Abstract
Because of the environmental impacts generated by civil construction, many researchers have studied the wastes of construction and demolition. It is possible to find in the scientific literature works focused on hardened cement paste. In this study, hydrated Portland cement paste (PCH) prepared from Portland cement CP V-ARI (CP-V) was dehydrated through heat treatments at 700 °C (700-PCD) and 900 °C (900-PCD) and then rehydrated. The structure and microstructure during hydration, dehydration and rehydration were investigated. For characterization of the morphological changes, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy were used. Thermogravimetric analysis was used to study the stages of dehydration of the original hydrated cement paste. The study of dehydration of PCH showed that at 700 and 900 °C new nesosilicates and CaO were clearly present in the samples. During the rehydration of the samples 700-PCD and 900-PCD partial rehydration and carbonation occurred. Specimens from CP-V and 0%, 2%, 10%, 40% and 60% of dehydrated cement powder (PCD) were prepared. Specimens prepared with up to 40% of PCD showed similar properties when compared to the pure cement paste prepared from CP-V, while additions of 60% PCD resulted in a decrease of the compressive strength.
Keywords:
cement paste; dehydrated cement paste; rehydration; compressive strength; porosity
