Aglomerante obtido à base de pastas de cimento tratadas termomecanicamente

Abstract

One of the major challenges facing the construction industry is to reduce greenhouse gas emissions and make it more sustainable. The search for innovations in cement production and the use of supplementary cementitious materials (SMCs) are measures that can help address climate change. Studies have been carried out on construction and demolition waste (CDW) and also on hardened cement paste. The objective of this study is to obtain an alternative binder obtained from pastes made with Portland cement CPV, water/cement ratio of 0.5 and hydrated for 28 days in a humid chamber. After curing, this material was subjected to crushing, grinding and heat treatment processes for 2 hours at 500ºC, 600ºC and 700ºC, followed by rapid cooling and slow cooling, obtaining the alternative binder. The binders were characterized according to their chemical, mineralogical and granulometric composition and mechanical performance. The results indicated that the heat treatment at 700°C for 2 hours, followed by rapid cooling, was the one that obtained the best performing binder. This binder was defined as recycled cement and was chosen to evaluate the properties in the fresh and hardened state of cementitious compounds with saturated cure or with autoclave cure. For this, mortars with a ratio of 1:0.25:3 (binder: ground sand: sand) were molded. The binder was formed by 0%, 25%, 50%, 75% and 100% replacement of CPV cement by recycled cement. Since recycled cement demands more water, two water/cement factors were used, one of 0.5 for the lowest substitution contents (0%, 25%, 50%) and another with 0.7 for the highest substitution contents (50%, 75% and 100%). The mortars were subjected to flow table tests, immersion absorption and porosity, morphological analysis, compressive strength, microstructure analysis and electrical resistivity. The results indicated good performance in the mortars with 50% replacement of recycled cement (w/c 0.5) when subjected to saturated curing. The porosity and immersion absorption were higher for autoclave curing, which indicates a reduction in mechanical performance for all conditions studied. Electrical resistivity was reduced when higher levels of recycled cement were added to the mortars. The results indicate the possibility of rehydration of the alternative binder used in the study and that saturated curing was more positive than autoclave curing.