Tensile over-saturated cracking of Ultra-High-Strength Engineered Cementitious Composites (UHS-ECC) with artificial geopolymer aggregates

Ultra-High-Strength Engineered Cementitious Composites (UHS-ECC) incorporating artificial geopolymer aggregates (GPA) were developed and over-saturated cracking (i.e., average tensile crack spacing smaller than the theoretical limit) was observed in this novel material. The developed UHS-ECC exhibited an ultra-high compressive strength (over 150 MPa) and an ultra-high tensile ductility (over 8%) simultaneously. The influences of GPA size on the matrix properties, tensile performance, micromechanics, and cracking behavior of UHS-ECC were systematically investigated. Over-saturated cracking and double-stage crack evolution (i.e., a bilinear relation between average crack width and tensile strain) were observed in UHS-ECC with GPA size smaller than 0.60 mm, while saturated cracking and single-stage crack evolution (i.e., a linear relation between average crack width and tensile strain) were observed in the other groups. Finally, the mechanism of over-saturated cracking and double-stage crack evolution was illustrated. The findings of this study extend the fundamental knowledge of ECC technology, which is meaningful for designing and developing UHS-ECC materials towards ultra-high tensile ductility.