Monitoring the setting and hardening behaviour of cement paste by electrical resistivity measurement

• Published in: Construction & building materials 2020-08, Vol.252, p.118941, Article 118941
• Main Authors: Yousuf, Farqad, Wei, Xiaosheng, Zhou, Jiangyin
• Format: Article
• Language: English
• Subjects: Electrical resistivity; Hydration process; Set-controlling admixtures; Setting time
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2020.118941

•Electrical resistivity measurement by the non-contact method successfully characterised the early age properties of cement paste, showing good agreement with results of other conventional methods, such as the Vicat needle, heat of hydration, and SEM observations.•The initial and final setting times of cement were alternatively determined based on two critical points on the curve of resistivity development rate.•The effect of set-controlling admixtures on hydration was comprehensively studied using the electrical resistivity method, revealing adequate information related to paste structure formation. Electrical resistivity measurements by a non-contact method successfully characterised the early age properties of cement pastes, showing good agreement with results of other conventional methods, such as the Vicat needle, heat of hydration, and scanning electron microscopy observations. The setting and hardening behaviour of cement pastes with different dosages of set-controlling admixtures was comprehensively studied. New general equations were developed to alternatively determine initial and final setting times based on critical points on the curve of electrical resistivity development rate. Specifically, two critical points were detected. Point (C1) occurred when the cement solution reached supersaturation with respect to CH during the dissolution process and the paste remained as a fluid. Point (C2) occurred when the resistivity acceleration trend started decelerating owing to the depercolation of pores, and the paste hardened. The period from point C1 to C2 was defined as the solidification period, in which the setting time of the cement paste occurred approximately in the middle. The duration of the solidification period was prolonged with a retarder and shortened with an accelerator, revealing the mechanism action of admixtures and their effect on hydration and paste structure formation. According to experimental results and Powers’ law, a model was proposed to estimate the solid volume fraction of cement pastes by measuring their electrical resistivity.