Development of high-strength engineered cementitious composites using iron sand: Mechanical and shrinkage properties

Abstract

High-strength engineered cementitious composites (HS-ECC) has gained significant attention due to its superior mechanical properties. Despite its advantageous properties, HS-ECC faces challenges such as high shrinkage and resource shortage due to a lack of coarse aggregate and excessive consumption of silica sand, resulting in challenges for practical applications. This research aims to replace silica sand with iron sand (sourced from iron ore tailings) to develop HS-ECC with better mechanical properties while balancing shrinkage and workability, considering the effect of sand to binder (s/b) ratio and aggregate size. Nine mixtures are designed with various s/b ratios (0.2, 0.4, 0.6, and 0.8), aggregate types (silica sand and iron sand), and aggregate sizes (0.125–0.180 mm, 0.180–0.425 mm, and 0.425–0.850 mm) to investigate their influences on the mechanical properties, workability, shrinkage properties, and material sustainability. The results showed that using iron sand and increasing sand content notably enhanced elastic modulus, while changes in aggregate type and size minimally affected compressive strength. Replacing silica sand with iron sand improved the ultimate tensile stress and strain of HS-ECC by 16.1 % and 15.6 %, respectively, as the s/b ratio was 0.6. Increasing the aggregate size weakened tensile properties, while the autogenous shrinkage was reduced by 29.7 %. Increasing the s/b ratio or the aggregate size reduced autogenous shrinkage, total shrinkage, and drying shrinkage. Furthermore, for the s/b ratio of 0.4, replacing silica sand with iron sand reduced autogenous shrinkage, total shrinkage and drying shrinkage by 14.1 %, 16.4 % and 23.0 %, respectively. Additionally, when the s/b ratio was 0.6, replacing silica sand with iron sand reduced the carbon footprint, cost, and energy consumption of HS-ECC by 2.5 %, 6.6 % and 1.7 %, respectively. A multi-scale analysis was conducted on the s/b ratio, aggregate type and aggregate size. This research verifies the feasibility of substituting silica sand with iron sand to produce HS-ECC with low shrinkage, and designable mechanical properties.