Mechanical characteristics of sea-sand concrete in simulated marine environment

Abstract

In the marine environment, concrete in both submerged zone and non-submerged zone could be attacked by seawater. To study the deterioration of sea-sand concrete partially submerged in seawater, an accelerated test with simulated marine environment was designed for seawater and siliceous sea-sand concrete (SSC), coral aggregate seawater concrete (CASC) and tap water and desalted siliceous sea-sand concrete (DTC). The mass, water absorption, mechanical properties (compressive strength and dynamic modulus) were tested. Thermodynamic simulation, EDS and MIP test were used to analyze the strength deterioration of different sea-sand concrete. With the dry-wet cycle, the dynamic modulus and mass of sea-sand concrete increased first and then decreased. After 365 days of dry-wet cycles, the water absorption of sea-sand concrete with high initial strength would increase more significantly. Different sea-sand concrete in the submerged zone and the non-submerged zone was mainly subjected to chemical seawater attack, and ettringite and gypsum were the main expansion phases. The most important influence of internal sea salt attack from mixing materials on the deterioration of concrete partially submerged in seawater was the change of pore distribution. Due to the combined effect of capillary transport and crystallization pressure, SSC and CASC with higher initial compressive strength had greater compressive strength loss in the submerged zone. In the non-submerged zone, under the combined action of capillary transport, crystallization pressure and “wick action”, the compressive strength of SSC, CASC and DTC varied with height in an “S”, parabolic and linear shape, respectively.