Rock Products

JAN 2019

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96 • ROCK products • January 2019 www.rockproducts.com LAST CALL In the early 1990s, Victor Li, a professor of civil and environmental engineer- ing at the University of Michigan, developed Engineered Cementitious Composites (ECC), also known as duc- tile or bendable concrete. More than 20 years later, researchers at LSU are close to bringing this material to mass adoption, producing a cost-effective ECC that utilizes readily available ingredients. Furthermore, through testing to-date, it is being called far superior to traditional concrete and could greatly improve transportation infrastructure. "Compared to typical concrete, our cost-effective ECC material has about 300 times more deformation capac- ity, more than two times the flexural strength, and a higher compressive strength," said Gabriel Arce, a senior research associate in LSU's Bert S. Turner Department of Construction Management and principal investiga- tor on the LSU ECC project. "The cost of our material is approximately 2.5 times that of regular concrete; typical ECC cost can be more than four times that of regular concrete. "However, when you factor in the possibility of building pavements at half the thickness and the enhanced construction productivity due to the ability to construct pavements with- out joints, the cost of pavements with our ECC material should be comparable to that of traditional concrete. ECC has the potential to provide [Louisiana] with more durable and reliable con- crete pavements that can mitigate the necessity of recurring repair, saving [the public] time and money," he said. New and Improved The new and improved ECC has been more than a year in the making. After graduating with his PhD from LSU, Arce submitted his proposal for the proj- ect, "Evaluation of the Performance and Cost-Effectiveness of Engineered Cementitious Composites (ECC) Pro- duced From Region 6 Local Materials" to the Transportation Consortium of South Central States, or Trans-SET. Trans-SET funded the project and testing began on four different types of sand; two types of recycled crumb rubber materials; five different types Bendable Concrete? By Mark S. Kuhar of fiber; and three different types of fly ash, which is a by-product of coal com- bustion and can be utilized to partially replace cement in concrete materi- als. Once the team settled on the raw ingredients, several ECC mixes were evaluated for compressive strength, tensile strength, deformation capac- ity, flexural performance, workability, and cracking performance. Those were refined based on testing outcomes and evaluated further. In the end, Arce and his team settled on the following ingredients: • A type of PVA fiber readily available in the U.S. market. It doesn't possess the oil coating typically used in PVA fibers for ECC application but it does substantially reduce the cost and increase practicality. They were also able to reduce the fiber content by 25 percent while still producing a ductile material. • Locally available fine river sand from the Mississippi River. The sand is fine enough to be implantable in ECC materials and is a replacement for the expensive and hard-to-obtain micro- silica sand normally used. •  Locally available fly ash, which replaced up to 75 percent of the cement utilized in the ECC mix. "We were able to tailor the cementi- tious mix and the interface between the fibers and the cementitious matrix in such a way that allowed for a ductile behavior of the concrete," Arce said. "In more simple terms, the formula utilizes the right materials in the right proportions." In the coming months, Arce and the team will further develop their work with a project at the Louisiana Trans- portation Research Center Pavement Research Facility.

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