Research on the durability degradation mechanism of early-age concrete and life prediction model under freeze-thaw-salt erosion coupling effect

In the Ruoqiang region of Xinjiang, this research investigates the durability damage process of early-age concrete (EAC). The apparent morphology, mass loss, compressive strength, and dynamic modulus of elasticity of earlyage concrete with air-entraining agent contents of 0.00%, 0.05%, 0.10 %, and 0.15 % were tested under freezethaw-sulfate coupling and freeze-thaw cycling conditions. The temporal evolution of concrete durability at early ages and the mechanism of action are revealed. Meanwhile, The entropy weight approach was utilized to characterize the early-age concrete durability values, and subsequently, the GM-GA-BP neural network concrete early-age durability model was brought out. The conclusions of the research are set out below: (1)Early-age concrete's durability was greatly increased by air-entraining agents; 0.10 % is the ideal amount of air-entrainingagents for freeze-thaw-sulphate linked conditions. (2) The discrepancies between the concrete evaluation indices were analyzed using the entropy weight method, and the durability value of the concrete at an early age demonstrated a change rule of increasing first and then dropping, which was in good accord with the test results. (3)The GM-GA-BP model gave the best prediction (R2 value of 0.9822 and MAPE value of 0.3677 %), and its accuracy was much higher than that of the GM(1,1) and GA-BP models. (4) The difference in the service life of early-age concrete in the two environmental conditions increases with time as the dose of air-entraining agent increases (the life expectancy in the freeze-thaw-sulfate coupled environment is shorter than that in the freezethaw environment).