Optimizing the Temperature and Chemical Stability of Fly Ash Aluminosilicate Composites at the Nanoscale

Princeton University, Princeton NJ

Investigators

Abstract

This research project centers on understanding and optimizing the temperature and carbonation resistance of low embodied energy cementitious composites for elevated temperature applications, such as fire walls and refractory materials. Use of Portland cement and refractory concrete in society accounts for a sizable amount of energy utilization due to the need for material manufacturing and transportation. Furthermore, Portland cement-based concrete does not perform adequately at elevated temperatures due to decomposition of the main strength-giving constituent, leading to costly repair and replacement. The research to be conducted in this project will promote the use of industrial byproducts in the construction and refractory industries, and therefore encourage further reductions in energy utilization associated with these sectors. The research outcomes of this project will be incorporated into high school teaching modules on materials relating to energy and the environment. In regards to promoting and encouraging underrepresented minorities in science, technology, engineering and mathematics, including young females, this project will enable high school and undergraduate interns to be trained in research during summers and over the academic year. The objective of this research project is to uncover and optimize the elevated temperature stability and carbonation resistance of chemically-activated cementitious composites, based on aluminosilicate chemistry, using a multifaceted experimental approach. Ambient temperature reaction kinetics and setting times will be investigated using ultrasonic analysis combined with isothermal calorimetry, where calcium-based additives will be utilized to control setting times and short-term mechanical behavior. The molecular structure of chemically-activated metakaolin- and fly ash-based pastes will be elucidated using X-ray pair distribution function analysis and infrared spectroscopy for a range of elevated temperatures, and the project will include the use of in situ carbonation/elevated temperature measurements at synchrotron facilities. Furthermore, given the susceptibility of cementitious materials to dehydration-induced cracking and loss of mechanical properties, the impact of alumina particle and fiber reinforcement on the microstructural (and atomic) behavior of the aluminosilicate composite will be uncovered using synchrotron and lab-based X-ray microtomography. Ultimately this project will generate the fundamental knowledge on the atomic and microstructural behavior of low embodied energy aluminosilicate cements at elevated temperatures, with the long-term aim of integrating this material into applications where conventional concrete quickly degrades due to exposure to high temperatures and aggressive chemicals.