Molar NaOH Research Articles

Compressive Strength Estimation of Geopolymer Composites through Novel Computational Approaches.

The application of artificial intelligence approaches like machine learning (ML) to forecast material properties is an effective strategy to reduce multiple trials during experimentation. This study performed ML modeling on 481 mixes of geopolymer concrete with nine input variables, including curing time, curing temperature, specimen age, alkali/fly ash ratio, Na2SiO3/NaOH ratio, NaOH molarity, aggregate volume, superplasticizer, and water, with CS as the output variable. Four types of ML models were employed to anticipate the compressive strength of geopolymer concrete, and their performance was compared to find out the most accurate ML model. Two individual ML techniques, support vector machine and multi-layer perceptron neural network, and two ensembled ML methods, AdaBoost regressor and random forest, were employed to achieve the study’s aims. The performance of all models was confirmed using statistical analysis, k-fold evaluation, and correlation coefficient (R2). Moreover, the divergence of the estimated outcomes from those of the experimental results was noted to check the accuracy of the models. It was discovered that ensembled ML models estimated the compressive strength of the geopolymer concrete with higher precision than individual ML models, with random forest having the highest accuracy. Using these computational strategies will accelerate the application of construction materials by decreasing the experimental efforts.

Ammonia recovery from acidogenic fermentation effluents using a gas-permeable membrane contactor

A gas-permeable membrane (GPM) contactor was used to recover ammoniacal nitrogen from a synthetic and a biowaste fermentation broth under different pH (from 6 to 11) and temperatures (35 and 55 °C). Ammonia mass transfer constant (Km) increased as pH and temperature increased. For synthetic broth, pH 10 provided the best results, when considering the Km (9.2·10-7 m·s-1) and the reagents consumption (1.0 mol NaOH·mol-1 TAN and 0.6 mol H2SO4·mol-1 TAN). Biowaste fermentation generated a broth with a high concentration of ammoniacal nitrogen (4.9 g N·L-1) and volatile fatty acids (VFA) (41.1 g COD·L-1). Experiments using the biowaste broth showed a lower Km (5.0·10-7 m·s-1 at pH 10) than the synthetic broth, related to the solution matrix and other species interference. VFAs were not detected in the trapping solution. Overall, these results show that GPM is a suitable technology to efficiently separate ammoniacal nitrogen and VFA from fermentation broths.

Sulfur concrete made with waste marble and slag powders: 100% recycled and waterless concrete.

In this research, the mechanical properties and durability of sulfur concrete with two different waste aggregates were evaluated. The waste aggregates included ground granulated blast-furnace slag and waste marble powder. The properties of sulfur concrete were also compared with those of the conventional binder concretes (i.e., Portland cement concrete and sulfate-resistant cement concrete). The durability parameters included measuring water absorption capacity and resistance to different harsh chemical environments (5% HCl solution, 5 Molar NaOH solution, and 16% NaCl solution). It was found that sulfur concrete made with slag as aggregate exhibited the maximum strength, i.e., about 2 times higher than that of Portland cement concrete and sulfate-resistant cement concrete. Sulfur concrete made with slag and marble waste powder showed superior mechanical performance compared to that made with river sand. Thus, sulfur binder develops more favorable properties with eco-friendly fillers than it develops with natural sand. In harsh chloride and acidic environment, sulfur concrete with slag powder exhibited about 90-95% lesser mass loss than Portland cement concrete.

Investigation of the Geopolymerization Potential of a Waste Silica-Rich Diabase Mud.

Diabase mud (DM) is a silica-rich residue yielding from aggregate crushing and washing operations in quarries. This work focuses on identifying the geopolymerization potential of a diabase mud through characterization of its mineralogical composition, investigation of its reactivity, and assessment of the early compressive strengths of alkali activated mixtures formulated based on the mud’s dissolution results. The findings suggest that considerably low amounts of Al and Si metals were dissolved following the dissolution tests conducted on DM, however, the incorporation of small quantities of CEM I, gypsum, and metakaolin (MK) moderately at a Na2SiO3:NaOH ratio of 50:50 and with a molarity of NaOH of 4 M enhanced the geopolymerization compared to low L/S ratio mixtures cured at different conditions. When M was increasing, the high L/S ratio mixtures exhibited fluctuations in strengths, especially beyond a 10 M NaOH molarity. Maximum strengths of mixtures at equivalent molarity of 10 were achieved when the Na2SiO3:NaOH ratio reached 30:70, regardless of the ambient conditions and the presence of CEM I. The curing conditions, the ratio of Na2SO3:NaOH, and the presence of CEM I in the DM-based mixtures did not appear to significantly affect the mixture when NaOH concentration was between 2 M and 4 M; at higher molarities, however, these enhanced the strengths of the geopolymerized DM.

Synthesis and Characterisation of Nano-silica Based on Pumice Using NaOH

Nano-silica was synthesised from pumice by extraction method using sodium hydroxide (NaOH), sulphuric acid (H2SO4) and hydrochloric acid (HCl). The raw material of pumice was collected from local area, Tanggamus-Lampung Indonesia. After grinding, the pumice powder was activated at 450°C for 2 h before mixing with NaOH for extraction. After extraction, the powder was heated at 800°C for 4 h, to maintain the silica is in amorphous phase. Physical characteristics were analysed using transmission electron microscopy (TEM) for measuring particle size, Brunauer-Emmett-Teller (BET) technique for surface area measurement, x-ray diffraction (XRD) for structure and x-ray fluorescence (XRF) for determination of oxides. XRD analysis proved that besides amorphous nano-silica, there are peaks of sodium sulfate (Na2SO4) as representation of crystalline structure. The maximum silicon dioxide (SiO2) content was found on 3.0 molar (M) NaOH. The highest surface area of 165 m2 /g was obtained in sample of 3.5 M NaOH. The truly amorphous nano-silica content was found in NaOH of 3.0 M. The formation temperature may occur between 1100°C–1200°C. The particle size is in the range of 9 nm–17 nm.

Study on the Influence of Processed Rice Straw Ash as a Binder on Compressive Strength and Water Absorption of Alkali Activated Mortar

Major concern today with cement production is its environmental issues. For the sustainable development the usage of cement is reduced day by day in the construction sector. The alkali activated binders (AAB) are eco-friendly and they do not cause any environmental effects which can be used as one of the alternatives to cement. AAB is a hardened cementitious paste made of industrial pozzolanas such as Fly Ash and GGBS, and alkaline solutions like sodium hydroxide and sodium silicate. Currently Fly Ash is the most commonly used AAB; but fly ash may become scarce because coal- fired power plants are declining due to the increasing popularity of renewable energy.
 Rice straw ash (RSA) is an agricultural waste which has the pozzolanic characteristics and contains about 70%-80% of amorphous silicon dioxide (SiO2) when burnt at 650c. Rice straw can be used as replacement of fly ash in Alkali Activated Mortar (AAM) by burning it at 650c and milling it for 10 minutes, 20 minutes and 30 minutes. The specimens are casted for Rice Straw based AAM and compressive strength and water absorption are studied for 7.5, 10, 16 molarity of NaOH and also RSA milled for 10,20 and 30 minutes and SEM EDX is studied for the hardened specimen at 28 days. 
 The RSA has significant positive effects on performance of AAM. The replacement of RSA by 20% has shown greater results and as the milling time of RSA is raised the surface area of RSA is increased which in turn resulted in improved strength and as the molarity of NaOH is increased the AAM at 3, 7, 28 and 56 days has the higher Compressive Strength and lower Water absorption.

Geopolymer Concrete with Lightweight Artificial Aggregates.

This article presents the physical and mechanical properties of geopolymer concrete with lightweight artificial aggregate. A research experiment where the influence of fly ash–slag mix (FA-S), as part of a pozzolanic additive, on the properties of geopolymers was carried out and the most favorable molar concentration of sodium hydroxide solution was determined. The values of three variables of the examined properties of the geopolymer lightweight concrete (GLC) were adopted: X1—the content of the pozzolanic additives with fly ash + flay ash–slag (FA + FA-S) mix: 200, 400 and 600 kg/m3; X2—the total amount of FA-S in the pozzolanic additives: 0, 50 and 100%; X3—the molarity of the activator NaOH: (8, 10 and 12 M). In order to increase the adhesion of the lightweight artificial aggregate to the geopolymer matrix, the impregnation of the NaOH solution was used. Based on the obtained results for the GLC’s compressive strength after 28 days, water absorption, dry and saturated density and thermal conductivity index, it was found that the most favorable parameters were obtained with 400 kg/m3 of pozzolanic additives (with 50% FA-S and 50% FA) and 10 NaOH molarity. Changes in the activator’s concentration from 8 to 10 M improved the compressive strength by 54% (for a pozzolana content of 200 kg/m3) and by 26% (for a pozzolana content of 600 kg/m3). The increase in the content of pozzolanic additives from 200 to 400 kg/m3 resulted in a decrease in water absorption from 23% to 18%. The highest conductivity coefficient, equal to 0.463 W/m·K, was determined, where the largest amount of pozzolanic additives and the least lightweight aggregate were added. The structural tests used scanning electron microscopy analysis, and the beneficial effect of impregnating the artificial aggregate with NaOH solution was proved. It resulted in a compact interfacial transition zone (ITZ) between the lightweight aggregate and the geopolymer matrix because of the chemical composition (e.g., silica amount), the silica content and the alkali presoaking process.

Hardened Mechanical Properties of Self Compacting Geopolymer Mortar

The self-compacting geopolymer mortar (SCGM) is a new revolutionary concept in the construction industry. This study presents a summary of different influencing parameters that effect the compressive strength of SCGM. The test results showed that the water to geopolymer solid ratio (W/GPS), sodium hydroxide (NaOH) concentration, curing temperature, and curing rest period were the important parameters that had a significant impact compressive strength of SCGM. The increase in fly ash to sand ratio from 0.5 to 0.67 had a negative impact on the compressive strength of SCGM. The increase in curing temperature from 50°C to 80°C resulted in a continuous increase in the compressive strength of SCGM, however, its effect was much more significant at higher NaOH concentrations. Moreover, a contin-uous increase in the rest period before heat curing also had a negative impact on the compressive strength of SCGM. The increase in mixer speed resulted in an increase in compressive strength due to proper mixing of high viscosity SCGM paste. The 28 days compressive strength of more than 20 MPa with good flowability can be achieved for SCGM mix with W/GPS less than 0.349, NaOH molarity of 16 M, and cured at 50°C to 80°C without any rest period.

Sustainable Management Strategy for Solidification/Stabilization of Zinc Plant Residues (ZPR) by Fly Ash/Clay-Based Geopolymers

Solidification/stabilization (S/S) of acid waste using Ordinary Portland Cement (OPC) is widely implemented, but, due to the impact on climate change, alternative methods are being investigated. In this work, first, the feasibility of using coal fly-ash/clay-based geopolymers for the S/S of Zn plant residues (ZPR), Cadmium Sponge (CS), and Anode Mud (AM) is proposed as a treatment prior to disposal in landfills. Different variables, such as the type of processing, molding (as-received waste), and pressing (dried waste), and activators, a commercial and an alternative residual sodium carbonate, have been studied. The technical and environmental assessments of the S/S process by means of compressive strength and the leaching of critical pollutants have been monitored. Immobilization efficiencies of Cd and Zn higher than 99% have been obtained by dosing 50% of the acid waste, 6 M NaOH solution (20 min contact time), cured at 75 °C (48 h) and at room temperature (28 days), achieving in the leachates pH values of 7 to 10 and [Cd] and [Zn] < 1 and 2.5 mg/kg, respectively. However, alkaline activation increases As leaching, mainly associated with the clay. Secondly, removing clay from the geopolymer formulation, the optimization of geopolymer parameters, acid waste/geopolymer ratio, liquid/solid ratio, and NaOH molar concentration enables obtaining a significant reduction in the release of As and Cd, and Zn is kept at acceptable values that meet the non-hazardous waste landfill disposal limits for the S/S of both acid wastes.

Solubility of Calcined Kaolinite, Montmorillonite, and Illite in High Molar NaOH and Suitability as Precursors for Geopolymers

Clays and clay minerals dissolve over a broad pH range, such as during sediment diagenesis and in a variety of applications, including nuclear waste storage, landfills, and geopolymer binders in the construction industry. The solubility depends on process parameters (pH, temperature, pressure, etc.) and material properties (phase content, clay mineral composition, particle size, etc.). Pretreatments such as calcination or severe grinding change the material properties and could enhance solubility, which is called activation. The aim of the current study was to determine the solubility of three different clay minerals after calcination (metakaolinite, metamontmorillonite, and metaillite) in high molar alkaline solutions (NaOH) up to 10.79 mol/L and pH = 14.73. Furthermore, the solubility of an Al(OH)3 powder in alkaline solution (NaOH) was analyzed, as it can be used to adjust the Si:Al ratio of geopolymer precursors. The residues of the clay minerals after the alkaline treatment were investigated to disclose potential alterations in their phase contents. Based on the results of the thermal and alkaline activation, conclusions about the suitability as geopolymer precursors were made. All clay minerals showed an increase in solubility proportional to the concentration of the alkaline solution. The solubility decreased in the order metakaolinite > metamontmorillonite > metaillite. Thereby, dissolution was incomplete for all three clay minerals (<90%) after 7 days and congruent for metakaolinite and metaillite but incongruent for metamontmorillonite.

THE EFFECT OF MODIFY NaOH CONCENTRATION ON THE STRUCTURE AND MAGNETIC PROPERTIES IN CO-PRECIPITATED NANOCRYSTALLINE BISMUTH SUBSTITUTED COBALT FERRITE

The structural and magnetic properties modification in the bismuth substituted cobalt ferrite nanopowder with various molar concentrations of NaOH has been successfully synthesized by the coprecipitation method. The crystalline structure was measured using X-ray diffraction (XRD), bond groups, and absorption strength was measured by Fourier Transform Infrared spectroscopy (FTIR) studies, and then magnetic properties were measured using a Vibrating Scanning Magnetometer (VSM). The XRD measurement results confirmed that the whole samples of bismuth cobalt ferrite owing single phase of inverse spinel face cubic center (fcc) with space group Fd-3m were obtained for variations in molar concentration of NaOH. The FTIR measurements obtained that the absorption characteristic in the frequency band 400 - 750 cm-1 according to resonance at octahedral and tetrahedral sites of the occurrence metal oxide. The VSM measurement showed that the magnetic properties of bismuth substituted cobalt ferrite available to tune with modifying NaOH concentration in the co-precipitation procedure. Thus, the effect of increasing the concentration of NaOH into bismuth-substituted cobalt ferrite can change the characteristics of the cobalt ferrite such as lattice parameters, shifts in the absorption peaks of functional groups, and changes in magnetic saturation. The significance of this research is to know the exact concentration value of bismuth substituted cobalt ferrite to obtain the best characteristics.

Facile Low-Cost Synthesis of Highly Photocatalitycally Active Zinc Oxide Powders

The industrial waste can cause significant harm to human health and to the environment. Organic dyes in particular are environmentally dangerous since they may cause the death of aquatic life or contaminate the feed chain. Thus, one of the current research fields consists of the development of an inexpensive and environmentally friendly method to purify wastewater from organic contaminants. Among the others, Zinc oxide (ZnO) is considered one of the most effective photocatalysts for the decomposition of organic pollutants in water. In this work, we developed a highly efficient low-temperature and environmentally safe synthesis method to obtain photocatalytically active nanostructured ZnO by chemical precipitation from a solution. The effect of the technological conditions of synthesis on the photocatalytic properties is considered in detail, the correlation with the morphology, structural, and optical properties of the synthesized ZnO samples is determined. It was found that the maximum photocatalytic activity with respect to the decomposition of the dye rhodamine-B (RhB) is achieved for samples synthesized at NaOH molar concentration from 0.4 to 0.7 M; in this case, the sizes of crystallites along the crystallographic direction 002 reach maximum values of ∼42 nm. On the contrary, the sizes of crystallites along the directions 100 and 101 decrease monotonically from 30 to 25 nm with an increase in the molar concentration of NaOH from 0.14 to 1 M.

Effect of Curing Regime on Compressive Strength of Geopolymer Concrete

Advancement of reasonable development materials has been the focal point of exploration globally in recent times. Considering the current scenario, finding options in contrast to Ordinary Portland concrete (OPC) is of incredible importance as a result of high CO2 emission during its production. Accordingly, supplementary material was acquainted as alternative to cement for concrete production. Utilisation of fly ash is eco-accommodating and furthermore saves cement cost. It is wealthy in silicate and alumina and it responds with alkaline solution to produce alumina silicate gel which helps in fastening the concrete ingredients. The fly ash based geo polymer offers better protection from the forceful condition and elevated temperature than the ordinary cement. Some factors like NaOH Molarity, NaOH/Na2SiO3 percentage assume a fundamental element in the development of the geopolymerization reaction became concept of. The investigation on the fly ash based geo polymer profoundly did in the present work, besides the impact of elevated temperature and time are not exceptionally recorded in the available literature. In this study the effect of curing temperature and curing time on the compressive strength (3, 7 and 28 days) of GPC at a constant molarity of NaOH and alkaline solution ratio and compare with controlled concrete. In the present work 10 molars of NaOH and 1:1.5 alkaline solution ratio was considered by varying curing temperature 60°, 90° and 120° C and 24, 48 and 72 hours of curing time. M30 grade concrete mix with the equivalent GPC is developed. From the experimental results, it was found that compressive strength was effected by curing temperature and curing time at 3, 7 and 28 days and maximum compressive strength i.e., 53.46 MPa was obtained at higher curing temperature (120° C) and lower curing time (24 hrs). Also, when compared with control concrete, the compressive strength is higher for GPC was observed.

Production of green bricks from low-reactive copper mine tailings: Chemical and mechanical aspects

To achieve sustainable construction and respond to the ever increasing demand for construction materials, including bricks, it is in an urgent need to use innovative technologies, like geopolymerization, to produce green and sustainable construction materials. Therefore, this study investigates the utilization of low-reactive copper mine tailings (MT) with slag (SG) as a supplemental cementitious material to produce green bricks based on the geopolymerization technology. To this end, the effects of several parameters including NaOH molarity (10 and 15 M), Na2SiO3/NaOH ratio (0, 0.5, 1, 1.5, 2, 2.5, and 3), slag (SG) content (0, 10, and 20 wt% of MT + SG), forming pressure (0, 5, 10, 15, 20, and 30 MPa), water-to-solid ratio (0.12, 0.14, and 0.16), and curing temperature (60, 75, 90, 105, and 120 ℃) on the physical and mechanical performance of geopolymer brick specimens are investigated through unconfined compression and water absorption tests. In addition, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses are conducted to understand the changes in microstructure and phase composition after geopolymerization. The results show that using only MT does not lead to a durable geopolymer product because of the low leaching of Si and Al species from the MT. However, with the incorporation of SG as a supplementary cementitious material, geopolymer bricks that satisfy the ASTM requirements can be produced.

Liquid scintillation counting can underestimate 14C-activity of 14CO2 trapped in NaOH

Mineralization of organic matter in environmental samples is frequently quantified by trapping 14CO2 released from the degradation of 14C-labelled compounds. However, when 14CO2 trapped in NaOH is quantified by liquid scintillation counting, 14C-activity can be gradually lost from the scintillation vials. When combining different molarities and volumes of NaOH and five commercial scintillation cocktails, we observed in some mixtures a rapid loss in 14C-activity of up to 10% after 0.5 h and 60% after 96 h, while other mixtures showed no loss of 14C-activity for at least 96 h. The 14C-activity loss depended on molarity, volume, and CO2 saturation of NaOH, as well as the scintillation cocktail used and the mixing ratio of the two components. We show that the decline of 14C-activity may be caused by the loss of 14CO2 from the scintillation vials. The loss of 14C-activity must be prevented and therefore we provide recommendations how to accurately quantify 14C-activity of 14CO2 trapped in NaOH using liquid scintillation counting.

Mechanical and microstructural characteristics of geopolymer mortars at high temperatures produced with ceramic sanitaryware waste

Excessive amounts of solid wastes are generated by the ceramic sanitaryware sector in the world. Recycling ceramic wastes is one of the crucial solutions to ensure their elimination. This experimental study investigates the mechanical and microstructural characteristics of geopolymer mortars with recycled ceramic sanitaryware waste powder (CSW) exposed to high temperatures. The geopolymer mixtures are produced using CSW with four different molarity (10, 12, 14, and 16 M) of NaOH as alkali-activator and two water/binder ratios (0.45 and 0.50). The investigated properties of the CSW-based Mortars (CSW-M) are the flowability, unit weight, apparent porosity, flexural strength, compressive strength, phase, and microstructure utilizing X-ray diffractometry (XRD), and scanning electron microscopy (SEM/EDS). The increase in NaOH concentration is observed to improve the flow workability of CSW-M and reduce the apparent porosity and water absorption of specimens. Mechanical test results indicate that strength values of CSW-M increase with increasing NaOH molarity. The highest strength is obtained on the CSW-M made with 16 M NaOH and 0.45 w/b ratio. The crystalline phases are determined to be mullite, quartz and albite derived from ceramic sanitaryware waste. Additionally, zeolite is formed by the secondary reaction product after elevated temperatures. Performance analysis results reveal that using ceramic sanitaryware waste is a strong alternative material as a binder to produce geopolymer mortars and contributes to the elimination of the waste.

Phase dissolution and improving properties of completely decomposed granite through alkali fusion method

Low-reactive completely decomposed granite (CDG) was successfully synthesized by thermal activation with the addition of NaOH at low alkali/CDG mass ratio of 0.1/1. During alkali fusion, the degree of amorphicity of CDG rich in kaolinite (Al2Si2O5(OH)4) increased and a significant reduction of the peak intensities occurring between 20 and 45 (o2 theta) was observed. Reactivity analysis indicated that, initial CDG requires high molar NaOH to provide a proper dissolution, whereas fused CDG exhibits high reactivity (29Si = 555.57 ppm; 27Al = 223.73 ppm) at low NaOH concentration. Moreover, results from the setting time, varied between 15 and 45 min, indicating that alkali fusion is very effective for improving the dissolution of the fused CDG under Na2SiO3 solution. However, the setting time decreases as the reaction degree accelerates. FTIR analysis of the fused CDG presented lower wavenumber band of around 975 cm−1, confirming a decline of crystalline phases. In addition, SEM-EDS characterization and alkalinity analysis showed a compactness of the structure due to the liberation of enough sodium aluminosilicate gel. Finally, results from the mechanical test (4.75–39.55 MPa) and water solubility inferred that, by enhancing the reactivity of CDG by alkali fusion and by addition of up to 15% GGBS, CDG can be optimally recycled as an alternative source material to produce geopolymers.

Reviewing mechanical performance of geopolymer concrete containing coal bottom ash

Concrete is one of the most demanding construction materials and also the third-largest emitter of greenhouse gases on the planet. Likewise, cement is a commonly used binder in concrete and its production accounts for nearly 7 percent of global greenhouse gasses resulting it into one of the most non-sustainable options. Geopolymer concrete (GPC) is a type of construction material made with the utilization of the waste products of industries (like fly ash, copper slag, coal bottom ash, etc.). It comprises the process of geopolymerisation with the help of alkali activators particularly made of sodium hydroxide and sodium silicate. Further, Coal Bottom ash (CBA), generated from thermal power plants is generally landfilled and has already created serious threats to the environment. The current review summarizes the present and past research trends of mechanical behavior of GPC made with different amounts of CBA either used as replacement of binder or as fine aggregates. Generally, the mechanical properties of GPC depend on various parameters like alkali solution content, liquid/binder ratio, molarity of NaOH, NS/NH ratio, grinding of CBA and type of curing. The literature indicates that, an increase in various parameters such as NS/NH ratio (1.5–4.9), molarity of NaOH (10 M−16 M) and the grinding period (12 h–36 h) improves the overall mechanical properties. Likewise, an increase in liquid/binder ratio (0.5–1) and alkali content reduces the strength properties of CBA based GPC at different curing regimes. The findings also suggest the adequate potential of CBA to be used as primary/secondary material in Geopolymer concrete. Last, the study briefly highlights the challenges and future scope of application of CBA in developing GPC.

Effect of molarity of NaOH and alkalinity ratio on compressive strength of geo-polymer concrete

Concrete is the most copious man-made material in the planet. One of the main ingredients in a normal concrete mixture is Portland cement. However, the production of cement emits approximately 5% of the world’s carbon dioxide (Greenhouse gas). On the other hand, the climate change due to global warming and environmental protection has become major concerns. The production of Portland cement involves the emission of carbon dioxide, thus replacing of the Portland cement with industrial waste can be one of the solutions for reduction of the carbon dioxide emission. At the same time, thermal power plants produce fly ash in a very large amount and it creates a huge problem for its disposal. Disposal of this fly ash requires approximately 40,000 ha of land every year. In order to avoid the above environmental issues as well as the disposal problem, researchers have employed fly ash an alternative of cement in making of concrete exploiting the binding property of fly ash thereby it led to make attempt to carry out more research on the replacement of cement by fly ash in the concrete. Therefore, the focus to work in this direction acquainting with the idea that the replacement of cement is possible with 100% fly ash and this alternative to regular concrete is known as Geo Polymer Concrete (GPC). The theme of the present work is fully replacement of cement with fly ash to produce the GPC. To produce the GPC, the main constituent materials used are Fly Ash (which is a by-product obtained from thermal power plants) and the alkaline activators in addition to aggregates and water. The alkaline activators used in this study for the polymerization are sodium hydroxide (NaOH) in flakes form and sodium meta -silicate (Na2SiO3) in gel form. The objective of the present work is to study the effect of NaOH molarity and alkaline activator ratios on the compressive strength (3, 7 and 28 days) of GPC at a constant curing period and curing temperature and compare with controlled concrete prepared using ordinary Portland cement (OPC). In the present work 5 and 10 M of NaOH and 1:1, 1:1.5 and 1:2 alkaline ratios were considered with constant curing temperature of 90° C and 24 h curing time. M20 grade of concrete mix design was carried out as per BIS (IS: 10262–2009) for control concrete and the same mix proportion was adopted for GPC also. From the experimental results, it was found that the both NaOH molarity and alkaline solution ratio effecting the compressive strength at 3, 7 and 28 days and maximum compressive strength was obtained at higher NaOH molarity (10 M) and medium alkaline solution ratio (1:1.5). Further, it was found that the compressive strength of GPC was higher than the controlled concrete prepared using OPC.

Effect of sodium hydroxide concentration on the compressive strength of geopolymer mortar using fly ash PLTU Tanjungjati B Jepara

Geopolymer concrete is concrete that uses environmentally friendly materials, using fly ash from waste materials from the coal industry as a substitute for cement. To produce geopolymer concrete, an alkaline activator is required, with a mixture of Sodium Hydroxide and Sodium Silicate. This research is an experimental study to determine the effect of variations in the concentration of sodium hydroxide (NaOH) 8 Mol, 10 Mol, 12 Mol, and 14 Mol on the compressive strength of geopolymer concrete. Mortar Geopolymer uses a mixture of 1: 3 for the ratio of fly ash and sand, 2.5: 0.45 for the ratio of sodium silicate and sodium hydroxide as an alkaline solution. The specimens used a cube mold having dimension 5 cm x 5 cm x 5 cm, then tested at 7 days and 28 days. The test resulted that concentration of NaOH 12 Mol obtained the maximum compressive strength of geopolymer concrete, that is 38.54 MPa. At concentrations of 12 Mol NaOH and exceeding 12M, the compressive strength of geopolymer concrete decreased.