中文摘要：

为分析长期荷载作用对粉煤灰混凝土抗碳化性能的影响,在CO2浓度（体积分数）为（20±3）%,相对湿度为（70±5）%,温度为（20±2）℃环境中,研究了水胶比为0.37、0.45、0.53,粉煤灰等质量替代水泥为0、30%、60%,40 mm×40 mm×160 mm的混凝土试件经标准养护28 d后,在相对湿度（60±5）%,温度（20±2）℃条件下,放置3 a的空载试件、加载试件（压应力水平为33%）以及加载3 a后卸载试件的快速碳化规律,并结合超声波声速分析了长期荷载作用对粉煤灰混凝土抗碳化性能影响的机理。结果表明：长期荷载作用可减缓粉煤灰混凝土的碳化进程,压应力作用3 a后超声波声速平均值较3 a龄期空载试件增大0.8%,表明其内部结构更为致密,各组粉煤灰混凝土的平均碳化深度增加值较3 a龄期空载试件降低19.2%;压应力作用3 a后卸载,混凝土超声波声速平均值较空载试件降低1.1%,内部可能产生了微损伤,加速了其碳化速率,各组粉煤灰混凝土的平均碳化深度增加值较3 a龄期空载试件增大14.5%。超声波声速测试结果佐证了长期荷载作用对粉煤灰混凝土抗碳化性能的影响规律。

英文摘要：

In order to analyze the effect of long-term loading on the carbonation resistance of fly ash concrete, the carbonation regularity of concrete specimens with the size of 40 mm×40 mm× 160 mm at a concentration （volume fraction） of CO2 （20±3）%, a relative humidity of （70±5）% and a temperature of （20±2） ℃ was investigated. After 28-d curing, the concrete specimens were loaded for 3 years （i.e., at compressive stress level of 33%）, placed for 3 years without loading and uninstalled after loading for 3 years at the relative humidity of （60±5）% and the temperature of （20±2） ℃, respectively. The water-binder ratio is 0.37, 0.45 and 0.53, and the content of fly ash substituting for the equal quality of cement by mass is 0, 30% and 60%, respectively. The mechanism of long-term loading effect on the carbonation resistance of fly ash concrete was analyzed by the sound velocity measurement. The result shows that the long-term loading can reduce the rate of concrete carbonation. The ultrasonic sound speed of specimens after loaded for 3 years is increased by an average of 0.8%, compared to the specimens unloaded, indicating that the internal structure is denser. The average increment value of carbonation depth of fly ash concrete in each group is decreased by 19.2%, compared to the specimens unloaded. The ultrasonic sound speed of specimens uninstalled after loading for 3 years is decreased by an average of 1.1%, compared to the specimens unloaded. The micro-damage in internal of concrete accelerates its carbonation rate. The average increment value of carbonation depth of fly ash concrete in each group is increased by 14.5%, compared to the specimens unloaded. The ultrasonic testing results can indicate the influence of long-term loading on the carbonation resistance of fly ash concrete.