Study on diffusion of oxygen in coral concrete under different preloads

Abstract

The diffusion law of oxygen in coral concrete under different loading conditions was investigated in this study. Compressive strength of nine groups of C30 coral concrete was measured to determine the ultimate compressive strength of coral concrete. Then, loads of 0, 25, 45, or 65% of the compressive strength were applied, and the damage to the specimens was quantitatively characterized via an ultrasonic method. Further, the oxygen diffusion coefficient of coral concrete was measured under different loads. Next, numerical simulations were carried out by using COMSOL software to verify and improve the oxygen diffusion test of coral concrete. The results show that the damage of the coral concrete increases with increasing load, while the ultrasonic velocity gradually decreases. Owing to its higher porosity, coral concrete exhibits a greater oxygen diffusion coefficient than mortar specimens with the same mix ratio, and the diffusion of oxygen in coral concrete follows an exponential rate law. With increasing pre-applied load on the specimen, an increase in the damage and the number of microcracks of the specimens as well as in the oxygen transmission rate and the final oxygen diffusion coefficient could be observed. The calculated values of the model obtained by using the numerical simulations exhibit a good correlation with the test results, which verifies the accuracy of the model established in this study.