UC Irvine

The cement industry is one of the most difficult sectors to decarbonize. The manufacturing of Portland cement – the most common type of cement used for structural concrete – presently accounts for roughly 2% of global energy usage and 8% of CO 2 emissions. The current manufacturing process has not changed substantially over the past 140 years and requires temperatures above 1450 °C with heat provided by the combustion of fossil fuels. The massive CO2 emission originates from: 1) fossil fuel combustion needed to heat the raw materials ultimately to ~1450 °C for calcination and sintering, and 2) decomposition of CaCO3 in the kiln. About 1 ton of CO2 is released for every ton of Portland cement produced in this manner. To date, most of the efforts to reduce CO2 emissions have focused on the use of supplementary cementitious materials. Other approach such as capturing CO2 from fossil fuel power plants and sequestering the carbon in building materials or geologically stable substances requires the building of vast infrastructure and remains to be proven. Future manufacturing approaches that can decarbonize cement and cement-based materials are needed.

This dissertation study establishes a new paradigm to decarbonize cement and cementitious materials through integrating novel manufacturing with cement chemistry and micromechanics. The new paradigm enables the novel design, manufacturing and validation of cement and cementitious materials with much reduced material-production-stage CO2 as well as life-cycle CO2 : (1) cement produced based on a clean electrochemical path instead of conventional fossil fuel combustion process; (2) ductile ultra-low-binder-content cementitious materials to reduce lifecycle CO2 by 65% and energy consumption by 70% of transportation infrastructure; and (3) an alternative low-temperature low-CO 2 “cement” clinker with additional CO2 sequestration functionality, which can be synthesized at room temperature and has potential of 4 times of CO2 uptake than conventional Portland cement. This research advances knowledge in understanding the reaction kinetics of alite and belite syntheses from electrochemically produced Ca(OH)2 and waste precursors, in tailoring the rheology, compaction self-assembly and micromechanics of fiber-reinforced low-binder cementitious materials, and in elucidating the chemistry, microstructure and properties of Ca(OH)2 -activated cementitious materials.