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.