AbstractsPhysics

This dissertation explored the development of several innovative guided radar technologies to characterize the hydration kinetics of cement based materials. A broadband time domain dielectric spectroscopy (TDS) technology was developed to study the interactions of concrete components in different scales. The signal analyses based on time domain interpretation were found to correspond to the low gigahertz and low kilohertz respectively. An innovative Thermo-TDR sensor was developed to measure the physical, thermal and other transport properties of construction materials including concrete. This sensor integrates the conventional TDR probe with a heat pulse measurement system. It can be used to collect both the TDR signals and thermal signals at the same time. With the assistance of these sensors, the effects of nano-cement, mineral nano-particles on the microstructure and durability of concrete was also studied in this dissertation, and experimental studies were carried out to evaluate the effects of mineral nano-particles on the microstructure of concrete. Besides the laboratory experiment, a multi-physics numerical model was developed to predict the development of cement paste hydration. The chemical reaction theory, heat transfer theory and diffusion theory were coupled in this model. The simulation results were validated based on field test phenomenon and experiential equations, and promising results were achieved. Besides predicting the development of the hydration process, this model also proposed a microstructure based approach to relate the chemical reactions to the strength of cement paste. Current results showed that this numerical model can help predict the early stage concrete behaviors.