Engineered Cementitious Composite as a cover concrete against chloride ingress

Abstract

Engineered Cementitious Composite (ECC) is a cement composite reinforced with synthetic fi-bres. When loaded in tension, ECC exhibits a pseudo strain-hardening characteristic through the process of micro-cracking. The ductile behaviour of ECC makes it an ideal material for remediation of concrete struc-tures, as the differential volume change due to thermal expansion of the original concrete structure and the applied ECC layer can be accommodated. Reinforcement corrosion due to insufficient cover thickness and degradation of concrete is an ongoing issue for concrete structures exposed to marine environment. This study investigates the effectiveness of ECC as a cover concrete for existing concrete structures to delay chloride in-gress to the reinforcement and therefore extending the structure’s service life. Six ECC mixes were tested and compared with a 40 MPa concrete mix using two different test methods, namely the ASTM C642 void test, and the ASTM 1556 bulk diffusion test. Additionally, the effect of differ-ent curing regimes (air, water, 3.5% NaCl solution) was investigated on the standard ECC mix. The test re-sults indicated that the best ECC mix could reduce the diffusion coefficient to less than 11.2 times lower than a 40 MPa concrete mix subjected to the same environment. It was also determined ECC samples that were air cured exhibited the highest resistance to chloride ingress. It is concluded using ECC as a cover concrete for existing concrete structures is an effective remediation method.