减水剂对混凝土早期收缩和总收缩的影响

在混凝土配合比不变的情况下，掺入减水剂能增大流动性，同时也显著增大早期收缩和总收缩，特别是24h内增幅特别大。当用水量减少、保持坍落度相同时，掺减水剂将进一步增大早期收缩和总收缩，且随水泥用量的增加，收缩显著增大，而对不掺减水剂的混凝土影响很小。因此，对掺减水剂的混凝土应特别加强早期施工养护，并尽可能采用纤维、减缩剂和补偿收缩剂等材料措施，才有可能减少裂缝、推迟裂缝产生。此外，脂肪族系、萘系和胺基磺酸盐系减水剂均增大收缩，且品种之间的差异较小。普通水泥与基准水泥对收缩的影响规律相似。

Influence of superplasticiser on early shrinkage and total shrinkage of concrete

The superplasticiser would increase early shrinkage and total shrinkage of concrete at the same mixing proportion especially for the first 24h.When reduced water and kept slump fixedness by adding superplasticiser,the early and total shrinkage would further increase,and,the shrinkage enhanced remarkably with the increasing of cement dosage,but not for concrete without superplasticiser.Hence,the early curing of concrete should be intensified especially,and,it will be necessary and effective for reducing and postponing crack by using fiber reinforcement,expanding compensation or shrinkage-reducing agent.Furthermore,all the three kinds superplasticiser increase shrinkage but there are little difference.