Abstract
This work aims to investigate the feasibility that alkali-based geopolymer foams produced from metakaolin and Na2O2 are applied for fire protection. Dry bulk density, porosity, mechanical strength, thermal conductivity, and fire resistance of the geopolymer foams are discussed as a function of the Na2O2 amounts. As Na2O2 content varies from 1% to 4%, dry bulk density, mechanical strength and thermal conductivity of the geopolymer foams approximately exhibit opposite trends with that of the porosity. At the later stage of the 3 h fire-resistance tests, the reverse-side temperatures of all tested samples were always maintained at 220–250 °C. Meanwhile, the amorphous skeleton structures have been converted to smooth ceramics during the high temperature processes, which is the main reason that the geopolymer foams possess a stable porous structure and excellent fire resistance. Therefore, we could conclude that alkali-activated geopolymer foams with extraordinary fire resistance have great potential for fire protection applications.
Highlights
High-strength concrete used in building constructions is unstable when exposed to fire, due to either explosive spalling or overheating of steel reinforcement bars within the lining [1,2]
Massive materials have been explored for building construction protection against high temperature attack, mainly including organic intumescent coatings and cementitious-based coatings [4]
1% to 4%, dry bulk density of the geopolymer foams decreases gently along with the increase in porosity. Both compressive strength and flexural strength are in correlation with the dry bulk density and porosity
Summary
High-strength concrete used in building constructions is unstable when exposed to fire, due to either explosive spalling or overheating of steel reinforcement bars within the lining [1,2]. Massive materials have been explored for building construction protection against high temperature attack, mainly including organic intumescent coatings and cementitious-based coatings [4]. Organic intumescent coatings are light, aesthetic, and smooth, they cannot provide sufficient protection over a long time in a fire, and may even join in the combustion reaction and produce toxic gases in narrow and long corridors and tunnels at high temperature [3,5]. Cementitious-based coatings are durable, wear-resistant, inexpensive, adhere to concrete, and could provide protection from moisture and high temperature attack [6,7,8]. Intumescent cementitious-based coatings have limitations, such as low mechanical properties and poor spalling resistance that cannot satisfy the requirements of fire protection of building constructions, while the non-intumescent cementitious-based coatings can provide adequate fire protection if they are thick enough [9,10,11,12].
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