Aluminosilicate Source Research Articles

Design of a novel ternary blended Self-Compacting Ultra-high-performance Geopolymer Concrete

In this research study, the Taguchi orthogonal array (TOA) optimisation method was used to design the optimum mixture proportions of ternary blended Self-Compacting Ultra-High-Performance Geopolymer Concrete (SCUHPGC). The SCUHPGC mixtures, cured at ambient conditions, included Ground Granulated Blast Furnace Slag (GGBFS), Fly Ash (FA), and Silica Fume (SF) as aluminosilicate sources and sodium hydroxide solution and sodium silicate solution as alkaline activators. The effects of six factors at three levels on the compressive strength of SCUHPGC were investigated. The considered factors were the binder content, the ratio of fly ash to ground granulated blast furnace slag (FA/GGBFS), the ratio of silica fume to binder content (SF/Binder content), the ratio of alkaline activator to binder content (AAL/Binder content), the ratio of sodium silicate to sodium hydroxide (SS/SH), and the concentration of sodium hydroxide solution. Twenty-seven SCUHPGC mixtures were evaluated. The slump flow diameter of the optimum SCHUPGC was 740 mm, which satisfies the requirements of self-compacting concrete. The maximum 28-day compressive strength of 132.7 MPa was achieved by the optimum SCUHPGC mixture, which contained a binder content of 1050 kg/m3, a FA/GGBFS ratio of 0.3, an SF/Binder content ratio of 0.05, an AAL/Binder content ratio of 0.4, a SS/SH ratio of 4.0, and an SH concentration of 12 M. The 28-day flexural strength and tensile strength of the optimum SCUHPGC mixture were 9.6 MPa and 4.9 MPa, respectively.

Machine Learning to Predict Workability and Compressive Strength of Low- and High-Calcium Fly Ash–Based Geopolymers

The potential substitution of Portland cement–based concrete with low- and high-calcium fly ash–based geopolymers was investigated. However, predicting the workability and compressive strength of geopolymers with the desired physical and mechanical properties is a complicated process because of the variety of chemical compositions found in aluminosilicate sources. Therefore, machine-learning techniques were used to predict the physical and mechanical properties of the geopolymers and eliminate the usual trial-and-error laboratory procedures. The experimental and predicted results of geopolymer properties using the multilayer perceptron regressor, voting regressor, and XGBoost techniques were compared. The XGBoost model outperformed the other models in terms of accuracy for predicting workability and compressive strength, producing the R2 of 0.96 and 0.89, respectively. Sensitivity analysis determined that the percentage of CaO had the largest effect on geopolymer workability of 27.13%. Fly ash content had the largest effect on compressive strength of 34.44%. Our approach offers a straightforward and dependable strategy for designing and optimizing fly ash–based geopolymers.

Utilization of eggshell powder in one-part alkali-activated metakaolin based binder

Eggshell is a waste of poultry and the proper disposal of such waste products is a worldwide issue. Alkaline activation of calcium-rich eggshell powder (ESP) as a binder with a suitable aluminosilicate source offers the opportunity to produce viable materials. Thus, this paper reports the innovative use of ESP as a precursor in metakaolin (MK)-based one-part alkali-activated materials (AAMs). The impact of ESP on the fresh, physical, mechanical, and microstructural properties of one-part AAMs was studied. Upon the addition of ESP, the setting time was extended and a consistent reduction in semi-adiabatic heat release was observed. ESP favored the rheological characteristics of the mixtures by lowering viscosity and yield stress which enabled a decrease in the water content of ESP containing mortars. The incorporation of ESP up to 40 % improved the compressive strength by 22 % and 46 % for paste and mortar samples, respectively, and resulted in a notable mitigation of mortar shrinkage (only 300 µɛ at 56th days). ESP plays dual function in microstructure of AAM as a binder and micro-aggregate. C-A-S-H type gels were observed in ESP-rich mixes due to its calcium-rich structure, and the contribution of ESP on the hydration reactions were clarified in detail via X-Ray diffraction and thermogravimetric analysis. Life cycle analysis results indicated that incorporating ESP could obtain similar compressive strength while reducing the ecological impact.

One-part geopolymer based on micronized sediments and fly ash mix: Mechanical, microstructural and leaching assessment

This study aims to investigate the leaching behavior of one-part geopolymer based on micronized sediments and fly ash. Four mixtures optimized in terms of mechanical performance and contain 0, 15, 30 and 50 % of sediments were studied. Mixtures characterization indicated that adding sediments increases compressive strength from 19 MPa to 29 MPa and increases mesoporosity (less than 50 nm) from 1.6 % to 3.5 %, with C-A-S-H and N-A-S-H gels coexistence. Given the use of dredged sediments in mixtures, it was important to study their environmental impact. The batch leaching test (0–4 mm) was carried out to study the environmental impact of mixtures at the end of their life cycle. Next, the potential for the release of chemical elements during the life cycle of the mixtures was studied through leaching tests on monolithic samples. The findings show that geopolymerization is effective for the chemical and physical immobilization of several contaminants contained in aluminosilicate sources. The geopolymer binders synthesized proved effective for the chemical immobilization of large metallic and metalloid trace elements (MMTEs) and anions (sulfate, chloride and fluoride). However, immobilization of oxy-anions MMTEs such as arsenic occurs by physical rather than chemical trapping, due to the low porosity of geopolymers. The concentration of arsenic (As) and selenium (Se) were below the non-hazardous wastes (NHW) threshold for all aluminosilicate sources but after activation the results show that these elements are mobilized due to elevated pH. This shows an effect of alkalinity on element mobilization/immobilization. It was demonstrated that carbonation could be a solution for immobilizing arsenic at the end of the mixtures' life cycle, as it reduced its concentration for all mixtures (between 20 and 51 % depending on the mixtures). In addition to these findings, the pH assessment (less than 12.5) showed that these binders can be considered as non-hazardous materials and can be assimilated to an ordinary non-corrosive binder.

A MAS-NMR analysis of 29Si, 27Al and 1H on the temperature's impact on geopolymer grouts derived from argillite and metakaolin

This study investigates how the curing temperature can enhance the reactivity of poorly reactive aluminosilicate source for geopolymer synthesis using a structural approach. The studied geopolymers are based on different aluminosilicate sources, a metakaolin and argillite, under varying curing temperatures (20 and 80°C). The impact of curing temperature on the reactivity of the two aluminosilicate sources and on the resulting consolidated materials was highlighted using pH value measurements, X-ray diffraction (XRD), and MAS-NMR for silicon (29Si), aluminum (27Al), and hydrogen (1H) nucleus. Metakaolin-based samples exhibited stable pH values, unvaried amorphous content, and structural consistency whatever the curing temperature. In contrast, argillite-based samples showed a significant drop in pH values (from 13 to 12) and a rise of amorphous content when cured at 80°C, indicating a reactivity change with temperatures. This was corroborated with MAS-NMR analysis, that highlighted a dissolution of the associated minerals such as illite and smectite. It was evidenced the presence of the geopolymer phase Q4(2Al) and Q4(3Al), in addition to two other networks based on silicon (Q4(1Al) and Q4(0Al)), and on aluminum Q4(4Al). The 1H MAS-NMR corroborated this finding by an increase of the bounded water (the band at 4.8 ppm) in the geopolymer network. All these data underline how temperature influences the reactivity of geopolymer materials, especially argillite-based samples by enhancing the dissolution of associated minerals (illite muscovite and smectite).

Acid resistance of alkali-activated binders based on clays from phosphate mining by-products

This paper outlines the results of studying the resistance of alkali-activated materials (AAM), based on calcined yellow clay from phosphate mine by-products as a precursor, to an acid attack (with sulfuric and phosphoric acids, 5 %, pH ≈ 0,8–2). Calcined yellow clay (YC850) is used as the source of aluminosilicates, containing montmorillonite, dolomite, and quartz. The alkali-activation of such materials allows the determination of an adequate valorization way and evaluating their durability leads to defining the range of application. The residual compressive strengths were measured after 1, 2, and 4 weeks of immersion in those acids. The deterioration suffered by the paste specimens was examined using different techniques.The degree of deterioration differs from one acid to another; in sulfuric acid, the strengths decrease from 47 MPa to 10.6 MPa presenting 77.4 %. While in phosphoric acid, the decrease was about 36.2 % (30 MPa) after 28 days of attack. This detriment in the strengths is associated with changes not only in the microstructure but also with the alteration of the reaction products, mainly the binding gels C-A-S-H and (C,N)-A-S-H, which undergoes dealumination and decalcification. What is more, the chemical attack involves several reactions; calcium coming from the precursor reacts with the sulfates (in the H2SO4 attack) inducing the precipitation of gypsum, which is responsible for the significant strength loss. In addition, the dissolution of crystalline minerals, such as periclase and gehlenite (present in the precursor) generates higher porosity explaining the obtained results.

Thermal behavior of Sicilian clay-based geopolymers

AbstractGeopolymers have been recently proposed for restoration of built heritage to substitute traditional mortars. Local materials and industrial wastes from the Italian region Sicily showed their potential as low-cost aluminosilicate sources for the preparation of geopolymers. Here, a set of Sicilian clays was studied by Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC), and its mineralogical composition was evaluated by X-ray diffraction (XRD). The raw materials were used to prepare geopolymers by alkaline activation with or without the addition of silicate. The thermal degradation profile of the final materials was studied by TGA and compared with that of the precursors, and the energetics of dehydration were investigated by DSC. Two statistical analyses (made by Principal Component Analysis) were performed on the TG data of raw materials and geopolymers and on the TG data of geopolymers and their mineralogical composition, respectively. The last analysis in particular showed a correlation between the mineralogical composition of the materials and the samples' thermal properties. Additional studies of samples subject to accelerated aging by UV irradiation and exposure to acetic acid vapors highlighted the different effects of these two agents on the samples’ stability. Graphical abstract

Geopolymer Implemented in Primary Casing Cementing

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 32218, “First Global Implementation of Geopolymer in Primary Casing Cementing,” by Mark Meade, SPE, Yeukayi Nenjerama, SPE, and Chris Parton, SPE, SLB, et al. The paper has not been peer reviewed. Copyright 2023 Offshore Technology Conference. _ Portland cements are integral components in the oilfield well-construction process; however, the confluence of various business drivers have created the need to find sustainable alternative materials. The complete paper presents the evaluation of geopolymer cementing for use in oil and gas wells, specifically the primary cementing of liner strings in the Permian Basin. Geopolymer cementing offers a unique opportunity for the oilfield industry to decrease CO2 emissions related to well construction and reduce dependence on the constrained supply of Portland cements. Introduction Manufacturing Portland cement emits approximately 1 ton of CO2 for every ton of cement produced. Additionally, the manufacturing of Portland cement is a complex process requiring specialized equipment. Thus, during spikes in demand of Portland cement, the supply of cement cannot be rapidly increased to meet demand. Geopolymers are slurries that set to become a hard, durable solid that can withstand stresses and strains and are resistant to corrosion. Moreover, geopolymers can be made from a broad range of aluminosilicate raw materials sourced from waste products from other industries, mined materials, and biowaste. The low manufacturing and processing requirements reduce the carbon footprint of geopolymers to a fraction of that of manufacturing Portland cement. Whereas Portland cement chemistry is driven by hydration of calcium aluminates and calcium silicates, geopolymer chemistry is based on the polymerization of aluminosilicates initiated by activators. The creation of geopolymers starts with dissolution of the aluminosilicate raw material into monomers by an increase in the pH of the fluid from the activator. Then, the activator provides a site for covalently bonded chains to form, and these chains undergo polycondensation to form the set 3D network of polymers. Implementation of this new material with such a different chemistry into the complex oilfield-construction process presents challenges that must be overcome. Challenges Existing geopolymer formulations typically are characterized as either two-step or one-step geopolymers. In two-step geopolymers, the activators are added into the mix fluid, whereas, in one-step geopolymers, the activators are dry blended with the aluminosilicate source. Implementation of two-step geopolymers would come with operational and logistical constraints impairing their scalability, along with increased service quality and health, safety, and environmental (HSE) risks. On the other hand, common existing one-step geopolymers are formulated with activator types that dissolve rapidly and disperse in the slurry. Therefore, development of novel chemistries for one-step geopolymers are required to introduce geopolymers into oilfield well construction. Such applications expose geopolymers to temperatures and pressures significantly above ambient for extended periods of time during slurry placement within the wellbore. To ensure quality assurance of job placement, hydraulic simulators should be reliable predictors of the top of the placement, and geopolymers set within the wellbore must be detectable using established sonic logging tools.

Towards a Sustainable Mining: Reuse of Slate Stone Cutting Sludges for New Geopolymer Binders

In recent years, the mining industry of slate stone in Spain, from Castille and Leon, has grown significantly due to construction and building sector demands. The continuous accumulation of cutting sludges in ponds from mining and processing operations brings associated environmental problems if the cutting sludges are not properly treated. A potential environmental mitigation measure is the valorization of cutting sludges for the development of new binder materials through geopolymerization. Therefore, this research focused its attention on studying the feasibility of slate stone cutting sludges as a source of aluminosilicates for geopolymer conformation. For this experiment, the mining raw material was analyzed through a typical characterization test campaign in order to validate its feasibility as a source of aluminosilicates for geopolymerization. Subsequently, geopolymers were prepared with slate stone cutting sludges and a 12 M concentration using different Na2SiO3/NaOH ratios (5, 2.5, 1.6, 1.25, and 1). Geopolymer samples were tested, and their physical and mechanical characteristics were evaluated. The test results show that an alkali activator with a 2.5 ratio led to better mechanical and physical properties, with a 7-day compressive strength value of 27.23 MPa. Therefore, this research aims to demonstrate that slate stone cutting sludge could constitute a sustainable binder material for construction purposes.

A study on the influencing parameters in developing construction and demolition waste-based geopolymer concretes and their sustainability assessment

Construction and demolition waste (CDW) has been recently identified as a potential aluminosilicate source for geopolymers. However, the available research has mainly focused on developing CDW-based geopolymer pastes and mortars, while studies on geopolymer concretes sourced from CDW have been very limited. Thus, the current study aimed at experimentally identifying different CDW materials suitable for producing geopolymer concretes. Additionally, the study analysed the mechanical, microstructural, and environmental properties of CDW- based geopolymer concrete produced. In this regard, the effect of relevant parameters on the compressive strength development of CDW-based geopolymer concretes was comprehensively investigated, including those related to precursor types/fineness, alkali activator solution, aggregate type/size and curing regimes. Microstructural analyses were also conducted on the selected samples (100% brick waste, 100% tile waste, 100% concrete waste and 75% brick waste + 25% GGBS). Finally, the environmental impact of geopolymer concrete was assessed and compared with similar traditional concrete. Results showed that employing CDWs alone is not suitable to achieve sufficient strengths under all curing regimes. However, the inclusion of 25% GGBS significantly improved the strength performance of CDW-based geopolymer concrete, in comparison to other supplementary cementitious materials (SCMs) such as Class-C fly ash and calcium hydroxide. The particle size of CDWs and concentration of alkaline activators highly affect the performance of CDW-based geopolymer concretes. Utilization of CDWs with particles finer than 75 μm and high concentrations of NaOH (12 M) is recommended to achieve good performance. The results also indicate that almost similar energy is needed for producing CDW-based geopolymer and OPC-based traditional concrete, whereas a huge reduction in CO2 emission (∼40%) was estimated in the case of geopolymers. The outcomes of the current study are expected to contribute to the advancement of geopolymer concrete derived from CDW in addition to providing valuable insights into this type of concrete for practitioners and academics.

Optimization of Alkali Activator on the Strength Properties of Fly Ash Based Geopolymer Repair Materials

Flexible and rigid road pavement deteriorates over time and needs high-performance patching repair materials. Cold mix asphalt patching is an easy and inexpensive repair material to repair potholes and other damaged roads. However, the repaired road pavement fails because it doesn’t have adequate compressive and bonding strength to the substrate. Thus, this research uses high-performance geopolymer repair materials to patch against road pavement potholes substrate. Geopolymer repair materials could improve the bonding strength, making them suitable for road repair purposes. For making geopolymer repair materials, the main materials used were high calcium aluminosilicate source materials such as fly ash, sodium hydroxide, sodium silicate, and water. This study tested the compressive and bonding strength of geopolymer repair materials after 1, 7, 14, and 28 days. This study found that the compressive strength of 90 g of alkali activator was the highest, at 37.0 MPa. The bonding strength improved gradually from day 1 to day 14, and then considerably on day 28. The compressive strength and bonding strength both increase in direct proportion to the amount of alkali activator present. Alkali activator is optimal at 90 grams for compressive strength and bonding strength of geopolymer repair materials.

Durability of slag-based alkali-activated materials: A critical review

As the world becomes increasingly aware of the devastating effects of climate change, the need for sustainable building materials that are both durable and environmentally friendly increases. Geopolymer and alkali-activated materials formed by a chemical reaction between an alkaline activator solution and an aluminosilicate source have gained popularity in recent years. The alkaline activator solution dissolves the aluminosilicate source, which then undergoes a polycondensation reaction to form a three-dimensional geopolymeric gel network. The development of this network ensures the strength and durability of the material. Today, this phenomenon of durability has been studied in detail to enable the development of superior construction materials, taking into account degradation mechanisms such as carbonation, leaching, shrinkage, fire, freezing and thawing, and exposure to aggressive environments (chlorides, acids, and sulphates). Although there are many unsolved problems in their engineering applications, slag-based alkali-activated materials appear to be more advantageous and are promising as alternative materials to ordinary Portland cement. First of all, it should not be ignored that the cure sensitivity is high in these systems due to compressive strength losses of up to 69%. Loss of strength of alkali-activated materials is considered an important indicator of degradation. In binary precursors, the presence of fly ash in slag can result in an improvement of over 10% in compressive strength of the binary-based alkali-activated materials after undergoing carbonation. The binary systems can provide superior resistance to many degradation mechanisms, especially exposure to high-temperature. The partial presence of class F fly ash in the slag-based precursor can overcome the poor ability of alkali-activated materials to withstand high temperatures. Due to the desired pore structure, alkali-activated materials may not be damaged even after 300 freeze–thaw cycles. Their superior permeability compared to cementitious counterparts can extend service life against chloride corrosion by more than 20 times. While traditional (ordinary Portland cement-based) concrete remains the most widely used material in construction, geopolymer concrete’s superior performance makes it an increasingly emerging option for sustainable and long-lasting infrastructure.

Use of spent fluid catalytic cracking catalyst (FCC) in Limestone Calcined Clay Cement (LC3) systems: Studies in pastes and mortars

This study evaluates the substitution of calcined clay for a waste from the petrochemical industry, spent fluid catalytic cracking catalyst (FCC), as a source of reactive aluminosilicates in Limestone Calcined Clay Cements (LC3) systems. Three carbonate types were used to make cement-type LC3: a high-purity calcium carbonate, waste from the marble industry, and another from a dolomite soil source. LC3 blends were prepared by mixing 50 wt% OPC, 5 wt% calcium sulfate dihydrate, 30 wt% FCC and 15 wt% from each carbonate source. A mixture than substituting the carbonate source for a siliceous source was prepared to analyse the influence of carbonate phases in LC3 systems. The hydration process of the LC3 blends was studied by X-ray diffraction, thermogravimetric analyses, isothermal calorimetry and FESEM. Mechanical properties were studied by measuring compressive strength at 7, 28 and 90 days. The obtained results corroborated that the mortars prepared with LC3 cements using the FCC obtained higher compressive strength than the control mortar prepared with ordinary Portland cement (OPC) at 28 and 90 curing days. It has been demonstrated that FCC is a by-product that can substitute calcined clay, and the different sources of carbonates such as high purity, waste or contaminated with magnesium do not interfere with the performance of this type of cement.

Production and characterization of geopolymers from diatomaceous earth

The world has been facing an increase in the average surface temperature of the earth due to the high release of carbon dioxide into the atmosphere. One of the main responsible for this release of CO2 is the manufacture of Portland Cement, associated with an emission of carbon dioxide of around 7% of the world's total emissions. In this way, there is a need to find alternatives to Portland cement. This work aims to contribute to this endeavor, proposing the application of a solid waste used as a wine filtration agent in the wine industry, diatomaceous earth, containing high amounts of silicon, to produce geopolymers. A geopolymer is an inorganic polymer produced with an aluminosilicate precursor reacted with an alkaline solution that has been studied as an alternative to cement. Diatomaceous earth and alumina were employed in this work as aluminosilicate sources for the geopolymer precursor, while sodium hydroxide and sodium silicate were used as the alkaline solution. The production process involved mixing all these raw materials of the geopolymers to create a fresh geopolymer. Following production, the geopolymers were characterized using XRD, FTIR, SEM-EDS, and pore property analysis. The results revealed that the most favorable geopolymer was produced considering a NaOH concentration of 10 M and a Si/Al ratio of 3,5. This combination resulted in a higher proportion of geopolymer phase, consequently improving mechanical properties.

Influence of Starch Powder on Compressive Strength and Microstructural Properties of Geopolymer Composite Materials Based on Metakaolin

The main objective of the present study is the investigation of the behaviour of starch powder incorporated at different levels (0, 5, 10, 15, 20, 25, and 30 wt%) on the compressive strength and microstructural properties of metakaolin-based geopolymers. Sodium silicate with a molar ratio of SiO2/Na2O of 1.6 was used as the hardener and standard metakaolin was used as the aluminosilicate source. The results showed that when metakaolin was replaced by starch from 0 to 15 wt%, the compressive strength increased from 36.50 to 64.12 MPa. When metakaolin was replaced by starch above 15 wt%, the compressive strength decreased from 64.12 to 29.43 MPa. That of the reference geopolymer material is 36.50 MPa.The infrared spectra of the geopolymer composites indicate that the Si-O-C bonds are formed. The thermal behaviour of geopolymer composites containing starch shows a mass loss at around 100 and 278 °C. The geopolymer material without starch only shows a loss of mass at around 100 °C. The micrographs of the geopolymer composite with 15% by weight of starch show that the matrix is more compact, more homogeneous, and denser than the one without starch. On the contrary, possibly due to a large amount of unreacted starch in its network, the micrographs of the geopolymer composite obtained after the incorporation of 30 wt% starch show a heterogeneous microstructure. It can be concluded that suitable starch content for the synthesis of geopolymer composites would be around 15% by weight.

Effect of reactivity of different metakaolin mixtures on geopolymer extrudability

Additive manufacturing of geopolymers is an innovative technology for research and development This work highlights effect of different metakaolin of mixtures reactivity on geopolymer extrudability. Extrudability tests were carried out on geopolymer pastes from different metakaolin ternaries diagrams using two alkaline (potassium silicates K and sodium silicate KNa) solutions. Extrudable areas were delimited. To understand the differences, the reactivity of the different metakaolin mixtures was evaluated. The results showed that for the extrudable areas, the zeta potential values of the metakaolin mixtures ranged from −50 to −60 mV with K solution and were around −60 mV with the change of solution (KNa). Moreover, the extrudable area corresponds to an energy of oligomer formation (determined by thermal analysis) determined between 1.67 and 1.85 kJ mol−1 with metakaolin ternary diagram M1-MI-M5 and 1.58 and 1.76 kJ mol−1 for metakaolin ternary diagram M1-M2-M5. Whatever the alkaline solution used, the alkaline cation concentration of the extrudable domains is greater than or equal to 2.80 mol. L−1. Mechanical strengths increase around 10 % from solution K to KNa. All these results are confirmed by using other aluminosilicate sources, such as argillite (clay calcined at 650 °C) and mixture of several clays (A65030-M170 and A65050-M150).

Low CO2 emission cement from alkali-activated gravel wash mud and quartzite dust

High CO2 emissions and rising energy costs result in an increasing demand for innovative, environmentally friendly and energy-efficient construction materials. Gravel wash mud (GWM) is a widely available industrial by-product from gravel mining which may be used as an aluminosilicate source in the production of cementitious materials. In this study, GWM from Eifel in the SW Germany was used for the synthesis of alkali-activated cement. A high NaOH leachable Si and Al content and fine grain-size makes this material particularly applicable for synthesis of alkali-activated cements and geopolymers. Silicate dust from quartzite mining in Saarland is other industrial by-product used to improve the physical properties of the cement. Both materials were thermally and mechanically processed prior to chemical activation. A single-compound activator of NaOH solution was used, leading to no addition of soluble silicates. The main advantages of the new cement are zero CO₂ emissions from raw materials during calcination, comparatively low energy demand due to short grinding time, low temperature of calcination and low demand of alkali activator/no need for soluble silicates and valorisation of GWM and quartzite dust from aggregate mining. Experiments show that calcined kaolinite clay acts as a very effective binder in the cement formulation with quartzite dust. Consequently, a very small quantity of metakaolinite in the cement mixture is necessary, which allows for a reduced quantity of alkali-activator and related production costs of the cement. Consequently, the alkali-activated cement can provide an environmentally-friendly and cost-effective material for special applications with a high heat resistance or resistance to aggressive environments.

Advancements in Concrete Performance by Using Waste materials in the Mixture

There have been serious research advancements in concrete materials to make construction more sustainable. Specifically, this is true with regard to alternative ingredients used for self-compacting concrete (SCC) production. To improve its sustainability, this study is aimed at adding Fine Recycled Concrete Aggregate (FRCA) and Recycled Concrete Aggregate (RCA) into SCC. Crushed and reclaimed asphalt (RCA), on the other hand, has many benefits including lower environmental impact and cost-effectiveness. Nevertheless, there are several issues associated with contractors’ knowledge among others being variations in their properties. It’s also known that FRCA can imbibe water faster; hence, mineral admixtures may be introduced to further enhance mechanical behaviour of the concrete. Fly ash and geopolymer synthesis are examples of waste products from industry as well as by-products of coal combustion which are useful in making green concretes. The best results would be achieved if fly ash, a popular Supplementary Cementitious Material (SCM) that reduces Ordinary Portland Cement’s (OPC’s) need is divided according to its oxide content. In order for geopolymers to become an alternative for cement making materials such as aluminosilicate source or alkali reactants are applied. Engineered Cementitious Composite (ECC) enhances performance of concrete even more with strain-hardening properties, especially in terms of durability and tensile capacity. On the whole, manufacturing concrete from recycled and industrial waste products is cost effective and environmentally beneficial. These materials can be maximized if prope performance-driven design strategies and contemporary waste management systems are put into place. This paper emphasizes how essential and crucial it is to incorporate sustainable methods in the production of concrete to create a more environment friendly construction industry.

Investigation on Feasibility of Utilizing Coffee-Husk Ash as an Alkaline Activator in Geopolymer Concrete

Cement production is the major source of global warming which induces 7% of total greenhouse gas emissions. Reducing the use of cement in construction industry needs to be adopted by any of the alternates. One of the best alternates to reduce the impact caused by the cement production process is geopolymer concrete which can completely replace the usage of cement. Geopolymer is trending technology which possess numerous advantages than ordinary Portland cement concrete technology. Geopolymer is produced by the mixing of solid precursor and monomer. Most widely used solid precursors are waste industrial byproducts such as fly ash, GGBS, metakaolin etc., and monomers are alkaline activators like sodium hydroxide and Na2SiO3. Meanwhile, the properties of geopolymer concrete are decided by the various parameters such as quantity of aluminosilicate source in precursor, ratio of NaO/SiO2, SiO2/Al2O3, NaOH/NaSiO3, solution to binder ratio, concentration of NaOH etc., The alkaline activators mostly used are chemical activators which is harmful to humans. Hence, there is a need of finding an alternate for chemical activators in the geopolymer concrete. In this proposed methodology, the chemical alkaline activators have been completely replaced by the waste residue product named coffee husk. Coffee husk is a residue produced from the coffee powder production industry. A total of 18.29 MMT of coffee husk ash has been produced every year. Coffee husk has an inbuilt composition of potassium which is one of the alkaline activators. However, the coffee husk ash needs to be calcinated by the use of oven before to use. In this research, an attempt has been made to utilize the Coffee husk ash (CA), as an alkaline activator and efficient activation mechanism of CA will be examined.

Properties of high calcium fly ash geopolymer incorporating recycled brick waste and borax

Geopolymer has attracted various interests all around the world since its introduction. It is known as a beneficial alternative to cement as it can be produced at room conditions, effectively cutting down CO2 emissions compared to the high temperature calcination process in cement production. Moreover, industrial waste or by-products can be upcycled by incorporating as the precursor in geopolymer production, reducing the environmental burden of waste disposal. High calcium fly ash is emerging as a viable option to produce geopolymer binder material. Recycled brick waste (RBW) on the other hand, may be a good source of aluminosilicate, which is vital to produce geopolymer binder material. However, the incorporation of both materials in the production of geopolymer binder materials has not been well-studied. Hence, this paper presents a study on the properties of geopolymer mortar made with high calcium fly ash incorporating 10 % RBW and borax additive at dosages of 3 % and 6 %. In the fresh state, the geopolymer with 10 % RBW and higher borax dosage had a lower temperature, but all mixes gradually exhibited a similar temperature range between 31.3 °C and 31.9 °C. The geopolymer containing RBW exhibited a 13 % higher compressive strength compared to the RBW-absent counterpart in both mixes with 3 % and 6 % borax while the inclusion of borax from 3 % to 6 % reduced the compressive strength by 22 %. The geopolymer had compressive strengths of about 11.8–15.9 MPa after prolonged exposure to an acidic solution, showing a decreasing trend due to the acid attack on the reaction products. The geopolymer mixes containing 6 % borax exhibited lower strength loss (30.2 % and 28.2 %) compared to those with 3 % borax (40.3 % and 42.3 %) on 800 °C heat resistance while the effect of RBW was negligible. On the other hand, the drying shrinkage of geopolymer did not benefit from the inclusion of either RBW or higher borax dosage. The study provided important insights into the incorporation of these materials in the properties of the geopolymer.