Papers by Keyword: Geopolymer

Abstract: Foundation engineering has large challenges with weak and loose soil, especially sandy soil, which has low shear strength and high compressibility. as known used pile raft to reduced excessive settlement, differential settlement, and to increase bearing capacity of the soil to carrying the loads from super structure. The benefit of use combined (raft piles) to improved load distribution and, increase bearing capacity and enhance stability. It is depending upon many influencing factors the load distribution mechanisms, the pile number, the space between piles and on the pile position. Geopolymers are inorganic formed by the reaction of aluminosilicate materials with alkaline activator. To produce geopolymers, two essential conditions must be fulfilled: the presence of source material abundant in Silicon (Si) and Aluminium (Al), and the addition of an alkali activator, such as sodium/potassium hydroxide..it has several advantage than other traditional soil stabilization method, which increased the soil's load-bearing capacity, enhance the soil properties. This study aims to review the studies of previous researchers and their practical and theoretical findings regarding the use of geopolymers as stabilising agents and pile raft to improve the soil's resistance properties.

Abstract: The aim of this study is to analyze the mechanical and physical properties of refractory bricks produced via geopolymerization using volcanic ash. Volcanic ash was combined with 12 M sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) as activators, with a liquid-to-solid ratio of 0.2. Two brick prototypes were produced: a cylindrical specimen for testing compressive strength and water absorption, and a rectangular prism for analyzing thermal conductivity. The bricks were calcined at 600°C and 800°C, showing favorable performance compared to well-known commercial refractory bricks. Cylindrical specimens calcined at 600°C reached an average compressive strength of 5.51 MPa, while those calcined at 800°C averaged 6.60 MPa—more than double the 2.80 MPa of commercial bricks. The average density of the specimens at both temperatures was similar, around 1.58 g/cm³, significantly higher than the 0.95 g/cm³ of commercial counterparts. Moreover, the average thermal conductivity of the geopolymer bricks was 0.008 W/m·K, indicating superior insulating properties compared to the 0.39 W/m·K of commercial refractory bricks. These results demonstrate optimal properties in refractory bricks made from geopolymer-based volcanic ash.

Abstract: The effective recycling of industrial waste is a globally significant issue. In this study, a geopolymer binder was synthesized using an alkaline activator derived from brown coal gangue and blast furnace slag, along with silica fume as an industrial waste material. Also, the properties of these geopolymer binders are examined using them as a briquette binder. At temperatures above 700°C, roasted brown coal gangue is more active than the initial state. The optimum dosage of alkaline activator is 10M NaOH, silica fume/NaOH ratio of 3, specific gravity of 1.42, and the addition of binder of 6%. The main polymerization products of the alkali activated brown coal gangue geopolymer samples are N-A-S-H gel and amorphous aluminosilicate gel, while the main polymerization products of the alkali activated brown coal gangue -blast furnace slag geopolymer samples are N-A-S-H gel, C-(A)-S-H gel and amorphous aluminosilicate gel. Blast furnace slag is added during the preparation of briquette binder by brown coal gangue geopolymer, which increase the mechanical strength of the geopolymer binder and the optimum dosage is 30%. This study demonstrates a high-value and sustainable pathway for co-utilizing multiple industrial by-products.

Abstract: Geopolymer is an alkali-activated aluminosilicate material that combine ceramic-like thermal performance with low thermal conductivity, high-temperature resistance, while remaining castable and structurally adaptable. It is synthesized from calcined kaolin (metakaolin) and fly ash, which react with alkaline solutions to form strong covalent bonds through geopolymerization. This material offers a viable alternative to conventional refractories and imported ceramic products.In this study, a geopolymer material was developed for welding applications and utilized as a weld backing strip for gas metal arc welding (GMAW) of ASTM A36 carbon steel. Weld backing strips are essential for achieving full penetration and consistent root quality in large-scale steel fabrication, particularly in structural, shipbuilding, and heavy industrial construction. The geopolymer binder consisted of 35 wt% metakaolin, 15 wt% fly ash, and a 1:1 ratio of 10 M NaOH and sodium silicate solution. To enhance thermal resistance, river sand, fine glass powder, or recycled SAW flux was incorporated as an external solid phase. Geopolymer specimens were thermally cured and fired at 500 °C to eliminate moisture and organic. Moreover, it was heated to 900 °C to simulate welding heat exposure. Microstructural, mineralogical, and functional group transformations were evaluated using XRD, SEM, and FTIR, while mechanical strength, thermal conductivity, and density were also assessed. The results indicated that glass-enhanced geopolymer exhibited the lowest thermal conductivity (0.89 W/m·K) and highest compressive strength retention after firing, owing to its partial crystallinity and preserved amorphous phase. Flux-based composites showed extensive ceramic phase formation, while sand-based composites retained high thermal conductivity and suffered severe strength loss. Welding trials confirmed that geopolymer backings effectively supported root bead formation with no cracking.

Abstract: Nowadays, researchers are trying to understand whether geopolymers have the potential to be used as a coating material, particularly for protecting metal from corrosion attack. This study aimed to evaluate the effectiveness of fly ash-based geopolymer coatings in protecting steel by immersing the coated samples in a 3.5 wt% NaCl solution for immersion periods of 1, 7, 14, and 28 days. The uncoated steel showed the NaCl color changed to yellowish and became darker with increasing immersion time, indicating severe corrosion on the uncoated steel after 28 days. Surprisingly, with 3mm geopolymer thickness coated on the steel, NaCl solution remain unchanged until 28 days immersion period. The corrosion rate exhibits a very gradual increase, with only 0.112 mm/year recorded after 28 days of immersion. No defects such as blistering, peeling, or cracking were observed on the coated steel. These results indicate that geopolymer holds considerable promise as a coating material, warranting further investigation for its potential applications in this area.

Abstract: Using cement as the primary material for making concrete, around 7%-15%, requires a significant amount of energy and generates abundant waste, thus significantly impacting the environmental conditions. Innovative materials are needed as alternatives to cement. Fly ash, as an environmentally friendly material, can be a solution to minimize the use of cement. The selected fiber is Poly-Vinyl Alcohol (PVA) fiber due to its high tensile strength, which can effectively inhibit the rate of crack development occurring in the beams. The research process was divided into two stages: geopolymer mortar compressive strength testing and beams flexural testing. Compressive strength testing of geopolymer mortar was conducted on 50x50x50 mm cube samples, tested at ages of 3, 7, and 28 days using both air curing and moist curing methods. Geopolymer mortar was created using fly ash as the base material, along with activators such as Sodium Hydroxide (NaOH) and Sodium Silicate (Na₂SiO₃). Meanwhile, flexural beams were tested in 5 samples of 150x200 mm beams with a length of 3300 mm each. The samples consisted of a control beam, a beam reinforced with commercial grouting mortar, a beam reinforced with commercial grouting mortar and PVA geopolymer fibers, a beam reinforced with geopolymer mortar, and a beam reinforced with geopolymer mortar and PVA fibers. The research results indicated that adding PVA fibers to geopolymer mortar could enhance the maximum load-bearing capacity and stiffness of the beams. Regarding failure modes, beams reinforced with PVA-free geopolymer mortar experienced delamination failure, whereas beams reinforced with PVA-containing geopolymer mortar encountered debonding failure.

Abstract: Rigid pavement is a type of pavement that uses cement as the main binding material and has a high level of stiffness. The prolonged use of cement has increasingly negative impacts on the environment. Using geopolymer as a substitute for cement can be an eco-friendly alternative solution. Geopolymer is an environmentally friendly material that can be developed as an alternative to cement concrete in the future. The purpose of this study is to determine the compressive strength of geopolymer concrete using rice husk ash and shell as fine aggregates in rigid pavement. The research method used is experimental. The method used for mix design calculation is AASHTO 1993, by making 8 test specimens. Each test specimen uses 4 aggregate and binder ratios, which are 75:25, 70:30, 65:35, and 75:25, each with 2 alkaline activator ratios, which are 3:1 and 5:2. The compressive strength testing of the specimens was conducted at 28 days. The concrete quality used, K225, is equivalent to 18.68 MPa. The compressive strength testing of geopolymer concrete achieved optimum compressive strength at a variation of 65:35 aggregate, 3:1 alkaline, 5% rice husk ash, and 5% shell, which was 18.9667 MPa. At the variation of 75:25 aggregate, 3:1 alkaline, 5% shell, the highest value was 21.4013 MPa. Based on the type of concrete according to its compressive strength, geopolymer concrete with fly ash, rice husk ash, and shell is classified as normal concrete because its compressive strength exceeds 15 MPa and can be a substitute for cement with relatively low strength.

Abstract: Geopolymer concrete is an environmentally friendly substitute for traditional Portland cement-based concrete. In contrast to conventional concrete, which contributes to substantial carbon dioxide emissions through Portland cement production, geopolymer concrete utilizes aluminosilicate materials like fly ash, slag, or metakaolin as binders. This innovative approach aims to reduce the environmental impact of construction materials by offering a more sustainable alternative to conventional cement-based concrete. Unfortunately, the technology of geopolymer concrete was mainly confined to laboratory research in developing countries due to the high cost of chemical activators used in its production. The current study explored the prospects of using wood ash (WA) lye as an alkaline activator in geopolymers. A single raw aluminosilicate material, class C palm oil fuel ash (POFA), was activated with WA lye and sodium silicate (Na₂SiO₃) to produce a geopolymer mortar. Both fresh and hardened properties tests were conducted to assess the WA lye-activated geopolymer mortar at 3, 7, 14, and 28 days. The optimum liquid/binder (L/B) ratio and alkali activator ratio (AAR) of WA lye-activated geopolymer mortar were 0.5 and 3.0, respectively. The outcome of this research indicate that WA lye can effectively be utilised to produce geopolymers with desirable properties, thereby providing an environmentally friendly and sustainable alternative to NaOH.

Abstract: The study investigates the impact of quaternary ammonium and pyridinium salts on the rheological properties of metakaolin-based geopolymer pastes, with a focus on their application in 3D printing technology The experimental results demonstrated that the addition of these salts increased both the plastic viscosity and yield stress of the geopolymer mixtures, with the effect intensifying with higher concentrations and longer aliphatic chains. The coefficient of consistency derived from Herschel-Bulkley model increased from 1.78 up to 3.83 Pa·sⁿ and the yield stress rose from 3.4 up to 31.8 Pa. The study also observed a shift from shear-thickening to shear-thinning behaviour and reduction in thixotropic properties with increased dosages of the admixtures, which is beneficial for 3D printing. The mechanical properties of modified geopolymer mortars were also tested and the results revealed quite negligible effect of admixtures on flexural strength. The compressive strength was slightly reduced by up to 12%. The findings suggest that these admixtures are effective in modifying the rheological properties of geopolymers, making them more suitable for advanced applications like 3D printing.

Abstract: The construction industry significantly contributes to global CO₂ emissions and environmental impact, mainly due to concrete usage, which consumes vast resources and energy while emitting CO₂. Researchers are exploring alternatives such as geopolymer concrete (GPC), formed without traditional cement but through alkaline activation of industrial by-products like fly ash, ground granulated blast furnace slag, bentonite, and metakaolin clay. This study evaluates the effects of incorporating bentonite and polypropylene (PP) fibers on the workability and strength properties of GPC based on slag. Bentonite substituted 10% of slag, and PP fibers were added at varying ratios (0.5%, 0.75%, and 1%). Both untreated and heat-treated bentonite, heated up to 200°C, were used. Workability was assessed using a slump cone, while mechanical properties, including compressive, split-tensile, and flexural strength, were analyzed. Notably, heat-treated bentonite and PP fibers exhibited significant enhancement in the mechanical properties of the GPC mixes.