Mechanical Performance of Engineered Cementitious Composites (ECC) Utilizing Magnesium-Silicate-Hydrate (MgO-SiO2) Binders

Engineered Cementitious Composite (ECC) is a type of fiber-reinforced concrete (FRC) that exhibits tensile strain-hardening behavior. Magnesium-silicate-hydrate (MSH) is a class of magnesium oxide and reactive silica-based cementitious binders (MgO-SiO2) that develop strength via hydration similar to Portland cement. This study presents the mechanical performance of ECC developed using MSH binders to expand the range of binders for ECC and promote broader applications. The influence of a few material factors – fiber type (PVA and PE), fiber volume fraction (2%, 1%, and 0.5%), inclusion of aggregates (microsilica sand), and silica source (silica fume and metakaolin) – was investigated experimentally. The mechanical characterization was performed under unconfined uniaxial compression and uniaxial tensile tests. The tensile behavior was characterized using three parameters – first cracking strength, ultimate tensile strength, and tensile strain capacity. The tensile strain capacity was higher for PE fiber than for PVA fiber. Using PE fiber, the tensile strain-hardening can be achieved using a fiber volume fraction as low as 0.5% due to the high brittleness of the MSH matrix. The tensile strain-hardening behavior was retained even after adding microsilica silica sand with just a 1% volume fraction of PE fiber. The use of metakaolin increased the toughness of the cementitious matrix and thus reduced the tensile strain capacity compared to when silica fume was used as a silica source. Overall, all the composites showed tensile strain capacity above 3% and compressive strength greater than 40 MPa, successfully demonstrating the feasibility of using MSH binders to develop ECC.