硫酸盐干湿循环下再生复合微粉混凝土的劣化机理

Deterioration Mechanism of Recycled Composite Powder Concrete under Dry-Wet Cycles of Sulfate

关键词:  再生复合微粉混凝土  硫酸盐侵蚀  干湿循环  微观结构

Key words:  recycled composite powder concrete  sulfate attack  dry-wet cycle  microstructure

摘要:

将再生砖粉和再生混凝土粉混合组成再生复合微粉，取代部分水泥制备再生复合微粉混凝土，对其进行干湿循环下硫酸盐侵蚀试验和微观结构表征，并基于其微观结构演化过程建立了SO42-侵蚀模型，揭示了硫酸盐侵蚀下再生复合微粉混凝土的劣化机理.结果表明：再生复合微粉混凝土的抗压强度损失率随着干湿循环次数的增加先降低后升高，且随着再生复合微粉取代率的增加，其变化幅度增大；低取代率的再生复合微粉较好地发挥了填充效应和成核作用，促进水泥水化，但其多孔性的初始缺陷提供了大量侵蚀通道，并造成孔隙内部压力分布不均，导致再生复合微粉混凝土的耐久性能加速劣化.

Abstract:

Recycled composite powder concrete was prepared by mixing recycled brick powder and recycled concrete powder to replace part of the cement. Sulfate attack tests and microstructure characterization under dry-wet cycles were carried out to analyze the pore structure parameters and the evolution process of interfacial transition zone. Based on its microstruture evolution process， SO42- attack model was established， which revealed the deterioration mechanism of recycled composite powder conclete under sulfate attack. The results show that compressive strength loss rate of the recycled composite powder concrete decreases and then increases with the increase of the number of dry-wet cycles， and the change is greater with the increase of the replacement rate of recycled composite powder. The recycled composite powder with low replacement rate has played a better role in filling effect and nucleation to promote cement hydration， but the initial defect of high porosity provides a large number of attack channels， which is the main reason for the accelerated deterioration of the durability performance of recycled composite powder concrete.