The development of a resistivity measurement has enabled Professor Zongjin Li, at the Hong Kong University of Science and Technology's Department of Civil Engineering, to monitor and interpret the hydration process of cement-based materials.
This testing process is non-contacting and non-destructive and produces highly accurate results and is regarded as important to the building and construction industry where strong and durable materials are essential for reliable and sustainable development.
Professor Li says that although concrete has been in widespread use for 100 years, the hydration process of cement based products is still not fully understood.
"We liken our studies of concrete to genetics… no two people in the world have a common genetic structure but fundamental pattern. The same principle applies to cement-based materials where the micro-structure varies incredibly. However, some basic configurations should exist which can lead to problems associated with durability and cement cracking. This in turn affects the life of a building as well as the cost of construction, maintenance and on going repairs.
"Our projects have helped us understand the influence of the water/cement ratio on the development rate and strength development rate in Portland cement paste, a commonly used, time-dependent component of mortar and concrete."
Professor Li and his team have gone on to identify the hydration stage itself, finding that hydration occurs at the minimum point of resistivity. The resistivity measurement is closely related to the setting time of concrete and the microstructure development in concrete or cement based material.
The next stage of the study is to find the relationship between the microstructure and the porosity inside concrete/cement based materials.