Compressive Strength Recovery Research Articles

Performance of crumb rubber concrete made with high contents of heat pre-treated rubber and magnetized water

For many years, several research has been conducted to investigate the use of tyre rubber waste as a substitute for concrete fine and coarse aggregates to decrease its unfavourable impacts on the environment. This resulted in producing crumb rubber concrete (CRC) with limited compressive strength. CRC strength enhancement approaches were introduced mostly through pre-treating the rubber aggregate using chemicals before using in concrete with impractical methodologies and contradictory findings. In the current research, the performance of CRC containing high contents of heat pre-treated rubber and magnetized water (MW), prepared in magnetic field strength of 1.4 T, was investigated. Rubber content, heating temperature, heating time, MW content, and water magnetizing time were the variables in this experimental investigation. Measurements of the concrete workability, mechanical properties, impact resistance, and microstructure analyses were conducted in this study. Water characterization before and after magnetization was also carried out. Promising performance was shown by CRC contained heat pre-treated rubber at 200 °C for 2 h and 100% MW treated for 24 h. These conditions resulted in compressive strength recovery of 74% and impact resistance enhancements of 2.2 times at first crack and 92% at ultimate failure when using rubber content of 40%. The microstructural analyses showed that rubber heat pre-treatment burnt out most of the unwanted materials in rubber aggregate, created an outer hard shell on the rubber particles, and decreased the zinc presence in rubber from 8.32% to 1.89%, which all resulted in CRC compressive strength and impact resistance enhancements.

Multiple Self-Healing Effects of Water-Absorbing Microcapsules in Cementitious Materials.

Concrete cracking has a negative impact on the durability of the structure. Pre-implanting microcapsules containing healing agents into the concrete are expected to induce the cracks to self-heal. However, the self-healing effect can potentially be influenced by several environmental conditions, thus limiting its applications. To address these challenges, we developed a new type of water-absorbing microcapsules, using calcium alginate hydrogel as the wall material and an adhesive epoxy polymer as the core material, to improve the self-healing adaptability in complex and changing environments. We explored the healing properties and mechanism of cementitious materials containing microcapsules under various environmental conditions. The experimental results showed that the water-absorbent microcapsules exhibit multiple self-healing effects under different external conditions: (1) in an anhydrous environment, fissures prompted the activation of microcapsules, and the epoxy polymer flowed out to seal the cracks. (2) When exposed to water, the microcapsules inflated to form a seal around the fissures. (3) The microcapsules facilitated the autogenous healing of cracks in the cementitious material when wet and dry conditions were alternated. The three self-healing mechanisms worked synergistically and contributed to the effective restoration of the impermeability and strength of concrete under different environments. Particularly, the recovery of compressive strength and impermeability exceeded 100% when the microcapsule content was 4% and the pre-pressure was 40% of fmax.

Inspecting the healing process in an artificial stone used for repair works containing crystallines

Stone has been a basic building material of different monuments and structural components such as foundations and masonry. At the same time, dif-ferent types of stones have been used for decorative architectural elements, such as cornices, reliefs, colonnettes, and corbels. The maintenance of stone ele-ments is essential for the continuity of these structures. Many studies have been performed to produce stones with artificial materials. This study aims to present a new approach to artificial stone with self-healing capability. Crystallines have been implied in two different dosages: 0.8 and 1.6% w./w, to achieve this goal. The addition of the crystalline admixtures affected the physical properties, de-creasing the porosity and the capillary absorption, proving the sealing properties of the admixtures. The self-healing efficiency has been tested with the sorption test, recovery of compressive strength, and 3D acoustic microscopy. The crys-talline admixtures accelerate the self-healing, increasing the sealing efficiency by 20% and recovering compressive strength by 15%. The analysis by 3D to-mography provided results that confirm the healing of the crack hasn't occurred only on the surface but extended to a certain depth.

Self-Healing Bio-Concrete Using Bacillus subtilis Encapsulated in Iron Oxide Nanoparticles.

For the creation of healable cement concrete matrix, microbial self-healing solutions are significantly more creative and potentially successful. The current study investigates whether gram-positive "Bacillus subtilis" (B. subtilis) microorganisms can effectively repair structural and non-structural cracks caused at the nano- and microscale. By creating an effective immobilization strategy in a coherent manner, the primary challenge regarding the viability of such microbes in a concrete mixture atmosphere has been successfully fulfilled. The iron oxide nanoparticles were synthesized. The examined immobilizing medium was the iron oxide nanoparticles, confirmed using different techniques (XRD, SEM, EDX, TGA, and FTIR). By measuring the average compressive strength of the samples (ASTM C109) and evaluating healing, the impact of triggered B. subtilis bacteria immobilized on iron oxide nanoparticles was examined. The compressive strength recovery of cracked samples following a therapeutic interval of 28 days served as a mechanical indicator of the healing process. In order to accurately correlate the recovery performance as a measure of crack healing duration, the pre-cracking load was set at 80% of the ultimate compressive stress, or "f c," and the period of crack healing was maintained at 28 days. According to the findings, B. subtilis bacteria greatly enhanced the compressive strength and speed up the healing process in cracked cement concrete mixture. The iron oxide nanoparticles were proven to be the best immobilizer for keeping B. subtilis germs alive until the formation of fractures. The bacterial activity-driven calcite deposition in the generated nano-/micro-cracks was supported by micrographic and chemical investigations (XRD, FTIR, SEM, and EDX).

Digital image processing for precise evaluation of concrete crack repair using bio-inspired strategies

• Bacillus pumilus was analyzed in retrofitting of mortar for the very first time. • Digital image processing is employed in monitoring crack healing. • Bio-Consortia significantly reduced the permeability of repaired mortar specimens. • Microbial repair is the potential and sustainable alternative to conventional repairs. Inadequacy of surface coatings and deleterious action to the environment by epoxy-based solution for surface treatment have received the attention for more sustainable techniques of concrete repair. This paper investigated the adequacy of Microbially induced calcite precipitate for mortar crack repair by using a non-ureolytic (avoid the production of ammonia), alkaliphilic bacterial strain with calcium source. The biological metabolic activity of Bacillus pumilus with Calcium lactate was used for crack repair. As Bacillus pumilus was first time reported for concrete repair, germination and growth characteristics were evaluated in the control microbiology laboratory before application to repair. The healing potency by bacterially mediated calcium carbonate was precisely investigated by Digital image processing using the OTSU method of thresholding. Crack healing of 99 – 100 % was achieved by biological repair for mortar samples having average crack width varying from 0.29 to 1.55 mm. The efficacy of crack repair by both bacterial repair and conventional treatments were evaluated through water permeability, water tightness, ultra-sonic measurement, and compressive strength recovery. The samples treated with bacterial treatments exhibited enhanced permeability and water tightness comparable to any other conventional treatments. The bacterial repaired mortar samples showed enhanced values of ultra-sonic measurement and recovered compressive strength equivalent to conventional repair. The enhanced durability of bacterially repaired mortar samples is due to the presence of dense precipitated CaCO 3 by the metabolic activity of bacteria. Further, forensic evaluation confirmed the formation of CaCO 3 in bio-precipitate as a result of metabolic activity triggered by inoculated bacterial consortia.

The role of crystalline admixtures in the long-term healing process of fiber-reinforced cementitious composites (FRCC)

Crystalline admixtures (CΑs), categorized as permeability-reducing admixtures according to ACI-212, are additives serving in the construction industry for decades and have recently been used as self-healing promoters. Although substantive research has been done on concretes' durability properties and healing efficiency at the macroscopic level, limited information was available regarding its microstructural features and chemical properties. Therefore, this paper aimed to analyze fiber-reinforced cementitious composites (FRCC) with polypropylene fibers (PP) in the long-term healing process. Initially, an analysis of the CAs raw materials was carried out. Then, the concrete compositions' physicomechanical properties were tested. For the healing analysis, specimens were pre-cracked after 28-days with an estimated crack width between 50 and 500 μm. The specimens were cured in three healing conditions: seawater immersion at 20 °C, immersed in tap water at 20 °C, and wet/dry cycles. The healing rate was evaluated based on the crack closure, recovery of compressive strength, and sealing efficiency through water absorption. An almost perfect surface healing was observed for specimens immersed in seawater and tap water. At the same time, the wet/dry condition proved to be insufficient for both CAs types. The analysis of the healing material highlighted significant differences in the agent's structure at the surface and inside the crack. Also, the influence of other compounds, such as Mg, during the hydration of C3S to the healing agents has been analyzed, indicating M-S-H compounds, magnesium calcite, and brucite according to SEM and XRD analysis.

Coupled effect of self-healing granules and permeable crystalline additive on early-age cracks repair in cement material

Cement-based materials are prone to cracks that affect their strength and durability. The service life of these materials can be extended through development of self-healing cement-based materials. This study independently designed and produced self-healing granules and explored the synergistic effects of using self-healing granules and permeable crystalline additive. The self-healing efficiency is evaluated via crack closure and the compressive strength recovery rate. The porosity and crack healing products were analyzed to discuss the self-healing mechanisms, revealing that the reaction of the granule inner core with cement precipitates can heal the cracks up to approximately 1 mm after the self-healing granules are ruptured, and permeable crystalline additives can greatly increase the compressive strength recovery rate by closing the microcracks/pores. Self-healing granules and permeable crystalline additives allow for the repair of microcracks and visible cracks in specimens, realizing self-healing at the macro- and micro-scale. These results provide promising self-healing cement-based materials and a novel research direction.

Utilization of sandstone waste in cement mortar for sustainable production of building materials through biomineralization

Sandstone waste generated during stone cutting and processing is a major environmental problem. In this study, different ratios of sandstone powder was utilized as a cement replacement and the mortar specimens were treated with bacteria to enhance the durability properties. With replacement ratio of sandstone powder (10% to 40%), strength loss was observed in all the sandstone-modified mortars. Due to bacterial treatment in CSB10, CSB20, CSB30 and CSB40 specimens, compressive strength was increased by 11%, 12.8%, 17% and 6%, respectively compared to their respective controls. Water absorption rate was significantly reduced and lower sorptivity coefficient was recorded in bacterial treated specimens. In bacterial treated CSB30 specimens, compressive strength recovery (17%) and reduced sorptivity coefficient (0.002) were observed. Present study results suggest that microbial treatment of sandstone modified mortar with a 30% replacement ratio of cement is a possible solution for utilizing stone waste in the construction industry.

Recovery Behavior of the Macro-Cracks in Elevated Temperature-Damaged Concrete after Post-Fire Curing.

Studying the recovery of fire-damaged concrete is of huge economic and environmental significance. The recovery of thermal-induced cracks of fire-damaged concrete leads to the recovery of strength after post-fire curing. To identify the crack recovery behavior of fire-damaged concrete after post-fire curing and its relationship with the recovery of strength, in this study, concrete samples exposed to 400, 600, and 800 °C were treated with the post-fire curing process. The compressive strength recovery was investigated, as well as the crack recovery in terms of the crack length. Moreover, the recovery of the cracks was studied and divided into the categories of mortar cracks and mortar-aggregate interfacial cracks. The results indicate that, after being exposed to high temperatures, the interfacial crack was the main type of crack, and it could clearly be recovered by post-fire curing. The recovery of compressive strength mainly resulted from the recovery of interfacial cracks. The findings of this study can provide practical guidance for the application of post-fire curing to the recovery of fire-damaged concrete structures.

Engineering a semi-interpenetrating constructed xylan-based hydrogel with superior compressive strength, resilience, and creep recovery abilities

Recent advances in the area of hydrogel synthesis have been directed to enhance the mechanical properties and biocompatibility, which are critical in their use as functional biomaterials. In this work, a green and facile method is introduced to produce a hydrogel based on xylan, a plant-based heteropolysaccharide, that is shown to successfully form hydrogen-bonded, semi-interpenetrating polymer networks with polyvinyl alcohol. Upon crosslinking with sodium trimetaphosphate, the obtained hydrogels achieved an exceptional compressive strength (up to 84.2 MPa at a fracture strain of 90 %), which surpasses any polysaccharide-based hydrogels reported so far. The hydrogels were further shown to have high degradation temperature (350–370 °C), to be mechanically resilient with a form and creep recovery of 95 % (78 % stress after 1000 cycles under 30 % strain) and 98 % in height, respectively. All materials used in the preparation of the hydrogels were non-toxic and biocompatible, which makes the synthesized hydrogels suitable potential candidates for soft-tissue engineering and biomedical applications.

Diatomite and Na-X zeolite as carriers for bacteria in self-healing cementitious mortars

The use of bacteria in the self-healing process of cementitious composites has been recently widely considered. In this study, diatomite and the Na-X zeolite were proposed as carrier materials impregnated by the Bacillus subtilis endospores. The effect of the impregnation method on a bacterial survival rate (BSR) and cement composites modification method on the strength parameters, was investigated. Additionally, the influence of modification and healing method on the flexural and compressive strength recovery and surface crack repair ratio, was assessed. Test results indicated higher BSR for a vacuum impregnated than immersed samples (up to 31% after 28 days of storage for the impregnated Na-X zeolite). The BSR in the self-healing mortar may be promoted by local pH reduction in the vicinity of carrier particles, especially diatomite (pHPZC = 4.6). Mortars containing medium dissolved in the mixing water showed an increase in the flexural and compressive strength (up to 10.4% and 18.0%, respectively). The addition of bacteria immobilized on the both carrier materials caused a decrease of strength properties (to 16.6%), while the series containing both bacteria and the medium attained the strength properties similar or better than the reference series and the series with carrier materials alone. Series containing bacteria immobilized on carrier material and with medium showed a self-healing ability, which was confirmed by the compressive strength recovery and surface repair ratio of 32.6% and 92.6%, respectively. The increased precipitation of CaCO3 was confirmed by the SEM and EDS analysis.

Effect of CO32- and Ca2+ on self-healing of cementitious materials due to “build-in” carbonation

In this study, the self-healing efficiency of mortar due to “build-in” carbonation was investigated. Sodium carbonate was selected as the healing agent to be carried by porous ceramsites to carry carbonate ions in the mortar as the healing components (HCs). The coating efficiency of the HCs and its effect on the fresh and hardened properties of the mortar were investigated. To investigate the effect of carbonate and calcium ions on formation of carbonates, the healing efficiency of mortars in the presence of an external calcium source only (P), an external carbonate source only (N), and an internal carbonate source combined with an external calcium source (C), was evaluated based on the mechanical property and pore structure by characterization of water absorption, mercury intrusion porosimetry (MIP) and backscattered electron imaging (BSE) measurements. The results showed that the incorporated HCs triggered “build-in” carbonation to heal the cracks. The mechanical regains and water absorption results demonstrated that the incorporated coated HCs significantly improved the self-healing capability of the pre-cracked mortars. The specimen containing 7.5 wt% of HCs showed the maximum compressive strength recovery rate of 1.35 and the greatest value of rate of water absorption was 64%. The MIP results showed a greatest reduction of pores in 100–1800 nm for the self-healing specimens after curing. The BSE results indicated that the main healing product for specimens with HCs was CaCO3. All the results by different measurements are consistent with each other and the best healing efficiency is seen for C, followed by N and P. The availability of carbonate ions is more critical in formation of calcite than the calcium source, particularly when the carbonate ions were provided internally. The optimum HCs dosage and environment for enhancing the self-healing capability of the mortars were 7.5 wt% and a saturated Ca(OH)2 solution, respectively.

Study on Autolytic Mechanism and Self-Healing Properties of Autolytic Clinker Microsphere in Alkaline Environment.

In this study, the autolytic clinker microsphere with clinker as core and polyvinyl pyrrolidone (PVP) as coating film was prepared. Pretreatment of clinker with silane coupling agent was firstly processed during the preparation. To investigate the autolytic mechanism, the microstructures of the autolytic clinker microsphere at different curing ages were observed using environmental scanning electron microscopy (ESEM), equipped with an energy dispersive spectrometer (EDS). The autolytic stages were also identified based on the microstructural evolution. The influence of pretreatment degree on autolytic behavior was also studied by measurements of micro-morphology and isothermal calorimetry. Experimental results indicated that the compressive strength recovery of specimens was increased by 15–19% due to the addition of autolytic clinker microspheres. The recovery of compressive strength was also improved with the increase of pH value. The improvements in compressive strength recovery of specimens with microspheres were in the range of 15–19%, 15–31%, 25–36%, and 29–50% with the pH value of 7, 8, 10, and 12, respectively. It was also found that inner damage of cement-based matrix had greater recovery when pre-cracked specimens were cured in alkaline environments.

Preparation and Characterization of Electromagnetic-Induced Rupture Microcapsules for Self-Repairing Mortars.

Cement-based materials are susceptible to internal cracks during service, leading to a reduction in their durability. Microcapsules can effectively self-repair cracks in cement-based materials. In this study, novel electromagnetic-induced rupture microcapsules (DWMs) were prepared by using the melt dispersion method with Fe3O4 nano-particles/polyethylene wax as the shell and epoxy resin as the repairing agent. The core fraction, compactness, particle size distribution, morphology, and chemical structure of DWMs were characterized. DWMs were subsequently incorporated into the mortar to measure the pore size distribution, compressive strength recovery, and maximum amplitudes of the pre-damaged mortar after self-repairing. DWMs were also evaluated for their ability to self-repair cracks on mortar surfaces. The results showed that the core fraction, remaining weight (30 days), and mean size of DWMs were 72.5%, 97.6 g, and 220 μm, respectively. SEM showed that the DWMs were regular spherical with a rough surface and could form a good bond with cement matrix. FTIR indicated that the epoxy resin was successfully encapsulated in the Fe3O4 nano-particles/polyethylene wax. After 15 days of self-repairing, the harmful pore ratio, compressive strength recovery, and maximum amplitude of the pre-damaged mortars were 48.97%, 91.9%, and 24.03 mV, respectively. The mortar with an initial crack width of 0.4–0.5 mm was self-repaired within 7 days. This indicated that the incorporation of DWMs can improve the self-repair ability of the mortar. This work is expected to provide new insights to address the mechanism of microcapsule rupture in self-repairing cement-based materials.

Organic acid cross-linked 3D printed cellulose nanocomposite bioscaffolds with controlled porosity, mechanical strength, and biocompatibility

SummaryHerein, we fabricated chemically cross-linked polysaccharide-based three-dimensional (3D) porous scaffolds using an ink composed of nanofibrillated cellulose, carboxymethyl cellulose, and citric acid (CA), featuring strong shear thinning behavior and adequate printability. Scaffolds were produced by combining direct-ink-writing 3D printing, freeze-drying, and dehydrothermal heat-assisted cross-linking techniques. The last step induces a reaction of CA. Degree of cross-linking was controlled by varying the CA concentration (2.5–10.0 wt.%) to tune the structure, swelling, degradation, and surface properties (pores: 100-450 μm, porosity: 86%) of the scaffolds in the dry and hydrated states. Compressive strength, elastic modulus, and shape recovery of the cross-linked scaffolds increased significantly with increasing cross-linker concentration. Cross-linked scaffolds promoted clustered cell adhesion and showed no cytotoxic effects as determined by the viability assay and live/dead staining with human osteoblast cells. The proposed method can be extended to all polysaccharide-based materials to develop cell-friendly scaffolds suitable for tissue engineering applications.

A porous monolith polysaccharide-based adsorbent aerogel with enhanced mechanical performance and efficient adsorption capacity

Recently, the preparation of environmentally friendly adsorbent aerogels with reinforced mechanical performance has attracted much attention. As one of the promising environmentally friendly bio-materials, polysaccharide-based aerogels have a high potential for use in environmental engineering, especially for the absorption of water pollutants. However, the poor mechanical properties have seriously restricted their practical applications hence the development of a polysaccharide-based adsorbent with high mechanical properties is a critical challenge. Herein, we successfully fabricated a new kind of κ-carrageenan/polyacrylamide double network aerogel containing graphene oxide (GO) nanosheets. The aerogel demonstrated excellent compressive strength (25.902 MPa), good toughness, resilience, and shape recovery, simultaneously. This could be mainly explained in terms of synergistic effects of newly formed reversible interactions induced by the formation of interpenetrating network structure, as well as the bridging effect of the GO nanosheets between the networks. Moreover, the adsorption experiments showed that the nanocomposite double network aerogel could effectively remove cationic and anionic dyes (maximum adsorption capacity: methylene blue = 105.18 mg/g, Congo red = 42.95 mg/g). It is hoped that this knowledge can contribute to the development of environmentally friendly adsorbent aerogels with high service life by enhancing their mechanical performances and can expand their applications, especially for the purification of contaminated aqueous media under high hydrostatic and hydrodynamic stresses.

Improving Self-Healing and Shrinkage Reduction of Cementitious Materials Using Water-Absorbing Polymer Microcapsules.

Self-healing cementitious materials are a promising means for ensuring sustainable concrete infrastructure and promoting long-term service lives. To obtain microcapsules that are versatile in varying environments, in this study, absorbing microcapsules with calcium alginate as the shell and epoxy resin as the core were prepared. The absorbing microcapsules exhibit self-healing and can reduce the shrinkage of cementitious materials. Volume changes of the microcapsules in the hardened paste with increasing hydration age were observed using three-dimensional X-ray computed tomography. In the hardened cement paste with a water-cement ratio of 0.29, the absorption of the microcapsules lasted for several days, and the release of water lasted for 28 days. The absorption of microcapsules affected the fluidity of cement paste, and it was significantly weakened and delayed due to the lower absorption rate. The addition of absorbing microcapsules significantly reduced the autogenous and drying shrinkage of mortars. For microcapsules with a core content of 55% added at 3.5% of cement weight, autogenous shrinkage was almost eliminated. Most importantly, the addition of absorbing microcapsules could achieve a certain degree of recovery of compressive strength as well as satisfactory recovery of impermeability in dry and wet environments.

Preparation and Characterization of Nano-CaCO3/Ceresine Wax Composite Shell Microcapsules Containing E-44 Epoxy Resin for Self-Healing of Cement-Based Materials.

As an intelligent material, microcapsules can efficiently self-heal internal microcracks and microdefects formed in cement-based materials during service and improve their durability. In this paper, microcapsules of nano-CaCO3/ceresine wax composite shell encapsulated with E-44 epoxy resin were prepared via the melt condensation method. The core content, compactness, particle size distribution, morphologies, chemical structure and micromechanical properties of microcapsules were characterized. The results showed that the encapsulation ability, mechanical properties and compactness of microcapsules were further improved by adding nano-CaCO3 to ceresine wax. The core content, elastic modulus, hardness and weight loss rate (60 days) of nano-CaCO3/ceresine wax composite shell microcapsules (WM2) were 80.6%, 2.02 GPA, 72.54 MPa and 1.6%, respectively. SEM showed that WM2 was regularly spherical with a rough surface and sufficient space inside the microcapsules to store the healing agent. The incorporation of WM2 to mortar can greatly improve the self-healing ability of mortar after pre-damage. After 14 days of self-healing, the compressive strength recovery rate, proportion of harmful pores and chloride ion diffusion coefficient recovery rate increased to 90.1%, 45.54% and 79.8%, respectively. In addition, WM2 also has good self-healing ability for mortar surface cracks, and cracks with initial width of less than 0.35 mm on the mortar surface can completely self-heal within 3 days.

Influencing Factors on the Healing Performance of Microcapsule Self-Healing Concrete.

The amounts of the components in a microcapsule self-healing system significantly impact the basic performance and self-healing performance of concrete. In this paper, an orthogonal experimental design is used to investigate the healing performance of microcapsule self-healing concrete under different pre-damage loads. The strength recovery performance and sound speed recovery performance under extensive damage are analyzed. The optimum factor combination of the microcapsule self-healing concrete is obtained. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are carried out on the concrete samples before and after healing to determine the healing mechanism. The results show that the healing effect of self-healing concrete decreases with an increase in the pre-damage load, and the sound speed recovery rate increases with an increase in the damage degree. The influence of the sodium silicate content on the compressive strength and compressive strength recovery rate of the self-healing concrete increases, followed by a decrease. The optimum combination of factors of the microcapsule self-healing system is 3% microcapsules, 30% sodium silicate, and 15% sodium fluosilicate. The results can be used for the design and preparation of self-healing concrete.

Fly-ash based geopolymer mortar for high-temperature application – Effect of slag addition

Geopolymers are used as a Portland cement alternative in some applications. The motivation for using geopolymers is their capacity of the by-products and waste incorporation, contributing to a cleaner environment. The present study aims to evaluate the impact of temperature exposure (up to 1000 °C) on the microstructure and the mechanical properties of the geopolymer mortars. Four mixes were investigated with fly ash as the main precursor with four levels of slag replacement 0, 10, 30, and 50 wt%. To evaluate damage evolution, mechanical performances and identification tests were performed: ultrasonic pulse velocity, scanning electron microscope, mercury intrusion porosimetry, thermal strains measurements, differential thermal analysis and thermogravimetry. The research aimed to develop a mortar composition that is thermally stable at high temperature. Although slag addition improves the mechanical performances of fly ash geopolymer mortar considerably (compressive strength above 100 MPa), the mortar with no slag addition yielded better performances at high temperature. In this study, manufactured mortars exhibited a 30% strength increase and doubled tensile strength at 200 °C. Moreover, for developed mixes, a compressive strength recovery of up to 90% at 1000 °C was observed, demonstrating the potential of fly ash geopolymer as high-temperature application material.