Effect of carbonation-drying-wetting on durability of coral aggregate seawater concrete

Based on the drying-wetting cycles experiment and the carbonation-drying-wetting cycles experiment for coral aggregate seawater concrete(CASC)with different strength grades,the effects of carbonation-drying-wetting on the durability of CASC are studied with the surface state,mass loss rate,relative dynamic elastic modulus,ultrasonic wave velocity and cube compressive strength as indices.Results show that the mass loss rate of CASC increases gradually with the increase in cycle times in the drying-wetting and carbonation-drying-wetting cycles.The mass loss rate increases relatively slowly at the initial stage but it increases remarkably after 10 cycles.The relative dynamic elastic modulus and ultrasonic wave velocity decrease gradually with the increase in cycle times.After 6 cycles,the decrease rate of the relative dynamic elastic modulus and ultrasonic wave velocity of CASC tends to be flat and the surface is slightly damaged.Compared with the initial 28 d cube compressive strength,the cube compressive strength of CASC decreases by 8.8%to 11.0%.Drying-wetting cycles and carbonation can accelerate seawater erosion on CASC,and drying-wetting cycles result in salting-out and accelerate the destruction of concrete.Therefore,the carbonation-drying-wetting accelerates the destruction of CASC.

不同试验条件下深部下组煤底板水岩相互作用特征

为探讨济北矿区深部下组煤底板岩石与水相互作用规律,以岱庄煤矿首采面底板5种不同类型岩性的岩样为研究对象,在自来水与饱和食盐水浸泡后并结合自然浸泡与湿–干交替循环浸泡条件下两两组合进行为期52 d的水稳性和相关电导率试验。研究结果表明:(1)根据20个岩样掉渣、表面裂隙、岩样开裂、饱水后强度和崩解等现象统计对比分析,发现不论是自来水还是饱和食盐水在自然浸泡条件下5种岩样的水稳性均相对较好,浸水后基本不崩解,但在湿–干交替循环作用条件下均会发生崩解现象;(2)通过对自来水浸泡岩样在自然与湿–干交替条件下电导率测试,发现所有岩样溶液中电导率增加幅度随时间均表现出比较明显的3个阶段,但同一岩样在不同条件下电导率增加幅度随时间变化具有较大差异性,湿–干交替岩样的电导率增加幅度明显大于自然浸泡岩样的;(3)电导率和岩样质量损失率基本呈正相关关系。研究结果对深部水岩相互作用导致岩石劣化的微观机制研究提供参考。