Influence of accelerated chloride corrosion on mechanical properties of sea sand ECC and damage evaluation method based on nondestructive testing

Abstract

Sea-sand engineered cementitious composite (SECC) is a new version of engineered cementitious composite for marine constructions that face the scarcity of river/manufactured sand. This study explores the effect of chloride corrosion on the mechanical properties of SECC with polyethylene fibers (PE/SECC) and polyvinyl alcohol fiber-reinforced sea-sand engineered cementitious composite (PVA/SECC), which are critical for its applications in marine engineering. The accelerated chloride corrosion test (dry-wet cycling/soaking), rapid chloride migration (RCM) test, and dry shrinkage test were conducted. In addition, the thickness of the damaged layer and changes in relative dynamic modulus of elasticity (RDME) of SECCs were analyzed by ultrasonic nondestructive testing. The results revealed that the chloride corrosion did not produce a significant effect on the compressive strength and RDME of SECCs. Furthermore, the drying shrinkage of SECCs and accumulation of Friedel's salt induced swelling stress inside the SECC. Under the corrosion action of chloride, a number of microcracks appeared on the surface of the polyethylene (PE) fibers, making the PE/SECC less ductile. For the purpose of assessing the damage to the SECC, a computing formula was proposed based on the damage degree, RDME, relative mass, and resistance to chloride ion penetration under the coupling effect of chloride corrosion, and dry-wet cycling or soaking. Using the formula, the obtained critical values for the dry-wet cycling and soaking system were γCN = 20.74 and γSN = 21.36, respectively. The research results promote the application of SECCs in practical engineering, and provides beneficial guidance for the design and application of SECCs in offshore structures, improving the chloride corrosion resistance of offshore structures.