Insight into the effect of sand size, sand-to-binder ratio, and water-to-binder ratio on micro- and macro-mechanical properties of HS-ECC

Abstract

This study quantitatively evaluates the effects of mixture design parameters, including maximum sand size (d_max: 0.6–2.36 mm), sand-to-binder ratio (s/b ratio: 0.2 to 0.6), and water-to-binder ratio (w/b ratio: 0.16 to 0.22), on the micromechanical properties of high-strength engineered cementitious composites (HS-ECC) using a factorial design approach. Statistical equations that account for the coupling effects of mixture design parameters were developed to predict micromechanical properties. Based on the developed equations and micromechanical theory, the mixture with 2.36 mm d_max, 0.6 s/b ratio, and 0.197 w/b ratio was determined as the optimum HS-ECC mixture. The experimental pseudo strain-hardening behavior trend was consistent with predictions. Incorporation of large-size sand modified flaw distributions, thereby improving tensile ductility and promoting saturated multiple cracking. However, improved flaw distribution does not guarantee high ductility; attention must also be given to the increased flaw quantity. Regression equations linking micromechanical parameters to tensile strength and strain capacity were proposed and experimentally validated. The fiber-matrix bond was the key factor affecting tensile strength, while matrix fracture toughness significantly impacted tensile strain capacity. The regression equations linking micromechanical parameters with tensile properties offer a valuable tool for designing HS-ECC properties to meet various structural requirements.