Abstract
Strain hardening cementitious composites (SHCC) are a class of fiber reinforced materials exhibiting tensile strain hardening behavior up to strain of several percent, accompanied by the formation of fine multiple cracks with openings below 50 μm. To model the full stress-strain relation of SHCC (which governs ductility and energy absorption) and the crack width versus strain relation (which governs durability), the sequential formation of cracks needs to be analysed. The cracking process is related to the internal structure of SHCC, such as the fiber and flaw size distributions, which varies with material rheology and mixing sequence. As a first study of the processing-structure-property relation of SHCC, tensile specimens are prepared with mixes exhibiting different viscosities. To account for sequential cracking, the variation in SHCC ‘structure’ is represented by the size variation of equivalent spherical flaws inside the member according to the normal distribution, while fibres are assumed to be uniformly distributed. By fitting the measured tensile stress-strain curves for various mixes with a micromechanical model developed at HKUST, the effect of matrix viscosity on the flaw size distribution is determined. The results will provide insight on the micromechanics-based design of SHCC for various requirements on ductility and crack control.
