Assessment of the effect of air-entraining agent content in reducing the severity of plastic shrinkage cracking in air-entrained concrete pavements

Plastic shrinkage cracking is one of the most common distress in concrete pavements, which reduces the durability and level of service. Using different admixtures in the optimal amount can reduce these cracks. This study investigates the effect of air-entraining agent content in creating intentional air in air-entrained concrete pavements, in controlling or reducing the severity of plastic shrinkage cracking. For this purpose, the effect of adding air-entraining agent in the amount of 0.04, 0.07, and 0.10% by weight of cement on the severity of plastic shrinkage cracking in concrete pavement mixture with water to cement ratios of 0.40, 0.45 and 0.49 was investigated by using ASTM C1579 method. The results showed that the addition of air-entraining agent reduced the severity of plastic shrinkage cracking in air-entrained concrete compared to the conventional one. It was seen that with more addition of air-entraining agent than a certain amount, the severity of cracking has increased, which is a specific and optimal amount of 0.07% in this study. The results showed that increasing the water to cement ratio at lower change intervals has a greater effect on the severity of cracking. Also, the percentage of entrained air due to the addition of the optimal amount of air-entraining agent is less than the maximum percentage of allowed entrained air in concrete pavements. Therefore, with the use of this admixture in the optimal amount, the severity of plastic shrinkage cracking in concrete pavements can be reduced.