摘要
低水胶比条件下水泥基材料的自收缩率已超过干燥收缩率成为导致混凝土过早开裂的隐患．以超细粉煤灰（ultra-fine fly ash，UFA）等量取代水泥20％～40％，配制了UFA水泥基复合胶凝材料，分别对固定水胶比和变水胶比两种情况下的UFA水泥砂浆早期（7d前）自收缩变形和干燥收缩变形进行试验研究．结果表明，在固定水胶比条件下，砂浆的自收缩率随UFA掺量增加递减，而干缩率却随之增大；在变水胶比条件下，砂浆的自收缩率随水胶比的增加递减，干缩率随之增大．且回归分析表明两种情况下砂浆的自收缩及干燥收缩变形均表现出较好的线性相关；UFA对水泥基材料改性作用明显，在保持相同流动度条件下，UFA的掺入可有效降低用水量，早期及后期强度能赶上甚至超过基准水泥胶砂，弥补了UFA早期不水化所引发的早期强度低缺陷；微观测试表明，UFA在水泥基材料中起到了较好的密实填充、减水分散及增强作用．
Autogenous shrinkage and dry shrinkage of cement based materials, produced by lower water/binder ratios, are the key factors resulting in the concrete early cracking. Experiments on ultra-fine fly ash （UFA） replaced 20%-40% equivalent cement and UFA blended cement mortars were conducted. Experimental results show that autogenous shrinkage （before 7-day） of UFA mortar reduces and dry shrinkage increase with increase of UFA amount under the condition of fixed water/binder ratio. On the other hand, the autogenous shrinkage of UFA blended cement mortar reduces and dry shrinkage increase with increase of water/binder ratio under the condition of variable water/ binder ratio. The better linear relationship between autogenous shrinkage and dry shrinkage is shown by regression analysis. The addition of UFA reduces water demand of cement based materials under the condition of keeping the same fluidity, so early strength and long-term strength of UFA mortar catch or surpass that of reference cement mortar, solving the problem of early strength of UFA mortar being lower because of no hydrating of UFA. The microscopic test results indicate that UFA has the better effects on dense packing, water reducing, dispersing and strength increasing.
出处
《深圳大学学报（理工版）》
EI
CAS
北大核心
2008年第1期97-102,共6页
Journal of Shenzhen University(Science and Engineering)
基金
国家高技术研究发展计划资助项目(2005AA332010)
中国博士后科学基金资助项目(20070410969)
关键词
超细粉煤灰
水泥基复合胶凝材料
自收缩
干燥收缩
ultra-fine fly ash
composite cement based materials
autogenous shrinkage
dry shrinkage
