Thermal evolution of hydrates in carbonation-cured Portland cement

The present study investigates the thermal evolution of hydrates in carbonation-cured Portland cement. Paste samples were placed in a carbonation chamber after the 24 h of initial curing, while reference samples were cured in a sealed condition until 28 days. Thermogravimetry, unconfined strength tests, X-ray diffractometry, and solid-state ²⁹Si and ²⁷Al MAS NMR spectroscopy were conducted. The results showed that the binder gel in carbonation-cured cement shares some structural similarities with aluminosilicate glass in terms of Si and Al analogues. This characteristic was also reflected by its thermogravimetric behavior, presenting much less weight loss associated with dehydration in comparison with hydrated cement. However, the binder gel in carbonation-cured cement underwent depolymerization into monomeric Si at 800 °C, similar to hydrated cement. Moreover, carbonation-cured cement underwent crystallization pathway identical to that of hydrated cement, displaying a hydrate-like thermal behavior.