Breaking strength-ductility trade-off dilemma for Engineered Cementitious Composites (ECC) through filler effect

Abstract

The outstanding strain-hardening and multiple cracking behavior of Engineered Cementitious Composites (ECC) is favored by maintaining a low fracture toughness (K_m) in its matrix. However, limiting K_m comes at the cost of diminished compressive strength (f_c), owing to their intrinsic positive correlation in general cementitious binders. Here, we explore the feasibility of decoupling the K_m-f_c relationship by applying the filler effect, aiming to improve the composite f_c and tensile ductility simultaneously. Our results show that K_m and f_c can be adjusted independently by manipulating the use of fillers with different cementitious reactivities, and incorporating the inert-particle-packing effect produced a densified matrix with increased f_c but nearly unchanged K_m. Micromechanical analyses revealed favorable changes in the fiber/matrix interfacial bond and pseudo-strain-hardening index, accompanied by an improved tensile strength, ductility, and crack control capability in the composite. These findings inform a cost-effective design strategy for ECC across wide-ranging applications.