An investigation of the mechanisms for strength gain or loss of geopolymer mortar after exposure to elevated temperature

Abstract

Abstract:When fly ash based geopolymer mortars were exposed to a temperature of 800 o C, it was found that the strength after the exposure sometimes decreased, but at other times increased. This paper shows that ductility of the mortars has a major correlation to this strength gain/loss behaviour. Specimens prepared with two different fly ashes, with strengths ranging from 5 to 60 MPa, were investigated. Results indicate that the strength losses decrease with increasing ductility, with even strength gains at high levels of ductility. This correlation is attributed to the fact that mortars with high ductility have high capacity to accommodate thermal incompatibilities. It is believed that the two opposing processes occur in mortars: (1) further geopolymerisation and/or sintering at elevated temperatures leading to strength gain; (2) the damage to the mortar because of thermal incompatibility arising from non-uniform temperature distribution. The strength gain or loss occurs depending on the dominant process.

Relationship between compressive strength and UPV of GGBFS based geopolymer mortars exposed to elevated temperatures

“…The reaction via a polymerization mechanism forms a solid cementitious material that has an amorphous 3D tetrahedral structure similar to glass [4]. At its simplistic stage, the mechanism behind geopolymers can be described http as a reaction in two or three parts [5][6][7]. Firstly, a dissolution of the aluminum and silicate elements of the aluminosilicate material reaction in high alkalinity solution resulting in the release of AlO 4 and SiO 3 ions, and secondly a mixture of aluminum, silicate, and aluminosilicate species, which, through a simultaneous process of polycondensation-gelation-further condensation, eventually creates an amorphous gel [5].…”

Estimation and Minimization of Embodied Carbon of Buildings: A Review

“…Geopolymer concrete is formed by a reaction of silicon and aluminium in byproduct materials such as fly ash, ground granulated blast furnace slag and rice husk ash with an alkaline liquid, which leads to the formation of a cement-like binder [48][49][50]. Numerous studies have been conducted to investigate the mechanical properties and durability of geopolymer concrete to explore its suitability as a replacement for Portland cement concrete and to assess its competitive performance in terms of compressive strength, tensile strength and modulus of elasticity as well as shrinkage, creep, corrosion resistance, sulphate resistance, fire resistance and acid resistance [47,[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66].…”

Fire Related Temperature Resistance of Fly Ash Based Geopolymer Mortar

“…Heat resistant properties of metakaoline based GPs were investigated and its thermal stability upto 1200-1400°C was reported. Heat resistant properties of alkali activated fly ash were investigated by several workers [10][11][12][13][14][15] and geopolymeric paste indicated high shrinkage as well as large changes in compressive strength at elevated temperature in the range 800-1200°C. To improve thermal resistance, alternate GSMs such as mine tailings, waste ceramics were tried and satisfactory thermo stable geopolymeric paste was obtained [16][17].…”