早龄期水泥基材收缩与电学性能相关性

Correlation of Shrinkage and Electrical Resistivity of Early-Age Cement-Based Materials

为了探索水灰比变化对水泥基材料收缩性能和电学性能的影响,采用电阻率测试方法,分别测试了水灰比为0.3、0.35、0.4、0.45的水泥浆体在3 d内的自收缩和电阻率变化.结果表明:水泥浆体3 d龄期总自收缩随着水灰比的增大而减小;水灰比0.3和0.35的试件在3 d龄期内体积呈现收缩一致性,水灰比0.4和0.45的试件分别在7.7 h和16.8 h内呈现膨胀趋势;浆体早期体积变化主要由自收缩发展、强度发展(抑制收缩)和水化升温导致热胀三者耦合作用控制.水泥浆体3 d龄期电阻率随水灰比的增大而减小,对于同一试件,电阻率呈现先减小后增大的发展趋势.结合电阻率变化和电阻率微分曲线可以将水泥水化过程分为溶解期、诱导期、水化加速期和水化减速期4个阶段.不同水灰比水泥浆体自收缩均随电阻率呈现出良好的指数变化,根据浆体电阻率的变化可以预测自收缩的发展趋势.

To study the effects of water-cement ratios on the autogenous shrinkage（AS）and the electrical resis-tivity（ER）,we used the resistivity measurement to test the AS and the ER of cement pastes at water- cementratios of 0.3,0.35,0.4 and 0.45 in 3 d,respectively. The results show that the total AS values decrease with theincrease of water-cement ratios;the pastes with water-cement ratios of 0.3 and 0.35 show consistently shrinkagein 3 d,while the pastes with water-cement ratios of 0.4 and 0.45 show a temporal expansion in 7.7 h and 16.8 h,respectively. The early-age volume changes of the cement pastes are mainly controlled by the AS development,strength development（restricting shrinkage） and thermal expansion. The ER values of the cement pastesdecrease with the increase of water-cement,and the ER values of each sample show an increase trend after theinitial decrease because of the ion dissolution. The hydration process of the cement pastes can be divided intofour distinct stages,dissolution period,induction period,hydration acceleration period and hydration decelera-tion period from the electrical resistivity development and the differential curves of the resistivity. The AS valuesof the pastes show a good exponential correlation with their ER values,thus the AS development trends can bepredicted by the ER changes.