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  • Forging Forward

    Crusher Helps Riverside Sand Diversify and Nail a New Market Niche. By Mark S. Kuhar   Read More
  • What a Rush

    On The Set of Gold Rush, Product Placement and Productivity Go Hand in Hand. By Jimmy Siler Read More
  • Here Comes The Helmet-CAM

    A Recent Advance In Technology Can Improve How Mine Operators Investigate And Assess Respirable Dust. By Andrew B. Cecala and Andrew D. O’Brien   Read More
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Rock from the Road: Blog and Travelogue

article thumbnailNov. 25, 2014 – Training is an essential part of the U.S. Mine Safety and Health Administration’s (MSHA) mission to keep miners safe and healthy. In order to do a more effective job of delivering its training resources, MSHA has rearranged its web-based presentation of training materials on workplace safety and health.

Prime-Time Products

article thumbnailThree updated models join John Deere’s industry-leading K-Series Four-Wheel Drive Wheel Loader lineup. The 744K-II, 824K-II, and 844K-II meet Final Tier 4 emissions standards while bringing added durability, productivity, increased uptime and lower daily operating costs to the jobsite.

Rock Stars

article thumbnailFormer U.S. Transportation Secretary Ray LaHood, appearing on 60 MINUTES, said that many of the roads and bridges we drive on every day are “on life support.”
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Manufacturers in Focus

article thumbnailNovember marks the 45th anniversary of Philippi-Hagenbuch Inc. which was co-founded by L.B. "Phil" Philippi (Pat Hagenbuch's Father) and LeRoy Hagenbuch, P.E. Since its founding, PHIL has grown into an international company focusing on innovations for haulage equipment that has a wide reach, yet retains its modest, family owned footprint...

People on the Move

article thumbnailSuperior Industries Inc. has hired industry veteran John Garrison as a new business development manager. Garrison’s strong experience in bulk processing will be used to develop new opportunities for Superior’s portable plants product line, its design-build division and the company’s new wet processing division, the company said.

Latest Digital Issue

The national estimated average price-per-gallon for off-highway diesel fuel as of Nov. 14 is $3.421. That is higher than the previous comparison price-per-gallon of $3.359.

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.