Molar Sodium Hydroxide Research Articles

Properties of Fly Ash-Slag-Based Geopolymer Concrete with Low Molarity Sodium Hydroxide

Most geopolymer concrete is produced using low-calcium fly ash and cured at high drying temperatures. Additionally, the activator is prepared with a sodium hydroxide (SH) solution of high molarity. This research proposes using a low molarity SH solution to produce fly ash-slag-based geopolymer concrete cured at room temperature. The properties to be investigated include workability, water absorption, and compressive strength. The influence of mixture composition, i.e., slag content, sodium silicate to sodium hydroxide (SS/SH) ratio, and alkaline activator to binder (Al/Bi) ratio on those properties is of interest. The slag substituted fly ash at 10, 20, 30, 40, and 50% replacement levels. The SS/SH ratio is 1.0, 1.5, and 2.0, with the SH molarity determined at 2M. The Al/Bi ratio is 0.40, 0.45, and 0.50. The results show that a higher percentage of slag reduces slump and water absorption but increases the compressive strength of the geopolymer concrete. The mixtures suitable for use are at the percentages of slag 20, 30, and 40%. An increase in the SS/SH ratio decreases the slump and water absorption. Geopolymer concrete with an SS/SH ratio of 1.5 gives maximum compressive strength compared to the other ratios. Increasing the ratio of Al/Bi increases the workability of geopolymer concrete. At an Al/Bi ratio of 0.45, the compressive strength is maximum and the water absorption is minimum. The recommended mix design in terms of workability, water absorption, and compressive strength of geopolymer concrete is a mixture with slag contents of 20, 30, and 40%, a SS/SH ratio of 1.0 and 1.5, and an Al/Bi ratio of 0.45 and 0.50. Doi: 10.28991/CEJ-2023-09-02-010 Full Text: PDF

Synthesis of Metakaolin Based Alkali Activated Materials as an Adsorbent at Different Na2SiO3/NaOH Ratios and Exposing Temperatures for Cu2+ Removal.

Water contamination is a major issue due to industrial releases of hazardous heavy metals. Copper ions are among the most dangerous heavy metals owing to their carcinogenicity and harmful effects on the environment and human health. Adsorption of copper ions using alkali activated materials synthesized through the polycondensation reaction of an alkali source and aluminosilicates is the most promising technique, and has a high adsorption capability owing to a large surface area and pore volume. This research focuses on the effect of the alkaline activator ratio, which is a sodium silicate to sodium hydroxide ratio. Various exposing temperatures on metakaolin based alkali activated materials on a surface structure with excellent functional properties can be used as adsorbent materials for the removal of copper ions. A variety of mix designs were created with varying sodium silicate to sodium hydroxide ratios, with a fixed sodium hydroxide molarity, metakaolin to alkali activator ratio, hydrogen peroxide, and surfactant content of 10 M, 0.8, 1.00 wt%, and 3.0 wt%, respectively. Most wastewater adsorbents need high sintering temperatures, requiring an energy-intensive and time-consuming manufacturing process. In this way, metakaolin-based alkali activated materials are adsorbent and may be produced easily by solidifying the sample at 60 °C without using much energy. The specific surface area, water absorption, microstructure, phase analysis, functional group analysis, and adsorption capability of copper ions by metakaolin based alkali activated materials as adsorbents were evaluated. The water absorption test on the samples revealed that the sodium silicate to sodium hydroxide 0.5 ratio had the highest water absorption percentage of 36.24%, superior pore size distribution, and homogeneous porosity at 60 °C, with a surface area of 24.6076 m2/g and the highest copper ion uptake of 63.726 mg/g with 95.59% copper ion removal efficiency at adsorption condition of pH = 5, a dosage of 0.15 g, 100 mg/L of the initial copper solution, the temperature of 25 °C, and contact time of 60 min. It is concluded that self-supported metakaolin based alkali activated material adsorbents synthesized at low temperatures effectively remove copper ions in aqueous solutions, making them an excellent alternative for wastewater treatment applications.

Experimental and microstructural analysis on flyash-GGBS based geopolymer concrete under ambient curing condition

The large-scale production of cement is posing environmental problems on one hand and unrestricted depletion of natural resources on the other hand. Each ton of Portland cement production results in loading about one ton of CO2 in to the environment. Environmental and economic reasons require there vision of present concrete making materials. Fortunately within this scenario a new player has emerged that can help in mitigating the problem and the player is Geopolymer Concrete. Hence, the present research work is focused on pozzolanic materials by replacing ordinary Portland cement (OPC) content in the concrete. The pozzolanic materials selected are in the form of geopolymer concrete (GPC) which utilizes waste materials like fly ash, ground granulated blast furnace slag (GGBS), silica fume, etc. Most of the researchers did significant amount of research on fly ash based GPC with heat curing methods. The parameters influencing compressive strength of GPC are total combined aggregate, alkaline to binder ratio, replacement of fly ash with GGBS, mass of sodium silicate to sodium hydroxide, molarity of sodium hydroxide and curing conditions. A total number of 24 cubes of size 150 mm × 150 mm × 150 mm with 14 molarity are prepared, combined total aggregate as 70%, alkaline to binder ratio as 0.30, partial replacement of fly ash with GGBS as 40%, mass of Na2SiO3 to NaOH is 2.5 and admixture as 1.75% mass of binder. The specimens are kept for ambient curing for required days. The mechanical properties are compressive strength test, flexural strength test and split tensile test and the results are 53.10 N/mm2, 4.73 N/mm2 and 4.13 N/mm2 respectively and done the tests on durability properties like absorption, the results is %water absorption 2.865 and the level “Excellent” and done for Sulphate test also. In this research investigation is carried out the mechanical and durability studies and also examine the microstructural behaviour of geopolymer concrete using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The existence of geopolymer structure due to the Ca with Ca/Si, Si with Si/Al ratios of 0.63 and 2.4 and the Si/Al ratio (2.4) is greater than the 1.65 indicates the presence of geopolymer products in the composition.

Dynamic Study and Modelling of Arsenic Removal from Groundwater Using Ferromagnetic Carbon as Fixed Bed Adsorbent in Column

This study investigated the performance of Ferromagnetic Carbon (FC) as an effective natural adsorbent for arsenic removal from groundwater in Dong Thap Province (Vietnam). To do this, leaching fixed-bed column experiments have been carried out. The influence of operating variables affecting the process was studied, under varying operating conditions and experimental data were modelled using bed depth service time (BDST) and mass transfer approaches. Speciation studies showed that the groundwater contained 48.5% of particulate arsenic and 51.5% of soluble arsenic. Indeed, As (III) and As (V) forms represented respectively 41.9% and 58.1% in the dissolved arsenic. As removal was parametric depending such as pH, flow rate, initial As and adsorbent mass, requiring an optimization for optimum conditions When the pH increased from 3 to 11, removal of As(V) decreased from 96.5% to 5% while As(III) removal increased from 40% to 69%. The increase of initial arsenic has caused an increase in removal efficiency of different forms of arsenic. The easy regeneration of FC using a molar sodium hydroxide solution suggests that is an efficient and low-cost material to reduce the contamination of arsenic in drinking groundwater.

Alkali Activated Concrete using Industrial and Agro Waste-Mix proportioning and Experimental Investigation

The demand for concrete is increasing day by day due to vast development in urbanisation. One of the important ingredients to manufacture concrete is cement whose production is leading to large amount of carbon dioxide (CO2) releases attributing to global warming. To reduce the usage of cement in concrete, Supplementary Cementitious Materials (SCM) are given importance and plenty of research is done on them. SCM’s can replace cement upto permissible limits and enhance the concrete properties. The concretes that can replace the cement content completely are Geo Polymer Concrete (GPC) and Alkali Activated Concrete (AAC). They are eco-friendly concretes in which the wastes coming from various types of industries, treatment plants and agro wastes can be used as binders. Alkaline activator solution is used to activate the binder materials which is a combination of silicates and hydroxides. GPC and AAC has wide range of applications like making of concrete benches in park, balusters, paver blocks and non-load bearing components etc. In this paper, a novel mix design for AAC for a constant alkaline solution to binder ratio of 0.4 is presented. The molarity of sodium hydroxide used in this study is 10M. Various mix combinations of binders using Fly ash, Ground Granulated Blast Furnace Slag (GGBS) and Rice husk ash (RHA) were considered. Workability, Physical and mechanical properties of AAC mixes were determined including Non-Destructive tests (NDT). Mixes with RHA resulted in poor compressive strength as the water demand was high and curing under ambient conditions proved to be of low impact especially for AAC with RHA.

Effect of glass powder on the rheological and mechanical properties of slag-based mechanochemical activation geopolymer grout

This article discusses the effects of glass powder (GP) replacements and sodium hydroxide (NaOH) molarity on the rheological, fresh, mechanical and microstructure characteristics of slag-based mechanochemical geopolymer (MG) grout. A conventionally activated geopolymer grout and an ordinary Portland cement (OPC) grout were also investigated for comparison. Four glass powder replacement ratios were used (0%, 10%, 20% and 30% by the total precursor weight) to prepare slag-based mechanochemical geopolymer at three NaOH concentrations (1.25, 2.5 and 3.75 molars). The experimental results showed that the rheological behaviour of MG grouts was considerably reduced, whereas the setting time and the bleeding capacity value increased when slag was substituted with 0%–30% GP. However, after 28 days, the unconfined compressive strength (UCS) improved by 2%–13% when 10%–20% GP was used as a slag replacement, then dropped by 4% when 30% GP was substituted. The results confirmed that both geopolymer grouts irrespective of the activation method had shorter setting time and more stable bleeding capacity than OPC grout. The results also revealed that the UCS of geopolymer grout is enhanced by 18% when the source materials are activated by the mechanochemical method compared to the conventional activation of geopolymer grout. The microstructure results revealed that the activation method had a considerable effect on the microstructure of geopolymer grout because the ball milling process increased the surface area and reduced the particle size of slag compared to conventionally activated geopolymer grout.

Characterization of a high-speed compression ignition engine fueled with ethyl and methyl esters of palm oil

The fossil energy issues and environmental pollution effects are a perilous plight. Fatty acid esters (FAEs) can solve these problems due to they produce from renewable materials. In Thailand, the palm is an economical plant that is produced throughout the year. The research is to study the fuel properties of FAEs from palm oil and their blends and the performance and pollutants of a compression ignition engine. They were transesterified by the same molar ratio and sodium hydroxide catalyst. The physical properties of palm oil ethyl ester (POEE) and its blends were slightly higher than the mixtures of palm oil methyl ester (POME). However, both esters and their blends reduced the engine performance according to increasing both esters as compared with diesel. Notably, the blends of POEE were trivially lower engine performance than POME mixtures. Both esters and their blends reduced carbon monoxide and particulate matter, but they increased carbon dioxide and nitric oxide by adding esters. Outstandingly, the POEE and its blends could decrease these pollutants, except carbon monoxide, compared to POME blends.

Determination of compressive strength of perlite-containing slag-based geopolymers and its prediction using artificial neural network and regression-based methods

This study has two main objectives: (i) to investigate the parameters affecting the compressive strength (CS) of perlite-containing slag-based geopolymers and (ii) to predict the CS values obtained from experimental studies. In this regard, 540 cubic geopolymer samples incorporating different raw perlite powder (RPP) replacement ratios, different sodium hydroxide (NaOH) molarity, different curing time, and different curing temperatures for a total of 180 mixture groups were produced and their CS results were experimentally determined. Then conventional regression analysis (CRA), multivariate adaptive regression splines (MARS), and TreeNet methods, as well as artificial neural network (ANN) methods, were used to predict the CS results of geopolymers using this experimentally obtained data set. Root mean square error (RMSE), mean absolute error (MAE), scatter index (SI) and Nash-Sutcliffe (NS) performance statistics were used to evaluate the CS prediction capabilities of the methods. As a result, it was determined that the optimum molarity, curing time, and curing temperature were 14 M, 24 h, and 110 ℃, respectively and 48 h of heat curing did not have a significant effect on increasing the CS of the geopolymers. The highest performances in regression-based models were obtained from the MARS method. However, the ANN method showed higher prediction performance than the regression-based methods. Considering the RMSE values, it was seen that the ANN method made improvements by 24.7, 2.1, and 13.7 %, respectively, compared to the MARS method for training, validation, and test sets.

Optimized Alkali-Activated Slag-Based Concrete Reinforced with Recycled Tire Steel Fiber.

This study employed Taguchi-Grey relational analysis to optimize the influences of binder content, the molarity of sodium hydroxide (SH) solution, alkaline solution to binder content (Al/Bi) ratio, water to alkali-activated solids (W/S) ratio, and sodium silicate to sodium hydroxide solution (SS/SH) ratio on the workability, setting time, and compressive strength of alkali-activated slag-based concrete (AASC). Then, the recycled tire steel fibers (RTSF) were introduced into the optimized mixture in different dosages, and the physical and mechanical properties of fiber-reinforced AASC (FR-AASC) were evaluated. RTSF inclusion negatively affected the workability and increased the density while slightly reducing the water absorption. Additionally, the compressive strength and flexural behavior of FR-AASC improved by increasing the RTSF content. The analysis of images taken from flexural specimens through the Digital Image Correlation technique (DIC) revealed that higher RTSF dosage caused a curved macro crack with several branches alongside, leading to a better post-cracking performance in terms of strength and toughness.

Design of Low Alkali activator Geopolymer Concrete Mixtures

<p class="Abstract">This paper presents the results of research on the design of geopolymer concrete mixes. The main objective of this research is to develop an efficient and easy design of low-alkaline activator geopolymer concrete mixture, which until now has been the biggest obstacle in the use of geopolymer concrete. The variables reviewed were the amount of alkaline activator was quite low at 4%, room temperature and 60oC ratio of alkaline activator/fly ash (AAS/FA) were 0.35, 0.4, 0.5, 0.6. The test results show the parameters of geopolymer concrete with low alkali activator 4%, sodium silicate/sodium hydroxide ratio 2.5%, sodium hydroxide molarity 14M, type F fly ash and the discovery of the relationship model of compressive strength and the ratio of alkali activator/fly ash with a very high correlation as basic development of geopolymer concrete mix design. The design of the geopolymer concrete mix developed is easy because it is application-based and efficient because it only requires 4% alkaline activator.</p>

Developing zero carbon emission pavements with geopolymer concrete: A comprehensive review

After industrial sector, construction sector utilizes significant quantity of natural raw materials and energy sources. Construction sector waste needs dumping spaces whereas the industrial sector waste like, fly ash and coal bottom ash poses health hazards as they contaminate water, air and soil. Pozzolanic concrete utilizes industrial waste by substituting a portion of cement (<60 %) and offers better durability with similar mechanical properties to normal concrete. Geopolymer concrete, a durable and high-strength concrete, has been devised to fully substitute cement with industrial wastes. This study reviews the requisites of geopolymer concrete to perform like pavement quality concrete while utilizing maximum quantity of wastes in both the binder and aggregate phase. This paper concludes that geopolymer concrete can be used in pavements even with more than 50 % virgin aggregate substitution with recycled aggregates. Further, the mix should be enriched with ground granulated blast furnace slag with sodium hydroxide molarity within 12–16.

Effect of Sodium Hydroxide Molarity on Compressive Strength of Porous Concrete Containing Fly Ash-based Geopolymer Binder

Effect of Sodium Hydroxide Molarity on Compressive Strength of Porous Concrete Containing Fly Ash-based Geopolymer Binder

Optimization of Pervious Geopolymer Concrete Using TOPSIS-Based Taguchi Method

This paper evaluates the effect of mix design parameters on the mechanical, hydraulic, and durability properties of pervious geopolymer concrete (PGC) made with a 3:1 blend of granulated blast furnace slag (GBFS) and fly ash (FA). A total of nine PGC mixtures were designed using the Taguchi method, considering four factors, each at three levels, namely, the binder content, dune sand addition, alkaline-activator solution-to-binder ratio (AAS/B), and sodium hydroxide (SH) molarity. The quality criteria were the compressive strength, permeability, and abrasion resistance. The Taguchi and TOPSIS methods were adopted to determine the signal-to-noise (S/N) ratios and to optimize the mixture proportions for superior performance. The optimum mix for the scenarios with a compressive strength and abrasion resistance at the highest weights was composed of a binder content of 500 kg/m3, dune sand addition of 20%, AAS/B of 0.60, and SH molarity of 12 M. Meanwhile, the optimum mix for the permeability-dominant scenario included a 400 kg/m3 of binder content, 0% of dune sand addition, 0.60 of AAS/B, and 12 M of SH molarity. For a balanced performance scenario (i.e., equal weights for the responses), the optimum mix was similar to the permeability scenario with the exception of a 10% dune sand addition. An ANOVA showed that the binder content and dune sand addition had the highest contribution toward all the quality criteria. Multivariable regression models were established to predict the performance of the PGC using the mix design factors. Experimental research findings serve as a guide for optimizing the production of PGC with a superior performance while conducting minimal experiments.

Enhancing class F fly ash geopolymer concrete performance using lime and steam curing

BackgroundProducing fly ash geopolymer concrete (FGPC) which can be cured by air, water, or steam instead of thermal curing without decreasing its mechanical properties will facilitate using FGPC in cast-in situ applications and precast concrete industry. Furthermore, it will decrease the consumed energy in FGPC production. This research attempts to achieve this goal by investigating the efficacy of supplementing class F FGPC with lime while using different curing processes to generate lime-fly ash geopolymer concrete (L-FGPC) that could be a feasible alternative to ordinary FGPC.MethodsThe studied variables included lime content, molarity of sodium hydroxide (NaOH), additional water content, curing type, and moisture of aggregates. The comparative criteria were setting times of fresh concrete, mechanical properties of hardened concrete, and voids ratio. SEM and X-ray diffraction tests were used to validate test results.ConclusionsSteam curing generated the best mechanical properties of L-FGPC. Using 2% lime content with steam-cured L-FGPC yielded proper setting times and the best mechanical properties. Microstructure tests revealed compact microstructure and decreased voids ratio upon using 2% lime content in L-FGPC. Increasing molarity of NaOH, decreasing additional water content, and decreasing moisture of aggregates enhanced L-FGPC’s mechanical properties.

Development and Optimization of Geopolymers Made with Desert Dune Sand and Blast Furnace Slag

This study assesses the effect of mix design parameters on the fresh and hardened properties, cost, and carbon footprint of geopolymer mortar made with desert dune fines (DDF) and blast furnace slag (BFS). Taguchi method was employed in designing the experiments. Four factors were considered, each having three levels, leading to a total of nine geopolymer mortar mixes. The factors comprised the DDF replacement percentage, alkali-activator solution to binder ratio (AAS/B), sodium silicate-to-sodium hydroxide ratio (SS/SH), and sodium hydroxide (SH) molarity. Ten performance criteria were evaluated, including the flowability, final setting time, hardened density, 1, 7, and 28-day compressive strengths, water absorption, sorptivity, cost, and carbon footprint. ANOVA was carried out to estimate the contribution of each factor towards the response criteria. Further, TOPSIS analysis was utilized to optimize the mixture proportions of DDF-BFS blended geopolymer mortar. Experimental results showed that up to 25% DDF replacement enhanced the density, strength, and durability of the geopolymers with minor impact on the flowability and setting time. Higher replacement percentages had a detrimental impact on the performance but could still be utilized in specific mortar construction applications. The other factors had more limited contributions to the performance, evidenced by the ANOVA. TOPSIS method revealed the optimum mix to be made with DDF replacement of 25%, AAS/B of 0.5, SS/SH of 1.5, and SH molarity of 10 M. Different multivariable regression models were also developed to predict the fresh and hardened properties of the DDF-BFS geopolymer mortars using the mix design parameters.

Structure, morphology and compressive strength of Alkali-activated mortars containing waste bottle glass nanoparticles

Alkali-activated materials (AAMs) have emerged as a sustainable, clinker free binder alternative to portland cement, with reduced consumption of raw materials and very low CO2 emissions. They are produced via the activation of aluminosilicates with alkaline solutions. Millions of tons of bottle glass waste are generated annually worldwide and only a small amount are re-utilized and recycled. Various recycling processes need to be innovated to reduce the volume of waste glasses, which is often landfilled, causing environmental concerns. Waste glass has been utilized as fine aggregate in concrete or as partial replacement for cement. In this study, waste bottle glass nanoparticles (WBGNPs) were incorporated as a precursor combined with ground blast furnace slag (GBFS) and fly ash (FA) to achieve high-strength alkali-activated mortars (AAMs). The effect of WBGNPs, sodium hydroxide molarity, solution modulus (SiO2:Na2O), alkaline solution content, and binder-to-aggregate ratio on the compressive strength development of AAMs were investigated. The strength characteristics of the studied AAMs were assessed by developing an informational model united with a metaheuristic shuffled frog-leaping algorithm (SFLA). The experimental results indicated that after 28 days of curing, AAM prepared with 5% of WBGNPs (precursor) as GBFS/FA replacement attained an improved compressive strength in the range of 16 to 18.4%. Additionally, the optimum mixture containing 5% of WBGNPs as GBFS replacement achieved a strength of 68.6 MPa after 28 days of curing. It was shown that the novel informational SFLA model attained accurate predictions and could appreciably simplify generative design in future computational intelligence of a construction materials platform in civil engineering.

Effect of Sodium Hydroxide Molarity on the Alkali-Activated Fly Ash and Granulated Slag Geopolymer Binders with Water Glass – Part I

Effect of Sodium Hydroxide Molarity on the Alkali-Activated Fly Ash and Granulated Slag Geopolymer Binders with Water Glass – Part I

One Shot of the Hydrothermal Route for the Synthesis of Zeolite LTA Using Kaolin

The zeolite LTA (Z-LTA) was successfully produced from the synthesis of kaolin and well-crystallized using a hydrothermal method. The main purpose of the synthesis Z-LTA from kaolin was to illustrate the transformation Z-LTA with different molarity of alkaline solution and crystallization time. The kaolin was heated in the furnace for 4 h at 500, 600, 700, and 800 °C, resulting in a metakaolinization process that transformed it into an amorphous state. The Z-LTA mixture was obtained by dissolving metakaolin in a sodium hydroxide (NaOH) solution without adding other silica or alumina sources. Before going through the hydrothermal synthesis process, the solution mixture was aged for 24 h. The crystal morphology and degree crystallinity (%) of Z-LTA were evaluated using the various molarity (M) of sodium hydroxide (NaOH) and crystallization time (h). The degree crystallinity of the Z-LTA increases from 62.83 to 86.8% when the molarity of NaOH is increased from 0.5 to 1 M but does not increase when the molarity of NaOH is increased to 1 M and 2 M (80.77% and 67.78%), respectively. The degree crystallinity (%) Z-LTA based on molarity proceeded with the various crystallization time (h) factors. 1 M NaOH with 9 h give highest degree crystallinity (88.45%) compared to other time, 12 h (86.16%), 16 h (87.11%), 24 h (86.80%) and 30 h (86.59%) respectively. The crystal morphology structure with Na, Al, O, and Si was seen in SEM images of the Z-LTA at a 1 M NaOH, 9 h crystallization time (Z-LTA, 1 M 9 h). The particle size of (Z-LTA, 1 M 9 h) is smaller, 0.329 µm, than kaolin, 0.497 µm. Under low alkali conditions and crystallization time, the hydrothermal process successfully generates high crystallinity from natural kaolin. As a result, low-grade Malaysian kaolin can be successfully transformed into Z-LTA using the traditional hydrothermal process when the composition parameters are carefully controlled. The hydrothermal synthesis from natural kaolin was the most cost-effective and efficient method, with comparable product quality to zeolite synthesized with conventional raw materials.

Rice husk ash and fly ash geopolymer hollow block based on NaOH activated

This research aimed to utilize rice husk ash (RHA) to produce rice husk ash and fly ash (FA) geopolymer hollow block based on NaOH activated. RHA was ground for 15, 30, 60, and 90 min. The RHA to FA ratios of 10:90, 20:80, 30:70, 40:60, and 50:50 by weight and 14 molar sodium hydroxide were used. The compressive strengths of geopolymer paste were tested at 7, 28, and 60 days. The compressive strengths and percentages of water absorption of the geopolymer blocks were tested at 7 and 28 days. The microstructure of block was also characterized using SEM and mapping techniques. The results showed that the increase in RHA content increased the compressive strength of the geopolymer. The RHA contained amorphous silica and increase the SiO2/Al2O3 ratio and strength. The compressive strength of geopolymer increased with the increase in RHA fineness. The mix with 50% RHA content, i.e. 50FA50RH-15 M mix with 28-days compressive strength of 8.5 MPa was chosen to produce rice husk ash and fly ash geopolymer hollow block. The microstructure of rice husk ash and fly ash geopolymer hollow block showed the presence of the geopolymerization reaction products with small amount of unreacted RHA and FA particles. The carbon footprint of rice husk ash and fly ash geopolymer hollow block was around two-third of that of the Portland cement system. The result confirms that the rice husk ash and fly ash geopolymer hollow block could be used with compressive strength and water absorption complied with standard.

Optimization of alkali-activated ladle slag composites mix design using taguchi-based TOPSIS method

This study examines the effect of various parameters on the properties of alkali-activated composites made with unprocessed ladle furnace slag. Taguchi method was used to design the experiments. A total of five factors, each with four levels, were considered, including ladle slag content (LS), alkaline-activator solution-to-binder ratio (AAS/B), sodium silicate-to-sodium hydroxide ratio (SS/SH), sodium hydroxide molarity (M), and crushed sand replacement by dune sand (CSR). A total of 16 alkali-activated ladle slag mixtures were designed, cast, and tested. The performance responses were the workability, setting time, and compressive strength. To assess the influence of the factors on the responses, Taguchi analysis and ANOVA were employed while determining the signal-to-noise (S/N) ratios. Further, TOPSIS analysis was carried out to optimize the mixture proportions of alkali-activated ladle slag composites. The optimum mix entailed 650 kg/m3 of ladle slag, AAS/B ratio of 0.45, SS/SH of 2, and CSR of 25% to maximize strength and workability. Meanwhile, the optimum mix to maximize workability and setting time included 650 kg/m3 of ladle slag content, AAS/B ratio of 0.6, SS/SH of 2.5, and CSR of 50%. Anticipated results of the optimum mixes were experimentally verified. Microstructure analysis of the optimum mixes (isothermal calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy) highlighted the accelerated rate of the activation reaction, the amorphous morphology, and the formation of calcium aluminosilicate hydrate gel.