Effects of Polyvinyl Alcohol on the Early-Age Mechanical Properties and Carbon Uptake of Lime-Enriched Binders: A Comparative Study with Pure Lime and Portland Cement Systems

With the development of novel production routes enabling near-zero emissions from lime manufacturing, the use of lime as a carbon-sequestering component in cementitious materials has attracted increasing attention. To address the intrinsically low early-age strength of lime-enriched binders (LP), this study investigates the modification effect of polyvinyl alcohol (PVA) on LP, with systematic comparisons to ordinary Portland cement (PO) and pure lime systems (LE). The results indicate that, in terms of mechanical performance, the incorporation of PVA significantly enhances the early-age strength of LP, particularly the flexural strength, which increases by 119.3%. In contrast, the strength of PO shows a certain degree of reduction after PVA addition. Regarding carbon uptake performance, the CO2 sequestration capacity of PO and LE increases by 16.8% and 16.9%, respectively, whereas that of LP slightly decreases by 5.5%. From the hydration perspective, both the heat release rate and cumulative heat of PO and LP are reduced after PVA incorporation. Combined with microstructural analysis, the mechanical enhancement of LP induced by PVA is mainly attributed to the polymer film-forming effect, which compensates for the negative impact caused by the inhibition of hydration.