Geopolymer Paste Research Articles

Axial compressive behaviour and physical characteristics of high strength self-compacting geopolymer concrete (HSGC) columns exposed to elevated temperature

The growing demand in the utilization of the cement has increased carbon emissions, necessitating the adoption of new technologies that are eco-friendly. Geopolymer concrete (GC) is a viable alternative to traditional cement-based concrete, with superior mechanical properties and sustainable performance. However, research on the elevated temperature exposure of geopolymer paste, mortar, and concrete is limited, particularly with respect to high-strength and self-compacting geopolymer concrete. This study aims to investigate the performance of high-strength self-compacting geopolymer concrete (HSGC) at room temperature and elevated temperatures up to 1029 ℃. The investigation is carried out consisting of two strength grades: normal strength GC and HSGC. Tests are conducted on both HSGC cube and column specimens to examine the residual compressive strength (CS) and axial compression performance of the concrete before and after exposure to elevated temperature. The fresh physical characteristics of HSGC are examined following EFNARC guidelines. Post-fire performance is analysed through physical observation, surface modification, crack pattern, weight loss (WL), and residual CS of HSGC samples. Load-Moment (P-M) interaction curves are developed to predict the ultimate load and ultimate moment capacity of the HSGC columns before and after exposure to elevated temperature. The ductility of heated and unheated HSGC columns is found to be almost same. Microstructural analysis, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) are performed to examine the internal morphology of the HSGC samples before and after exposure to elevated temperature. Furthermore, a life-cycle assessment (LCA) is conducted to compare the cost of HSGC production with conventional cement-based concrete. The analysis indicates that HSGC emits 6.15% less CO2-e than its counterpart cement-based concrete.

Development of sustainable geopolymer materials made with ground geopolymer waste powder as renewable binder up to 100%

Reusing ground geopolymer waste powder (GWP) as renewable binder in sustainable geopolymer offers a valuable approach for recycling geopolymer waste. This study investigated the micro–macro characteristics of fly ash (FA)-based geopolymer, including the replacement of FA with GWP up to 100%. The GWP comprised the GWPG from GGBS-based geopolymer paste, the GWPGF from GGBA-FA-based geopolymer paste, and the GWPF from FA-based geopolymer paste, respectively. The findings revealed that GWPG exhibited higher alkali-activated reactivity compared to GWPGF and GWPF. The geopolymer made with 100% GWPG demonstrated a better microstructure than FA-based geopolymer, but the microstructure of geopolymer deteriorated with the inclusion of GWPGF and GWPF. The average pore diameter of geopolymer made with 100% FA, 100% GWPG, 100% GWPGF, and 100% GWPF was measured at 18.06, 15.69, 116.50, and 92.62 nm, respectively. Mixing GWP led to an increase in drying shrinkage. The strength and permeability resistance of eco-friendly geopolymer initially decreased and subsequently improved with increasing substitution of GWPG, with geopolymer made with 100% GWPG exhibiting superior strength and permeability resistance compared to FA-based geopolymer. However, the strength and permeability resistance of eco-friendly geopolymer exhibited a continuous decline with the increasing replacement of GWPGF or GWPF, up to 100%. When the content of GWP was identical, GWPG blended geopolymer exhibited superior micro-structure and macro-properties compared to GWPGF or GWPF blended geopolymer. Thus, it is recommended to substitute GWPG for 100% FA in fully recycled geopolymer owning good strength and permeability resistance. However, caution should be exercised when incorporating high volumes of GWPGF or GWPF in eco-friendly geopolymer.

Microstructure and physical properties of fly-ash-based geopolymer with the addition of expanded vermiculite

Fly-ash-based geopolymer pastes with the addition of expanded vermiculite (EV) powder were synthesised and their microstructure, compressive strength, setting time, moisture control, extent of efflorescence and thermal conductivity were studied. It was found that the addition of EV resulted in an increase in the standard-consistency water consumption and setting times. As a consequence, excessive addition of EV resulted in a larger amount of harmful pores, which was detrimental for the compressive strength of the paste. However, geopolymer pastes with an appropriate amount of EV (2–7 wt%) showed a slight increase in compressive strength because of the filler effect. Mg2+ and Fe3+ diffused from the EV interlayers through ion exchange between the EV and the geopolymer, and participated in geopolymerisation. This was reflected by the formation of N-(M)-A-(F)-S-H, as evidenced by scanning electron microscopy with energy dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. In addition, Na+/Mg2+ or Na+/Fe3+ ion exchange reduced the mobility of Na+ the ions and therefore decreased the extent of efflorescence. Moreover, EV addition favoured an improvement in moisture content and the thermal conductivity properties of the geopolymer paste.

Sodium gluconate as a retarder modified sewage sludge ash-based geopolymers: Mechanism and environmental assessment

In this study, sewage sludge ash (SSA) was utilized to prepare geopolymers at room temperature, with the aim of achieving the utilization of sewage sludge resources. The study primarily investigates the effects of alkali activators and the sodium gluconate on the setting properties and mechanical properties of geopolymers prepared using a 2:3 wt ratio of SSA and ground granulated blast-furnace slag (GGBS). Results indicated that the addition of sodium gluconate significantly inhibited the reaction of geopolymers paste setting time of the geopolymer compared to changing the alkali activators parameters. An increase in sodium gluconate dosage from 0% to 3% significantly delays the initial setting time of geopolymer pastes from 31 min to 183 min. Microstructural analyses demonstrate that sodium gluconate interferes with the dissolution of precursor materials and the growth of the hydration gel in geopolymer, leading to an inhibitory effect on the early hardening process. The introduction of 3% sodium gluconate increases the area fraction of unhydrated SSA by over 45% and unhydrated GGBS by 13%, as quantified by BSE analysis. Importantly, environmental and economic analyses suggest that delaying the setting of geopolymer through the inclusion of sodium gluconate presents a more environmentally favorable option than altering the alkali activators.

Effect of Curing Temperature on Mechanical Properties of Sanitary Ware Porcelain based Geopolymer Mortar

The objective of this study was to investigate the effect of curing temperature on the mechanical properties of sanitary ware porcelain powder-based geopolymer paste and mortar under various curing temperatures. The setting time, porosity, water absorption, and compressive strength of specimens mixed with alkaline concentrations of 8M, 10M, 12M, and 14M were compared. All mortar cube (50×50×50 mm) specimens were placed into drying ovens for 24 hours at 60°C, 75°C, 90°C, and 105°C, respectively. The specimens were then air-cured for 1, 3, 7, 14, and 28 days. The results showed that the elevated curing temperature accelerated the polymerization process of the porcelain geopolymerization reaction. The setting time varied between 89 mins and 380 mins. It showed variability depending on alkaline concentration and initial curing temperature. The setting time of pastes decreased when alkaline concentrations increased. An increasing temperature in the drying oven decreased the initial and final setting times. Similar to this, the rate of water absorption and permeability of porcelain-based geopolymer mortar specimens decreased with drying oven temperatures and increments in alkaline concentration. The lowest water absorption and porosity of the specimen were 2.1% and 15.7%, respectively. The compressive strength increased as drying oven temperatures and alkaline concentrations increased. The highest 28 day compressive strength was found in 14M specimens with 105°C curing temperatures. The ultimate compressive strength was 64.45 N/mm2. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were investigated to study the microstructural properties of the geopolymers. Doi: 10.28991/CEJ-2023-09-08-01 Full Text: PDF

Properties of Geopolymers Based on Metakaolin and Soda-Lime Waste Glass.

The paper determines the properties of geopolymer pastes based on metakaolin and soda-lime waste glass. The density, alkaline activity, strength and microstructure of the reference geopolymer, as well as geopolymers with a 10%, 30% and 50% soda-lime waste glass content instead of metakaolin, were tested. The experimental results indicate that the properties of the geopolymers with waste glass largely depend on the ratio of the liquid to solid substance. Increasing the content of waste glass causes an increase in the fluidity of the geopolymer paste, which in turn allows the amount of water glass, i.e., an activator during the obtaining of geopolymers, to be reduced. On the basis of the conducted tests, it was found that the strength of geopolymers can be increased by adding up to 50% of soda-lime waste glass instead of metakaolin and by having a lower content of water glass.

Doping Silica Fume Enhances the Mechanical Strength of Slag/Fly Ash Geopolymer Paste under Frost Attack

Benign design of alkali-activated slag/FA geopolymer paste has attracted increasing attention for optimizing its service performance. Therefore, the replacement of fly ash (FA) with 10 wt% silica fume (SF) is investigated by mechanical strength after freeze–thawing cycles and microstructure characterization. The results show that an appropriate dosage (30 wt%) of slag is necessary to prepare heat-free curing alkali-activated slag/FA geopolymer paste with excellent mechanical performance. The SF/slag/FA (SF:slag:FA = 10:30:60, wt%) geopolymer paste exerts an enhanced compressive and flexural strength of 95.2 and 3.2 MPa, respectively. Meanwhile, the doped 10 wt% SF facilitates the propagation of (N, C)-A-S-H chains, rather than the formation of C-S-H gels. It is evidenced by the absent exothermic peak at about 861 °C from the differential scanning calorimetry (DSC) curves. The pores volume and tortuosity also rise for the pore diameter < 20 nm from mercury intrusion porosimeter (MIP) results, corresponding to an improved freezing–thawing resistance with the residual compressive strength of 52.8 MPa and the weight loss of 10.5% after 300 freeze–thawing cycles. It explores a cost-effective and benign facile approach to designing heat-free curing alkali-activated slag/FA geopolymer paste with good freezing–thawing resistance.

Experimental Study on Mechanical Properties and Drying Shrinkage Compensation of Solidified Ultra-Fine Dredged Sand Blocks Made with GGBS-Based Geopolymer

As natural aggregates become increasingly scarce, attention has turned to ultra-fine dredged sand (UDS) generated in waterway regulation engineering. UDS is typically challenging to utilize due to its high clay content and high water demand. This article uses ground granulated blast-furnace slag (GGBS)-based geopolymer to solidify UDS, along with sodium silicate (SS) and sodium hydroxide (SH) as alkaline activators. This paper explores the effects of SS modulus (SiO2/Na2O molar ratio) and mass percentage content of Na2O on the fluidity, setting time, mechanical properties, and shrinkage behavior of hybrid UDS-GGBS geopolymer (HUGG) paste. According to the research findings, increased SS modulus and Na2O content lead to decreased fluidity and setting time. When the Na2O content reaches 6%, flash coagulation occurs in the slurry, leading to more internal shrinkage cracks and pores. This has been confirmed by scanning electron microscope (SEM) analysis. When Na2O content is 5%, and SS modulus is 1.0, the 90-day maximum compressive strength reaches 56.53 MPa, corresponding to a splitting tensile strength of 6.83 MPa, which can be considered the optimal formulation. Meanwhile, basalt and polypropylene fibers (BF and PPF) are chosen to compensate for the susceptibility to drying shrinkage. Both BF and PPF can significantly inhibit the linear drying shrinkage of the HUGG paste. The BF’s ability to enhance mechanical properties is more robust than PPF’s, which can make the paste more homogeneous. The research contributes an effective method for the resource utilization of UDS.

Experimental study on the characteristics, rheological factors, and flowability of MK-GGBFS geopolymer slurry

In this study, we investigated the effects of concentration and modulus of alkaline activator, liquid–solid (L/S) ratio, and sand volume fraction on rheological properties and flowability of metakaolin (MK)–ground granulated blast furnace slag (GGBFS) geopolymer slurry (pastes and mortars). The rheological property of geopolymer slurry was consistent with the Bingham model. A decrease in the modulus and the L/S ratio, or an increase in the concentration increased the plastic viscosity of geopolymer paste. The geopolymer pastes with higher plastic viscosity exhibited a lower fluidity. The yield stress of geopolymer paste was negatively correlated with concentration, modulus, and L/S ratio. An increase in the sand volume fraction increased the plastic viscosity and yield stress of geopolymer mortar, and decreased the consistency and fluidity of that. Moreover, the correlation between rheological parameters of the geopolymer mortar and paste, and the relationship between the flowability parameters and rheological parameters of geopolymer slurry were constructed.

Phase change materials incorporation into 3D printed geopolymer cement: A sustainable approach to enhance the comfort and energy efficiency of buildings

The advent of 3D printing has revolutionized conventional construction, offering cost-effective and fast construction of complex structures. Nevertheless, there remain challenges to be addressed regarding the effective integration of functional additives into 3D printing construction materials. Herein, we present a straightforward and environmentally friendly approach to promote sustainable buildings while reducing energy consumption. This is achieved by integrating Macroencapsulated Phase Change Materials (MEPCM) into a 3D printable geopolymer paste (GPP) derived from fly ashes. The research followed a systematic methodology, encompassing the assessment of fresh and hardened properties of geopolymer pastes with varying amounts of MEPCM, analyzing their thermal properties, and investigating the thermal performance by printing miniature houses without and with 20 vol% MEPCM. Notably, MEPCM demonstrated its dual functionality as a thermal energy management component and a viscosity modifier for 3D printable geopolymer paste. Overall, this study paves an innovative path toward sustainable construction, highlighting the significance of energy efficiency and waste reduction.

Bio-mechanical efficacy for slag/fly ash-based geopolymer mingled with mesoporous NiO

The main target of this research is the fabrication of pre-cast/self-cleaning eco-friendly building materials with adequate mechanical properties to be used in constructions exposed to bacteria, such as hospitals, to prevent the spread of epidemics and diseases. The impact of different doses of mesoporous NiO (MP-NiO) on the compressive strength value of 50 wt%slag+ 50 wt%fly-ash geopolymer paste was studied at different curing regimes. At 28-days of normal curing, the strength values for the modified pastes containing 0%, 0.5%, 1%, and 2% MP-NiO were 47, 62.4, 65.9 and 58.5 MPa, respectively, while these values completely changed under hydrothermal treatment to become 98.6, 104.8, 105.6 and 100.8 MPa, respectively at 6bars for 4hrs. XRD, TGA/DTG, and SEM techniques affirmed the dual effect of MP-NiO and hydrothermal curing in the production of CSHs, CAHs, CASHs, zeolitic phases, nickel-aluminate spinel (NiAl2O4) and calcium-nickel-silicate (CaNiSi2O6) that reinforced the internal microstructure. The self-cleaning test was conducted via the agar diffusion method. High bacterial resistivity was observed in the cases of discs containing 1% mesoporous NiO, whatever the curing conditions, as these discs strongly resisted the growth of Salmonella, K.Pneumonia, and E. Faecalis and the measured inhibition zones around normally cured discs were 44 ± 1, 44 ± 1, and 52 ± 2, respectively while the measured inhibition zones around autoclaved discs were 45 ± 1, 43 ± 1, and 48 ± 2, respectively.

Hybrid geopolymer paste from high calcium fly ash and glass wool: Mechanical, microstructure, and sulfuric acid and magnesium sulfate resistance characteristics

Geopolymer is a sustainable binder composed of source materials containing aluminosilicates under strongly alkaline conditions promising for use in place of cement in building materials due to its low carbon footprint. Although high calcium fly ash can be used as a source material for geopolymer binder, it has rarely been studied with other wastes especially, glass wool waste. Therefore, this study presents the use of glass wool (GWF) from the insulating materials waste and high calcium fly ash (HCFA) as binary precursors to produce geopolymer paste. HCFA was replaced by GWF at a ratio of 10–40% by weight. The sodium silicate-to-sodium hydroxide (NS/NH) ratio of 1.0 and a liquid-to-binder ratio of 0.6 were used. The geopolymer pastes were cured at room temperature before mechanical, microstructural, and durability property analyses. The results showed that the setting time and slump flow increased with increasing GWF content. The incorporation of GWF had little effect on the early strength of the geopolymer paste, but the 28-day compressive strength was significantly enhanced up to ∼67% (30% replacement) higher than that of the HCFA geopolymer paste. Likewise, the flexural strength increased with increasing GWF replacement content. The total porosity of the hybrid geopolymer paste was lower than that of the HCFA one resulting from the reaction and filling effect of the geopolymer matrix. The XRD, FTIR, and SEM-EDX analyses showed the presence of geopolymerization products with calcium silicate hydrate regardless of the geopolymer mixture composition. This suggested that GWF could react with alkaline activators to form geopolymer products even though some unreactive GWF was observable when GWF replaced at 40% by weight. Furthermore, an increase in GWF content led to better resistance to sulfuric acid and magnesium sulfate attack, which was observed within 180 days. All of these results suggested that GWF was an effective secondary precursor for improving the fresh and hardened properties of HCFA-based geopolymer paste. In addition, the residue acts as a reinforcing material in the matrix paste. Consequently, improved resistance to acid corrosion and sulfate expansion were significant.

Pelindung Dinding Terhadap Hujan Asam Menggunakan Geopolimer Berbasis Nanosilika dan Cellulose Nanocrystals

Geopolymers have a weakness in durability against exposure to acid rain. Nano-silica and Cellulose Nanocrystals (CNCs) can be incorporated to enhance the acid rain resistance of geopolymers. This study aims to investigate the durability of geopolymer-based nano-silica and CNCs against exposure to acid rain. This study employed a rain simulation infiltration method. The concentrations of nano-silica and CNCs used were 4% and 1%, respectively. The compressive strength of the geopolymer specimens was tested before and after exposure to assess the effects of acid rain. Additionally, SEM and XRD tests were conducted to analyze microstructural changes. The results revealed a significant reduction in the compressive strength of the geopolymer without nano silica and CNCs (36.14% and 26.73% at pH 4 and 5, respectively). In contrast, the geopolymer paste containing nano-silica and CNCs exhibited lower reductions of 22.93% and 19.77% at pH 4 and 5, respectively. These findings indicate that the addition of nano-silica and CNCs contributes to the preservation of compressive strength. The observed effect is attributed to the ability of nano-silica and CNCs to impede acid attack on the geopolymer paste, thereby preventing the degradation of calcium levels present in the fly ash within the geopolymer. The strength degradation of the geopolymer paste resulted from the breakdown of Al–O, Si–O, and calcium bonds within the system, triggered by the reaction with H2SO4 from the acid rain. Nano-silica and CNCs-based geopolymers exhibit positive effects and can be utilized as a coating on the walls of buildings.

Effect of industrial waste-based precursors on the fresh, hardened and environmental performance of construction and demolition wastes-based geopolymers

The main goal of this study is to evaluate the effects of incorporation of the industrial wastes into Construction and Demolition Waste (CDW)-based geopolymer mixtures. To do this, a series of CDW-based geopolymer paste mixtures were produced and blast furnace slag (BFS), fly ash (FA), and silica fume (SF) were used to partially replace the CDW-based materials at the substitution rate of 10 and 20 % by weight. Flow table, buildability, vane shear, ram extruder and compressive tests were performed to assess some engineering performances of produced mixtures. Besides that, life cycle assessment analysis was conducted to reveal both the environmental impact of CDW-based mixtures and effects of industrial wastes. The results demonstrated that the geopolymer mixture with higher flowability and longer open time can be obtained by the incorporation of industrial waste precursors. Among them, FA incorporation resulted in the highest improvement in flowability while more decrement in shear yield stress was obtained from the SF-incorporated mixtures. Substitution of CDW-based precursors with industrial wastes provided higher compressive strength test results. Although 100% CDW-based geopolymer paste had lower environmental burden, the mixture using FA, BFS and SF followed very closely behind it. The transportation-related impacts were the most determinative factor for the differences between the environmental performance of geopolymer mixtures containing and non-containing industrial waste-based precursors. Overall, the main sources of environmental burdens of CDW-based geopolymer systems were the alkaline activators, electricity, and transportation. Results showed that industrial waste-based precursor can be successfully used in CDW-based geopolymer matrix to adjust engineering properties without endangering the environmental burden of the mixture.

Efflorescence Formation Mechanism and Control for Geopolymer Paste Specimens Made from Natural Pozzolan and Calcium Hydroxide Binders

Efflorescence Formation Mechanism and Control for Geopolymer Paste Specimens Made from Natural Pozzolan and Calcium Hydroxide Binders

Microstructural Analysis and Compressive Strength of Fly Ash and Petroleum Sludge Ash Geopolymer Mortar under High Temperatures

The development of sustainable building materials and construction to decrease environmental pollution in both production and operational stages of the materials’ life cycle is appealing to great interest in the construction industries worldwide. This study evaluated the negative effect of temperature up to 1000 °C on the compressive strength and microstructure of fly ash and petroleum sludge ash (PSA) geopolymer mortar. A sodium silicate and sodium hydroxide mixture is used as an activator. The synthesized mortar was investigated using X-ray Diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR), Mercury Intrusion Porosimetry (MIP), and Field Emission Scanning Electron Microscopy (FESEM). As the temperature increased, the compressive strength of the geopolymer mortar decreased. The strength degradation is due to the damage to microstructure because of the temperature-induced dehydroxylation, dehydration thermal incompatibility between geopolymer aggregate and paste of geopolymer mortar at high temperatures. With an increase in temperature, the cumulative pore volume increased. The FESEM image showed the decomposition of the geopolymer matrix started at a temperature of 600 °C. Incorporating PSA in geopolymer mortar could result in an eco-friendly and sustainable environment that may reduce the problems associated with sludge disposal.

Optimization of process parameters for the synthesis of class F fly ash-based geopolymer binders

The Taguchi optimization approach was applied in this study to identify the optimal mix ratios for the production of geopolymer paste that uses fly ash as an aluminosilicate precursor. The method allows for probing the combined effect of selected process parameters on the output response with the least number of experiments possible, thereby reducing overall process time, cost, and effort. The compressive and splitting tensile strength values of the geopolymer paste specimens were explored in terms of alkali activator to binder ratio, NaOH concentration, Na2SiO3 to NaOH mass ratio, and standing time. A total of sixteen different proportions of mixtures were prepared, and the mechanical strengths of the specimens were evaluated using a universal testing machine. XRD and SEM analyses were used to examine the microstructures of the fly ash and the proposed optimized geopolymer paste. Results showed that a combination of alkali activator to binder ratio of 0.46, NaOH concentration of 14 M, Na2SiO3 to NaOH mass ratio of 1.5, and standing time of 72 h were found to be the best parameter settings yielding the highest strength of the paste specimens. The maximum compressive and splitting tensile strengths were 24.96 and 4.40 MPa, respectively, at the corresponding optimal values of the parameters. The apparent density of the specimens at these optimal conditions was determined to be 1835 kg/m3. From ANOVA results, it was observed that standing time and NaOH concentration had a significant influence on compressive and splitting tensile strength values, respectively. Based on the confirmation test, a variation of 4.1% and 2.2% in compressive and splitting tensile strengths, respectively, were observed as a result of extraneous variables.

Effect of rice husk ash on properties of slag based geopolymer pastes

With the increasing commercialization of fly ash and slag, the price of slag is gradually increasing and there is a need to reduce slag consumption and utilize China's large rice husk production to introduce rice husk ash (RHA) as the raw material. In this experiment, the amount of RHA accounted for a high proportion (50%–80%), and the influence of the amount of RHA on compressive strength, flexural strength, water absorption and moisture absorption coefficient was studied. It is proposed that the degree of efflorescence can be judged according to the water evaporation rate, and the efflorescence degree can be quantitatively characterized by Image-Pro Plus® 6.0, mass weighing of efflorescence substance and pH measurement. In addition, microstructural experiments (SEM, XRD and MIP analysis) were also conducted to confirm the macroscopic experimental phenomena. The test results show that considering the compressive strength and flexural strength, 60% RHA and 40% slag (R6S4) are used together as the precursors to obtain the best mechanical properties. Increasing RHA can raises the water absorption performance, which can play the role of internal curing; meanwhile, it reduces the water evaporation rate by changing pore structure, and fewer free water as carriers inside the sample migrates to the outer surface, inhibiting efflorescence.

Investigation of Corrosion Behaviour of Mild Steel Embedded in Geopolymer Paste with Curing and Non-Curing Process

Investigation of Corrosion Behaviour of Mild Steel Embedded in Geopolymer Paste with Curing and Non-Curing Process

Pemanfaatan Lusi dan Fly Ash Sebagai Material Bautan Berdasarkan Nilai Berat Jenis Agregat Halus dan Porositas

Sidoarjo mudflow (Lusi) still occurs today, various efforts to stop and reduce the eruption have been made but have not stop able to stop the Sidoarjo mud. To help reduce the mud being ejected, it is necessary to utilize Sidoarjo mud. Researchers aim to reduce the mud caused by Sidoarjo mud by utilizing artificial materials as substitutes for natural materials. Utilization is also carried out for fly ash which is waste from the PLTU. Sidoarjo mud and fly ash are combined with an alkaline activator to form geopolymer paste and cement paste. The geopolymer paste specimen were tested for specific gravity of fine aggregate and its porosity. The result show Sidoarjo mud has a specific gravity of fine aggregate of 2.519 and fly ash of 2.525 which is greater than specific gracity of water, namely 1. The porosity of the geopolymer paste is 3% and that of cement paste is 3.8%.