## 1 Introduction  
Geopolymers are known as a new generation of materials. These materials consist of aluminosilicate powder, which is activated using the alkali solution. Commonly, a by-product of coal combustion (fly ash) or calcinated kaolinite clay (metakaolin) is used as raw materials. The combination of these materials results in the geopolymeric gel binder phase [1]. [PERSON] [2] mentioned that geopolymers act similar to zeolites and feldsparoids, which adsorbs toxic chemical waste. The geopolymer matrix helps deactivated hazardous elemental waste and turns it into an adhesive solid. According to the reaction to high-temperature exposure, many researchers have learned this behavior and stated that the alkali-activated aluminosilicate materials have better fire-resistance than the Portland cement mortar. [PERSON] [3] reported that geopolymer materials are mineral materials and act similar to thermsetting organic resins, having thermal stability up to 1200 and 1400 \({}^{\circ}\)C. Previous investigations showed geopolymer mortar with metakaolin and fly-ash as raw materials that have a better performance in high temperatures than the Portland cement mortar or the commercial mortar, especially in compressive and bond strength [4]. The concern of expanding sustainable insulation material is increasing. One alternative is foamed geopolymer [5]. [PERSON] [6] mentioned that a low thermal conductivity is needed when using the geopolymer as an insulation product because it was designed to reduce the protected materials' heat conduction. Decreasing the density of geopolymer results in lower thermal conductivity [7]. The foamed geopolymer is an adequate alternative protection to fire corresponding to their properties, non-inflammatory materials and have a low thermal conductivity [8]. The type of foaming agent and its amount significantly affect the lightweight geopolymer's thermal properties. [PERSON] et al. [9] reported that the thermal conductivity of porous fly ash-based geopolymer materials (as low as 0.0564 W/mK) through a physical foaming and non-sintering method. [PERSON] et al. [10] pointed out that a lightweight mortar with identical properties similar to commercial cement-based ones used as fire protection occurred when the expanded perlite and H\({}_{2}\)O\({}_{2}\) were used to produce a lightweight mortar. A combination of surfactant and foam reported by [PERSON] et al. [11] produced a smaller and narrower pore size distribution. Furthermore, he explained that geopolymer foam could be classified as Class II structural and insulating materials. Fiber materials were used to increase the mechanical properties of materials, especially in foamed material. As the density in foamed material decreases, its effect on their mechanical properties such as tensile strength, compressive strength, spalling or cracking increases. [PERSON] and [PERSON] [12] investigated the PP fibers effect on the mechanical properties of geopolymer composite. The PP fiber was mixed into the admixture in 0%, 0.5%, and 1.0% by volume. Their result showed an enhancement in compressive strength of geopolymer in the addition of PP fiber. [PERSON], [PERSON], and [PERSON] [13] reported the thermal and mechanical properties of cement mortars with a varied amount of PP fibers after being heated to elevated temperatures of 150 \({}^{\circ}\)C, 200 \({}^{\circ}\)C, 450 \({}^{\circ}\)C, and 600 \({}^{\circ}\)C. The residual compressive strength of cement mortar was increased with the presence of PP. They also showed that the thermal conductivity decreased as the temperature increased. However, the thermal conductivity of the reinforcement mortar was higher than the plain mortar when the temperature reached 200 \({}^{\circ}\)C. [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [14] reported that in the range of 0.20%, 0.25% and 0.30% amount of PP fibers in lightweight concrete, the highest compressive strength occurred when the foamed concrete contained 0.20% of PP fibers.