Life cycle assessment (LCA) of alkali-activated cements and concretes

Cleaner production of the lightweight insulating composites: Microstructure, pore network and thermal conductivity

“…Focusing the production of the insulating materials; substitution of raw materials and auxiliary materials (especially renewable materials and energy); increase in lifespan of auxiliary materials; re-use of waste or waste recycling [10], new, low waste processes and technologies are the main parameters to be considered according to Andrew [11]. The SiO 2 :Al 2 O 3 ratio is the most important factor controlling Global Warming Potential for both metakaolin and bentonite meta-clay geopolymers(GWP).…”

“…The lowest GWP can be achieved for mixes with SiO 2 :Al 2 O 3 ratios in the range of 3.5-4.0:1, which corresponds to ratios which provide highest strength. The hypothesis that it is possible to provide significant reductions in the GWP of clay-based geopolymers without affecting their chemical composition and therefore mechanical performance has been conclusively Page 4 of 20 A c c e p t e d M a n u s c r i p t 4 proven [10]. The use of multiple precursors, activators and curing temperatures for geopolymer manufacture can lead to complex mix design, but has the potential to reduce the GWP to a level well below that of "just add water" Portland cement [10][11][12][13][14][15].…”

Recent update on the environmental impact of geopolymers

“…Furthermore, we need to calculate appropriate values for K, which is related with the quality of the aggregate and can be calculated with a cement based concrete using similar aggregates as the alternative concrete but without having necessarily the same compressive strength. This concrete mix is just used to calibrate the K value [44].…”

“…Geopolymer concrete have been compared with ordinary Portland cement (OPC) concrete considering the same paste volume in the previous papers of Habert et al [22,44]. Other papers on environmental impact of AAC compares concrete with similar strength but that do not always have the same amount of aggregates, which induce a bias in the results.…”

“…The main underlying concept is that the clinker used in these binders provides a first and fast reaction that allows early strength but also provides heat to help the activation of fly ash and to hasten the polymerization reaction. To assess the environmental impact of these binders, we used the mixes detailed in [48] and the adapted equation from de Larrard for cement paste calculation further detailed in [44] The GWP of the studied hybrid cement is 70% lower than of an OPC binder. This result is in the same range as the current AAC.…”