Bendable concrete, also known as Engineered Cementitious Composites (ECC), has been around since the early 1990s. But a team of researchers at Louisiana State University (LSU) is close to finally bringing the material to market.
Scientists at LSU have been developing and testing an ECC mixture that has proven far superior to traditional concrete. ECCs can withstand the kind of deformation stress that would crack regular concrete—stress that is 100 to 500 times greater than regular concrete can handle.
The team, led by Gabriel Arce, senior research associate in LSU’s Department of Construction Management, put its ECC material to the test in October by repairing two sections of a sidewalk on the LSU campus.
"Compared to typical concrete, our cost-effective ECC material has about 300 times more deformation capacity, more than two times the flexural strength, and a higher compressive strength," said Arce.
The project is sponsored by the Transportation Consortium of South-Central States, or Tran-SET, which is a collaborative partnership between LSU and other educational institutions in that region of the U.S. Trans-SET funded the project with an eye toward using locally available materials.
Initial testing began on four different types of sand; two types of recycled crumb rubber materials; five different types of fiber; and three different types of fly ash, a by-product of coal combustion that can be used to partially replace cement in concrete.
Once the team settled on the ingredients, it started testing different ratios to determine the best mix. Several mixtures were evaluated for compressive strength, tensile strength, deformation capacity, flexural performance, workability, and cracking performance.
The final list of materials includes a type of PVA fiber easily found in the U.S. market, fine river sand from the Mississippi River, and locally available fly ash. Not only were these materials capable of withstanding deformation stresses, but they were also much less expensive than other ECCs.
“We were able to tailor the cementitious 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.”
The team’s next step is to build a 210-foot-long section of ECC pavement at the Louisiana Transportation Research Center Pavement Research Facility. There, the team will use a machine that compresses years of road wear into a few months to simulate how the material might stand up to the wear and tear of sustained vehicle traffic.
Eventually, this customized ECC mixture could be used in roads across the Southeastern United States, made from home-grown materials.
Read more about high-tech construction materials at 3D-Printed Cement Paste Uses Biomimicry to Strengthen After Cracking.