减缩剂对混凝土早期自收缩的影响

采用自行设计制作的混凝土早期自收缩测试装置,研究了减缩剂在不同混凝土强度等级、掺粉煤灰或矿粉与否等对混凝土早期自收缩的影响。试验结果表明,减缩剂能有效降低混凝土的早期自收缩,减缩率随混凝土强度等级提高而提高。对掺粉煤灰或矿粉的混凝土,减缩剂同样具有优异的早期减缩效果。粉煤灰和矿粉能在一定程度上减小混凝土的早期收缩,对减少混凝土的早期收缩裂缝是有利的。减水剂极大地增加混凝土的早期收缩,即使掺入减缩剂,其收缩率仍大于不掺减水剂的混凝土。因此,对掺减水剂的混凝土应特别加强早期养护。

Influence of Shrinkage Retarder on Early Self-Shrinking of Concrete

Effects of different strengths of concretes with shrinkage retarder, whether or not with addition of fly ash ormineral powder on early self-shrinking of concretes were studied by means of early self-shrinking testing plant self designedand manufactured for concrete. Testing results indicated that shrinkage retarder could effectively reduce early self-shrinkingof concrete, its shrinking retardation would increase along with increase of concrete strength. Shrinkage retarder would alsoexert excellent early shrinkage retardation effects on concretes containing fly ash or mineral powder. Fly ash and mineralpowder could reduce early shrinkage of concrete to a certain extent which would be beneficial to reduction of early stageshrinkage crack of concrete, shrinkage ratio of the concrete even though with addition of shrinkage retarder would still bemore than that of the concrete without addition of water reducer, therefore for concrete admixed with water reducer stressshould be in particular put on early stage curing.