Influence of Aggregate Type and Size on Ductility and Mechanical Properties of Engineered Cementitious Composite

This paper presents the results of an investigation on the influence of aggregate type and size on the mechanical and ductility properties of engineered cementitious composites (ECC). ECC is a micromechanically-based designed high-performance fiberreinforced cementitious composite with high ductility and improved durability due to tight crack width. Standard ECC mixtures are typically produced with microsilica sand (200 µm [0.008 in.] maximum aggregate size). In this study, ECC mixtures containing either crushed dolomitic limestone sand or gravel sand with maximum sizes of 1.19 or 2.38 mm (0.047 or 0.094 in.) were investigated. For each aggregate type and maximum aggregate size, three different ECC mixtures with fly ash/portland cement (FA/C) ratios of 1.2, 2.2, and 4.2 were cast. Specifically, the effects of maximum aggregate size, aggregate type, and FA/C on the uniaxial tensile, flexure, and compressive properties, as well as crack development and drying shrinkage behavior, were experimentally determined. The experimental results show that the ECC mixtures produced with crushed dolomitic limestone sand and gravel sand with higher maximum aggregate sizes exhibit strain-hardening behavior with strain capacities comparable with the standard microsilica sand ECC mixtures, provided that a high FA content is employed in the matrix. For these mixtures, the tensile ductility can maintain 1.96 to 3.23% at 28 days of age, with tensile strengths of 3.57 to 5.13 MPa (0.52 to 0.74 ksi). The use of crushed dolomitic limestone sand and gravel sand can also play the role of drying-shrinkage arrestors in the paste, further improving the material behavior