高效减水剂及其与膨胀剂复合对地铁用混凝土收缩开裂的影响

Influences of high performance superplasticize and expansive agent composite application on the performance of shrinkage and crecking about subway concrete

主要研究了萘系高效减水剂、减缩型聚羧酸高效减水剂单掺及其与膨胀剂复合使用对地铁用混凝土干燥收缩、塑性开裂和干缩开裂的影响。试验结果表明:钙矾石类膨胀剂对早期收缩有较好的抑制作用,然而对后期收缩仍难控制,膨胀结束后的干燥收缩落差较大,养护条件对其体积稳定性有着显著影响,从而必须加强早期水养护并尽可能延长水养护时间。减缩型聚羧酸减水剂抑制混凝土收缩开裂性能不仅优于萘系高效减水剂,甚至比萘系高效减水剂与膨胀剂复合使用效果好。高效减水剂与膨胀剂复合使用后对抑制混凝土收缩开裂的效果更明显。

Focuses on the naphthalene superplasticizer and shrinkage-reducing polycarboxylate-based superplasticizer on the concrete shrinkage and cracking,and combined with the expansive agent on the concrete shrinkage cracking.The results show that It benefited to control the early shrinkage by Ettringite expansive agent.However,after the expansion the drop in elevation of drying shrinkage was still great.So the results suggest that it is necessary to enhance the water curing at the early age and try the best to prolong the curing time.Combined use of superplasticizer and expansion agent can significantly reduce the shrinkage,compared with single-doped,compound used effect on the inhibition of cracking more obvious,and hrinkage-reducing polycarboxylate-based superplasticizer inhibitory effect of shrinkage and cracking better than the naphthalene superplasticizer.