Conference Agenda

This study developed an efficient in-situ carbonation activator with enhanced carbon capture, using organic additives in an aqueous solution. The fresh carbonated cement suspension was mixed with raw materials through secondary mixing to improve cement mortar hydration. Various organic additives were tested for their ability to leach calcium and aluminum ions, affecting carbonation efficiency and products. Characterization showed that these additives increased carbon capture and influenced calcium carbonate morphology. The activator, rich in silica gel and calcium carbonate polymorphs, acted as a filler and nucleating agent, accelerating hydration and promoting carboaluminate formation. This method reduced mortar porosity, improved pore structure, and enhanced mechanical strength while achieving effective carbon sequestration.

Reactive magnesia cement (RMC) hardens through hydration and carbonation, where it sequesters CO₂ from the air. The hydration and carbonation of RMC is an intrinsically volume-expansion process. A sample calculation for the changes in molar mass and molar volume during hydration and carbonation is provided below. The hydration product, brucite undergoes carbonation and forms hydrated magnesium carbonates (HMCs), which is the primary contributor to the strength of carbonated cement. This work studies and quantifies the effect of carbonation on the volume change of RMC. The development of the microstructure over time, as it relates to volume change, was examined. Reactive magnesia cement (RMC) paste, without any additives, typically undergoes setting in 2 hours or less. The length at final setting was used as the reference point for measuring length change. After demoulding at final setting, the RMC paste was cured in a high humidity chamber for 24 hours before undergoing accelerated carbonation (10% CO₂, 23C, 85%RH). The length of the RMC specimens was measured at days 1, 3, 5, 7, 14, and 28 to quantify the volume change due to carbonation. The effect of factors such as Water-to-cement ratio, and Hydration agent were explored.

Cement is an important sealing material for geological CO₂ storage (GCS) reservoirs. The durability of cement exposed to CO₂-saturated water environments is critical for the long-term integrity of GCS structures, as groundwater and CO₂ interact with cement, which may significantly affect its microstructure and mechanical properties. In this study, Class G oil well cement was exposed to CO₂-saturated water under various liquid-to-solid ratios (L/S), temperatures, and pressures for up to four months. After the exposure, the carbonation depths and the mineral compositions of the specimens were analysed using XRD and EDS techniques. The results revealed that exposure to CO₂-saturated water caused the formation of distinct carbonation zones in the specimens. Especially, the dissolution of cement might occur under specific conditions, and it could result in a significant decrease in mechanical properties. This could pose a serious threat to the integrity of the cement, where the influence of the L/S ratio was found critical. Higher L/S ratios led to marked dissolution of the cement, accelerating the loss of mechanical properties. While in the cases of lower L/S ratios, abundant calcium carbonate precipitation was observed in the cement specimens, leading to densification of microstructure and strength enhancement, which might instead help to maintain structural integrity. Furthermore, thermodynamic modelling based on GEMS was performed to provide an evaluation of cement mineral composition changes. The importance of L/S ratio, temperature, and pressure on cement degradation in CO₂-rich environments was emphasised, and the critical L/S corresponding to cement dissolution at different environments was revealed. The findings of this research implied that the local exposure conditions are very important for the structural integrity and sustainability of GCS structures in the long term.

Many coastal communities are located in areas of high seismic activity. Saltwater flooding can exacerbate the corrosion of lateral force-resisting systems of structures in these communities, impacting their seismic resilience. Evaluating the compounding risk from flood and seismic hazards in these communities is a necessary step toward ensuring the safety of coastal populations and infrastructure. This paper studies the loss of rebar in coastal reinforced concrete buildings over time due to both atmospheric and saltwater flooding-related corrosion and evaluates their effects on the performance of the lateral load resistance of these buildings. A previously developed corrosion model was modified to incorporate the impacts of annual coastal flooding on the corrosion rate. Finite element models of a reinforced concrete moment frame were created with rebar cross-sectional areas corresponding to various levels of corrosion. Pushover analyses were performed to determine the lateral strength and ultimate displacement capacity under different scenarios: atmospheric corrosion only, lower- and upper-bound corrosion rate changes due to flooding, corrosion of exterior columns or all columns due to flooding, and varying exposure durations (60 years or 80 years). The results show that although atmospheric corrosion does not lead to considerable change in lateral response, annual coastal flooding may result in up to 26% loss in lateral strength and up to 83% loss in displacement capacity. When the post-cracking corrosion rate is assumed to be four times higher than the pre-crack corrosion rate, the strength loss for buildings where all first-floor columns flooded becomes significant (>20%) over an 80-year period. In contrast, the displacement capacity loss is more sensitive to corrosion; even when the corrosion rate is assumed to simply double after cracking, with only the exterior columns exposed to seawater, displacement capacity decreases significantly (>10%) after 60 years.

Cementing is one of the most critical stages in oil well construction, as it ensures the proper fixation of the casing and prevents fluid migration through permeable zones. Class G cement, used in this process, is subjected to harsh conditions, particularly at great depths, where both temperatures and pressures are elevated. Exposure to brine and CO₂ under extreme conditions can compromise the durability of the cement and the well’s integrity by altering its physical, chemical, and mechanical properties. Given the significance of these factors, it is essential to investigate their influence on the cement sheath. This study exposed Class G cement samples for three months in autoclaves under high pressure (20 MPa) and temperature (88 ^◦C) in environments saturated with brine and brine with CO₂. Uniaxial and triaxial compression tests, porosity analysis, X-ray diffraction, and pH measurements were conducted. The results showed that confining pressure significantly impacted samples exposed to brine+CO₂, leading to plastic deformations at pressures above 20 MPa, even before the application of deviatoric stresses. Exposure to brine+CO₂ reduced compressive strength by 45% compared to the reference samples, likely due to micro defects forming during curing and chemical reactions with acidic gases. To determine whether the contribution of micro defect formation caused by the loading and unloading during the curing procedure was more significant than the chemical reactions, samples cured under the same pressure and temperature conditions but exposed only to brine were tested. The results showed that the reduction in strength and alterations in the material’s elastic properties were more closely related to the adopted curing procedure than to the chemical reactions resulting from the acidic environment.