrete available, created by varying the proportions of the main ingredients below. In this way or by substitution for the cemetitious and aggregate phases, the finished product can be tailored to its application with varying strength, density, or chemical and thermal resistance properties.

The mix design depends on the type of structure being built, how the concrete will be mixed and delivered, and how it will be placed to form this structure.

Cement
Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar, and plaster. English masonry worker Joseph Aspdin patented Portland cement in 1824; it was named because of its similarity in colour to Portland limestone, quarried from the English Isle of Portland and used extensively in London architecture. It consists of a mixture of oxides of calcium, silicon and aluminium. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay, and grinding this product (called clinker) with a source of sulfate (most commonly gypsum).

Water

Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and allows it to flow more freely.

Less water in the cement paste will yield a stronger, more durable concrete; more water will give an freer-flowing concrete with a higher slump. Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure.

Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles, and other components of the concrete, to form a solid mass.

Reaction:

Cement chemist notation: C3S + H → C-S-H + CH
Standard notation: Ca3SiO5 + H2O → (CaO)·(SiO2)·(H2O)(gel) + Ca(OH)2
Balanced: 2Ca3SiO5 + 7H2O → 3(CaO)·2(SiO2)·4(H2O)(gel) + 3Ca(OH)2

Aggregates

Fine and coarse aggregates make up the bulk of a concrete mixture. Sand, natural gravel and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition and excavation waste) are increasingly used as partial replacements of natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.

Decorative stones such as quartzite, small river stones or crushed glass are sometimes added to the surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers.

The presence of aggregate greatly increases the robustness of concrete above that of cement, which otherwise is a brittle material, and thus concrete is a true composite material.

Redistribution of aggregates after compaction often creates inhomogeneity due to the influence of vibration. This can lead to strength gradients.

Reinforcement

Concrete is strong in compression, as the aggregate efficiently carries the compression load. However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete solves these problems by adding either steel reinforcing bars, steel fibers, glass fiber, or plastic fiber to carry tensile loads. Thereafter the concrete is reinforced to withstand the tensile loads upon it.
Chemical admixtures

Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement, and are added to the concrete at the time of batching/mixing. The common types of admixtures are as follows.

Accelerators speed up the hydration (hardening) of the concrete. Typical materials used are CaCl2, Ca(NO3)2 and NaNO3. However, use of chlorides may cause corrosion in steel reinforcing and is prohibited in some countries, so that nitrates may be favored.
Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable. Typical polyol retarders are sugar, sucrose, sodium gluconate, glucose, citric acid, and tartaric acid.
Air entrainments add and entrain tiny air bubbles in the concrete, which will reduce damage during freeze-thaw cycles, thereby increasing the concrete’s durability. However, entrained air entails a tradeoff with strength, as each 1% of air may result in 5% decrease in compressive strength.
Plasticizers increase the workability of plastic or "fresh" concrete, allowing it be placed more easily, with less consolidating effort. A typical plasticizer is lignosulfonate. Plasticizers can be used to reduce the water content of a concrete while maintaining workability, and are sometimes called water-reducers due to this use. Such treatment improves its strength and durability characteristics. Superplasticizers (also called high-range water-reducers) are a class of plasticizers that have fewer deleterious effects, and can be used to increase workability more than is practical with traditional plasticizers. Compounds used as superplasticizers include sulfonated naphthalene formaldehyde condensate, sulfonated melamine formaldehyde condensate, acetone formaldehyde condensate, and polycarboxylate ethers.
Pigments can be used to change the color of concrete, for aesthetics.
Corrosion inhibitors are used to minimize the corrosion of steel and steel bars in concrete.
Bonding agents are used to create a bond between old and new concrete.
Pumping aids improve pumpability, thicken the paste, and reduce separation and bleeding.

Mineral admixtures and blended cements

There are inorganic materials that also have pozzolanic or latent hydraulic properties. These very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures), or as a replacement for Portland cement (blended cements).

Fly ash: A by product of coalfired electric generating plants, it is used to partially replace Portland cement (by up to 60% by mass). The properties of fly ash depend on the type of coal burnt. In general, siliceous fly ash is pozzolanic, while calcareous fly ash has latent hydraulic properties.
Ground granulated blast furnace slag (GGBFS or GGBS): A by-product of steel production is used to partially replace Portland cement (by up to 80% by mass). It has latent hydraulic properties.[18]
Silica fume: A by-product of the production of silicon and ferrosilicon alloys. Silica fume is similar to fly ash, but has a particle size 100 times smaller. This results in a higher surface to volume ratio and a much faster pozzolanic reaction. Silica fume is used to increase strength and durability of concrete, but generally requires the use of superplasticizers for workability.[19]
High reactivity Metakaolin (HRM): Metakaolin produces concrete with strength and durability similar to concrete made with silica fume. While silica fume is usually dark gray or black in color, high-reactivity metakaolin is usually bright white in color, making it the preferred choice for architectural concrete where appearance is important.
Concrete production

The processes used vary dramatically, from hand tools to heavy industry, but result in the concrete being placed where it cures into a final form. Wide range of technological factors may occur during production of concrete elements and their influence to basic characteristics may vary

When initially mixed together, Portland cement and water rapidly form a gel, formed of tangled chains of interlocking crystals. These continue to react over time, with the initially fluid gel often aiding in placement by improving workability. As the concrete sets, the chains of crystals join and form a rigid structure, gluing the aggregate particles in place. During curing, more of the cement reacts with the residual water (hydration).

This curing process develops physical and chemical properties. Among these qualities are mechanical strength, low moisture permeability, and chemical and volumetric stability

Mixing concrete

Thorough mixing is essential for the production of uniform, high quality concrete. For this reason equipment and methods should be capable of effectively mixing concrete materials containing the largest specified aggregate to produce uniform mixtures of the lowest slump practical for the work.

Separate paste mixing has shown that the mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete.[21] The paste is generally mixed in a high-speed, shear-type mixer at a w/cm (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, plasticizers, pigments, or silica fume. The premixed paste is then blended with aggregates and any remaining batch water, and final mixing is completed in conventional concrete mixing equipment.

High-energy mixed (HEM) concrete is produced by means of high-speed mixing of cement, water, and sand with net specific energy consumption of at least 5 kilojoules per kilogram of the mix. A plasticizer or a superplasticizer is then added to the activated mixture, which can later be mixed with aggregates in a conventional concrete mixer. In this process, sand provides dissipation of energy and creates high shear conditions on the surface of cement particles. This results in the full volume of water interacting with cement. The liquid activated mixture can be used by itself or foamed (expanded) for lightweight concrete. HEM concrete hardens in low and subzero temperature conditions and possesses an increased volume of gel, which drastically reduces capillarity in solid and porous materials.
Workability

Main article: Concrete slump test
Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (vibration) and without reducing the concrete’s quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration), and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures will increase concrete workability. Excessive water will lead to increased bleeding (surface water) and/or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. The use of an aggregate with an undesirable gradation can result in a very harsh mix design with a very low slump, which cannot be readily made more workable by addition of reasonable amounts of water.

Workability can be measured by the concrete slump test, a simplistic measure of the plasticity of a fresh batch of concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface. It is then filled in three layers of equal volume, with each layer being tamped with a steel rod in order to consolidate the layer. When the cone is carefully lifted off, the enclosed material will slump a certain amount due to gravity. A relatively dry sample will slump very little, having a slump value of one or two inches (25 or 50 mm). A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by using the Flow table test.

Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio. Some other admixtures, especially air-entraining admixture, can increase the slump of a mix.

High-flow concrete, like self-consolidating concrete, is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted.

After mixing, concrete is a fluid and can be pumped to the location where needed.

Curing

In all but the least critical applications, care needs to be taken to properly cure concrete, to achieve best strength and hardness. This happens after the concrete has been placed. Cement requires a moist, controlled environment to gain strength and harden fully. The cement paste hardens over time, initially setting and becoming rigid though very weak, and gaining in strength in the weeks following. In around 3 weeks, typically over 90% of the final strength is reached, though strengthening may continue for decades. The conversion of calcium hydroxide in the concrete into calcium carbonate from absorption of CO2 over several decades further strengthen the concrete and making it more resilient to damage. However, this reaction, called carbonation, lowers the pH of the cement pore solution and can cause the reinforcement bars to corrode.

Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage cracking. The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. Strength of concrete changes (increases) up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation.

During this period concrete needs to be kept under controlled temperature and humid atmosphere. In practice, this is achieved by spraying or ponding the concrete surface with water, thereby protecting the concrete mass from ill effects of ambient conditions. The pictures to the right show two of many ways to achieve this, ponding – submerging setting concrete in water, and wrapping in plastic to contain the water in the mix.

Properly curing concrete leads to increased strength and lower permeability, and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing, or overheating due to the exothermic setting of cement (the Hoover Dam used pipes carrying coolant during setting to avoid damaging overheating). Improper curing can cause scaling, reduced strength, poor abrasion resistance, and cracking.

Properties

Main article: Properties of concrete
Concrete has relatively high compressive strength, but much lower tensile strength, and for this reason is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion, and shrinks as it matures. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.

Tests can be made to ensure the properties of concrete correspond to specifications for the application.
Environmental concerns

Carbon dioxide emissions and climate change

The cement industry is one of two primary producers of carbon dioxide (CO2), creating up to 5% of worldwide man-made emissions of this gas, of which 50% is from the chemical process, and 40% from burning fuel. The embodied carbon dioxide (ECO2) of one tonne of concrete is around 100 kg/tonne. The CO2 emission from the concrete production is directly proportional to the cement content used in the concrete mix. Indeed, 900 kg of CO2 are emitted for the fabrication of every ton of cement. Cement manufacture contributes greenhouse gases both directly through the production of carbon dioxide when calcium carbonate is thermally decomposed, producing lime and carbon dioxide, and also through the use of energy, particularly from the combustion of fossil fuels. However, some companies have recognized the problem and are envisaging solutions to counter their CO2 emissions. The principle of carbon capture and storage consists of directly capturing the CO2 at the outlet of the cement kiln in order to transport it and to store the captured CO2 in an adequate and deep geological formation.

Surface runoff

Surface runoff, when water runs off impervious surfaces, such as non-porous concrete, can cause heavy soil erosion. Urban runoff tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants from sidewalks, roadways and parking lots. The impervious cover in a typical urban area limits groundwater percolation and causes five times the amount of runoff generated by a typical woodland of the same size. A 2008 report by the United States National Research Council identified urban runoff as a leading source of water quality problems.

Urban heat

Both concrete and asphalt are the primary contributors to what is known as the urban heat island effect.
Using light-colored concrete has proven effective in reflecting up to 50% more light than asphalt and reducing ambient temperature. A low albedo value, characteristic of black asphalt, absorbs a large percentage of solar heat and contributes to the warming of cities. By paving with light colored concrete, in addition to replacing asphalt with light-colored concrete, communities can lower their average temperature.

In many U.S. cities, pavement covers about 30-40% of the surface area. This directly affects the temperature of the city, and contributes to the urban heat island effect. Paving with light-colored concrete would lower temperatures of paved areas and improve nighttime visibility. The potential of energy saving within an area is also high. With lower temperatures, the demand for air conditioning decreases, saving energy.

Atlanta has tried to mitigate the heat-island effect. City officials noted that when using heat-reflecting concrete, their average city temperature decreased by 6 °F The Design Trust for Public Space found that by slightly raising the albedo value in in New York City, beneficial effects such as energy savings could be achieved.[citation needed] It was concluded that this could be accomplished by the replacement of black asphalt with light-colored concrete.

However, in winter this may be a disadvantage as ice will form more easily and remain longer on the light colored surfaces as they will be colder due to less energy absorbed from the reduced amount of sunlight in winter.

Concrete dust

Building demolition and natural disasters such as earthquakes often release a large amount of concrete dust into the local atmosphere. Concrete dust was concluded to be the major source of dangerous air pollution following the Great Hanshin earthquake

Health concerns

The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns. Natural radioactive elements (K, U and Th) can be present in various concentration in concrete dwellings, depending on the source of the raw materials used. Toxic substances may also be added to the mixture for making concrete by unscrupulous makers. Dust from rubble or broken concrete upon demolition or crumbling may cause serious health concerns depending also on what had been incorporated in the concrete.

Concrete handling/safety precautions

Handling of wet concrete must always be done with proper protective equipment. Contact with wet concrete can cause skin chemical burns due to the caustic nature of the mixture of cement and water. Indeed, the pH of fresh cement water is highly alkaline due to the presence of free potassium and sodium hydroxides in solution (pH ~ 13.5). Eyes, hands and feet must be correctly protected to avoid any direct contact with wet concrete and washed without delay if necessary.
Damage modes

Main article: Concrete degradation

Concrete spalling caused by the corrosion of reinforcement bars after that carbonation of cement decreased the pH below the passivation threshold for steel.Concrete can be damaged by many processes, such as the expansion of corrosion products of the steel reinforcement bars, freezing of trapped water, fire or radiant heat, aggregate expansion, sea water effects, bacterial corrosion, leaching, erosion by fast-flowing water, physical damage and chemical damage (from carbonation, chlorides, sulfates and distillate water)

Concrete repair

Concrete pavement preservation (CPP) and concrete pavement restoration (CPR) are techniques used to manage the rate of pavement deterioration on concrete streets, highways and airports. Without changing concrete grade, this non-overlay method is used to repair isolated areas of distress. CPP and CPR techniques include slab stabilization, full- and partial-depth repair, dowel bar retrofit, cross stitching longitudinal cracks or joints, diamond grinding and joint and crack resealing. CPR methods, developed over the last 40 years, are utilized in lieu of short-lived asphalt overlays and bituminous patches to repair roads. These methods are often less expensive[citation needed]than an asphalt overlay but last three times longer and provide a greener solution.[38]

CPR techniques can be used to address specific problems or bring a pavement back to its original quality. When repairing a road, design data, construction data, traffic data, environmental data, previous CPR activities and pavement condition, must all be taken into account. Pavements repaired using CPR methods usually last 15 years. The methods are described below.

Slab stabilization restores support to concrete slabs by filling small voids that develop underneath the concrete slab at joints, cracks or the pavement edge.
Full-depth repairs fixes cracked slabs and joint deterioration by removing at least a portion of the existing slab and replacing it with new concrete.
Partial-depth repairs corrects surface distress and joint-crack deterioration in the upper third of the concrete slab. Placing a partial-depth repair involves removing the deteriorated concrete, cleaning the patch area and placing new concrete.
Dowel bar retrofit consists of cutting slots in the pavement across the joint or crack, cleaning the slots, placing the dowel bars and backfilling the slots with new concrete. Dowel bar retrofits link slabs together at transverse cracks and joints so that the load is evenly distributed across the crack or joint.
Cross-stitching longitudinal cracks or joints repairs low-severity longitudinal cracks. This method adds reinforcing steel to hold the crack together tightly.
Diamond grinding, by removing faulting, slab warping, studded tire wear and unevenness resulting from patches, diamond grinding creates a smooth, uniform pavement profile. Diamond grinding reduces road noise by providing a longitudinal texture, which is quieter than transverse textures. The longitudinal texture also enhances surface texture and skid resistance in polished pavements.
Joint and crack sealing minimizes the infiltration of surface water and incompressible material into the joint system. Minimizing water entering the joint reduces sub-grade softening, slows pumping and erosion of the sub-base fines, and may limit dowel-bar corrosion caused by de-icing chemicals
Concrete recycling

Concrete recycling is an increasingly common method of disposing of concrete structures. Concrete debris was once routinely shipped to landfills for disposal, but recycling is increasing due to improved environmental awareness, governmental laws, and economic benefits.

Concrete, which must be free of trash, wood, paper and other such materials, is collected from demolition sites and put through a crushing machine, often along with asphalt, bricks, and rocks.

Reinforced concrete contains rebar and other metallic reinforcements, which are removed with magnets and recycled elsewhere. The remaining aggregate chunks are sorted by size. Larger chunks may go through the crusher again. Smaller pieces of concrete are used as gravel for new construction projects. Aggregate base gravel is laid down as the lowest layer in a road, with fresh concrete or asphalt placed over it. Crushed recycled concrete can sometimes be used as the dry aggregate for brand new concrete if it is free of contaminants, though the use of recycled concrete limits strength and is not allowed in many jurisdictions. On March 3, 1983, a government funded research team (the VIRL research.codep) approximated that almost 17% of worldwide landfill was by-products of concrete based waste.

Recycling concrete provides environmental benefits, conserving landfill space and use as aggregate reduces the need for gravel mining.

World records

The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 16 million cubic meters over 17 years. The previous record was 3.2 million cubic meters held by Itaipu hydropower station in Brazil.

Concrete pumping

The world record was set at on 7 August 2009 during the construction of the Parbati Hydroelectric Project, near the village of Suind, Himachal Pradesh, India, when the concrete mix was pumped through a vertical height of 715 m (2,346 ft).
Continuous pours

The world record for largest continuously poured concrete raft was achieved in August 2007 in Abu Dhabi by contracting firm Al Habtoor-CCC Joint Venture. The pour (a part of the foundation for the Abu Dhabi’s Landmark Tower) was 16,000 cubic meters of concrete poured within a two day period.[44] The previous record (close to 10,500 cubic meters) was held by Dubai Contracting Company and achieved March 23, 2007.

The world record for largest continuously poured concrete floor was completed November 8, 1997, in Louisville, Kentucky by design-build firm EXXCEL Project Management. The monolithic placement consisted of 225,000 square feet (20,900 m2) of concrete placed within a 30 hour period, finished to a flatness tolerance of FF 54.60 and a levelness tolerance of FL 43.83. This surpassed the previous record by 50% in total volume and 7.5% in total area.

The record for the largest continuously placed underwater concrete pour was completed October 18, 2010, in New Orleans, Louisiana by contractor C. J. Mahan Construction Company, LLC of Grove City, Ohio. The placement consisted of 10,224 cubic yards of concrete placed in a 58 hour period using two concrete pumps and two dedicated concrete batch plants. Upon curing, this placement will allow the 50,180-square-foot (4,662 m2) cofferdam to be dewatered approximately 26 feet (7.9 m) below sea level to allow the construction of the IHNC GIWW Sill & Monolith Project to be completed in the dry

Use of concrete in infrastructure

Mass concrete structures

These include gravity dams such as the Hoover Dam, the Itaipu Dam, and the Three Gorges Dam and large breakwaters. Concrete that is poured all at once in one block (so that there are no weak points where the concrete is "welded" together) is used for tornado shelters.

Reinforced concrete structures

Reinforced concrete contains steel reinforcing that is designed and placed in the structure at specific positions to cater for all the stress conditions that the structure is required to accommodate.
Prestressed concrete structures

Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose those found when in use. This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement. For example a horizontal beam will tend to sag down. If the reinforcement along the bottom of the beam is prestressed, it can counteract this.

In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.

Concrete textures

When one thinks of concrete, the image of a dull, gray concrete wall often comes to mind. With the use of form liner, concrete can be cast and molded into different textures and used for decorative concrete applications. Sound/retaining walls, bridges, office buildings and more serve as the optimal canvases for concrete art. For example, the Pima Freeway/Loop 101 retaining and sound walls in Scottsdale, Arizona, feature desert flora and fauna, a 67-foot (20 m) lizard and 40-foot (12 m) cacti along the 8-mile (13 km) stretch. The project, titled "The Path Most Traveled," is one example of how concrete can be shaped using elastomeric form liner.

Building with concrete

Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction, can gain strength over time. Structures made of concrete can have a long service life. Concrete is the most widely used construction material in the world with annual consumption estimated at between 21 and 31 billion tonnes
Environmentally sustainable

With its 100-year service life, concrete conserves resources by reducing the need for reconstruction. Its ingredients are cement and readily available natural materials: water, aggregate (sand and gravel or crushed stone). Concrete does not require any CO2 absorbing trees to be cut down. The land required to extract the materials needed to make concrete is only a fraction of that used to harvest forests for lumber.

The Baths of Caracalla, Rome, Italy, in 2003.Concrete absorbs CO2 throughout its lifetime through carbonation, helping reduce its carbon footprint. A recent study [48] indicates that in countries with the most favorable recycling practices, it is realistic to assume that approximately 86% of the concrete is carbonated after 100 years. During this time, the concrete will absorb approximately 57% of the CO2 emitted during the original calcination. About 50% of the CO2 is absorbed within a short time after concrete is crushed during recycling operations.

Concrete consists of between 7% and 15% cement, its only energy-intensive ingredient. A study [49] comparing the CO2 emissions of several different building materials for construction of residential and commercial buildings found that concrete accounted for 147 kg of CO2 per 1000 kg used, metals accounted for 3000 kg of CO2 and wood accounted for 127 kg of CO2. The quantity of CO2 generated during the cement manufacturing process can be reduced by changing the raw materials used in its manufacture.

A new environmentally friendly blend of cement known as Portland-limestone cement (PLC) is gaining ground all over the world. It contains up to 15% limestone, rather than the 5% in regular Portland cement and results in 10% less CO2 emissions from production with no impact on product performance. Concrete made with PLC performs similarly to concrete made with regular cement and thus PLC-based concrete can be widely used as a replacement. In Europe, PLC-based concrete has replaced about 40% of general use concrete. In Canada, PLC will be included in the National Building Code in 2010. The approval of PLC is still under consideration in the United States
Energy efficiency

Energy requirements for transportation of concrete are low because it is produced locally from local resources, typically manufactured within 100 kilometers of the job site. Once in place, concrete offers significant energy efficiency over the lifetime of a building.[50] Concrete walls leak air far less than those made of wood-frames. Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete’s thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs. While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both insulation and thermal mass to create an energy-efficient building. Insulating Concrete Forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

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