Properties Of Geopolymer Mortar Research Articles

Enhancing geopolymer mortars for environmental sustainability: A novel approach using frits and ceramic waste

This study investigates the potential of transparent frits as a sustainable aluminosilicate precursor to enhance geopolymer mortars, aiming to reduce environmental impact by repurposing industrial waste. White ceramic waste (WCP) and frits (F) were assessed for their ability to improve mortar properties while contributing to eco-friendly construction materials. The optimal mixture, containing 50% F and 50% WCP, achieved a compressive strength of 38.71 MPa and displayed a dense microstructure. In contrast, mortars made entirely from WCP had higher porosity of 19.12% and lower compressive strength of 9.89 MPa. Although 100% F mortars gained strength more slowly, they eventually outperformed the WCP mortars, demonstrating higher compressive strength and forming a honeycomb-like calcium-aluminum-silicate-hydrate (C-A-S-H) structure. These results highlight the environmental benefits of using frits to improve both the mechanical and structural properties of geopolymer mortars. By incorporating industrial waste materials, this approach offers a sustainable solution for producing high-performance, eco-friendly construction materials, paving the way for further green innovations in geopolymer technology.

Sustainable utilization of basalt waste dust as replacement of river sand in one‐part geopolymer mortar

AbstractWith growing environmental concerns due to the excessive use of natural river sand in construction, finding sustainable alternatives is crucial. This study explores the potential of basalt waste dust, a by‐product of basalt rock crushing, as a replacement for river sand in one‐part geopolymer mortar. The experimental program is segmented into three series: replacing river sand with basalt waste dust at 25%, 50%, 75%, and 100%; adjusting the activator‐to‐binder ratio as 0.12, 0.15, 0.18, and 0.21; and modifying the aggregate‐to‐binder ratios (1, 1.4, 1.8, and 2.2). Results are discussed using various test results such as fresh property, hardened property, and microstructural property to provide a detailed analysis of mixture properties. Findings in series 1 reveal that replacing 50% of river sand with basalt waste dust optimally enhances the fresh and hardened properties of geopolymer mortar. In series 2, the varying activator‐to‐binder ratio with optimum replacement from series 1, activator‐to‐binder ratio 0.15, was found to be optimal, improving hardened properties. Further opting for this ratio in series 3 and increasing the aggregate‐to‐binder ratio to 2.2 was found to positively impact both the hardened and microstructural properties of one‐part geopolymer mortar. This study demonstrated that basalt waste dust plays a crucial role in these improvements and emphasizes the necessity of optimizing mix proportions to achieve superior performance, establishing basalt waste dust as a viable and sustainable alternative to river sand.

Development of high-strength geopolymer mortar based on fly ash-slag: Correlational analysis of microstructural and mechanical properties and environmental assessment

Given the insufficient mechanical performance of existing fly ash-based geopolymer mortars under ambient curing conditions, this study is dedicated to developing a high-strength geopolymer mortar that meets the requirements of modern structural engineering. Based on the rheological performance tests of the fresh geopolymer mortar, the evolution of its rheological characteristics was revealed. Through macroscopic mechanical performance tests, the influence of slag content on the compressive and flexural strength of geopolymer mortar was clarified. Employing microstructural performance testing methods such as Thermogravimetric and Mercury Intrusion Porosimetry, the micro-mechanisms behind the improvement of mechanical properties were revealed. Utilizing the grey relational analysis method, a framework was established to analyze the correlation between the microstructural and macroscopic mechanical properties of geopolymer mortar. Additionally, an assessment system for evaluating environmental and economic benefits was developed using statistical analysis methods. The results show that increasing slag content enhances the yield stress and plastic viscosity of geopolymer mortar. Optimizing slag content boosts the compressive strength of fly ash-based geopolymer mortar, reaching up to 88.13 MPa under ambient curing conditions. An optimal amount of slag also promotes gel formation during polymerization, improving the internal pore structure. Furthermore, the content of reaction products correlates more strongly with macroscopic mechanical properties than pore structure characteristics. Geopolymer mortar also presents significant environmental and economic advantages over traditional cement-based materials, with its carbon and economic intensity indices at only 5.50 % and 10.80 %, respectively, of those in cement-based materials.

Durability properties of slag–waste glass binary geopolymer

The durability properties of geopolymer mortars prepared using different contents of slag and glass powder (GP) were examined and compared with the properties of Portland cement mortar (PCM). The slag–GP mixes were activated with a 6 M sodium hydroxide solution at a liquid-to-solid ratio of 0.35. The performance of 28-day cured specimens after high-temperature exposure, wetting–drying and freezing–thawing cycles, water slaking, surface abrasion and alkali–silica reaction (ASR) were examined. Scanning electron microscopy was carried out to identify the microstructural changes in the materials. The results showed that an appropriate GP content (10%) enhanced the performance of the slag–GP binary geopolymer and improved its durability. However, ASR expansion was found to increase marginally. The geopolymer specimens achieved higher strength and durability than PCM due to their dense and compact microstructure with significant gel formation.

Effect of recycled fine powder as a calcium source on fresh and hardened properties of geopolymer mortar

This study explores the efficacy of Recycled Fine Powder (RFP) derived from construction and demolition waste as a sustainable substitute for Ordinary Portland Cement (OPC) as a Calcium (Ca) source in geopolymer mortar. Fresh properties of Geopolymer Mortar (GPM) were evaluated in terms of slump-flow, initial-final setting time, whereas hardened properties were evaluated in terms of Compressive Strength (CS), Water Absorption (WA), porosity, acid attack, and dry shrinkage at both ambient and heat curing. Results indicate that the RFP performs well in all mixes. However, mix C10R10 shows the overall best results, as 17% higher compressive strength was observed as compared to mix C20R0, which further increases to 88% when compared to mix C0R0. Thus, RFP provides sufficient Ca content as an activator in GPM.

Study on the synergistic effects of OPC and silica fume on the mechanical and microstructural properties of geopolymer mortar

This study investigated the synergistic effects of ordinary Portland cement (OPC) and silica fume (SF) in fly ash-based geopolymer mortar (FA-GPM). The research comprehensively evaluated the impact of replacing fly ash (FA) with varying proportions of OPC and SF on the flowability and mechanical properties of the geopolymer mortar (GPM). Furthermore, this study analyzed the interaction mechanisms of these effects by examining the microstructure and hydration products. The results showed that increasing amounts of SF initially enhanced but subsequently reduced flowability, while the inclusion of OPC consistently decreased it. The combination of SF and OPC significantly improved the mechanical performance and microstructure of the GPM. Optimal mechanical performance, with compressive strengths of 37.66 MPa at 7 days and 50.52 MPa at 28 days, was achieved by adding 10% SF and 20% OPC. Microstructural analysis revealed that using OPC and SF together enhanced the dissolution of alumino-silicate materials in the alkaline activating solution, leading to increased polymerization reactions in the GPM. This process resulted in the formation of calcium-alumino-silicate-hydrate (C-A-S-H) gel, sodium-alumino-silicate-hydrate (N-A-S-H) gel, and calcium-silicate-hydrate (C-S-H) gel, creating a denser structure with reduced porosity and enhanced mechanical properties. This study highlights the advantages of incorporating SF and OPC into FA-GPM, providing valuable insights for further research and practical applications of geopolymer materials.

Laboratory investigation of the effect of using metakaolin and clay on the behaviour of recycled glass powder-based geopolymer mortars

Civil infrastructure relies on cement, a common building material. However, Portland cement production pollutes the world by consuming mineral resources and emitting carbon dioxide. Using modern, cost-effective, and eco-friendly cement materials seems necessary. One such material is geopolymer cement, also known as green cement, composed of aluminosilicate base materials and alkaline-silicate activators. In the present study, waste glass powder was utilised to provide a rich aluminosilicate base material by substituting 10%, 20%, and 30% of the metakaolin or clay with calcium carbide residue as an alkaline activator. The samples were processed under two distinct temperature conditions: natural environment and thermal processing at 80 °C in an autoclave. The mechanical and microstructural properties of the mortars were evaluated regarding compressive strength, bending strength, setting time, volume control, and Scanning Electron Microscope (SEM). The results indicate that the type and amount of glass powder alternatives significantly determine the final sample strength. Substituting 10% metakaolin and 20% clay for glass powder maximises compressive strength. The optimal bending strength of geopolymer samples was obtained by substituting 10% clay with 10% metakaolin. SEM images validate this discovery by exhibiting a more compact and cohesive arrangement. Additionally, the processing conditions of geopolymer samples significantly influence the mechanical properties of geopolymer mortars. The results of the V-cut test indicate that geopolymeric mortars are sluggish and require additional time to reach their primary and secondary strength. This study suggests that geopolymers could produce environmentally friendly concrete by reducing cement use and advancing economic and environmental goals.

The Effect of the Utilization of Sustainable Materials on Some Mechanical Properties of Geopolymer Mortar

Geopolymer concrete has been developed as a means of reducing carbon dioxide (CO₂) emissions due to concrete manufacturing, which account for around 5–10% of the total global CO₂ emissions. Additionally, this innovative material aims to utilize industrial waste as a sustainable resource. This study concentrates on developing a geopolymer mortar composition comprising 70% fly ash and 30% metakaolin. The mixture also includes 14 molars of sodium hydroxide, sodium silicate, saturated surface dry sand, water at a volume of 10% of the mix, and 1.5% superplasticizer. The solution-to-solid materials ratio was established at 0.55 while the ratio between sodium silicate and sodium hydroxide was established at 2.5:1. The geopolymer mortar was enhanced by rice husk fibers at varying volume percentages of 1%, 1.5%, and 2%. Additionally, waste paper, in the form of paper ash, was introduced as filler at a volume percentage of 5%. Following the demolding process, the specimens were cured in the controlled environment of an oven, with the temperature set at 60 °C for a period of 24 hr. Subsequently, the cured samples were stored for 7 and 28 days and then were tested. When different amounts of rice husk fibers were mixed in with a fixed amount of 5% paper ash, the flexural resistance of the geopolymer mortar increased significantly. After 7 days of curing, it was seen that the flexural strength experienced an increase of 4%, 13%, and 25%, and a further increase of 11%, 18%, and 31% after 28 days of curing. The results of the impact test showed a notable enhancement in impact resistance and energy absorption when incorporating paper ash and rice husk fibers. Specifically, the initial crack results exhibited a 50% rise, while the specimen failure after 28 days of curing showed a 66% improvement.

KARAKTERISTIK MORTAR GEOPOLIMER BERBASIS FLY ASH KELAS C DENGAN PENAMBAHAN BORAKS

Cement has been widely utilized as a primary material in the construction of structural and architectural elements. The cement factory industry can contribute to 30% of global carbon dioxide emissions. Geopolymers were first introduced by Davidovits in 1979 to represent inorganic polymers produced from geochemistry. Geopolymer materials make use of waste materials such as fly ash as a substitute for concrete binders. In this study, Class C (high calcium) fly ash from the Paiton Power Plant was used. The mix design for geopolymer mortar in this study employed the absolute volume calculation method. Absolute volume calculations are based on the absolute volume proportions of each constituent material within 1 m3. The compressive strength of geopolymer mortar with the addition of 5% borax to the molarity value, the alkali/cementitious ratio showed good performance in the mechanical properties of geopolymer mortar. Alkali/cementitious ratios of 0.3, 0.35, and 0.4 in Class C-based geopolymer mortar with 5% borax addition exhibited good workability, making it suitable for use as a base material in architectural material production.

Characterization of Waste Clay Brick Powder and its Effect on the Mechanical Properties and Microstructure of Geopolymer Mortar

Fly ash is known as a common geopolymer precursor. However, it is important to search for suitable alternatives as the availability of fly ash will reduce with the move to more renewable energies. This paper evaluates the feasibility of using waste clay brick powder (WCBP) as a partial alternative for fly ash in geopolymer mortars with ground granulated blast furnace slag (GGBFS), under ambient and heat curing conditions. The physical, mechanical, and mineralogical properties of geopolymer mortar with 10 to 40% WCBP were investigated. Microstructural properties of WCBP and geopolymer mortars were investigated using X-ray fluorescence (XRF), X-ray diffraction (XRD), tescan integrated mineral analyzer (TIMA), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Reductions of the flow of fresh mortar were observed with the increase of WCBP. The highest 28 days compressive strengths were obtained in the mortars containing 40% WCBP, both at ambient and heat curing conditions. Microstructural analysis highlighted compact structure and reduced porosity, which are attributed to the role of WCBP in enhancing fly ash-GGBFS mortar properties by promoting geopolymer gel formation.

Physico-Mechanical Properties of Geopolymer Mortars for Repair Applications: Impact of Binder to Sand Ratio

Deterioration of concrete structures made with ordinary portland cement (OPC) as a binder is inevitable, and this requires repair or rehabilitation using appropriate repair materials. A strong and highly adhesive repair material is very important in order to ascertain the safety of damaged concrete structures. The existing repair materials, especially those that utilized conventional OPC-based materials, appear to require a certain curing condition, which prior studies have revealed to result in a weak link between the repair material and the repaired structures. Hence, an alternative material which is geopolymer mortar was utilized in this study as a repair material, and the impact of geopolymer mortars with various binder-to-sand ratios was evaluated. The physical and mechanical properties of the geopolymer mortars were assessed in addition to their performance as a repair material in terms of their bonding characteristics to conventional concrete. Findings from this study revealed that geopolymer mortar with a binder-to-sand ratio of 1:2 exhibited the highest bonding strength. In addition, geopolymer mortars with a binder-to-sand ratio of 1:3 to 4:1 exhibited better bonding strength compared to when geopolymer paste was used.

The effects of waste iron powder and steel fiber on the physical and mechanical properties of geopolymer mortars exposed to high temperatures

Geopolymer (GP) concretes have the potential to be an excellent alternative to cement-based traditional concretes for more sustainable concrete production. GP concretes have advantages such as low production temperature, low energy consumption, low carbon dioxide (CO2) emission, and rapid strength gain. However, GP concretes, similar to conventional concretes, lose a large part of their residual strength and durability capacities when exposed to possible high temperatures such as fire due to the deterioration of their internal structures. One efficient way to minimize the loss of strength and durability properties of GP concretes subjected to high temperatures is to use various waste materials and fibers in GP mixtures. This study aimed to improve GP mortar's physical and mechanical properties by adding steel (ST) fiber and waste iron powder (WIP) to GP mixtures. This study fundamentally investigates the spreading diameters (SD), mass loss (ML), external surface changes, residual compressive strength (RCS) and residual flexural strengths (RFS), and microstructural properties of GP mortars reinforced with ST fiber and WIP before and after high-temperature effects. According to the results, although ST fiber and WIP negatively affected GP mortars' workability and reduced GP mortars' SD values, they significantly increased GP mortars' RCS and RFS capacities. At 800 degrees (C), the RCS and RFS capacity reductions of the S0 control sample were 83.30% and 75.27%, respectively.In contrast, the drops in the RCS and RFS capacity of the S6 sample, in which 20% of WIP and 2% of ST fiber were used in hybrid form, decreased by 70.72% and 65.31%, respectively. However, ST fibers and WIP slightly reduced the ML of the GP mortars after the high-temperature effect due to ST fibers and WIP being ineffective in preventing peeling on the sample surface. At 800C, while the ML of the S0 control specimen was 4.47%, the ML values of S1-S6 specimens where WIP and ST fibers were used in single and hybrid forms varied between 4.16% and 4.38%.

Effects of microencapsulated phase change materials on chloride ion transport properties of geopolymers incorporating slag and, metakaolin, and cement-based mortars

The addition of microencapsulated phase change materials (MPCMs) to geopolymers is a technological alternative for meeting the thermal comfort and energy efficiency requirements of buildings. However, current research is limited to the effects of MPCM addition on mechanical and thermal performances of geopolymers. New MPCM applications, therefore, require additional research on durability indicators (chloride diffusivity, porosity, absorption, etc.). The objective of this research is to examine the effects of MPCM addition on sodium chloride ion transport properties of geopolymer mortars based on a combination of blast furnace slag and metakaolin, and Portland cement based mortars. Twelve different mortars (three cement-based and nine geopolymer-based) are studied by varying the MPCM content (0%, 5% and 10%, respectively) within two types of mortar: a geopolymer mortar (GPM) and a cement mortar (CM). With this aim in view, a series of characterizations are conducted, including determination of total porosity by water saturation, analysis of pore structure distribution by mercury intrusion porosimetry (MIP), measurement of electrical resistivity, capillary water uptake, stationary-state migration coefficient “Dss” and non-stationary-state migration coefficient “Dnss”, and determination of chloride ion binding capacity. The results show that MPCM addition increases total porosity, which in turn increases capillary water absorption and decreases GPM and CM electrical resistivity. Conversely, MPCM addition also reduces critical diameter and pore connectivity, due of the agglomeration effect. MPCMs also increase chloride ion binding capacity. Both effects results in decreased stationary state migration coefficient. Finally, the study shows that the chemical reaction of GPM with chloride ions delays chloride penetration in stationary state conditions. However, the same is not true for the non-stationary state method. This demonstrates the technical limitations of this method for the characterization of GPM in comparison to CM.

Effects of mono and binary recycled aggregates on the rheological properties of geopolymer mortars synthesized with construction and demolition waste-based binders

This study comprehensively investigated the effect of different types of fine construction and demolition waste (CDW)-based aggregates, including recycled concrete aggregate (RCA), recycled ceramic tile aggregate (RTA) and recycled brick aggregate (RBA) on the fresh rheological properties of geopolymer mortars (GPMs) derived from CDW-based aluminosilicate binders. The results were compared to those of silica sand (SSA) and natural sand (NSA) with equivalent particle size distribution. In addition, the binary inclusion of RCA, RTA and RBA with 50% SSA or NSA fine aggregates was also considered in an attempt to reach rheological behavior closer to that of SSA and NSA-based GPMs. All mortars were blended with a CDW-binder composed of a ternary mixture of brick (RBP), ceramic (RTP) and concrete waste (RCP) powders optimized at pre-targeted chemical parameters of SiO2/Al2O3 and Na2O/SiO2 of 5.7 and 0.18, respectively. The geometrical shape parameters and packing densities of RCA, RTA, RBA, SSA and NSA aggregate skeletons and geopolymer mortar systems were also evaluated to examine their relationship with the rheological parameters of static and dynamic yield stresses, apparent and plastic viscosities, shear stresses and strains and thixotropy of GPMs. Although the incorporation of CDW-based aggregates resulted in enhanced rheological parameters, they exhibited shear-thinning or pseudoplastic behavior similar to SSA and NSA-GPMs. Yet the addition of RCA with a lower consumption of suspending fluids and reduced non-colloidal interactions than RBA and RTA resulted in overall rheological properties closer to those of SSA and NSA-GPMs, which further improved when combined with SSA or NSA in binary-aggregate-based GPM systems.

Effect of GGBS on Fly Ash Based Geopolymer Mortar at Ambient and Heat Curing

AbstractThis study investigates and shows the effect of incorporation of ground granuated blast furnace slag (GGBS) content in fly ash (FA) based geopolymer mortar by assessing the strength properties of geopolymer mortar in both ambient (25 °C) and heat (60 °C) curing. The percentage of GGBS is varied from 0% to 50% with FA in geopolymer mortar. Sodium silicate (SS) and sodium hydroxide (SH) solutions are used to activate the main binders. For all the mixes the alkali/binder ratio, molarity (M), and sodium silicate (SS)/sodium hydroxide (SH) ratio are fixed to 0.45, 12 M, and 2, respectively. The fresh property in terms of slump flow and other properties like compressive strength, water absorption, and dry density of the geopolymer mortar are determined. The result of this study shows that the inclusion of GGBS content in FA‐based geopolymer mortar significantly increases the compressive in both the curing conditions. Maximum compressive strength of 44.33 MPa is obtained when 50% GGBS is added to the mixes at a curing temperature of 60 °C.

Experimental study on high temperatures performance of rubberized geopolymer mortar

Nowadays, fire accidents occur frequently, and both buildings and structures or traffic roads are threatened by fire to varying degrees, and the mortar structure is often in direct contact with fire. Therefore, it is necessary to study the performance of mortar under high temperature. Geopolymer is a new type of green environmental protection building material with good high temperature resistance. Waste rubber will soften and decompose under high temperature, and the holes formed can release the steam pressure inside the structure, which is helpful to ease the internal cracking of the structure. At present, it has been proved that waste rubber has a beneficial effect on the resistance of mortar to high temperature. The research of waste rubber in Portland cement mortar has made relevant achievements, but the research on the combination of geopolymer rubber is relatively small. Therefore, in view of this lack, this study supplements the material properties of geopolymer mortar under four rubber particle sizes (4, 1.7, 0.83, and 0.27 mm) and five temperatures (25, 200, 400, 600 and 800 °C), namely, surface observations, mass loss, compressive and flexural strengths, ultrasonic pulse velocity (UPV) and microstructure change. The results show that the addition of rubber particles will increase the mass loss of rubberized geopolymer mortar (RGM), but the advantage is that it can reduce the burst risk. The addition of fine particle rubber can improve the ability of RGM to resist cracking and deformation at higher temperatures. The results shows that the UPV can reflect the mass and intensity change of RGM laterally. The microscopic results shows that the main reason for the lower strength is the expansion of microcracks and pores in RGM matrix at high temperature.

Characterisation of cementitious composite materials based on calcined clay activated by silicate from rice husk ash and Ingessil silicate - activator: sodium hydroxide (NaOH)

The ever-increasing cost of cement and its production of harmful carbone dioxide (CO2) has led development actors to continuously search for less environmentally polluting and low-cost binders. Hence the interest in the valorisation of agricultural resources through the production of different binders such as silicate for the elaboration of geopolymers at low manufacturing temperatures (<100 °C). In this study, Ingessil industrial silicate and rice husk ash silicate were used as pozzolan raw materials to prepare geopolymers with sodium hydroxide as activator at a concentration of 12 M. Two types of samples were developed: geopolymer mortars based on Ingessil silicate and geopolymer concretes based on Ingessil industrial silicate and rice husk ash silicate. Sand and gravel were used as fine and coarse aggregates for the production of geopolymer concretes. They were represented 80% of the mass of the geopolymer concretes according to the standards of elaboration.The porosity values obtained were of the order of 30%, i.e. water absorption values of about 18%, apparent specific weight of about 5% and bulk density of 1.7%. The mechanical values of BGAC-RHA samples are higher than those of BGAC-I. The physico-chemical properties of geopolymer mortars and concretes were similar.

Performance of Geopolymer Mortar Containing PVC Plastic Waste from Bottle Labels at Normal and Elevated Temperatures

This work focused on reusing polyvinyl chloride (PVC) plastic waste from bottle labels (BLWA) as lightweight aggregates in geopolymer mortar. This way of reusing plastic waste is beneficial for diminishing the negative impacts of plastics on the environment and reducing CO2 emissions by using geopolymer as an alternative cementing material. BLWA was used to partially substitute natural fine aggregate at ratios of 0, 5, 10, 15, and 20% by volume. The geopolymer mortar properties were tested, and the durability after exposure to elevated temperatures was also assessed. It was found that the strengths were adversely affected by increasing BLWA content. The water absorption and porosity were also increased with beneficial benefits on the reduced density (9–17%) and thermal conductivity (28–44%). The geopolymer mortar containing 5–15% BLWA satisfied the requirement of a lightweight mortar used in masonry work. After exposure to temperatures up to 600 °C, the properties of geopolymer mortar containing BLWA reduced more than that of the control mortar due to the thermal degradation of BLWA at high temperatures. However, when increasing the temperature from 600 °C to 900 °C, there was no further loss in strength. Microstructure analysis indicated that increasing temperatures caused more increased voids and microcracks in geopolymer mortars, especially the ones containing BLWA. However, after exposure at 900 °C, these voids and cracks were minimized at 900 °C due to sintering effects. The findings in this work confirmed the feasibility of using this PVC waste derived to produce lightweight construction material with thermal insulation properties.

Effect of granite flour proportion on the strength properties of geopolymer mortar based on fly ash

Given global trends and challenges, the development of binders for the production of geopolymer concretes has become a topical area of building science. The purpose of this study is to determine whether granite can replace traditional construction aggregate, such as river sand, during geopolymer production, as well as to demonstrate the effect of the proportion of granite flour on the strength properties of fly ash-based geopolymer mortar. A combination of granite flour, quartz sand, and fly ash in various proportions was used as an aluminosilicate precursor. The scope of the study includes density measurements, compressive and flexural strength tests, abrasion by the Boehme method, and microstructural observations. Based on the obtained results, it can be concluded that granite can be successfully used as a replacement for quartz sand during the production of fly ash-based geopolymers. Moreover, the addition of granite makes it possible to improve the strength properties of geopolymers, compared to a geopolymer composite containing quartz sand. Angesichts globaler Trends und Herausforderungen ist die Entwicklung von Bindemitteln für die Herstellung von Geopolymerbetonen zu einem aktuellen Thema der Bauwissenschaft geworden. Ziel dieser Studie ist es, festzustellen, ob Granit bei der Herstellung von Geopolymeren den herkömmlichen Bauzuschlagstoff, wie z. B. Flusssand, ersetzen kann, und die Auswirkung des Granitmehlanteils auf die Festigkeitseigenschaften von Geopolymermörtel auf Flugaschebasis aufzuzeigen. Eine Kombination aus Granitmehl, Quarzsand und Flugasche in verschiedenen Anteilen wurde als Aluminosilikat-Vorprodukt verwendet. Der Umfang der Studie umfasst Dichtemessungen, Druck- und Biegefestigkeitsprüfungen, Abrieb nach der Boehme-Methode und mikrostrukturelle Untersuchungen. Die Ergebnisse lassen den Schluss zu, dass Granit als Ersatz für Quarzsand bei der Herstellung von Geopolymeren auf Flugaschebasis erfolgreich eingesetzt werden kann. Darüber hinaus ermöglicht der Zusatz von Granit eine Verbesserung der Festigkeitseigenschaften von Geopolymeren im Vergleich zu einem Geopolymerverbundwerkstoff mit Quarzsand.

Drying shrinkage behavior of geopolymer mortar based on kaolinitic coal gangue

The coal industry generated tons of waste over the years of mineral extraction, and the waste disposal leads to soil and air pollution caused by acid mine drainage and spontaneous combustion. Seeking environmental sustainability, this paper investigated the valorization of coal tailings as a primary precursor in geopolymer mortar. The effect of Portland cement as a hardened admixture was evaluated on the mechanical and physical properties of geopolymer mortar, by replacing the coal tailings with a lower amount of Portland cement. Six mortars were characterized by several standard tests besides ultrasonic pulse velocity, mercury porosimetry (MIP), and drying shrinkage, the microstructure was evaluated by SEM/EDS analysis and X-Ray diffraction. The workability was slightly higher for geopolymer mortars with calcium by almost 5%, and the addition of sugarcane molasses and flue gas desulfurization increased the fluidity, reaching 220 mm. The Portland cement improved the early strength of geopolymer mortar by almost 10 MPa at 7 days, due to the acceleration of chemical reaction yielding a denser and heterogeneous matrix. The SEM/EDS analysis evidenced the co-existence of the polymeric matrix and C-A-S-H gel. The compressive strength at 28 days was higher than 20 MPa for all geopolymer mortars. A higher reaction rate provided by calcium addition leads to higher densification of the aluminosilicate matrix at early ages. The ultrasonic pulse velocity (UPV) confirmed denser matrix formation, and the geopolymer with 05 wt% of Portland cement presented UPV of 2700 m/s at 07 days, while the non-calcium geopolymer showed 2000 m/s. The denser matrix formed limited the water loss, decreased the open porosity, and improved the stiffness of geopolymer mortars, yielding a drying shrinkage almost 50% lower than for geopolymer without calcium addition. Finally, this paper established the lower replacement (5 wt%) of coal tailings for Portland cement produced efficient geopolymer mortar, with excellent physical and mechanical properties for in situ application without a thermal cure.