Thermoactivated cementitious materials – A review

Influence of the Treatment Temperature on the Microstructure and Hydration Behavior of Thermoactivated Recycled Cement

“…The thermal activation of the waste cement was carried out in a rotary tube furnace from Thermolab Scientific Equipments, by heating at 10 °C/min up to the treatment temperature. The tested temperatures were 400, 450, 500, 600, 650, 700, 750, 800 and 900 °C, covering a range from the beginning of calcium hydroxide (CH) phase dehydration to the end of cement decarbonation (at which point the eco-efficiency and rehydration activity of RC is expected to decrease [ 1 , 11 , 12 ]). The residence time at the treatment temperature was always 3 h, followed by cooling inside the oven until room temperature was reached.…”

“…Over the past decades, concern regarding the sustainable development of the construction industry has led to the search for new more eco-efficient solutions, addressing some of the main environmental issues introduced by concrete production [ 1 ]. These include natural resources depletion, energy consumption, greenhouse gas emissions, as well as the worldwide production of high volume of construction and demolition waste [ 1 , 2 ]. The significant economic and environmental impact therefore legitimates concrete recycling and materials circular economy as a priority in the construction industry.…”

“…Recently, efforts have been made towards the recovery of the cementitious part of waste concrete through thermal activation. in order to explore the rehydration ability of thermoactivated recycled cement (RC) [ 1 , 4 ]. Some authors simply concentrated on a single treatment temperature [ 5 , 6 ] and others approached only a few properties, namely the fresh behavior and the mechanical strength [ 4 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ].…”

“…Other studies were dedicated to the incorporation of varying percentages of RC in mortars and concrete [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Furthermore, results reported in the literature are contradictory, reflecting the lack of knowledge of these poorly explored new binders [ 1 ].…”

“…Regarding the microstructure development, only some qualitative analysis, essentially based on scanning electron microscopy analysis (SEM), have been carried out for a limited range of treatment temperatures [ 4 , 5 ]. A more detailed review of the current state-of-the-art in recycled cements is presented in Carriço et al [ 1 ].…”