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  • Major League Material Handling

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Rock from the Road: Blog and Travelogue

article thumbnailJune 28, 2015 – Land surveyors discovered a mummy that could be 2,000 years old on the site of the planned Singleton Stone quarry in south Lake County, Ind., and archaeologists are investigating whether they stumbled onto a Native American burial ground.

Prime-Time Products

article thumbnailMetso has introduced its Metso NW Series crushing and screening plant to the global market. The plant enables rapid setup in less than 12 hours without heavy cranes, according to the company. This allows customers to make even the most challenging crushing sites more profitable; and moving to the next site easier than ever. The Metso NW Series fits compactly into standard 40-ft. (12 m)...

Rock Stars

article thumbnailRon DeFeo, chairman and chief executive officer of Terex Corp. is the sole recipient of the American Road & Transportation Builders Association’s (ARTBA) highest honor – the 2014 “ARTBA Award.” It was presented at an April 14 luncheon during the association’s Federal Issues Program in Washington, D.C.
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Manufacturers in Focus

article thumbnailHer Majesty Queen Elizabeth was shown a scale model of the Warman slurry pump on a visit to the Weir Advanced Research Centre (WARC) at the University of Strathclyde’s Technology and Innovation Centre in Glasgow,...

People on the Move

article thumbnailKPI-JCI and Astec Mobile Screens hired Said Vivas Saenz as its new regional contract sales manager for Mexico and Central America.  

Latest Digital Issue

The national estimated average price-per-gallon for off-highway diesel fuel as of June 5 is $2.623. That is higher than the previous comparison price-per-gallon of $2.613.

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.