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 2 4h内增幅更大。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。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 ,并尽可能采用纤维、减缩剂和补偿收缩剂等材料措施 。
The effect degree on shrinkage is weakened of the shrinkage ratio tested depending on GBJ 82 because of the superplasticiser increasing early shrinkage significantly. Superplasticiser increased early shrinkage and total shrinkage of concrete at the same mixing proportion, especially for the first 24 h. 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. The three superplasticisers increased shrinkage all, but the difference in different additives is lesser. The shrinkage-reducing agent (SRA) can reduce the early and total shrinkage significantly and also for concrete mixing blast furnace slag powder or pulverized fly-ash. The early shrinkage and shrinkage reducing efficiency increased with the concrete grade elevation. The superplasticiser made the cracking time advancing and the crack number increasing, and the SRA can defer cracking and reduce crack amount. Hence, the early curing should be intensified for adding superplasticiser concrete, especially. It would be necessary and effective for reducing and postponing crack by using fiber reinforcement, expanding compensation or shrinkage-reducing agent.
出处
《铁道科学与工程学报》
CAS
CSCD
北大核心
2004年第2期19-25,共7页
Journal of Railway Science and Engineering
基金
国家中小企业创新基金 ( 0 2C2 62 13 3 0 0 5 99)
浙江省科技厅重点科技项目资助 ( 2 0 0 3C2 10 18)
关键词
减水剂
混凝土
收缩程度
裂缝程度
减缩剂
superplasticiser
early shrinkage
drying shrinkage
crack
shrinkage-reducing agent
concrete
