Mechanism of fineness and content of quartz powder on the improvement of carbonation curing efficiency

Quartz powder is a byproduct of quartzite processing. To date, research on the use of quartz powder in carbonation curing is extremely limited, and the carbonation curing mechanism of concrete containing quartz powder is still unclear. In this study, we focused on the effects of fineness and content of the quartz powder on carbonation curing for cement-quartz powder binary mixtures and compared the results with those from sealed curing to clarify the effects of the quartz powder under carbonation curing and sealed conditions. The quartz powder's action is primarily influenced by nucleation and dilution effects, altering the coupling of hydration and carbonation, thereby influencing carbonation curing outcomes. Experimental results reveal distinct mechanisms under sealed and carbonation curing. Under sealed curing conditions, the smaller particles of quartz-S5 (sample SC-Q10-S5) promoted cement hydration more effectively under the influence of nucleation, and the samples showed better compressive strengths, electrical resistivities, and ultrasonic pulse velocity gains when the quartz powder replaced 10% of the cement. The introduction of larger quartz-S20 particles (sample CC-Q10-S20) promoted the carbonation reaction more significantly (Affected by the dilution effect, which promotes CO2 diffusion) and showed better compressive strength, electrical resistivity, and ultrasonic pulse velocity gain compared to the smaller particles of quartz-S5 during carbonation curing. In summary, adding quartz powder as a partial substitute for cement in the carbonation curing process standardized the carbonation curing, and under the coupling of hydration and carbonation reactions, larger particles are more beneficial for enhancing carbonation curing properties compared to smaller particles.