Tensile properties and constitutive model of engineered cementitious composites made with waste basalt powder and basalt sand

Ultrafine basalt powder (UBP) and basalt sand (BS) were used to replace fly ash (FA) and quartz sand (QS), respectively, in the preparation of engineered cementitious composites (ECCs). The substitution rates of UBP and BS were 0%, 25%, 50% and 100%. Uniaxial tensile experiments were conducted on the prepared ECC specimens to examine the tensile strength and ductility of the ECCs with varying mix ratios. A constitutive model integrating a straight line and a curve (called the L&C model) was established based on the sigmoid function. The findings indicated that when UBP was used as a complete substitute for FA, the ultimate strain, fracture elongation and tensile strength of the ECC exhibited increases of 140.1%, 187.1% and 44.7%, respectively. In addition, the pseudo strain strengthening coefficients, specifically σ₀/σ_c and J_b/J_tip, increased from, respectively, 2.30±0.22 and 14.58±1.86 in the control group to 2.97±0.29 and 27.49±1.95. When BS was used as a complete replacement for QS, the tensile strength decreased by 23.4%. However, σ₀/σ_c and J_b/J_tip improved from, respectively, 1.42±0.08 and 13.49±1.18 in the control group to 1.90±0.13 and 19.58±1.51, enabling the ECC to better satisfy strength and energy criteria. Consequently, the ultimate tensile elongation and fracture elongation increased by 42.2% and 53.1%, respectively. After conducting a thorough analysis and comparison, it is evident that the L&C model based on the sigmoid function demonstrated a higher correlation than the traditional bilinear model.