硬化水泥浆体体积电阻和孔结构的关系

Relation Between Bulk Resistance and Pore Structure of Hardened Cement Pastes

用交流阻抗技术研究了硬化硅酸盐水泥浆体体积电阻和孔结构的变化特征。结果表明:硬化水泥浆体的体积电阻在前7d增长迅速,7d龄期时,体积电阻已经达到了总电阻的60%～70%,水灰比对体积电阻增长率的影响也主要体现在前7d。根据硬化水泥浆体中连通孔隙和闭合孔隙的特点,提出了硬化水泥浆体固、液相的串并连模型,建立了体积电阻与水泥硬化浆体中连通孔隙和非连通孔隙的关系。基于该模型和压汞法测试的总孔隙率的计算表明:当孔隙率接近20%时,闭合孔隙在总孔隙中所占的比例急速提高;当孔隙率大于25%时,连通孔隙所占的比例明显增大。

The characteristics of bulk resistance and pore structure of hardened Portland cement pastes were investigated by al- ternating current （AC） impedance spectroscopy. The results indicate that the bulk resistance increases rapidly during the initial 7 d hydration, then the increased rate decreases afterwards. The water-cement ratio has an effect on the bulk resistance before 7 d hydration. At the age of 7 d, the bulk resistance was up to 60%-70~ of it at the latest measured age. Based on the conduc- tive characteristics of solid, liquid of cement paste and connected pores and blocked pores in handed cement paste, a series-par- allel model was proposed to simulate the electrical conduction of handed cement paste. The proportions of connected and bloeked pores were estimated by the similated data by the model and the measurement results of total porosity. It is indicated that the proportion of blocked pores increases rapidly when the porosity of cement paste is 20%. Also, the proportion of con- nected pores increases significantly when the porosity is 〉 25%.