Properties Of Geopolymer Research Articles

Factors affecting the property of open-cell fly ash-based porous geopolymer via replica method

Fly ash (FA) is a silicate solid waste produced by coal-fired power plants, encroaching on land and polluting the soil. Aluminosilicate can be hydrated using alkali activators to form a high-strength geopolymer. Using organic foam impregnation, geopolymer slurry can be converted into lightweight, high-strength, and porous geopolymer. Herein, FA and a sodium-based alkaline activator were mixed to prepare a geopolymer slurry. Immersing a polyurethane sponge in the slurry and adjust the roller spacing yielded a porous geopolymer with a uniform structure. Different process parameters were adjusted, revealing that the modulus of the alkali activator at 1.5% and 10% water content resulted in a high-strength FA geopolymer. When the dispersant dosage was set at 1%, the slurry with an excellent slurry-hanging effect. Adjusting the roller spacing produced a porous geopolymer with a porosity of 71%, a thermal conductivity of 0.1454 W·m−1·K−1, and a strength of 1.33 MPa. This study highlights the potential for repurposing FA into environmentally friendly and versatile geopolymer materials.

Lunar Regolith Geopolymer Concrete for In-Situ Construction of Lunar Bases: A Review.

The construction of lunar bases represents a fundamental challenge for deep space exploration, lunar research, and the exploitation of lunar resources. In-situ resource utilization (ISRU) technology constitutes a pivotal tool for constructing lunar bases. Using lunar regolith to create geopolymers as construction materials offers multiple advantages as an ISRU technique. This paper discusses the principle of geopolymer for lunar regolith, focusing on the reaction principle of geopolymer. It also analyzes the applicability of geopolymer under the effects of the lunar surface environment and the differences between the highland and mare lunar regolith. This paper summarizes the characteristics of existing lunar regolith simulants and the research on the mechanical properties of lunar regolith geopolymers using lunar regolith simulants. Highland lunar regolith samples contain approximately 36% amorphous substances, the content of silicon is approximately 28%, and the ratios of Si/Al and Si/Ca are approximately 1.5 and 2.6, respectively. They are more suitable as precursor materials for geopolymers than mare samples. The compressive strength of lunar regolith geopolymer is mainly in the range of 18~30 MPa. Sodium silicate is the most commonly utilized activator for lunar regolith geopolymers; alkalinity in the range of 7% to 10% and modulus in the range of 0.8 to 2.0 are suitable. A vacuum environment and multiple temperature cycles reduce the mechanical properties of geopolymers by 8% to 70%. Future research should be concentrated on the precision control of the lunar regolith's chemical properties and the alkali activation efficacy of geopolymers in the lunar environment.

The Different Properties of Geopolymer Composites Reinforced with Flax Fibers and Carbon Fibers.

The main motivation for this research was to improve the properties of geopolymers by reinforcement using synthetic and natural fibers, and to gain new knowledge regarding how the nature and/or the quantity of reinforcement fibers influences the properties of the final geopolymers. The main objective was to investigate the effects of different types of reinforcement fibers on the properties of the geopolymers. These reinforcement fibers were mainly environmentally friendly materials that can be used as alternatives to ordinary Portland cement. The authors used fly ash and river sand as the raw materials for the matrix, and added carbon fibers (CF), flax fibers (FF), or a hybrid of both (CFM) as reinforcements. The samples were prepared by mixing, casting, and curing, and then subjected to various tests. The main research methods used were compressive strength (CS), flexural strength (FS), water absorption (WA), abrasion resistance (Böhme's disk method), microstructure analysis (SEM), chemical composition (XRF), and crystal structure analysis (XRD). The results showed that the addition of fibers partially improved the mechanical properties of the geopolymers, as well as reducing microcracks. The CF-reinforced geopolymers exhibited the highest compressive strength, while the FF-reinforced geopolymers showed the lowest water absorption. The authors, based on previous research, also discussed the factors that influence fiber-matrix adhesion, and the optimal fiber content for geopolymers.

Effect of Synthesis Parameters on Fresh and Hardened Properties of Slag-Waste Glass Binary Geopolymer

Effect of Synthesis Parameters on Fresh and Hardened Properties of Slag-Waste Glass Binary Geopolymer

Unveiling physico-mechanical and acoustical characteristics of fly ash geopolymers through the synergistic impact of density and porosity

This paper investigates the physico-mechanical and acoustic properties of fly ash geopolymers via casting and pressing methods. The existing research lacks comprehensive insight into the relationship between variations in geopolymer density and their impacts on both physico-mechanical properties and sound insulation and absorption capabilities. Geopolymers, as sustainable construction materials, are pivotal in mitigating noise and providing structural strength. To surpass these limitations and achieve either higher or lower densities in geopolymers, alternative approaches are necessary. Casting (non-foamed and foamed with 1.0, 2.0 and 3.0 foam-to-geopolymer paste ratio) and pressing methods were employed to produce a range of geopolymer densities between 1400 kg/m3 – 2200 kg/m3. The pressing method produced a highly dense geopolymer with an excellent compressive strength of 116 MPa. While the lightest geopolymer produced by adding a foaming agent had a compressive strength of 13 MPa. Good sound transmission loss (66.1 dB) was achieved by highly dense pressed geopolymers. Highly porous geopolymers achieved an excellent sound absorption coefficient of 0.79. The density variation and preparation methods greatly affected the pore size and distribution which subsequently affected the acoustical properties of the geopolymers. Manipulating the density and porosity of the geopolymers is essential for creating spaces with optimal acoustics to meet building codes and noise control regulations.

Effect of metakaolin content and shape design on strength performance of lightweight rubberized geopolymer mortars incorporated slag-waste glass powders

Lightweight rubberized geopolymer (LRGP) has gained attention due to its economic, engineering, and environmental benefits. With the rising human demands, the need for alternative materials to meet the requirements of infrastructural expansion, and global industrialization required. Based on those facts, this study aimed to develop of lightweight geopolymer mortars using wastes rubber as fine aggregate (WRA) to replace the natural aggregates, which metakaolin (MK), wastes bottle glass (WBG) and granulated blast furnace slag (GBFS) used as precursor materials with alkaline activator contained low molarity of sodium hydroxide solution and sodium silicate and cured at ambient temperatures. The effect of WRA on physical, mechanical, and microstructural properties of metakaolin-based rubberized geopolymer has been evaluated by using several tests such as compressive, flexural and tensile strength. As well as morphology and chemical reaction on LRGP by using AFM, FESEM, EDX, FTIR and XRD tests. In addition, a sustainable shape design has been cast and subjected to compressive strength to obtain the strength performance of the proposed LRGP mortar. At optimal mixture, the SEM images exhibited improvement in the interfacial transition zone (ITZ) among WRA and binder, leading rubberized geopolymer with 15% WRA to achieve a strength of 27.47 MPa after 28 days and with a reduction in density by 7.2%. The findings of this study can provide valuable insights on utilizing WRA in the shape design and formulation of geopolymer mortar, a key ingredient in the development of functional environmentally friendly building materials.

The Influence of Diatomite Addition on the Properties of Geopolymers Based on Fly Ash and Metakaolin.

Geopolymer materials, considered to be an alternative to Portland cement-based concretes, can be produced from various types of waste aluminosilicate raw materials. This article presents the results of research related to the use of diatomite as an additive in geopolymers. The results of testing geopolymer composites with 1%, 3%, and 5% additions of diatomite with a grain size of 0-0.063 mm after and without thermal treatment were presented. This article presents the physical properties of the diatomite additive, the morphology of diatomite particles SEMs, thermal analysis, and compressive strength test results. In this research, diatomite was treated as a substitute for both fly ash and metakaolin (replaced in amounts of 1 and 3%) and as a substitute for sand introduced as a filler (in this case, 5% of diatomite was added). As a result of this research, it was found that the addition of diatomite instead of the main geopolymerization precursors in amounts of 1 and 3% had a negative impact on the strength properties of geopolymers, as the compressive strength was reduced by up to 28%. The introduction of crushed diatomite instead of sand in an amount of 5% contributed to an increase in strength of up to 24%.

Towards sustainable construction: Performance evaluation of slag-cenosphere geopolymers under different NaOH concentrations

The incorporation of industrial wastes into construction materials, such as geopolymers, is highly desirable to improve their environmental impact. The choice of source materials, such as slag and cenosphere, and the amount of activator used significantly impact the properties of geopolymers. For instance, including high-reactivity precursors and optimizing activator composition may enhance mechanical strength and durability. However, no studies have evaluated the effect of cenosphere addition on the properties of geopolymer composites. This research study aims to unveil the synthesis of a binary geopolymer material by integrating slag and cenosphere as precursors, activated by sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). Geopolymer composites were prepared to assess the impact of cenosphere addition (by substituting the slag with cenosphere in different percentages of 25, 50, and 75 %) and NaOH concentration (specifically 6 M, 9 M, and 12 M) on the material's properties. Additionally, one conventional mortar with a water-to-cement ratio of 0.5 was also prepared. Compressive strength, ultrasonic pulse velocity (UPV), electrical resistivity, water absorption, density, and thermogravimetric analysis were conducted. Results showed that increasing the cenosphere percentage increased the water absorption and decreased the compressive strength, UPV, electrical resistivity, and density compared to the geopolymer mixture with 100 % slag content. However, up to 50 % substitution of cenosphere, the geopolymer mix performed better than conventional mortar. Notably, results suggest a potential increase in CO2 uptake due to the addition of cenosphere, further enhancing the environmental performance of geopolymer composites. The findings of this study suggest the potential use of slag-cenosphere geopolymer as an alternative and sustainable construction material.

Effect of activator type and Pozzocrete waste on the mechanical and microstructural properties of eco-friendly geopolymer incorporating electric arc furnace slag

ABSTRACT The precursor type and activator are two primary factors that significantly affect the properties of geopolymers. Most of the previous studies used byproduct materials such as fly ash (FA) and slag as geopolymer precursors, while too limited studies used electric arc furnace slag (EAFS) for this purpose. The EAFS is a type of steel slag, which can be produced when scrap steel is melted. The preliminary usage of EAFS as a precursor in the geopolymer system has not been sufficiently highlighted. To make this come true, the current procedure employed EAFS as a precursor material for the geopolymeric system. Due to superior properties, EAFS was partially replaced with 10–50 wt% pozzocrete (Pz). Two different types of alkaline activators, NaOH and Na2CO3, were used to activate EAFS slurries supported by Pz. The results indicated that the optimal ratio of Pz to be replaced by EAFS to achieve the target properties varies according to the type of activator. The inclusion of 10% Pz exhibited maximum compressive strength when Na2CO3 was used, whilst 50% Pz exhibited maximum compressive strength when NaOH was used. The coexistence between N-A-S-H from Pz and C-(A)-S-H gel from EAFS is the main reason for the enhanced strength.

Molecular insight into the structural and mechanical properties of Ca-based geopolymers

Ca-based geopolymers are a principal product of introducing calcium into geopolymers. Analyzing Ca-based geopolymers structural and mechanical properties aids in optimizing mix design of geopolymers. In this paper, partially reacted low-polymerization and fully reacted high-polymerization models were constructed to examine the structural and mechanical properties of Ca-based geopolymers with varying calcium contents via molecular dynamics simulations. Results show that Ca-based geopolymers contain pentacoordinate aluminum and tricluster oxygen which is more brittle and makes the structure loose. In low-polymerization models, an increase in calcium content accelerates the polymerization rate by overcoming the low-temperature reaction barrier. However, calcium content hinders the formation of pentacoordinate aluminum, decreasing the final degree of polymerization, resulting in weakened mechanical properties. In high-polymerization models, increased calcium decreases tricluster oxygen content, resulting in improved mechanical properties. While the hydrolysis reaction reduces mechanical properties, the weakening effect of water is greater than the enhancing effect of calcium.

Use of Alkaline-Activated Energy Waste Raw Materials in Geopolymer Concrete.

Silica fly ash, Certyd aggregate, and an alkaline solution were used to produce lightweight geopolymer concretes. The compressive strength, water absorption, and bulk density results, along with SEM photos showing the structure of the obtained composite, were obtained. Tests conducted on the specifications of lightweight geopolymer concretes have revealed significant chemical interactions between the ash aggregate and the geopolymer mortar, particularly when the coarse aggregate surface has been pre-treated with an alkaline solution. A statistical analysis of the experimental data, which investigated the influence of three key variables on the compressive strength, water absorption, and bulk density of lightweight geopolymer concrete (LBG), identified the following factors as having the most substantial impact: the quantity of alkali used, the curing temperature, and the concentration of alkali in the mixture. The optimal test series exhibited a commendable compressive strength of 20.14 megapascals (MPa), accompanied by a water absorption rate of 14.72%, and a bulk density of 1486.6 kg per cubic meter (kg/m³). These findings underscore the importance of alkali content, curing temperature, and alkali concentration in tailoring the properties of lightweight geopolymer concrete to meet specific performance requirements.

Effect of silica fume type on rheology and compressive strength of geopolymer mortar

Silica fume (SF) is widely used in the developing of high-performance geopolymer systems. Previous studies have shown that using different types of SF may have different influences on the performance of geopolymers. What are the key factors (affecting the properties of geopolymers) still need to be clarified? This paper investigated the effects of three types of silica fume (SF1− SF3) with various silica contents (98.0%, 94.7% and 53.1%) and particle sizes (D50: 3.3 μm, 3.1 μm and 11.8 μm) on the rheology and compressive strength of alkali-activated calcium alumina cement (CAC)/fly ash mortar. The incorporation of SF can significantly increase the plastic viscosity. The increase in plastic viscosity was due to the ball-bearing action of the spherical SF particles, which reduced the friction between the particles under shearing. Replacing 20% of the fly ash with SF1 and SF2 improved the compressive strength of geopolymer mortars while the incorporation of SF3 decreased the compressive strength at the same replacement ratio. Inductively coupled plasma (ICP) spectrometry results indicated that the amorphous silica in the SFs was dissolved in an alkali solution. Activators with high concentrations of monomer and dimmer silicon groups may promote the reaction between precursors and activators. The formation of additional aluminosilicate gels reduced the amount of large capillary pores (500 nm to 1000 nm), leading to improved strength. The incorporation of coarse SF3 introduced extra voids in the mixture, as suggested by calculations of packing density, leading to reduced strength.

MECHANICAL AND HYDRAULIC PERFORMANCE OF PERVIOUS RECYCLED AGGREGATE GEOPOLYMER CONCRETE

The widespread expansion of the global economy and the increase in human population have been major contributors to pollution and environmental complications. Construction and demolition wastes (CDW), impervious pavement surfaces, and industrial waste disposal sites have emerged as serious environmental challenges over the past decade. These challenges must be addressed through the synergic use of different sustainable practices, including pervious surfaces, CDW, and industrial wastes. Their combined utilization produces a pervious geopolymer concrete made with recycled concrete aggregates (RCA). This research aims to develop and assess the mechanical and hydraulic properties of pervious geopolymer recycled aggregate concrete (PGRAC) with a design porosity of 15%. The mixes were made with two binder blends of ground granulated blast furnace slag and fly ash (1:0 and 1:1) and RCA replacement of 0 and 100%. The mechanical and hydraulic performance were characterized by compressive strength and permeability, respectively. Results showed that pervious concrete made with natural aggregates and comprising a binder blend of slag:fly ash of 1:0 demonstrated 36% higher compressive strength than counterparts having a binder blend of 1:1. Meanwhile, the permeability was unaffected by the variation in the binder. At 100% RCA, the compressive strength of mixes having a binder blend of 1:0 was 192% higher than that of the equivalent mix having a binder blend of 1:1. Yet, the latter had 12% higher permeability than the former. These research findings demonstrate the ability to produce sustainable PGRAC for use in pavement applications.

MECHANICAL AND HYDRAULIC PERFORMANCE OF PERVIOUS RECYCLED AGGREGATE GEOPOLYMER CONCRETE

The widespread expansion of the global economy and the increase in human population have been major contributors to pollution and environmental complications. Construction and demolition wastes (CDW), impervious pavement surfaces, and industrial waste disposal sites have emerged as serious environmental challenges over the past decade. These challenges must be addressed through the synergic use of different sustainable practices, including pervious surfaces, CDW, and industrial wastes. Their combined utilization produces a pervious geopolymer concrete made with recycled concrete aggregates (RCA). This research aims to develop and assess the mechanical and hydraulic properties of pervious geopolymer recycled aggregate concrete (PGRAC) with a design porosity of 15%. The mixes were made with two binder blends of ground granulated blast furnace slag and fly ash (1:0 and 1:1) and RCA replacement of 0 and 100%. The mechanical and hydraulic performance were characterized by compressive strength and permeability, respectively. Results showed that pervious concrete made with natural aggregates and comprising a binder blend of slag:fly ash of 1:0 demonstrated 36% higher compressive strength than counterparts having a binder blend of 1:1. Meanwhile, the permeability was unaffected by the variation in the binder. At 100% RCA, the compressive strength of mixes having a binder blend of 1:0 was 192% higher than that of the equivalent mix having a binder blend of 1:1. Yet, the latter had 12% higher permeability than the former. These research findings demonstrate the ability to produce sustainable PGRAC for use in pavement applications.

Fly ash and ceramic residue based geopolymer mortars

A binary geopolymer in the basis of fly ash and ceramic residue was developed under ambient temperature. The alkali medium comprises of commercial Na2SiO3 and NaOH with 10 M dan 12 M. Analyses were carried out to characterize the raw materials and their geopolymer properties. characterization was conducted through X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscope (SEM). The compressive strength, porosity and abrasion rates were measured for determining geopolymer performance. The ceramic residue consists mainly of SiO2 and Al2O3, which is similar to the fly ash. The highest compressive strength produced from the specimens was at 25.2 MPa with the age of 28 days, which complies with class 1 in standard SNI 03-0349-1989. This highest strength was followed by the lowest water absorption and abrasion rate, which are at 1.99% and 0.007 mm/minute, respectively.

Effects of Different Calcium Sources on Mechanical Properties of Metakaolin Geopolymers.

Metakaolin-based geopolymers have substantial potential as replacements for cement, but their relatively inferior mechanical properties restrict their application. This paper aims to enhance the mechanical properties of metakaolin-based geopolymers by incorporating appropriate amounts of calcium sources. CaCO3, Ca(OH)2, and CaSO4 are three types of calcium sources commonly found in nature and are widely present in various industrial wastes. Thus, the effects of these three calcium sources on the performance of metakaolin-based geopolymers were studied. Through the analysis of the mechanical properties, heat-release behavior during hydration, hydration products, and microstructure of geopolymers, the effectiveness of the aforementioned calcium sources in improving the performance of metakaolin-based geopolymer was evaluated, and the mechanisms of action were elucidated. The results indicate that the pozzolanic reaction between CH and MK could promote MK hydration and increase the proportion of CASH gel in the hydration products, thereby facilitating the setting of the geopolymer and enhancing its strength. CS could react with the active aluminates in MK to form ettringite, thus forming a higher early strength. CC had a lower reactivity with MK and does not improve the performance of MK-based geopolymers.

Perlite incorporation for sedimentation reduction and improved properties of high-density geopolymer cement for oil well cementing

Portland cement (PC) is known for its environmental and technical concerns and massive energy consumption during manufacturing. Geopolymer cement is a promising technology to totally replace the use of PC in the oil and gas industry. Although geopolymers are widely used in the construction industry, it is yet to see a full-scale application in the petroleum industry. High-density geopolymer cement development is essential to substitute heavy-weight Portland cement slurries for high pressure well cementing applications. Sedimentation issue is associated with high-density cement slurries which use high specific gravity solids such as weighting materials. This problem causes heterogeneity and density variation along the cemented sections. The main target of this work is to evaluate the use of perlite powder to address the sedimentation issue in the heavy weight geopolymer systems. Hematite-based Class F fly ash (FFA) geopolymer cement slurries with perlite concentrations of 0, 1.5, and 3% by weight of binder (BWOB) were prepared. The sedimentation problem was investigated using three techniques: API method, nuclear magnetic resonance (NMR), and computed tomography (CT) scan. The perlite effects on different geopolymer properties such as unconfined compressive strength (UCS), porosity, elastic and rheological properties were assessed. The results proved that perlite incorporation in high-density hematite-based FFA geopolymer significantly reduced sedimentation issue by increasing yield point and gel strength. NMR and CT scan showed that perlite decreases porosity and density variation across the geopolymer samples. The UCS increased with increasing perlite percentage from 0 to 3%. The measured Young’s moduli (YM) and Poisson’s ratios (PR) showed that the developed perlite based geopolymer systems are considered more flexible than Class G cement systems. It was found that the optimum perlite concentration is 3% BWOB for tackling sedimentation and developing a slurry with acceptable mixability and rheological properties.

Microstructure and transport properties of metakaolin-based geopolymers subjected to accelerated leaching

Towards the development of net-zero carbon concrete and the wider application of geopolymers, understanding the durability of geopolymers has become essential. However, knowledge on the evolution of microstructure and transport properties of the materials under aggressive conditions due to their interaction with external chemicals is limited. Therefore, this study investigated the leaching behaviors of metakaolin-based geopolymers with high water-to-binder (w/b) ratios under a 6 M NH4NO3 attack, focusing on their microstructure and transport properties. Microstructural insights were assessed through N2-adsorption, Mercury intrusion porosimetry, and water porosity analyses. After 28 days of leaching, total porosity slightly decreased, but pore size distribution (PSD) shifted towards larger pore sizes. The materials close to the exposed surface exhibited a relatively higher porosity and larger PSD than the deeper parts. The potential formation of Al(OH)3 and silica layers as a result of dealumination, confirmed by mass gain and SEM/EDS, contributed to the pore structural evolution. These alterations led to slight reductions in water permeability and CH4 diffusion coefficients but mostly increased the He diffusion coefficients of the geopolymers after 28-day leaching. These findings underscored the inherent microstructural characteristics of geopolymers (e.g., porosity, pore size distribution, and tortuosity) and the size of diffusing species as key factors shaping the transport properties. Notably, the permeability and diffusivity of both leached and intact geopolymers exhibited exponential correlations with the accessible porosity.

Mechanical properties and hydration of fly ash-based geopolymers modified by copper slag

Copper slag (CS) is mostly used as concrete aggregate due to its low activity, which limits its application. Although CS can exhibit high activity in geopolymer systems, the mechanical properties of high-volume CS geopolymers are still poor, which limits the utilization of CS and the application of geopolymers. In this paper, CS and fly ash (dry grinding fly ash (DFA) and wet grinding fly ash (WFA)) were used to prepare geopolymers with high-volume CS, and the effects of CS on the mechanical properties, microstructure and hydration of fly ash-based geopolymers were investigated. The results showed that the addition of CS could effectively improve the compressive strength of fly ash-based geopolymers. Compared with geopolymer samples without CS, 40 % CS can increase the 7d and 28d compressive strength of dry grinding fly ash-based geopolymers by 37.8 % and 33.6 %, respectively; 50 % CS can increase the 7d and 28d compressive strength of wet grinding fly ash-based geopolymers by 59.2 % and 49.2 %, respectively. The addition of CS can promote the formation of N(C)-A-S-H and Fe-rich gels, and then improve the mechanical properties and microstructure of fly ash-based geopolymers.

The Precursors Used for Developing Geopolymer Composites for Circular Economy-A Review.

Considering recent climate changes, special importance is given to any attempt to depollute and protect the environment. A circular economy seems to be the ideal solution for the valorization of mineral waste, resulting from various industrial branches, by reintroducing them in the process of obtaining alternative building materials, more friendly to the environment. Geopolymers can be considered as a promising option compared to Portland cement. Information about the influence of the composition of the precursors, the influence of the activation system on the mechanical properties or the setting time could lead to the anticipation of new formulations of geopolymers or to the improvement of some of their properties. Reinforcement components, different polymers and expansion agents can positively or negatively influence the properties of geopolymers in the short or long term.