原位监测水泥基材料早期电阻率的变化过程

为了考察辅助性胶凝材料和细骨料对水泥水化的影响,利用新型无电极电阻率仪原位连续监测水泥基材料早期的微结构演变进程,系统分析了水胶比、硅灰掺量、矿渣掺量、粉煤灰掺量、细骨料体积分数和骨料粒级对水泥基材料电阻率的影响.试验结果表明:在水化3 000 min内,根据水泥基材料电阻率的发展曲线,可将水泥水化过程分为溶解期、诱导期、加速期和减速期4个阶段;电阻率的发展速率随水胶比的增加而显著下降;在水胶比相同的情况下,砂浆电阻率高于净浆电阻率;掺加矿物掺合料致使后期电阻率的变化速率降低,掺加硅灰则导致水化加速期提前;在早期水化过程中,硅灰的活性最高,矿渣的活性次之,粉煤灰的活性最低;细骨料的体积分数和骨料粒级越大,砂浆的电阻率越大.

In-situ monitoring of early-age electrical resistivity change process of cement-based materials

To explore the effect of the supplementary binders and fine aggregates on the hydration process,the early-age microstructure evolution process was in-situ continuously monitored by using a new electrodeless resistivity apparatus for various cement-based materials.The influence of the water-to-binder ratio,the silica fume replacement percentage,the slag replacement percentage,the fly ash replacement percentage,the volume percentage of fine aggregates and the grain size of fine aggregates on the electrical resistivity were systematically investigated.The experimental results show that according to the development curve of the electrical resistivity of the cement-based materials,the 3 000 min early-age hydration process of the cement-based materials can be clearly classified into four stages: the dissolution stage,the dormant stage,the acceleration stage,and the deceleration stage.The development rate in the electrical resistivity decreases with the increase in the water-to-binder ratio.The electrical resistivity of the mortar is greater than that of the cement paste at the same water-to-binder ratio.The change rate of the electrical resistivity in the late stage is reduced by the mineral admixtures,while the hydration acceleration stage is advanced by the addition of the silica fume.During the early-age hydration process,the silica fume has the highest activity followed by the slag,and the fly ash has the lowest activity.The larger the volume percentage and grain size of the fine aggregates,the higher the electrical resistivity of the mortar.