Semi-dry carbonated recycled concrete paste as alternative to limestone and its reactivity in LC3.

Recycled concrete paste (RCP) can be transformed to the carbonated RCP (cRCP) as supplementary cementitious materials (SCM). By blending cRCP with calcined clay prepared from excavated waste, a distinctive limestone calcined clay cement (LC3) was produced. The aim of this research was to assess the reactivity of LC3 produced from the cRCP utilizing different carbonation procedures, via isothermal calorimetry. The carbonation process occurred at 100% R.H. and 20 vol.% CO2 concentration. To investigate the effect of pre-wetting treatment on the carbonation degree, the RCP was pre-wetted using either deionized water or 0.1 mol L−1 NaOH solution. The carbonation degree and microstructure of cRCP were analyzed using thermogravimetric analysis, X-ray diffraction, and solid-state nuclear magnetic resonance. The results revealed that pre-wetting methods significantly impact carbonation degree, while the alkali solutions had moderate influence. Notably, the pre-wetting procedure aided in decalcifying other hydrates apart from portlandite, leading to compositional variations within the cRCP. Nevertheless, these variations did not significantly affect the cRCP's reactivity in LC3. [ABSTRACT FROM AUTHOR]