The early hydration of cement

Abstract

This thesis details the development and use of an electrical response technique for monitoring the chemical and physical changes occurring within the cement paste during the initial 24 hours after gauging with water. Traditional empirical tests and the more sophisticated laboratory examinations such as X-ray diffraction, scanning and transmission electron microscopy are critically reviewed. The study involves the electrical measurements on realistic sample sizes and constituent proportions. A modified electricalmodel for the response of cement paste to an applied electrical field is proposed. An automated microcomputer data logging system has been developed to facilitate electrical measurements. It has been demonstrated that the electrical response measurements of cement paste can be related to the physio-chemical processes that take place during hydration. Extensive microstructural examination of fracture surfaces of cement pastes using Scanning Electron Microscopy revealed that regions of definite crystallization and the prediction as to the hydrate morphology can be linked to the electrical response. The technique could be offered as an additional tool for investigating the structure building processes and microstructure development within cement paste. The electrical response data can be used to monitor cement hydration and it is shown that assessment of the effect of varying chemical composition; age of cement; addition of admixtures and environmental conditions have a definite influence on hydration processes.