Materials for sustainable infrastructure

Materials for Sustainable Infrastructure

This research theme studies the chemistry of construction materials with special focus on the application of the structure-property relationship principles, to design, synthesize and develop new construction materials that feature high performance and high durability. We utilize both experimental and computational approach and have applied such to a diverse range of construction material systems.

Rheology-Based Protocol to Establish Admixture Compatibility in Dense Cementitious Suspensions

Chemical admixtures are often added to concentrated cementitious suspensions in an effort to adjust their (1) rheology, i.e., yield stress and viscosity; (2) time of set, i.e., when plasticity is lost; and (3) hardening rate. Although the first adjustment is affected by dosage of dispersants, the subsequent two adjustments are made by dosing chemical additives that alter the binder’s reaction rate. To ensure desirable field performance, e.g., at subambient temperatures, dispersants and reaction rate enhancers may be dosed simultaneously. In such cases, it is critical to ensure that the dosed additives are compatible with each other. To assess such admixture compatibility and synergy, an original rheology-based method is developed.

Compatibility of cement hydrate phases

Phase relations of C3AH6 and Ca3Al2(SiO4)x(OH)4(3 − x) at sulfate and carbonate activities conditioned respectively by (gypsum and SO4-AFt) and (calcite and CO3-AFt) have been determined experimentally in the range 5–85 °C. The results confirm the instability of Si-free hydrogarnet with carbonate and sulfate-bearing cement phases, but do indicate that a range of silica-substituted hydrogarnet solid solutions are stable under conditions likely to be encountered in blended cement systems…

Strätlingite: compatibility with sulfate and carbonate cement phases

The stability of strätlingite in the presence of sulfate and carbonate phases relevant to cement systems are reported. Results show that strätlingite persists at the sulfate activity conditioned by gypsum, ettringite and at carbonate activity conditioned by the presence of calcite, carbonate AFm, or carbonate AFt. Structural incorporation of anions such as carbonate or sulfate in strätlingite was not observed in the temperature range 20–85 °C.

Clinkering-free cementation by fly ash carbonation

The production of ordinary portland cement (OPC) is a CO2 intensive process. Specifically, OPC clinkering reactions not only require substantial energy in the form of heat, but they also result in the release of CO2; i.e., from both the decarbonation of limestone and the combustion of fuel to provide heat. To create alternatives to this CO2 intensive process, this paper demonstrates a new route for clinkering-free cementation by the carbonation of fly ash; i.e., a by-product of coal combustion. It is shown that in moist environments and at sub-boiling temperatures, Ca-rich fly ashes react readily with gas-phase CO2 to produce robustly cemented solids.

Ongoing project includes:

Rheology of cement-based materials
Hydration, microstructure, and durability of cement-based materials
Nanoengineered cement-based systems
Thermodynamics-based design of materials for sustainable infrastructure
Advanced chemical admixtures for cement systems
Mitigation of deteriorative reactions in cement-based materials