Alkali Activator Solution Research Articles

Review of Recent Developments in Tensile Properties of Engineered Geopolymer Composites

Engineered Cementitious Composite (ECC) is a type of highly ductile cementitious material. However, due to its characteristics of high energy consumption and high carbon emissions, it is necessary to seek a new type of low-carbon and environmentally friendly substitute. Engineered Geopolymer Composite (EGC), as a promising construction material for replacing ECC, has broad application prospects. Through visual analysis of the relevant literature in Web of Science, it was discovered that the research on EGC mainly concentrates on aspects such as the types of precursors, the chemical composition of the alkali-activated solution, and the related parameters of fibers. This paper mainly combines the relevant experimental research data on the tensile properties of EGC conducted by scholars at home and abroad, and focuses on analyzing the influence of precursor types, the chemical composition of the alkaline activator, and fibers on the tensile properties of EGC. The statistical results indicate that fly ash and ground granulated blast-furnace slag (GGBFS) are the most commonly used precursor materials. Replacing an appropriate amount of fly ash in the precursor with GGBFS can significantly enhance the tensile strength of EGC. The type of alkaline activator and its molarity have a relatively obvious influence on the tensile properties of EGC. An increase in the molarity of NaOH within a certain range can enhance the tensile strength of EGC. Furthermore, the incorporation of fibers, especially synthetic fibers such as polypropylene (PP) and polyvinyl alcohol (PVA) fibers, as well as inorganic fibers such as glass fibers (GF) and carbon fibers (CF), can effectively enhance the tensile strength and tensile strain capacity of EGC. The use of hybrid fibers may further improve the tensile properties.

Development of Fly Ash-Based Geopolymer Lightweight Aggregates

This research delves into the utilization of microwave hybrid heating as a curing technique for producing fine aggregates from fly ash. Various concentrations of alkali activator solutions were employed as binders to pelletize the fly ash (ranging from 0% to 10%). The resultant green fly ash-based geopolymer (FAG) aggregates were subjected to a 15-minute microwave kiln treatment. The microwave-sintered FAG fine aggregates, varying in sizes from 0.60 to 2.36 mm, were then utilized to fabricate 50 mm cubic cement mortar samples. Findings indicated that the density of FAG aggregates was approximately 36% lower than that of natural sand, while the water absorption capacity of FAG aggregates exhibited a fivefold increase compared to natural sand. Notably, cement mortar samples made with FAG aggregate of 4% alkali activator exhibited maximum compressive strengths of 31, 37, and 42 MPa at 7, 14, and 28 days of curing, respectively. These compressive strengths were only 12% lower than those of cement mortars made with natural sand across all curing periods. The use of microwave hybrid heating to transform fly ash into aggregates with sufficient strength appears viable, suggesting that these manufactured FAG aggregates could serve as substitutes for natural aggregates in concrete production

Fabrication of a Concrete Roof Tile by Geopolymerization of Red Clay with Container Glass Wastes

We report the production of concrete roof tiles using a red clay-based geopolymer binder with container glass waste and river sand as a concrete filler. Clear and colored container glass wastes were separately ground to powder and blended with low-grade red clay to achieve a SiO2/Al2O3 ratio of approximately 7.0. The powder blends were converted to geopastes with a solid-to-alkali solution ratio of approximately 0.8 using a 12-molar alkali activator solution containing a mixture of potassium hydroxide and sodium hydroxide. Rheological analysis showed that the geopaste binders with transparent and colored glass powders exhibited high shear thinning behavior. A higher viscosity was observed for the geopaste with colored glass powder due to the presence of colorants. Fine and coarse particles of river sand were prepared and mixed with different ratios of geopaste binder to river sand of 1:2.0, 1:2.5, and 1:3.0, respectively. All geopaste and river sand formulations were poured into acetate molds and heated in a metal chamber at 80 °C for 24 h, then aged at room temperature for 14 d. The highest flexural strength of 2.33 MPa was obtained from the formulation with a 1:2 ratio of geopaste with transparent glass powder and fine sand. The measured strength corresponded to an apparent porosity of 6.30% and a water absorption of 4.50%. The bulk density was approximately 1.16 g/cm³, which is classified as a lightweight material. A prototype geopolymer concrete roof tile was successfully produced with a sorption coefficient of approximately 0.170 mm/min1/2. This measured sorption coefficient and the physical properties indicate that the produced roof tile is a potential building material.

Reverse osmosis reject water management by immobilization into alkali-activated materials

Water-intensive industries face challenges due to water scarcity and pollution. In the management of these challenges, membrane processes play an important role. However, they produce significant amounts of reject waters, in which the separated salts and pollutants are concentrated. This study aims to develop a novel management concept for reject waters using alkali activation to immobilize salts in a solid phase using metakaolin, blast furnace slag (BFS), or their mixture as precursors and to create alkali-activated materials with sufficient properties to be potentially used in construction applications. Seven different waters were used to prepare the NaOH-based alkali activator solution: deionized water, three simulated seawaters with increasing salinity, and three reverse osmosis (RO) reject waters from mining or pulp and paper industries. Overall, BFS-based samples had the highest immobilization efficiency, likely due to the formation of layered double hydroxide phases (hydrotalcite, with anion exchange capacity) and hydrocalumite (chloride-containing mineral). Moreover, high-salinity water enhanced the dissolution of precursors, prolonged the setting time, and increased the compressive strength compared with nonsaline water. Thus, the obtained materials could be used in construction applications, such as backfilling material at mines where RO concentrates are commonly produced.

Fabrication of porous geopolymers utilizing aluminum wastes as foaming agent

Porous geopolymers (PG) are attractive due to their simple fabrication and diverse applications. This work presents a method for fabricating PG by using aluminum salt slag (ASS) as a foaming agent and metakaolin (MK) as the precursor. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) are used as alkali activator solutions. The results show that the PG is fabricated by using the sequence mixing method. ASS was milled to a size of 4 µm, then mixed with an NaOH solution for 30 min. After that, MK and Na2SiO3 solution were added. The weight ratio of Na2SiO3/NaOH and solid/liquid was 2.0 and 0.6, respectively. The 7-day cured PG with 5 wt% ASS achieves a strength of 15 MPa, which is close to the minimum requirement of Portland cement of 19 MPa. PG strength decreases, while setting time and pore size increase with increasing ASS content. The knowledge of this work enables the utilization of ASS as a valuable geopolymer foaming agent.

Immobilization properties and reaction mechanism of municipal solid waste incineration fly ash with alkali activation technology

Municipal solid waste incineration fly ash (MSWIFA) needs proper treatment prior to security landfilling because of considerable amounts of heavy metals and soluble chloride. Nowadays, alkali activation technology has become an effective solidification/stabilization (S/S) technology for MSWIFA. But few studies have been systematically carried out on the preparation techniques and reaction mechanism of MSWIFA S/S body. The effects of the technical parameters (alkali activator, sodium silicate modulus, alkali equivalent, water-solid ratio, curing regime) on the immobilization properties (compressive strength and heavy metal leaching toxicity) of MSWIFA S/S bodies were studied in this work. The hydration characteristics and reaction mechanism were also explored in depth based on the structure properties and microstructure characterization. Ca2+, Na+, SiO42−, [Al(OH)4]-, OH− dissociated from MSWIFA and alkali activator solution chemical reaction to form the silicates, aluminates and aluminosilicates with lower polymerization, and promoted the gel hydration products formation via depolycondensation. Lower Ca/Si molar ratio was conductive to the formation of amorphous substance, compactness of matrix pore structure and immobilization properties. Compared to the hydration products including halite, sylvine, glauberite, gypsum, calcite crystal, C–S–H gel contributed much more to the pore structure and strength improvement of MSWIFA S/S bodies. These findings will provide valuable theoretical basis for MSWIFA management and resource utilization promotion.

Strength and Compressibility Characteristics of An Expansive Soil with addition of GGBS and Alkali Activated Slag

Abstract: The phenomenal development in civil engineering infrastructure in developing countries like India, soil stabilization has emerged as à key problem in the engineering industry. Engineers have been attempting to enhance the engineering properties of low-quality soil due to their negative impact on project performance. With increasing awareness of environmental issues, there has been a remarkable shift towards green and sustainable technologies. Reuse of waste materials have been advocated for quite a while to improve the properties of poor soils open up to new avenue and double advantage of waste management. In the project investigation an attempt to evacuate the Plasticity characteristics, Strength characteristics and Compressibility characteristics were conducted on selected soil as per Indian Standards using GGBS and Alkali Activated Solution (AAS) with different percentages and curing for 0,3,7,14, and 28 days to analyze the variation of engineering properties. From the results combination of (GGBS + AAS) proved to increase of strength and reduce compressibility characteristics. The combination of GGBS + AAS is cost effective, non-destructive, low energy demanding and ecofriendly than GGBS to the selected expansive soil.

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 production variables for metakaolin and rice husk ash-based geopolymer cement

Geopolymer concrete has emerged as an eco-friendly alternative to conventional Portland cement-based concrete, boasting superior mechanical performance and a significantly reduced carbon footprint. This research delves into the effects of incorporating rice husk (RH) and metakaolin (MK) as supplementary materials in geopolymer concrete, with the goal of enhancing its properties and sustainability while making productive use of industrial by-products. The research commences with a comprehensive characterization of the raw materials, including rice husk ash (RHA) and metakaolin, via physical, chemical, and mineralogical analyses. Different combinations of RH and MK are then blended with an alkali activator solution to formulate geopolymer paste mixtures. The findings of this study reveal that the incorporation of RH and MK as partial substitutes for conventional materials in geopolymer concrete yields positive effects on its performance. The utilization of rice husk ash enhances workability and reduces the alkaline activation time of the geopolymer paste, leading to improved early-age strength development. This study demonstrates that the synergistic use of rice husk and metakaolin in geopolymer concrete promotes a more sustainable construction material with a diminished environmental impact. It offers valuable potential to guide engineers, researchers, and industry professionals in adopting sustainable and cost-effective strategies for enhancing the properties of geopolymer concrete, thus fostering its wider adoption in the construction sector.

Compositions and Microstructures of Carbonated Geopolymers with Different Precursors.

It is thought that geopolymers are easy to carbonate, especially when they are cured in ambient temperatures. Matrix gel's composition and microstructure, and new products of geopolymers (GPs) after carbonation were investigated in this study on the basis of XRD and SEM-EDS measurements and ternary diagram analysis, which were prepared from low-lime fly ash (FA) and ground granulated blast-furnace slag (GGBS) alone or a blend, as a precursor. The specimens were hardened in a 20 °C environment with alkali activator solution (S/N = 1.1 in mole), followed by storage under sealing or accelerated carbonation. XRD patterns show that carbonation products were nahcolite for the sole FA-based GP and calcite for the GPs using GGBS alone or as a blend. The SEM images of carbonated samples show that there were cube-shaped calcite and small calcite particles in the GGBS-based GP, but hail-like particles in the FA/GGBS blend-based GP. The hail-like particles were complexes of calcite and C-A-S-H gels determined by ternary diagram analysis, and were found to plug the top of the pores of the spongy C-A-S-H gels. We also confirmed that combined ternary diagram analysis of S-(C + M + N)-A and A-(C + M)-N are very effective in determining the gel type of a geopolymer, as well as the products and compositional changes after carbonation, in which oxide components of gels are determined by SEM-EDS. In the former diagram, C-A-S-H gels were plotted linearly along the (C + M + N)-albite (Ab) join, while N-A-S-H gels showed a scattered distribution. In the latter diagram, the plots for N-A-S-H and C-A-S-H gels are distributed in different zones. N = Na2O, C = CaO, M = MgO, A = Al2O3, S = SiO2, H = H2O.

Evaluation of Alkali-Activated Mortar Incorporating Combined and Uncombined Fly Ash and GGBS Enhanced with Nano Alumina

The present research focuses on assessing the fresh and hardened properties as well as the durability performance of alkali-activated mortar in an ambient environment and the impact of integrating nano-alumina (NA) at a 2% ratio as a substitute for binder materials in alkali-activated mortar (AAM). Additionally, it assesses the effectiveness of alkali-activated mortar employing different blends of ground granulated blast furnace slag (GGBS) and fly ash as environmentally friendly substitute building materials. Fly ash (FA), ground granulated blast slag (GGBS), and an equal mixture of GGBS and FA make up these binder ingredients. As a result, the main binders contain GGBS, FA, or a 50/50 mixture of GGBS and FA. The sodium hydroxide (NaOH) concentration is fixed at a 12-molarity level, and the alkali activator solution to binder ratio is kept at 0.5. In the alkali solution, the ratio of sodium silicate to sodium hydroxide is always 2.5. The study evaluates various properties of AAM, such as compressive strength, flowability, unit weight, flexural tensile strength, and durability, under ambient conditions at a steady room temperature of 23±3°C. Results indicate that AAM mixtures devoid of NA exhibit a higher flow rate compared to those containing NA. Nonetheless, the flowability of AAM mixtures aligns well with standard requirements, being modest yet adequate. Significantly, the inclusion of NA enhances the mechanical properties and durability of AAM, demonstrating its beneficial effects. Doi: 10.28991/CEJ-2024-010-03-016 Full Text: PDF

Optimisation of an alkali activator solution to enhance the performance of roller-compacted concrete for pavements (RCCP)

ABSTRACT Considering a recent surge in reducing greenhouse gases and promoting sustainable construction, geopolymer binder-based concrete materials have gained significant interest. Due to the intricacy of alkali activation and the sensitivity of roller-compacted concrete to water, alkali-activated roller-compacted concrete is rarely studied. This work optimises the performance of alkali-activated roller-compacted concrete for pavements (AA-RCCP) to address a research gap. A binder blend of 80% ground granulated blast furnace slag and 20% fly ash by the total weight of the binder was alkali-activated to produce AA-RCCP. To optimise AA-RCCP performance, 15 mix designs were developed and tested by varying five NaOH molarities ranging from 4M to 12M and three NaOH to Na2SiO3 ratios of 3R, 2R, and 1R, whereas ‘M’ signifies the molarity of NaOH, and ‘R’ denotes the NaOH to Na2SiO3 ratio. Initially, fresh properties such as optimum moisture content and maximum dry density were assessed. The effect of variation in the alkali activator solution on hardened properties, including compressive strength, flexural strength, and split tensile strength, was also evaluated. Alkali activator solution optimisation maximised mechanical performance in mix design 12M-3R. Based on the findings of this study, AA-RCCP is an effective and sustainable option for constructing pavements and other facilities.

Seismic performance of ternary composite geopolymer recycled concrete columns: Experimental study and modeling

In order to achieve seismic-resistant structures cast from green building materials, a new kind of column, ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates (GRA-RFBAC) column, was proposed in this paper. The ternary binder material in GRA-RFBAC was produced by the combination of industrial by-products (ground granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA)) and alkali-activated solution. Cyclic loading tests of five reinforced GRA-RFBAC columns, each with a shear-to-span ratio of 3.07, were conducted to investigate the seismic performance. The influence of the recycled aggregate containing recycled fireclay brick aggregate (RA-RFBA) replacement ratio, stirrup spacing, and axial compression ratio on the seismic performance of GRA-RFBAC columns was discussed. The results indicated that all specimens showed similar flexural failure modes under cyclic loading. The first cracking of concrete occurred within the drift ratio range of 0.18%–0.41%, the failure drift ratio varied from 3.27% to 4.11%, and the peak load of the specimens ranged from 237.50 kN to 288.87 kN. Although increasing the RA-RFBA replacement ratio led to a decrease in both the bearing capacity and lateral stiffness of the columns, the GRA-RFBAC columns showed comparable or even better seismic performance than Portland cement concrete columns. Moreover, a prediction model for the skeleton curve of GRA-RFBAC columns was proposed and verified by comparing the prediction results with the test results.

Axial compressive behavior of steel reinforced GGBS-RFBP-FA ternary composite geopolymer recycled fireclay brick aggregates concrete columns

In this study, the axial compressive behaviors of steel reinforced ternary composite geopolymer recycled fireclay brick aggregates concrete columns were investigated. The ternary binder material used in this study was produced by the combination of industrial by-products (i.e., granulated blast furnace slag (GGBS), recycled fireclay brick powder (RFBP), and fly ash (FA)) and alkali-activated solution. A total of 60 square steel reinforced composite columns (with a 200-mm side length and 600-mm height) were tested under axial compression. The tested variables included the mix proportion of ternary composite geopolymer concrete with recycled aggregates containing recycled fireclay brick aggregates (GRA-RFBAC), the recycled coarse aggregate replacement ratios (0%, 30%, 50%, 70%, 100%), the longitudinal reinforcement ratios (1.13%, 2.01%), and the hoop stirrup reinforcement ratios (0.81%, 1.62%). Each group contained three identical samples. The ductility, failure mode, and axial load-bearing capacity of the columns were recorded and analyzed. The experimental results revealed that the damage progression and patterns of steel reinforced GRA-RFBAC columns were similar to those of ordinary Portland cement based recycled concrete columns. The ultimate bearing capacity of steel reinforced GRA-RFBAC columns decreased with an increasing replacement ratio of recycled coarse aggregate and increased with an increasing reinforcement ratio of longitudinal and hoop stirrups. Meanwhile, the stress-strain model of steel reinforced GRA-RFBAC columns under axial compression was proposed based on the experimental results. The present study suggests an efficient and environmental-friendly compression member.

Using Palm Oil Fuel Ash as a Source Material for Alumina Silicate

This research investigated the utilization of palm oil waste as a source material for developing an alkaliactivated binder with alumina-silicate properties. The geopolymer synthesis involved a combination of palm oil fuel ash (POFA) and fly ash (FA), as well as sodium silicate and sodium hydroxide as alkali activator solutions. The study assessed the physical, mechanical, water-transport and thermal performances of the binder, including the influence of oxide ratios on its strength-gain characteristic. The highest strength achieved was 54.7 MPa for a blend of POFA-FA in a ratio of 20:50 with a molarity of NaOH at 12M. The experimental results revealed good water-transport performance due to the dense nature of the binder that restricted water movement. However, the material's insulation performance did not produce significant results with the lowest thermal conductivity value of 0.59 W/mK. Overall, the developed binder has potential industrial applications, as it performed well in the technical aspects studied. KEYWORDS: Palm oil fuel ash, Alkali-activated binder, Waste, Sustainability, Water-transport performance.

Influence of partial replacement of calcined red clay by gypsum-bonded casting investment waste on geopolymerization reaction of red clay-based geopolymer

The main objective of this research is to study the influence of partial replacement of calcined red clay by gypsum-bonded casting investment waste (GCIW) from precious metal casting process on geopolymerization reaction of a red clay-based geopolymer. Calcined red clay was partially replaced by GCIW powder with different contents before mixing with sodium-based alkali activator solution to produce the geopolymers. The results indicate that the GCIW significantly impacted the reaction of flesh geopolymers detected by Differential scanning calorimetry (DSC). The reaction products (hydration products and others) of 28-day geopolymers detected by Fourier transform Infrared spectroscopy (FTIR) and X-ray diffractometry (XRD) were employed to support the reaction results. Moreover, the relation between reaction products and compressive strength was discussed. This work concluded that the calcium sulfate compounds contained in GCIW play an important role on geopolymerization reaction, reaction products, and mechanical properties of geopolymer. Furthermore, the results could be employed to propose a reaction mechanism that occurred in geopolymers. The potential use of GCIW as an additive for red clay-based geopolymer bricks preparation was confirmed in this research.

Optimizing the Fly Ash/Activator Ratio for a Fly Ash-Based Geopolymer through a Study of Microstructure, Thermal Stability, and Electrical Properties

Fly ash (FA)-based geopolymer was prepared using sodium hydroxide and sodium silicate (in 2.5ratio) as an alkali activator liquid (AL). The condition of FA/AL was optimized for achieving 1.00, 1.25, 1.5, and 1.75 ratios by varying the alkali concentrations, which are referred to as GP1, GP2, GP3, and GP4, respectively. The influence of slight variations in the FA/AL ratio on microstructure, morphology, functional groups, and composition was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). FESEM detected a homogeneous fused matrix of fly ash and alkali activator solution up to 1.5 ratios; GP3 showed a dense morphology. FTIR confirmed that the formation of aluminosilicate gel induced a shift in the T–O (T = Si or Al) asymmetric stretching band, nearing a lower frequency. XRD showed an amorphous structure with phases, including quartz, mullite, hematite, and sodalite. The thermogravimetry and differential thermal analysis (TGA–DTA) indicated that the geopolymer samples were thermally stable. The electrical study concluded that the geopolymer possessed insulating properties.

Engineering Attributes of Ternary Geopolymer Mortars Containing High Volumes of Palm Oil Fuel Ash: Impact of Elevated Temperature Exposure

Geopolymer mortars made from various waste products can appreciably reduce carbon dioxide emissions and landfill-related issues, making them viable substitutes for ordinary Portland cement, a workhorse in the concrete industry. Thus, a series of ternary geopolymer mortars were made and characterized to determine the effects of exposure to elevated temperatures (from room temperature up to 900 °C) on their engineered (residual compressive strength, weight loss, and slant shear bond strength) and microstructural properties. These mortars, which contain fly ash, ground blast furnace slag, and a high volume of palm oil fuel ash, were designed to activate via the incorporation of an alkali activator solution at a low concentration (molarity of 4). The elevated temperature-mediated deterioration of the ternary geopolymer mortar was quantified using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The results revealed an improvement in the ternary geopolymer mortars’ resistance against elevated temperatures when the palm oil fuel ash level in the mortar matrix was raised from 50 to 70% and when slag was replaced by fly ash. It was asserted that the proposed ternary geopolymer mortars may contribute to the advancement of green concretes demanded by the construction sectors.

Properties of Geopolymer Mortar Mixtures Containing Waste Glass Aggregates and River Sand

This paper evaluates the properties of fly ash (FA) and ground granulated blast furnace slag (GGBFS) based geopolymer mortar mixtures with waste glass sand (WGS) obtained by crushing glass bottles. A total of seven mixtures, including the partial substitution of river sand (RS) with WGS (0%, 15%, 30%, and 45%) with two alkali activator solution to binder (AAS/b) ratio groups (0.4 and 0.3), were designed. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) were used as the alkali activators. The experimental program evaluated compressive strength, hardened density, alkali-silica reaction (ASR), drying shrinkage, and thermal conductivity of geopolymer mortar mixtures. Test results indicated that the compressive strength of the geopolymer mortar increased with the addition of WGS for AAS/b = 0.4, but it had a negative effect for AAS/b = 0.3. The FA and GGBFS-based geopolymer mortar helps to reduce the ASR expansion of the mixture containing WGS. The drying shrinkage of the geopolymer mortar decreases with the increase of the WGS content. The increase of WGS decreases the thermal conductivity of geopolymer mortar in the case of mixtures with AAS/b = 0.4, but interestingly thermal conductivity value increases in the case of mixtures with AAS/b = 0.3. The findings of this study suggest that using WGS as partial RS substitution material in geopolymer mortar offers sufficient mechanical and thermal insulation properties without causing durability issues.

Development of Alkali-Activated 3D Printable Concrete: A Review

The construction world has changed day by day and is becoming more digitalized by introducing new technologies. Three-dimensional concrete printing (3DCP) is one such technology that has automated building process along with several benefits such as reduced material waste, reduced human hazard, and time savings. Traditionally, this technique utilizes cement to construct numerous structures, resulting in a significant carbon footprint and negative environmental impact. There is a need to find alternate solutions to reduce cement consumption. Alkali activation technology has replaced cement completely. The scope of development of alkali-activated 3D printable concrete utilizing agro-industrial byproducts is presented in this study. A review of the fresh and hardened properties of alkali-activated 3D printable concrete was the primary objective. The change in properties of 3D concrete mixes with the variation of additives that influence the ultimate strength parameters is presented. This study explores the curing conditions and in-depth behavior of uses of 3DCP in the construction industry. The environmental benefits over conventional concreting technology are presented. As per previous studies, the optimum mix composition per cubic meter concrete is 600–700 kg/m3 of binder content, 450 kg/m3 of alkali activator solution, and 600–800 kg/m3 of fine aggregate content. This study contributes to the making of 3D printable alkali-activated concrete.