Early-age Electrical Resistivity and Reactive Capacity of Mineral Admixtures in Mortars

摘要

A non-contacting electrical resistivity measurement device was used to investigate the effect of different types and contents of mineral admixtures on the hydration performance of mortars during early age. The experimental results show that the changes of measured resistivity with time of hydration can be used to describe the hydration characteristics of cement- based materials, as well as the physical and chemical behavior of fly ash; blast furnace slag and silica fume at the very early ages. With an increasing replacement ratio of mineral admixtures, for the specimens blended with fly ash or slag, the resistivity increases firstly, then the following flatting period extends and after setting the resistivity increasing becomes slow and consequently a, lower resistivity value at 24 hours occurs. This is due to the dilution effect and lower pozzolanic/hydraulic activity of fly ash and slag. However, for the samples incorporated, with silica fume, the resistivity value through 24 hours is lower with shorter flatting period and larger slope in the resistivity curves, which is because of its particle size effect and higher pozzolanic activity of silica fume. Moreover, non- contacting resistivity measurement might provide a helpful information to predict the long term performance including the durability of cement- based materials at early ages.