|
| 摘要: |
| 采用多通道椭圆环收缩开裂试验、自由收缩试验和强度试验综合评价了萘系（UNF）、聚羧酸类（PC）高效减水剂对水泥砂浆体积稳定性及早期开裂的影响．结果表明，高效减水剂的掺入延长了水泥砂浆的初始开裂时间，从而降低了水泥砂浆的开裂敏感性．高效减水剂降低水泥砂浆开裂敏感性的效果为：聚羧酸类〉高浓型萘系〉普通型萘系．掺高效减水弃1均增大了水泥砂浆的自由收缩值，且水泥砂浆自由收缩值随着高效减水剂掺量的增加而增大．高效减水剂控制水泥砂浆体积稳定性的效果为：聚羧酸类〉普通型萘系〉高浓型萘系．聚羧酸类高效减水剂的掺入减小了水泥砂浆的最大裂纹宽度，而萘系高效减水剂的掺入则加快了水泥砂浆最大裂纹宽度的发展速度．在干燥养护条件下，掺聚羧酸类高效减水剂比掺萘系高效减水剂更能有效地提高水泥砂浆28d的强度． |
| 关键词: 高效减水剂 早期开裂 体积稳定性 初始开裂时间 |
| DOI： |
| 分类号:TU528.0 |
| 基金项目:国家863高科技计划资助项目(2002AA335050)，国家重点基础研究发展规划(973)资助项目(2001CB610704-3) |
|
| Study on Early-age Cracking of Cement Mortar with High Range Water Reducing Admixtures |
|
MA Bao-guo WANG Xin-gang LIANG Wen-quan LI Xiang-guo HE Zhen YE Qun-shan
|
| Abstract: |
| The addition of high range water reducing admixture(HRWRA) is an important approach to prepare high performance cement mortar.The effect of high concentration type naphthalene series(superplasticizer(H-UNF)),common type naphthalene series(superplasticizer(C-)UNF) and polycarboxylate type superplasticizer(PC) on early-age cracking and volume stability of cement mortar was investigated by means of multi-channel ellipse ring shrinkage cracking test,free shrinkage and strength test.The general effect of UNF and PC is to increase initial cracking time of cement mortars,and decrease cracking sensitivity of cement mortars.As for decreasing cracking sensitivity of cement mortars,PC>H-UNF>C-UNF.To incorporate HRWRA apparently increases free shrinkage of cement mortars when keeping the constant m_w/m_b ratio and the content of cement pastes.As for the effect of controlling volume stability of cement mortars,PC>C-UNF>H-UNF.Maximum crack width of cement mortars with PC is lower,but the development rate of maximum crack width of cement mortars with H-UNF is faster in comparison with control cement mortars.Flexural and compressive strength of cement mortars at 28 d increase with increasing superplasticizer dosages under drying conditions.PC is superior to naphthalene series superplasticizer(UNF) in the aspect of strength increase. |
| Key words: high range water reducing admixture,early-age cracking,volume stability,initial cracking time |
