www.acpa.org T E C H N O L O G Y , P A R T I INNOVATION IN THE CONCRETE PAVEMENT INDUSTRY IS NOT JUST “A NICE THING TO HAVE” but is a necessity to ensure that contractors can meet owner and agency expectations for long-lasting, environmentally sound, low-maintenance pavements that provide the most value for the dollar. The concrete pavement industry has forged ahead with innovations enhancing the sustainability, efficiency, and quality of concrete pavements. Driven by a pursuit of excellence and helped along by various federally funded research projects and private-sector research and development initiatives, the industry has developed a growing number of options to reduce the environmental impact of concrete pavements. A fewof themany innovations that have propelled the concrete pavement industry forward are explored in this article—the first of a two-part series looking at the techniques and technologies shaping the concrete pavements of today and tomorrow. Portland limestone cement: reducing greenhouse gas emissions As project owners raise their expectations for greener, environmentally sound construction practices, portland-limestone cement (PLC) offers pavement contractors an option to meet continues on page 12 » expectations while maintaining high strength and quality standards. PLC is a cement with up to 15% limestone content, which results in a reduction of greenhouse gas emissions by an average of 10–12%.1,3 “We’ve been using PLC in trials, demonstration projects, and full-scale projects for about 15 years and found that it works equally as well as portland cement,” says Jason Weiss, Ph.D., Professor of Civil and Construction Engineering at Oregon State University. Designed as a direct substitute for portland cement, the use of PLC is not disruptive to a contractor’s normal operations. “A slight adjustment to admixtures may be needed, but other than that, no changes in operations or equipment are required.” In 2018, only 27 state transportation agencies had standards that allowed PLC use. As of February 2022, the number has grown, with only six state agencies not yet having approved the use of PLC.2 This widespread acceptance of the product will increase manufacturers’ ability to produce PLC for more markets. “There is only a certain amount of storage space, so many cement producers will only produce one type of cement at a plant,” Weiss said. “As demand for the product grows, so will supply.” In addition to reducing the carbon footprint of concrete pavement, the production of PLC has the added benefit of extending the life of quarries, said Weiss. The broad focus on sustainability and a need to better use resources will continue to drive the use of PLC in concrete pavement. “I estimate that in a few years, PLC will be the dominant cement used in the United States,” says Weiss. Real-time smoothness: achieving smoothness during paving One of the most significant technologies developed as part of the Second Strategic Highway Research Program (SHRP) is real-time smoothness (RTS), said Peter Taylor, Ph.D., Director of the National Concrete Pavement Technology Center at Iowa State University. Because pavement smoothness is a prominent aspect of a road that the general public notices, state agencies set standards for smoothness. However, achieving smoothness has never been an integrated part of the whole paving process. Instead, contractors would do the best they could to lay a smooth pavement, but agency measurements after constructionmight require grinding or removal and replacement of pavement sections. “An RTS system helps contractors meet smoothness requirements as the pavement goes down,” 11 Quarter 2, 2022
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