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  • KICKING MORE APP

    A Look at Mobile Apps With Equipment and Technology in Mind.  By Josephine Smith Read More
  • The Bar Has Been Raised

    There May Be Better Ways To Help Adults Learn And Retain Information They Gain From Educational Or Training Events. By Joseph P. McGuire and Billy Snead   Read More
  • Rocking the Volcanoes

    A Contractor Drills Rock in Hawaii with a New Generation of High-Tech Rigs. By Mark S. Kuhar   Read More
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Rock from the Road: Blog and Travelogue

article thumbnailOct. 16, 2014 – “The success of the aggregates industry and the success of our nation are undeniably linked,” said Mike Johnson, president and CEO of the National Stone, Sand & Gravel Association (NSSGA), to its board of directors when he previewed the association’s effort to promote the industry via an informational video. The three-minute spot, entitled “If the Aggregates Industry is Doing...

Prime-Time Products

article thumbnailDexter + Chaney, developer of Spectrum Construction Software, debuted the latest in its new line of mobile applications for the construction industry: Spectrum Equipment Field Entry.  

Rock Stars

article thumbnailIf there is a company on the grow, it is Summit Materials. Chief Executive Officer Tom Hill is the driving force behind the company, which has made a number of acquisitions this year. Tom has also held a variety of leadership roles in the transportation industry. He served as Chairman of the American Road and Transportation Builders Association from 2002 to 2004. He helped develop legislative...
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Manufacturers in Focus

article thumbnailYokohama Tire Corp. (YTC) announced  it is relocating its corporate headquarters from Fullerton, Calif., to nearby Santa Ana, Calif. to accommodate business growth. The move is expected to take place in November.

People on the Move

article thumbnailCaterpillar’s Board of Directors has elected Tom Pellette, currently a Caterpillar vice president and the president of Solar Turbines Inc., a wholly owned subsidiary of Caterpillar Inc., as group president with responsibility for Construction Industries, replacing Ed Rapp, who will now take over responsibility for Resource Industries.

Latest Digital Issue

The national estimated average price-per-gallon for off-highway diesel fuel as of Oct. 7 is $3.473. That is lower than the previous comparison price-per-gallon of $3.508.

Limestone Cited as Benefit to Green Concrete


By Mark S. Kuhar

Adding limestone powder to “green” concrete mixtures – those containing substantial amounts of fly ash, a byproduct of coal-burning power plants – can significantly improve performance, according to researchers from the national Institute for Standards and technology (NIST) and the Federal Highway Administration (FHWA).

The promising laboratory results suggest a path to greatly increasing the use of fly ash in concrete, leading to sizable reductions in greenhouse gas emissions, energy use, construction costs and landfill volumes. Global production of cement for concrete accounts for 5 to 8 percent of human-caused greenhouse gas emissions, according to NIST.

Currently, fly ash accounts, on average, for about 15 percent of the binder powders in the ready-made concrete used in the U.S. To produce a more green concrete, NIST is researching new material combinations and procedures that could help the industry use fly ash to routinely replace 40 to 50 percent of the ordinary portland cement (OPC), the main binding and hardening agent in concrete.

Because of delays in setting times and questions about its strength in the first few days after application that both “impact its constructability,” said NIST chemical engineer Dale Bentz, “green concrete has been a tough sell in large parts of the construction industry.” However, Bentz and his FHWA colleagues found that a “judicious combination of fine limestone powder” can help to put these concerns to rest.

So-called high-volume fly ash “ternary” mixtures (including some limestone) that replace between 40 percent and 60 percent of the cement portion not only set at rates comparable to those for typical concrete, but also were superior in terms of key properties.

Initially, the strength of the green concrete mixtures after 28 days slightly lagged that of concrete without any fly ash. However, the team was able to tweak their fly ash-limestone-OPC mixture to overcome the gap, primarily by lowering the water-to-powder ratio and switching to a different standard composition of OPC (ASTM Type III).

Today, global production of OPC totals about 3.5 billion metric tons (3.85 billion tons) annually. Generation of each ton of OPC emits about a ton of carbon dioxide into the atmosphere.

Greater use of high-volume fly ash mixtures could significantly reduce this environmental burden and, at the same time, reduce costs for concrete construction, said Bentz.

For Bentz and his team, the next research challenge is to test their limestone-enhanced mixtures in the field, where curing conditions can vary. A later report will be issued with additional findings.