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  • Building To Another Level

    Source Energy Services Enlists Legacy Building Solutions To Construct Large Frac Sand Storage Facility By Mark S. Kuhar   Read More
  • Digging In

    Prairie Material Gets a Greenfield Operation Rolling in Indiana. By Mark S. Kuhar   Read More
  • Playing the Waiting Game: Outlook/Forecast 2015

    In 2014, Congress Was No Help in Addressing Our Transportation Funding Crisis, However There Are Encouraging Signs That 2015 Will Be a Good Year For Aggregates Producers. By Mark S. Kuhar and Josephine Smith   Read More
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Rock from the Road: Blog and Travelogue

article thumbnailJan. 14, 2015 – On January 8, a 63-year-old sales manager with 11 years of experience was killed at a sand and gravel mine.

Prime-Time Products

article thumbnailPolydeck’s Armadex high-performance, bolt-down rubber screening solution, seen in booth 1734, addresses the most abrasive, most abusive scalping applications, according to the company.

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.”
More inRock Stars  

Manufacturers in Focus

article thumbnailMcLanahan Corp. announced an internal restructuring. The Mineral Processing Division and the Power and Energy Division (formerly the HSS Sampling System Division) have been combined to form one new division – the Mineral, Power and Energy (MPE) Division. This new division is managed by Jarrett Sidney, formerly general manager – Power and Energy Division.

People on the Move

article thumbnailKPI-JCI and Astec Mobile Screens has hired Stephen Whyte to manage the company’s track-mounted product lines in efforts to further develop the innovation behind its mobile equipment.

Take the Survey

Rock Products' 2015 Outlook/Forecast Survey will attempt to gauge the state of mind of aggregates producers all over the country. Please help us by taking the following 20-question survey. Your answers will be a service to the industry and will help us provide our audience with critical benchmarking information. Thank you for being a loyal reader and for your continued support. Click here to take the survey.

Latest Digital Issue

The national estimated average price-per-gallon for off-highway diesel fuel as of Jan. 6 is $2.903. That is significantly lower than the previous comparison price-per-gallon of $3.336.

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.