资源描述：
《减水剂对混凝土收缩和裂缝的负影响》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、第1卷 第2期铁道科学与工程学报Vol11No122004年9月JOURNALOFRAILWAYSCIENCEANDENGINEERINGSept.2004X减水剂对混凝土收缩和裂缝的负影响钱晓倩,詹树林,方明晖,孟 涛,钱匡亮(浙江大学建筑工程学院,浙江杭州310027)摘 要:由于减水剂显著增大混凝土的早期收缩,根据我国现行外加剂收缩率比试验方法测得的结果,弱化了减水剂对收缩的影响程度。当混凝土配合比不变时,掺入减水剂增大流动性,同时也显著增大早期收缩和总收缩,特别是24h内增幅更大。当用水量减少保持
2、坍落度相同时,掺减水剂将进一步增大早期收缩和总收缩。当水泥用量增加时,掺减水剂混凝土收缩显著增大,而对不掺减水剂的混凝土影响很小。试验用的3种不同减水剂均增大收缩,但品种之间的差异较小。减缩剂能有效降低混凝土的早期收缩和总收缩。减缩剂对掺矿粉和粉煤灰混凝土同样具有显著的减缩效果。混凝土强度等级提高,掺减水剂混凝土的早期收缩显著增大,减缩效果相应增加。减水剂的掺入使混凝土的开裂时间提前,裂缝数量显著增加。而减缩剂能使开裂时间大大延迟,裂缝数量显著减少。因此,对掺减水剂混凝土应特别加强早期施工养护,并尽可能采
3、用纤维、减缩剂和补偿收缩剂等材料措施,才有可能推迟裂缝产生并减少裂缝。关键词:减水剂;早期收缩;干燥收缩;裂缝;减缩剂;混凝土中图分类号:TU528 文献标识码:A 文章编号:1672-7029(2004)02-0019-07NegativeinfluenceofsuperplasticisersonshrinkageandcrackingofconcreteQIANXiao2qian,ZHANShu2lin,FANGMin2hui,MENGTao,QIANKuang2liang(Collegeo
4、fCivilEngineeringandArchitecture,ZhejiangUniversity,Hangzhou310027,China)Abstract:TheeffectdegreeonshrinkageisweakenedoftheshrinkageratiotesteddependingonGBJ82becauseofthesuperplasticiserincreasingearlyshrinkagesignificantly1Superplasticiserincreasedearly
5、shrinkageandtotalshrinkageofconcreteatthesamemixingproportion,especiallyforthefirst24h1Whenreducedwaterandkeptslumpfixednessbyaddingsuperplasticiser,theearlyandtotalshrinkagewouldfurtherincrease,and,theshrinkageenhancedremark2ablywiththeincreasingofcement
6、dosage,butnotforconcretewithoutsuperplasticiser1Thethreesuperplasticisersin2creasedshrinkageall,butthedifferenceindifferentadditivesislesser1Theshrinkage-reducingagent(SRA)canre2ducetheearlyandtotalshrinkagesignificantlyandalsoforconcretemixingblastfurnac
7、eslagpowderorpulverizedfly-ash1Theearlyshrinkageandshrinkagereducingefficiencyincreasedwiththeconcretegradeelevation1Thesuper2plasticisermadethecrackingtimeadvancingandthecracknumberincreasing,andtheSRAcandefercrackingandre2ducecrackamount1Hence,theearlyc
8、uringshouldbeintensifiedforaddingsuperplasticiserconcrete,especially1Itwouldbenecessaryandeffectiveforreducingandpostponingcrackbyusingfiberreinforcement,expandingcompensa2tionorshrinkage-reducingagent1Keywords:supe
