Thermal evolution of hydrates in carbonation-cured Portland cement

Abstract

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 29 Si and Al-27 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 thermo-gravimetric 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 degrees C, similar to hydrated cement. Moreover, carbonation-cured cement underwent crystallization pathway identical to that of hydrated cement, displaying a hydrate-like thermal behavior.