Multiaxial Shear Performance of Coarse-Aggregate ECC: Damage Evolution and Interfacial Characteristics

The widespread application of engineered cementitious composites (ECC) necessitates addressing two critical challenges: excessive shrinkage deformation and prohibitive economic costs. Incorporating coarse aggregates (CAs) into ECC (CA-ECC) presents an effective solution strategy for these limitations. In civil and hydraulic engineering applications where shear-dominated failure prevails under complex loading conditions, establishing the correlation between CA content and the damage evolution characteristics as well as failure mechanisms of CA-ECC under shear stress states becomes imperative. This investigation examines the multiaxial shear performance of CA-ECC through the multiaxial shear tests considering four CA contents and five axial compression ratios. The digital image correlation technique was employed to analyze the damage evolution, complemented by microstructural characterization to elucidate the mechanisms of CA on shear performance of CA-ECC. The results indicate that increasing the CA content and axial compression ratio can both cause CA-ECC to crack prematurely, with the cracks increasing significantly. A positive correlation exists between CA content and shear strength enhancement, peaking at 36.91% improvement with 30% CA content. Notably, maximum peak shear displacement (33.86% increase) was achieved at 10% CA content. However, high axial compression can weaken the improving effect of CA on the shear performance of CA-ECC. Furthermore, the increase in CA content expands its interfacial transition zones, alters the fiber distribution characteristics, and consequently changes the failure mechanism of CA-ECC. Finally, a modified damage constitutive model of CA-ECC was proposed in this article, which was demonstrated to accurately predict the shear mechanical properties of CA-ECC.