Advances in Civil Engineering

Review Article

Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Table 3

Strength characteristics of FA geopolymers at high temperature.
ResearchersThokchom et al. [62]Rickard et al. [44]Shaikh and Vimonsatit [63]Rickard et al. [64]Junaid et al. [65]Ze et al. [66]Vickers et al. [51]Timakul et al. [67]Chithambaram et al. [68]Pan et al. [69]Abdulkareem et al. [29]Saavedra and de Gutiérrez [70]Hussin et al. [71]Ranjbar et al. [27]Rashad and Ouda [72]KÜRKLÜ [73]Messina et al. [74]Yang et al. [75]
AdditiveNoneNoneNoneNoneNoneNoneα-Alumina and wollastonite fillersTiO2Ground granulated blast furnace slag (GGBFS)NoneNoneGranulated blast furnace slag (GBFS)Pulverized fuel ash (PFA) and POFAPOFAQuartz powder (QP)Blast furnace slag (BFS)BFS and MKRed mud (RM)
VariableSi/Al ratio in 1.7–2.2Amorphous Si/Al ratio in 1.2–8.8Aggregate sizesPretreatmentDuration of exposure timeSiO2/Al2O3 mole ratioFiller types and amountsTiO2 additive amountAmount of GGBFSOPC/geopolymer paste and concreteFine aggregate and lightweight aggregate (LWA)FA/GBFS and FA/OPC concreteBlended ash geopolymer (BAG) and OPC concreteThe addition of POFAThe addition of QPThe addition of BFSDifferent curing temperatures (CT)Different temperatures
The result of strengthThe residual strength of geopolymers with Si/Al of 2.2 is the highest.The fly ash geopolymers with high Si/Al (>5) has high compressive strength at 1000°C.Small size aggregate can reduce strength loss.Leaching in water and gradually drying prior to heating improve the residual strength.Most of the changes in strength occurred in the first two hours. Then, the duration of exposure has insignificant effect on the strength.The strength of geopolymers with SiO2/Al2O3 ratio of 3.8 is the highest after firing.The addition of inorganic filler exhibits high-level strength after firing, and wollastonite is much better.TiO2 is significant for improving the compressive strength and thermal shock resistance when the content is 5 wt%.30% partial replacement of FA by GGBFS reaches the highest strength irrespective of NaOH concentration.The strength of geopolymer and OPC paste increases by 192% at 500°C. But, a significant loss of strength appears after cooling.The addition of aggregates (fine or fine + LWA) can promote the fire resistance significantly.The residual strength of FA/GBFS and FA/OPC concrete at 1100°C is 15 MPa and 5.5 MPa.The strength of BAG concrete increases with the temperature and reaches its peak at 600°C, while OPC concrete only reaches at 200°C.All FA/POFA samples can obtain strength when exposed up to 500°C. The increasing content of POFA delays the temperature of peak strength.With the increase of QP content, the compressive strength before and after firing increases.The compressive strength of the mortars increases with the increase in amount of BFS, while the flexural strength decreases with that of FA.BFS and MK can increase the reactivity at early age and improve mechanical performances without higher CT.It keeps good retention under 600°C, while the strength drops quickly above 600°C.
Residual strengthFor the Si/Al ratio of 1.7 and 2.2, respectively, it is about 90% and 79% at 600°C and 62% and 52% at 900°C.For the amorphous Si/Al ratio of 1.2 and 8.8, respectively, it is about 18% and 400% at 1000°C.It is about 100% at 600°C and 97% at 800°C for the aggregate size of 10 mm, while it is about 87% at 600°C and 84% at 800°C for 20 mm.It is about 90%, 185%, and 279% at 600°C, 800°C, and 1000°C, respectively.It is about 53% and 58% at 600°C and 900°C, respectively.It is about 290% at 800°C and 260% at 1000°C for the geopolymers with SiO2/Al2O3 ratio of 3.8.It is about 52%, 72%, and 247% at 600°C, 800°C, and 1000°C, respectively.It is about 50% and 37% for composites with 5% and 0 content of TiO2 after 15 thermal cycles (800°C).It is about 53% at 600°C and 45% at 800°C, respectively.It is about 40% and 36% for geopolymer and OPC concretes, respectively, at 550°C.It is about 61.4% and 73.3% at 600°C and 47.7% and 61.0% at 800°C for mortar and concrete with LWA, respectively.It is about 41% and 25% at 900°C and 33% and 24% at 1100°C for FA/GBFS and FA/OPC concrete, respectively.It is about 120% and 67% at 600°C and 84% and 45% at 800°C for BAG and OPC concrete, respectively.It is about 53% and 22% at 600°C and 800°C, respectively, for the POFA/FA ratio of 25 : 75.It is about 163%, 185%, and 233% at 600°C, 800°C, and 1000°C, respectively, for the inclusion of 30% QP.It is about 77.5%, 44.7%, and 41.9% at 600°C, 800°C, and 1000°C, respectively, for the compressive strength of 100% BFS content.After exposure to 800°C, it is about 75% (MK/FA) and 66% (BFS/FA) for 20°C CT, 76% (MK/FA) and 64% (BFS/FA) for 40°C CT, and 61% (MK/FA) and 73% (BFS/FA) for 60°C CT.It is about 82% at 600°C and 27% at 800°C.