<p>In this study, reaction products and reactivity of carbonation-cured limestone-calcined clay cement (LC³) were investigated. The LC³ pastes were prepared by introducing Portland cement, metakaolin, and limestone. The LC³ samples with various water-to-binder ratios were normally or carbonation-cured for 28&#xa0;days. The mechanical properties and microstructural changes over time were evaluated by analyzing the flexural strength, compressive strength, thermogravimetry, X-ray diffraction, and ²⁹Si nuclear magnetic resonance results. The test results revealed that the carbonation-cured LC³ samples commonly experienced a rapid rate of carbonation ingress and low mechanical strength compared to the samples composed solely of Portland cement. The use of LC³ with a high water-to-binder ratio increased the CO₂ uptake level in the sample. In addition, the reaction degrees of the Portland cement clinkers and metakaolin in the LC³ samples were significantly enhanced upon carbonation curing.</p>