Study on the Disposition of Water in Fly Ash-Based Geopolymers Using ATR–IR

Abstract

This paper addresses the question of whether the main product of low calcium fly ash-based geopolymer is a hydrate, namely, sodium aluminosilicate hydrate (N-A-S-H). The answer to this question is important for understanding geopolymer characteristics. One of these is its fire resistance. In this study, fly ash-based geopolymers were synthesized using the combination of Na 2 CO 3 and Ca(OH) 2 . Samples were cured at ambient temperature for 7 days, then placed in the oven at 105°C for 24 h, and then calcined at 1050°C for 48 h. IR was used to examine the produced geopolymers at each stage so as to further knowledge on the following issues: the possibility of co-existence of calcium aluminosilicate hydrate (C-A-S-H) and N-A-S-H, the roles of cations as compensator and network modifier as well as the role of water. The results obtained suggest that the primary geopolymerization products, which are potentially good fire-resistant, are unlikely to contain hydrates. Even if there were hydrates, their amount must be very small such that the escaping of water does not compromise the structure's integrity.

Siliceous fly ash and blast furnace slag based geopolymer concrete under ambient temperature curing condition

“…He demonstrates that calcium or sodium hydrates are soluble in water and will not form any polymer to bind the materials in the system. Prof Davidovits observation finds an agreement with Liu et al 25 They reported that the produced geopolymer is not primarily comprise of C‐S‐H or N‐A‐S‐H or C‐A‐S‐H as the backbone of geopolymer chemistry. Although higher amount of CaO in the base material like GGBFS can leads to the development of C‐A‐S‐H and C‐S‐H gel 26 but they will coexist with geopolymer in the system 27 .…”

Investigations on the coefficient of thermal expansion of a low‐calcium fly ash‐based geopolymer concrete

“…In the study by Davidovits, it is even pointed out that a geopolymer is not a hydrate. Liu and Fang found that there is no or very little chemical water in N‐A‐S‐H. These results can indicate that the water consumption during the geopolymerization is much lower than in the hydration of Portland cement.…”