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Carbon capture utilization and storage technique (CCUS) is an effective way to mitigate climate change. Carbon dioxide (CO2) sequestration binders (CSB) composed of hydrated lime (CH) and cement has great application prospects in CCUS. Although CH in CSB can improve the carbon absorption capacity, it causes a significant decrease in flexural strength. This study focused on the effect of polyvinyl alcohol (PVA) on the CO2 absorption capacity and flexural strength of CSB. The results show that PVA is beneficial to enhancing the flexural strength of CSB either under natural carbonation or accelerated carbonation. This enhancement is more pronounced at an early age for CSB with high CH content. Furthermore, CO2 uptake experiments show that the PVA would not reduce the CO2 absorption of CSB and even has a slight improvement effect. Finally, thermodynamic modeling and price calculation were adopted for CSB to illustrate the chemical phase and economic cost changes. The outcomes of this study shed new light on PVA to optimize CSB. [ABSTRACT FROM AUTHOR]

This work investigates the influence of calcium leaching on mechanical and physical properties of limestone powder (LS)–cement pastes cured under different temperatures. In order to achieve this goal, three different mass percentages of LS (10%, 30%, and 50%) were selected to replace cement, and the LS–cement pastes were cured under three different temperatures (5°C, 20°C, and 50°C). The LS–cement pastes were soaked in NH4Cl solution to accelerate the calcium leaching and simulate the leaching influence from water. The mechanical and physical properties including the compressive strength, flexural strength, Vickers hardness (VH), leaching depth, and electrochemical impendence spectroscopy (EIS) were conducted. The prediction model of VH and the relationship between equivalent VH and mechanical strength were built. The microstructure of LS–cement pastes is characterized by X-ray diffraction (XRD), thermogravimetric (TG), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests. Experimental results demonstrate that with the increase of LS, the decrease degree of mechanical and physical properties of LS–cement pastes increases gradually; Furthermore, the leaching damage degree of LS–cement pastes is the largest under curing temperature of 5°C, followed by 50°C and 20°C. The microstructure results reveal that the Ca(OH)2 in the leached zone of LS–cement pastes is completely dissolved, and the calcium leaching makes the LS–cement pastes cured under 5°C obtain the loosest structure and the most serious leaching damage, followed by 50°C and 20°C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined use of waste glass and RHA greatly alleviates wastes disposal at landfills. • Use of RHA improved mechanical and durability of cement mortar. • Addition of RHA suppressed RG-induced ASR expansion. • RHA holds great promise as eco-friendly pozzolanic materials. Using recycled glass (RG) to replace river sand in the production of cement-based materials saves the increasingly depleting natural sand resources. Previous studies have shown that the smooth surface and reactive silica of RG adversely affected its bonding with the cement paste and thereby caused a potential alkali-silica-reaction (ASR). This study used rice husk ash (RHA) as an eco-friendly mineral admixture to ameliorate the properties of the RG incorporated mortar. A fixed replacement of 50% RG was used to replace sand, while varying proportions (10%, 20% and 30%) of RHA were adopted to replace cement. For comparison, a mixture containing only sand and cement was used as the reference sample. The flexural and compressive strength, water absorption, ASR expansion, and rapid chloride mitigation (RCM) of the hardened samples were evaluated. In addition, SEM, XRD, and TG analysis were employed to analyze the microstructures and chemical compositions of different samples. The results showed that incorporating RG as a river sand replacement in cement mortar reduced flexural and compressive strength and increased water absorption and chloride ion penetration. Moreover, the ASR expansion value (0.34%) was beyond the permissible limit (0.1) indicated by the ASTM C1260. The addition of RHA improved the mechanical properties and durability of the cement mortar at a later curing age as a result of the RHA-induced pozzolanic reaction and micro-filler effect. By converting portlandite (CH) derived from cement hydration into secondary C-S-H, the use of RHA greatly reduced the porosity (augmenting the compressive and flexural strength) and concurrently suppressed the RG-induced ASR expansion. The results of XRD, SEM and TG analysis corresponded well with the macro-property analysis and helped to elucidate the underlying mechanisms of the RHA-induced beneficial effects. Findings from this study provide new insights into the potential use of eco-friendly RHA in addressing the mechanical and durability problems associated with the use of RG as aggregate in cementitious materials. [ABSTRACT FROM AUTHOR]