Eco-friendly high strength, high ductility engineered cementitious composites (ECC) with substitution of fly ash by rice husk ash

In this study, an agricultural waste-rice husk ash (RHA) is proposed to substitute fly ash in high strength, high ductility engineered cementitious composites (ECC). The experimental results showed that the substitution of fly ash by RHA accelerated hydration process, promoted pozzolanic reaction, and refined pore distribution in ECC matrix, thereby increased compressive strength of ECC mixtures significantly from 82 MPa to 108 MPa. On the other hand, tensile properties of ECC mixtures were improved with addition of RHA, except ECC mixture with substitute ratio of 50% showed a slight reduction in strain capacity yet exhibited highest strength. At micro-scale, incorporating RHA into ECC reduced the theoretical complementary energy (Jb′) as a result of enhanced fiber/matrix interface, meanwhile, lowered crack tip toughness (Jtip) in ECC matrix which mainly due to the evidently increased modulus of ECC; subsequently lead to the increment of pseudo strain-hardening PSH (=Jb′/Jtip) index, and thus ductility.