预湿轻集料对混凝土内部相对湿度特性的影响

Influence of prewetted lightweight aggregate on internal relative humidity of concrete

为缓解混凝土的早期自干燥,减小自收缩,用预湿轻集料对其内部相对湿度进行调控.采用湿度测试仪和混凝土收缩测试仪,研究了水胶比、矿物掺合料对混凝土内部相对湿度与自收缩的影响规律,及预湿轻集料对自收缩的抑制效果.研究表明:混凝土内部相对湿度早期下降快,后期下降慢;降低水胶比、掺加硅灰会加快内部相对湿度的下降速度,而粉煤灰的加入可延缓低水胶比混凝土早期内部相对湿度的下降过程.预湿轻集料的引入可对混凝土内部相对湿度起到补偿作用,减小自收缩,作用效果随轻集料引入水量的增大而增强.

Prewetted lightweight aggregate （PLA） was employed to regulate the internal relative humidity （IRH） of concrete to mitigate the self desiccation and autogenous shrinkage （AS） at its early age. The influence of water/binder ratio （w/b） and mineral admixtures on IRH and AS and the mitigating effect of PLA were investigated by relative humidity sensor and shrinkage apparatus. Results indicated that the IRH of concrete decreased rapidly at early age and slowed down at late age ; a smaller w/b ratio and the addition of silica fume （SF） accelerated the decrease of IRH, and the addition of fly ash （FA） retarded the decrease of IRH at early age. Incorporation of PLA could compensate the loss of IRH, and the reduction of AS could be enhanced by the increasing of water content entrained by PLA.