Part A: Development of Lightweight Concrete Mixtures

This research project used three types of lightweight aggregate to develop lightweight concrete mixtures for a bridge deck and for prestressed bridge girders.

Two of the lightweight aggregates were expanded shale obtained locally from the Buildex Company. One deposit was located in Marquette, Kansas, and the other in New Market, Missouri. The third lightweight aggregate source was expanded slate obtained from the Stalite Company in North Carolina.

Aggregate properties including absorption, gradation, and L.A. Abrasion were evaluated. Over 150 lightweight concrete mixtures were created and tested and several mix design variables such as water-to-cement ratio, cement content, and coarse-to-fine aggregate ratio were evaluated.

From these results, optimized bridge deck and optimized prestressed concrete mixtures were developed for each type of lightweight aggregate.

Special concerns for lightweight aggregate concrete are addressed. These optimized concrete mixtures were then tested for Kansas Department of Transportation (KDOT) acceptability standards for the concrete properties of compressive strength, tensile strength, modulus of elasticity, freeze-thaw resistance, permeability, alkali-silica reactivity, drying shrinkage, and autogenous shrinkage.

The “Green Concrete” that was used for Tampines Concourse comprises a number of sustainable materials, namely copper slag, recycled concrete aggregates (RCA) and ground granulated blast furnace slag (GGBS).

(SINGAPORE) — In support of the Government’s strategy for sustainable development in Singapore, City Developments Limited (CDL) as a green developer, is taking an affirmative step, setting yet another milestone for Singapore in environmental sustainability.

Today, at a ceremony officiated by Guest-of-Honour, Mr Mah Bow Tan, Minister for National Development, CDL’s newly-completed 11 Tampines Concourse was unveiled as the first CarbonNeutral® development in Singapore and Asia Pacific.

The establishment of Tampines Concourse as a CarbonNeutral® development represents a natural progression of CDL’s commitment towards building greener properties. It is a forward-looking approach towards long-term sustainability.

Mr Kwek Leng Joo, Managing Director of CDL, explained the Group’s bold move, “This voluntary initiative reaffirms our commitment to reduce our carbon footprint. For many years now, we have been consciously monitoring and taking deliberate efforts to reduce our carbon emissions as part of our Environmental, Health and Safety policy.

Carbon offsetting is relatively new in this part of the world and being the first to foray into uncharted territory, we hope to encourage more Singapore corporations to take a stronger stand in tackling climate change. In addition to Tampines Concourse, we have also embarked on neutralizing the carbon emissions of our corporate office operations. Going CarbonNeutral® is in line with CDL’s overall Corporate Social Responsibility (CSR) commitment.”

Designed and built with environmental sustainability in mind, Tampines Concourse, awarded the BCA Green Mark GoldPlus this year, is a sterling example of a green development from start to finish. Beyond sustainable design features such as an energy-efficient building envelope design and ecofriendly fittings for energy and water efficiency, concerted efforts were made to introduce innovative building materials to reduce the usage of natural resources in the construction process.
Tampines Concourse is the first building project in Singapore to be constructed with a wide range of recycled materials for its structural building components.

The “Green Concrete” that was used for Tampines Concourse comprises a number of sustainable materials, namely copper slag, recycled concrete aggregates (RCA) and ground granulated blast furnace slag (GGBS). Apart from sustainable construction materials, other prominent green features include a natural day-lighting system to leverage on natural lighting in areas such as the atrium and lift lobbies. It is also the first development in Asia Pacific to incorporate an innovative, indoor non-compressor fresh air cooling system for smart temperature and humidity control. This system uses water as a cooling agent instead of ozone-depleting chemical refrigerants to cool incoming outdoor air through a natural heat exchange process. Together, these features are expected to result in energy savings of over 620,000 kWh per year, for the 108,000 lettable square feet complex, resulting in the lowering of the building’s carbon footprint.

“Sustainable construction through the use of recycled materials is an excellent strategy for Singapore’s continuing journey of sustainable development. It serves the twin objectives of prolonging the lifespan of our Semakau Landfill and also provides an alternative to natural materials that have to be imported. CDL’s holistic approach to environmental friendliness, especially in its use of sustainable construction methods and materials, has not only made Tampines Concourse an important milestone for CDL, but also an example and benchmark for the rest of the building industry.” says Dr John Keung, Chief Executive Officer of the Building and Construction Authority.

“We are happy to note that CDL has incorporated energy saving features and technologies from the design stage for this new development. This initiative is expected to result in significant energy savings for the development, and will contribute to the national efforts to improve resource efficiency. We encourage other developers to also integrate energy efficient design in their buildings”, says Mr Andrew Tan, Chairman of the Energy Efficiency Programme Office and Chief Executive Officer of the National Environment Agency.

In turning this development CarbonNeutral®, CDL will reduce carbon emissions to “net zero” for Tampines Concourse by offsetting some 6,750 tonnes of carbon dioxide equivalent. (tCO2-e) for 2009. The amount of CO2-e to be offset through this exercise represents the total estimated CO2-e generated during the construction phase (5,243 tCO2-e) and for the first year of operations (1,507 tCO2-e). Moving forward, the building’s carbon emissions will be measured and offset on an annual basis, which is estimated to be approximately 1,500 tCO2-e per year.

The process of attaining CarbonNeutral® development status was facilitated by The CarbonNeutral Company, one of the world’s leading carbon offset and carbon management companies with a proven track record of working with 300 large organisations and 200 carbon offset projects across six continents. Underpinned by a well-recognised standard known as the Carbon Neutral Protocol, every tonne of carbon sold by The CarbonNeutral Company is guaranteed such that, any shortfall is made up for in the unlikely situation of a project failure.

Jonathan Shopley, Managing Director, The CarbonNeutral Company said, “We are privileged to be working with CDL as they extend their leadership position on sustainability by taking Tampines Concourse CarbonNeutral®. This means CDL plays its part in a solution to tackle climate change as they chart a course for profitable growth while reducing greenhouse gases (GHG) emissions to net zero.”

Shopley continues, “Businesses in Singapore now have a viable alternative to demonstrate their commitment to the environment by locating in Tampines Concourse.”

In the case of Tampines Concourse, the estimated CO2 emissions generated during the construction and annual operational phases have been measured and will be offset by the purchase of carbon credits which will fund carbon offsetting projects in Asia through The CarbonNeutral Company.

For 2009, the carbon credits CDL has purchased under this exercise will fund three projects in Asia, including one renewable energy project (Guizhou Hydro Power Project in China) and two resource conservation projects (Fujian Landfill Project and Jilin Methane Power Project in China). All three projects have been verified to the international Voluntary Carbon Standard (VCS) and are pre-Clean Development Mechanism (CDM) projects.

Without the injection of carbon finance, these projects would be unviable. Beyond generating climate benefits, these projects also bring about social benefits such as employment and training opportunities, as well as improving the quality of life for the local community. This is also in line with CDL’s commitment to CSR.

Given the continual development of new carbon offsetting projects in Asia, CDL will maintain a flexible approach evaluating its portfolio of carbon offsetting projects on an annual basis, throughout the building’s lifetime.

As the first CarbonNeutral® development in Singapore and Asia Pacific, Tampines Concourse represents the ideal office address for like-minded businesses looking to enhance their position as an environmentally conscious company and reduce their carbon footprint.

SOURCE: http://www.greenbusinesstimes.com

Local Palestinian NGO Mercy Association for Children began building a school for handicapped children in Gaza City on 24 May to test a recently developed method using clay blocks, salt and rubble. The source material coming mainly from the hundreds of buildings demolished during the Israeli offensive (27 December 2008 – 18 January 2009).

Fourteen construction workers on the 5,000 square metre building site in the Shujayah neighbourhood of the city haul buckets of clay for moulding into large blocks from which the structure, with its domed ceiling, will be made.

“If the school, upon completion, proves structurally sound we will move forward with other construction projects in Gaza,” said lead engineer Maher Batroukh of the Mercy Association for Children. “The school is the first building of its kind in Gaza.”

The three-storey school, occupying about 1,025 square metres, will contain no steel, cement or concrete, said Batroukh.

The US$190,000 project is being funded by the Kuwaiti charity Arab Fund for Social and Economic Development, and will take at least six months to complete, according to Mercy Association for Children project manager Muna Abu Shareh.

Watching

International organizations and UN agencies in Gaza are watching the project to assess the potential of the building technology in Gaza.

“If they succeed…, it will be relevant in terms of responding to the destruction from the war,” said Norwegian Refugee Council (NRC) architect Jonathan Dames. NRC leads the “shelter cluster”, a coalition of international organizations and UN agencies working on post-conflict shelter issues in Gaza.

“After one or two winter seasons we will be able to see how the material responds,” Dames said.

Gaza’s environment authority and the public works ministry would also be monitoring the project, amid concerns that the use of large quantities of clay could affect agriculture.

“It may be a good method in the future, but the use of clay on a large scale could harm agricultural land, already scarce in Gaza,” said Gaza environment authority engineer Al-Ghaza. “It must first be studied.”

Engineer Batroukh of Mercy Association said the school would be tested to ensure the structure was safe by placing cement blocks on the ceiling and by stress testing individual clay blocks at the Islamic University of Gaza.

Owing to space restrictions in densely populated Gaza, for a building technology to be relevant it must be able to cope with at least four-storey buildings, Dames said. He explained that several clay-only houses had been constructed, but all were single storey homes.

TYPES OF AGGREGATE
Aggregates are used for a variety of purposes. Each purpose requires a specific aggregate type, and specific properties of the aggregate. In general, aggregates are naturally occurring relatively inert materials formed by various geologic processes. The geologic process of formation imparts some of the properties to the aggregate that make it more or less useful.
The aggregates fall into two broad categories, based on their size distribution: Coarse Aggregates and Fine Aggregates. They may be used separately or in combination, depending on their purpose. Natural coarse aggregates are obtained by crushing stone or gravel into desired size distribution. Some coarse aggregates are obtained from recycled material such as slag or old concrete. Fine aggregates fall into two broad categories: natural and manufactured sands. The former are obtained from water-deposited sources, either fluvial or glacial. The latter are screened from the finer fraction of the rock crushing process.
The purpose to which the aggregate is produced determines both the grain size and quality requirements. The quality requirements, from the highest to lowest, are for use in: concrete, filter stone, bituminous mix, base, and sub base. There are, of course, myriad of other uses, but the above mentioned require greatest volumes
The aggregates normally used for concrete are natural deposits of sand and gravel, where available. In some localities, the deposits are hard to obtain and large rocks must be crushed to form the aggregate. Crushed aggregate usually costs more to produce and will require more cement paste because of its shape. More care must be used in handling crushed aggregate to prevent poor mixtures and improper dispersion of the sizes through the finished concrete. At times, artificial aggregates, such as blast-furnace slag or specially burned clay, are used.

FINE AGGREGATE
Fine aggregate is defined as material that will pass a No. 4 sieve and will, for the most part, be retained on a No. 200 sieve. For increased workability and for economy as reflected by use of less cement, the fine aggregate should have a rounded shape. The purpose of the fine aggregate is to fill the voids in the coarse aggregate and to act as a workability agent.

COARSE AGGREGATE
Coarse aggregate is a material that will pass the 3-inch screen and will be retained on the No. 4 sieve. As with fine aggregate, for increased workability and economy as reflected by the use of less cement, the coarse aggregate should have a rounded shape. Even though the definition seems to limit the size of coarse aggregate, other considerations must be accounted for. When properly proportioned and mixed with cement, these two groups yield an almost void less stone that is strong and durable.

In strength and durability, aggregate must be equal to or better than the hardened cement to withstand the designed loads and the effects of weathering. It can be readily seen that the coarser the aggregate, the more economical the mix. Larger pieces offer less surface area of the particles than an equivalent volume of small pieces. Use of the largest permissible maximum size of coarse aggregate permits a reduction in cement and water requirements. One restriction usually assigned to coarse aggregate is its maximum size. Larger pieces can interlock and form arches or obstructions within a concrete form. That allows the area below to become a void, or at best, to become filled with finer particles of sand and cement only.

(ELIE, MANITOBA, Canada) — At 79 years of age, late-blooming inventor and former gravel-pit operator Guy Bergeron is likely responsible for filling more sandbags than any other person alive.
“Twelve bags every 7.5 seconds,” the Manitoban says proudly.

He’s talking about his invention, The Sandbagger, a tarantula-like machine that automates the backbreaking work of stuffing sandbags.

Over the past 19 years, his Sandbaggers have pumped out millions of bags and stopped millions of litres of floodwater from inundating towns all over North America.
Volunteers in Grand Forks, N.D., use The Sandbagger, invented by Guy Bergeron of Elie, Man. He drew the plans for the invention in 1990 while he was convalescing from open-heart surgery. ‘If you’re really moving, it can fill 5,700 bags an hour,’ Mr. Bergeron says.

Volunteers in Grand Forks, N.D., use The Sandbagger, invented by Guy Bergeron of Elie, Man. He drew the plans for the invention in 1990 while he was convalescing from open-heart surgery. ‘If you’re really moving, it can fill 5,700 bags an hour,’ Mr. Bergeron says.
The Globe and Mail

But millions of bags don’t necessarily translate to millions of dollars. Mr. Bergeron was about to retire the business this year until he got a call from North Dakota last month.

“It was Fargo,” Mr. Bergeron recalls. “They wanted one, maybe two machines. And they wanted them right away.”

With that call, the Bergerons quickly hauled two Sandbaggers to Fargo, where they played a pivotal role in helping avert a catastrophic flood last month.

“I’m not sure we could have done it without them,” says Terry Ludlum, an official who looked after sandbagging efforts in Fargo, where a second Red River crest is expected later this month. “And with this next rise coming, we’ll be cranking them up again quite soon.”

The idea for The Sandbagger first sprouted in Mr. Bergeron’s restive brain three decades ago. In the spring of 1976, the gravel-pit operator lent his hand to a sandbagging operation near Elie, 45 kilometres west of Winnipeg. The military was running a gravel conveyor belt that funnelled sand down a single stovepipe and into a bag.

“They were filling one at a time, barely faster than hand-filling,” Mr. Bergeron remembers. “I knew right then there was something that could be done to improve the process.”

To understand this inventive compulsion, one must understand Mr. Bergeron. He is a precise man who abhors inefficiency. He walks 6.4 kilometres every day. When poor weather cuts his strolls short, he paces around his basement, along a measured-out figure-eight, until he hits his 6.4-km goal. His current house, a grey rancher, took two years to build because “the builders kept getting it wrong.”

He bubbles with ideas. During a two-hour interview earlier this week, he conceived several new inventions and fashioned a long metal tool for opening locked car doors.

For 14 years, he harboured his idea for an improved sandbagging machine. In 1990, while he was convalescing from open-heart surgery, he finally found time to draft plans.

At first, his wife was worried. “After his surgery, the doctors took me into a room and warned that the drugs he would be taking could cause him to get emotional or angry,” Ria Bergeron says. “So when we get home and he tells me about this machine, I just assumed the medication had made him crazy.”

Within months, he had a working prototype that appears identical to his latest models. The whole steel mechanism looks like a massive 12-legged octopus. A conveyor belt transports sand to a rotating head four metres off the ground. Turning a full rotation every 7.5 seconds, the head funnels sand down 12 spouts, which trail off like tentacles toward someone holding an empty bag.

“If you’re really moving, it can fill 5,700 bags an hour,” Mr. Bergeron says. “In Fargo, we had them putting out 5,000 bags in the first hour alone.”

The Bergerons have sold The Sandbagger as far west as Abbotsford, B.C., and as far south as Minnesota. Winnipeg flood authorities own four and the province has several more.

They won’t say how many of the $30,000 machines they’ve sold in all. “You save one basement and it’s paid for itself,” says Mr. Bergeron, who has no engineering experience and dropped out of high school at age 14. “But I’m not a great salesman. Nobody really wants to think about buying one of these things until the water is up to their eyeballs. By then, it can be too late.”

That could change. Fargo officials have been singing The Sandbagger’s praises to an international audience. The Army Corps of Engineers has recently been in touch, as have flood experts as far away as Britain and Australia.

That interest may be too late. The restless Mr. Bergeron is already onto his next invention. “It has to do with truck tires,” he says coyly. “The application is already at the patent office.”

PATRICK WHITE

Aggregate Industries, which hosted the tour, is a Rockville-based producer of aggregate and construction materials and was selected to participate in the event because of the Company’s commitment to developing and deploying sustainable products and solutions in the building materials market.

Along with organizers from the Carbon Finance Unit at the World Bank, members from the National Asphalt Pavement Association and representatives from the World Bank’s client country transport agencies, representing more than ten countries from around the world, attended the asphalt plant tour hosted by the plant manager, David Jones. During the tour, Jones explained the history, vision, products, and other significant facts about the plant to the visitors.

Aggregate Industries’ Bladensburg asphalt plant was commissioned on April 9, 2008. When the decision to go forward with the project was made in 2006, the DC market presented a unique opportunity, whereby market growth and a consolidated competitive market provided favorable conditions for an investment of this nature. This strongly competitive location and materials advantage, raw materials supplied direct from the quarry by rail, allow Aggregate Industries to capture market growth and market share from its competitors. Currently, the Bladensburg asphalt plant possesses a warm mix asphalt capability for all base and surface pavements as specified by surrounding jurisdictions and the private sector, while approval for the public sector is pending.

As a committed provider of “green” building materials, Aggregate Industries manufactures warm mix asphalt. Manufacturing warm mix asphalt consumes less energy and results in lower carbon emissions. Warm mix also uses RAP (recycled asphalt product) to produce new product.

The Company leads the way in warm mix application in several markets, including the Mid-Atlantic and Northeast regions of the country. In Massachusetts, the Company successfully introduced warm mix asphalt for a paving commission at Logan Airport, completing the first runway to use the material. Since then, the use of warm mix has been added to the specifications for runway paving in the state. Aggregate Industries has been awarded a second paving contract to begin next month. In addition, the Company also successfully introduced the product to Mass Highway for the paving of I-93.

Aggregate Industries is actively promoting the use of the product in a number of major markets, as evidenced by its plant tour for World Bank officials. The Company is committed to greenhouse gas reduction and to minimizing emissions produced by the building materials industry. Aggregate Industries is a member of the EPA’s Climate Leaders program and is the only national partner of the Cool Climate Concrete program. This program focuses on reducing emissions by providing offset payments to concrete companies that use higher percentages of recycled products, like fly ash and slag, in lieu of Portland cement in their mix designs. To learn more about Aggregate Industries and its green building products, please visit http://www.aggregate-us.com.

Billy Norrell, executive director of the Alabama Road Builders Association, said state road contractors could bring concrete equipment in from out-of-state but doubts that is feasible.

While the state’s road builders can do smaller-scale concrete projects, such as culverts and barrier walls, Norrell said, “I’m not certain if any of our folks are geared up to do this on a large scale.”

Most of Alabama’s road builders rely on asphalt as their method of paving. The last major concrete-paving project was I-459, which was built in the mid-1980s.

Asphalt contractors say money from the $787 billion federal economic stimulus bill earmarked for Alabama should be spent with Alabama companies. ALDOT says concrete is the better way to repair the interstate.

State transportation officials have violated their own engineering policies by limiting the repairs to concrete, said Mel Monk, executive director of the Alabama Asphalt Paving Association.

Monk said ALDOT’s bid restrictions could make the job significantly more expensive, require the closing of half the interstate for months while work is under way, and limit the work to out-of-state contractors.

“There are no concrete pavers in Alabama, and this I-59 work will go to an out-of-state crew,” Monk said. “The stimulus money is to create jobs for Alabamians. This won’t do it.”

He said his association asked ALDOT officials not to stipulate that the driving surface must be concrete or to at least allow an asphalt surface as an alternative on the bid.

“They said no. We were disappointed, because we knew we could do the work cheaper with asphalt,” he said. “There is no alternate on the bid; that closes the door on Alabama companies.”

The state allowed bidders on the Corridor X projects to submit proposals for either concrete or asphalt. With just one segment left to bid, the entire stretch from Birmingham to the Mississippi line has been paved with asphalt. Only two out-of-state companies submitted bids for concrete on one section; their bids were far higher than the asphalt contractors’ bids.

Monk said using asphalt on I-59 would be 22 to 23 percent cheaper.

State Transportation Director Joe McInnes said it was his decision to require a concrete driving surface on the rebuilt I-59, and said one travel lane in each direction will remain open while repairs are under way.

“The decision was made 45 to 50 years ago to construct our interstates with concrete,” he said. “We are just replacing a concrete highway with concrete.”

ALDOT made the decision to do the segment in concrete because of the long-term durability of concrete.

“We can pave with concrete, and it will have a service life of from 40 to 50 years; or we can pave with asphalt and within 10 to 15 years, it will likely need to be replaced,” McInnes said. We are making the initial investment now for a long life for this roadway.”

He noted that all previous ALDOT resurfacing job during his tenure have allowed asphalt surfacing.

McInnes said the I-59 project will include subsurfaces of asphalt. “This project also will have 81,000 tons of asphalt in it,” he said. “That’s almost $5 million worth of asphalt” likely to come from Alabama contractors.

McInnes said seven of ALDOT’s 15 sets of plans for the I-59 work were sold to Alabama contractors.

The director acknowledged that the contractor submitting the winning bid for the repairs is likely to be from out of state, but said he thinks the materials will come from Alabama.

“Alabama is the fifth-largest producer of cement. While there’s no guarantee that the contractor will use Alabama cement, I would think because of shipping and delivery costs that it will come from Alabama,” McInnes said.

But Monk said there is no guarantee that the contractor will buy Alabama cement. “It could come from Mexico,” he said.

The use of concrete to make the I-59 repairs, while new to Alabama, is not an experiment. McInnes said numerous states, including South Carolina, North Carolina, Florida and Georgia, are using concrete overlays on interstates. “Around Greenville, (S.C.), the interstate rides like a sheet of glass,” he said.

Georgia is repairing I-85 using concrete, he added.

The director said he feels concrete repairs will stand up better to increased truck traffic.

McInnes said gasoline was almost $4 a gallon when the decision was made to do the I-59 work with concrete. “Asphalt prices were very close to concrete prices then,” he said. “And that helped make the decision.”

In the long run, he said, allowing concrete paving could cultivate competition that could lower the cost of paving.

gmacdonald@bhamnews.com

Licensing agreement will offer advanced concrete technology for high rise structures, industrial buildings, residential complexes and public works projects in New York City and New Jersey.
New York City’s recent shift to performance-based construction standard in concrete motivates the joint marketing effort.

(HOUSTON, TEXAS) — Eastern Concrete Materials, Inc., a subsidiary of U.S. Concrete, Inc. (NASDAQ: RMIX) and iCrete, LLC, have announced a licensing agreement, whereby Eastern will offer iCrete’s advanced technology for concrete mix designs for infrastructure and major construction projects in the New York City and New Jersey markets, including high rise structures, industrial buildings, residential complexes and various agency (NYDEC, PANYNJ, NYDOT etc.) infrastructure projects.

Eastern and the entire U.S. Concrete family of companies are committed to environmentally friendly technologies that reduce potential carbon dioxide (CO2) emissions through their EF Technology product line. Utilization of the iCrete mix designs will allow Eastern to further reduce greenhouse gases while continuing to deliver superior quality products to our customers.

Juan Carlos Terroba, Chief Executive Officer of iCrete said, “Eastern and U.S. Concrete are leaders in sustainable technology in the building products industry. We are delighted to be associated with them, as they continue to expand their EF Technology product line.”

The companies will work together on major construction and infrastructure projects, where federal, state and local governments increasingly require stronger, safer, more durable and more sustainable materials with a smaller carbon footprint.

“There have been significant advancements in concrete technology over the past quarter century, but they have not been fully utilized in traditional construction projects, which are often encumbered by the current prescriptive-based construction standards,” said Michael L. Gentoso, U.S. Concrete’s Vice President – Atlantic Region. “New York City, however, is now leading the nation in shifting to these newer performance based construction standards in concrete that will allow us to deliver improved quality and durability through our high performance environmentally designed mixes.”

About U.S. Concrete

U.S. Concrete (NASDAQ: RMIX) services the construction industry in several major markets in the United States through its two business segments: ready-mixed concrete and concrete-related products; and precast concrete. The Company has 132 fixed and 12 portable ready-mixed concrete plants, eight precast concrete plants, one concrete block plant and seven producing aggregates facilities.

During 2008 (including acquired volumes), these plant facilities produced approximately 6.5 million cubic yards of ready-mixed concrete, 0.9 million eight-inch equivalent block units and 3.5 million tons of aggregates. For more information on U.S. Concrete, visit http://www.us-concrete.com.

About iCrete

iCrete is a clean-technology provider of advanced concrete production systems to the construction industry. iCrete’s mission is to elevate the construction and concrete industries to a new standard of profitability, standardization and environmental stewardship.

iCrete’s core business is licensing the iCrete System, a mix design and quality solution for concrete producers, which is transforming the way ready mixed and precast concrete is designed, produced and used worldwide. For more details, visit us at http://www.icrete.com on the Web

The material makes high-performance paving material asphalt that is cheaper, longer lasting, and more environmentally friendly than conventional asphalt, the scientists report.

In the new study, Zhenming Xu and colleagues note that millions of tons of electronic waste (e-waste) pile up each year. The printed circuit boards used in personal computers, cell phones, and other electronic gear, contain toxic metals such as lead and mercury and pose a difficult disposal problem. The boards also are difficult to recycle. Xu’s group, however, realized that the boards, which provide mechanical support and connections for transistors and other electronic components, contain glass fibers and plastic resins that could strengthen asphalt paving.

The scientists describe a new recycling method that quickly separates toxic metals from circuit boards, yielding a fine, metal-free powder. When mixed into asphalt in laboratory tests, the powder produced a stronger paving material less apt to soften at high temperatures, the researchers say.

SOURCE: http://www.sciencedaily.com