Influence of Superplasticizers on Strength and Shrinkage Cracking of Cement Mortar under Drying Conditions  

作　　者：马保国 

机构地区：[1]Key Laboratory of Silicate Materials Science and Engineering(Ministry of Education),Wuhan University of Technology

出　　处：《Journal of Wuhan University of Technology(Materials Science)》2007年第2期358-361,共4页武汉理工大学学报（材料科学英文版）

基　　金：the National "973" Program (2001CB610704-3);the National "863" Program (2002AA335050)

摘　　要：The effects of polynaphthalene series superplasticizers（PNS） with a low content of sodium sulfate （H-UNF）,with a high content of sodium sulfate（C-UNF） and polycarboxylate type superplasticizer （PC） on strength and shrinkage cracking of cement mortar under drying conditions were investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase the initial cracking time of mortars, and decrease the cracking sensitivity of mortars. As for decreasing the cracking sensitivity of mortars, PC〉H-UNF〉C-UNF. To incorporate superplasticizers is apparently to increase the free shrinkage of mortars when keeping the constant w/b ratio and the content of cement pastes. As for the effect of controlling the volume stability of mortars, PC〉C-UNF〉H-UNF. Maximum crack width of mortars containing PC is lower, but the development rate of maximum crack width of mortars containing H-UNF is faster in comparison with control mortars. The flexural and compressive strengths of mortars at 28-day increase with increasing superplasticizer dosages under drying conditions. PC was superior to PNS in the aspect of increasing strength.The effects of polynaphthalene series superplasticizers（PNS） with a low content of sodium sulfate （H-UNF）,with a high content of sodium sulfate（C-UNF） and polycarboxylate type superplasticizer （PC） on strength and shrinkage cracking of cement mortar under drying conditions were investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase the initial cracking time of mortars, and decrease the cracking sensitivity of mortars. As for decreasing the cracking sensitivity of mortars, PC〉H-UNF〉C-UNF. To incorporate superplasticizers is apparently to increase the free shrinkage of mortars when keeping the constant w/b ratio and the content of cement pastes. As for the effect of controlling the volume stability of mortars, PC〉C-UNF〉H-UNF. Maximum crack width of mortars containing PC is lower, but the development rate of maximum crack width of mortars containing H-UNF is faster in comparison with control mortars. The flexural and compressive strengths of mortars at 28-day increase with increasing superplasticizer dosages under drying conditions. PC was superior to PNS in the aspect of increasing strength.

关 键 词：SUPERPLASTICIZERS shrinkage cracking ellipse ring DRYING 

分 类 号：TQ177.62[化学工程—硅酸盐工业]