Abstract
Geopolymer as an alternative to cement has gained increasing attention. The aim of this article is to study the influence of the silica fume content and activator type on the porous fly ash-based geopolymer with silica fume as foaming agent. Geopolymeric foams were fabricated using low-calcium fly ash, silica fume, and sodium-based alkaline activator as initial materials. The designed silica fume contents were 0, 15, 30, and 45 wt % and two kinds of activators of water glass and sodium hydroxide were used for comparison. Phase composition, microstructure, mechanical properties and sound insulation properties of as-prepared bulks were systematically investigated. It was found that, with increasing silica fume content, the density and compressive strength decreased simultaneously, whereas the porosity and sound insulation performance were effectively enhanced. At the silica fume content of 45% with sodium hydroxide as activator, the porosity was increased 3.02 times, and, at the silica fume content of 45% with water glass as activator, the mean sound insulation value of 43.74 dB was obtained.
Highlights
Geopolymers have been gained increasing attention since the 1990s owing to their light weight and low energy consumption
The diffraction peaks of aluminosilicate gel phase are shifted to the right relative to the amorphous phases of silica fume (SF) and fly ash (FA), implying that “depolymerization-rearrangement” process occurred during the chemical treatment [20,21]
The microstructure, compressive strength, and sound insulation performance of fly ash-based geopolymers were systematically investigated with SF content and activator type as variables
Summary
Geopolymers have been gained increasing attention since the 1990s owing to their light weight and low energy consumption. The specific reactions are not the same for different alkaline activators and raw materials, the backbone reactions are similar. The basic structure in the alkali-activated system is a highly crosslinked and disordered aluminosilicate gel. Both Si and Al exist in tetrahedral coordination, and the tetrahedral charge balance is achieved by the association of the alkali metal cation with the gel skeleton [1]. It has been reported that the lightweight geopolymers possess excellent properties of low shrinkage [2], high sound absorption, high thermal insulation [3,4,5], and high resistance to acids [6]
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