UCLA

Concrete presents a significant challenge to the environmental sustainability of the construction sector, being responsible for nearly 9 % of annual global carbon dioxide (CO2) emissions that contribute to climate change. CO2 emissions related to concrete construction may be reduced by: (a) improving the thermal performance of building envelopes to minimize heating/air conditioning energy inputs, (b) extending the service lifetime of concrete infrastructure, or (c) replacing ordinary portland cement (OPC) by alternative binders that emit less CO2 in their production. Three pathways towards these ends are highlighted:

a. Using concretes that contain functional inclusions (e.g., phase change materials – PCMs) is one method to improve the thermal performance of building envelopes. While the energy benefits of these concretes have been well-established, the potential for soft PCM inclusions to degrade the mechanical performance of concrete composites may limit their use.

b. Reducing the tendency of steel reinforcement within concrete to corrode is a critical step towards extending infrastructural service lifetimes. Typical corrosion mitigation strategies do not directly reduce the abundance of deleterious chloride ions (e.g., from de-icing salts or seawater) and are therefore difficult to implement successfully.

c. To directly reduce the embodied CO2 emissions of concrete, it is necessary to develop low-carbon cementitious binders, i.e., carbonate binders that gain strength by converting gaseous CO2 into stable solid minerals. Development of material formulations and processing routes for scalable production of concrete components via carbonation has remained a critical challenge.

This dissertation provokes and addresses research questions pertinent to each of these pathways. First, the mechanical behavior of cementitious composites containing PCMs is studied to aid in the development of improved predictive models and PCM dosage guidelines. Second, a novel cementitious formulation featuring unprecedented chloride-scavenging potential is designed and predicted to significantly delay the onset of reinforcing steel corrosion via finite element modeling. Finally, the CO2 mineralization reactions and strength development of carbonate binders containing portlandite (Ca(OH)2) are investigated, towards the production of low-carbon concrete by CO2 capture/utilization from flue gases. These advancements stimulate pathways for the design of sustainable concrete composites that reduce CO2 emissions from the construction sector.