Rock Products - The Leading Voice of the Aggregate Industries.
  • ConExpo-Con/Agg Revisited

    Major Announcements, Powerful Products and More from a Record-Breaking Show. ConExpo-Con/Agg and IFPE 2014 took center stage in Las Vegas March 4-8 with tremendous energy and serious buyers. Total registration of 129,364 soared past the last edition of the shows as they achieved the second-highest attendance in their history. The shows also set new records for exhibit space, number of exhibitors and education tickets sold. Read More
  • Giants of Generation

    Wendling Quarries Opts for Portable Power to Keep Crushers and Other Equipment Humming. By Mark S. Kuhar Read More
  • Putting on the Brakes to Move Forward

    Nugent Sand’s Barge-Spotting Operation Uses Oil Shear Brakes to Slash Winch Downtime and Operating Costs. By Mark S. Kuhar Read More
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Rock from the Road: Blog and Travelogue

article thumbnailAugust 23, 2014 – The Associated Equipment Distributors (AED) has been ringing alarm bells about the Highway Trust Fund for more than a year. New numbers released by the Congressional Budget Office project the fund will run out of money by the end of August, which could cause significant disruptions during the busy summer construction season. AED stresses that the precarious fiscal position is the...

Prime-Time Products

article thumbnailBTI's fifth generation NT-E Series Rockbreaker stationary hydraulic boom system, which comes with the newly engineered PP60 Power Pack, is loaded with innovative features such as robust connections, improved pedestal mounting and common cylinders sizes.

Manufacturers in Focus

article thumbnailApril 8, 2014 – Astec Industries Inc. announced that it has completed the acquisition of Omagh, Northern Ireland-based Telestack Ltd. for $36 million.

People on the Move

article thumbnailApril 4, 2014 – W.S. Tyler has named Douglas Lima as its new service manager. Lima has 34 years of industry experience and has spent the past 16 years as a service technician with W.S. Tyler and its sister company, Haver & Boecker Latino Americana. He earned his engineering degree at the Methodist University of Piracicaba (UNIMEP) in Piracicaba São Paulo, Brazil.

LIVE from ConExpo-Con/Agg

article thumbnailMarch 8, 2014 - ConExpo-Con/Agg 2014 concluded today, capping a hugely successful week of exhibits, educational sessions, product demonstrations and equipment introductions. Mining Media International and Rock Products were a visible presence at the show. Look for a full report both online and in upcoming print editions.
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Off-Highway Diesel Prices


The national estimated average price-per-gallon for off-highway diesel fuel as of April 8 is $3.691. That is lower than the previous comparison price-per-gallon of $3.720.

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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.