Tensile size effect of engineered cementitious composites (ECC): Experimental and theoretical investigations

Size effect is a common phenomenon in construction materials and influences the application of concrete from laboratory to engineering practices. However, the impact of length variation on the tensile properties of engineered cementitious composites (ECC) lacks a comprehensive understanding from both experimental and theoretical aspects. This paper proposed three-level size effect laws (SELs) for the tensile size effect of ECC. The 1st and 2nd level SELs are established by an existing Weibull theory to determine the size effect on cracking strength (σ_c) and tensile strength (σ_tu), respectively. Afterward, a novel 3rd SEL is constructed to determine the size effect on tensile strain capacity (ɛ_tu) by combing the 1st and 2nd level SELs with strength criterion. To validate the SELs, uniaxial tensile tests were conducted on specimens with gauge length of 100 mm, 300 mm, and 500 mm. Results show that with the increase of gauge length, the σ_c, σ_tu, and ɛ_tu decrease by 10.4%, 21.7%, and 61.6%, respectively. A high prediction accuracy of abovementioned mechanical parameters is achieved (R² = 0.98, 0.95, and 0.90, respectively). The findings reveal that the SELs can accurately predict the tensile properties of ECC with different lengths based on laboratory-obtained parameters to facilitate structural design.