Production Of Geopolymer Concrete Research Articles

Development of a ternary high-temperature resistant geopolymer and the deterioration mechanism of its concrete after heat exposure

A geopolymer paste (GP) synthesised using fly ash, slag, and metakaolin was developed to enhance the heat resistance of industrial by-product-based geopolymers. The GP exhibited a 28-day strength of 60 MPa and maintained at least 80 % of its initial strength and elastic modulus even at temperatures up to 900°C. Subsequently, the GP was blended with aggregates (sands and stones) to produce geopolymer concrete (GPC) with a 28-day strength of 45 MPa. Compressive tests on the GPC after exposure to 100–1000°C revealed that the GPC retained 90 % of its compressive strength up to 500°C, but experienced a 60 % loss in elastic modulus and a fourfold increase in peak strain after 300°C exposure. Stress-strain relation, physical properties, and microstructure were analysed to explore the property evolution mechanisms after heat exposure. The combined effect of geopolymer shrinkage (100–780°C), stone expansion (> 200°C), and stone decomposition (> 500°C) was the primary factor for the GPC property decline. At 800°C, a complete loss of mechanical properties in both the stone and interface transition zones led to significant deterioration of the GPC. These findings offer valuable insights for developing durable construction materials suitable for high-temperature applications, ensuring structural integrity and performance under extreme thermal conditions.

Fully recycled engineered geopolymer composite: Mechanical properties and sustainability assessment

Combining the two advantages of mitigation of dependence on cement and natural sand resources and recycling waste concrete material, the utilization of recycled concrete powder (RCP) and recycled fine sand (RFS) to produce geopolymer concrete is of great value. However, the insufficient compressive strength and inherent brittleness of the existing RCP or RFS geopolymer concrete hampered its application. This paper aims to develop a high-performance engineered geopolymer composite (EGC) by maximizing the recycle amount of RCP and RFS. The effects of RCP and RFS on the physical, mechanical, and microscopic properties of EGC were investigated. The results indicated that, the less reactivity of RCP decreased the amount of gel products and compromised the strength development, while favored the multi-cracking behavior and the robust ductility. RFS showed a stronger interfacial bond with paste than quartz sand, compensating the degradation of strength driven by RCP and marginally affecting the tensile strain capacity. The developed EGC incorporating 50% RCP and 100% RFS possessed an 84 MPa compressive strength, 7.4 MPa tensile strength, and 8.1% tensile strain, which are at the highest level among the existing RCP or RFS geopolymer concretes. The main products included the coexistence of calcium aluminosilicate hydrate and alkali aluminosilicate (C(N)-A-S-H) gel and layered double hydroxide (LDH). The energy- and carbon-reduction were 16% and 57%, respectively, compared to the M45-ECC.The current findings prove the feasibility of utilizing high amounts of recycled materials to produce high value-added concrete.

Recycled foam concrete masonry and porcelanite rocks-based lightweight geo-polymer concrete at elevated temperatures

This study investigated the mechanical and microstructural properties of lightweight aggregate geo-polymer concrete (LWAGC) produced by alkali-activating glass powder (GP) and Fly Ash (FA) at elevated temperatures ranging from 200 to 800°C. It also examined the effects of incorporating crushed foam masonry (RFA) and crushed porcelanite rock aggregates (PA) into FA and GP-based geo-polymer concrete, both before and after exposure to ambient and high temperatures. A low-calcium type of FA was used as a binder in the geo-polymer concrete paste, with a 10 % replacement of glass powder. The concrete samples were heated at temperatures of 200°C, 400°C, 550°C, and 800°C for a duration of 60 minutes, with a heating rate of 7°C per minute. It was observed that the inclusion of weaker coarse aggregate resulted in a reduction of the compressive strength of the concrete. The geo-polymer concrete was subjected to tests for water absorption, mass loss, cracking, and microstructure analysis at elevated temperatures. The findings indicate that at heating temperatures of 400°C and above, the geo-polymer concrete underwent degradation and dehydration. The test findings also revealed residual compressive strengths of 104.9 %, 97.2 %, 81.8 %, and 64.2 % for the (RFA) types, and 107.3 %, 94.8 %, 78.3 %, and 58.8 % for the (PA) types. Additionally, the density decreased by 1.02 %, 4.88 %, 8.10 %, and 13.88 % for (RFA) and (PA) types, respectively, and by 0.27 %, 1.91 %, 4.67 %, and 10.79 % overall. The results indicate that the compressive strength of the concretes increased after exposure to elevated temperatures of 35°C and 200°C. However, when exposed to temperatures ranging from 400°C to 800°C, the strength of the LWAGC started to degrade and decline. Based on the obtained findings, the present study recommends performing laboratory tests on construction waste generated during demolition while developing and evaluating numerical models that predict the behavior of the resulting demolition materials when incorporated in the production of geo-polymer concrete.

Proposed simplified methodological approach for designing geopolymer concrete mixtures

The development of geopolymer concrete offers promising prospects for sustainable construction practices due to its reduced environmental impact compared to conventional Portland cement concrete. However, the complexity involved in geopolymer concrete mix design often poses challenges for engineers and practitioners. In response, this study proposes a simplified approach for designing geopolymer concrete mixtures, drawing upon principles from Portland cement concrete mix design standards and recommended molar ratios of oxides involved in geopolymer synthesis. The proposed methodology aims to streamline the mix design process while optimizing key factors such as chemical composition, alkali activation solution, water content, and curing conditions to achieve desired compressive strength and workability. By leveraging commonalities between Portland cement concrete and geopolymer concrete, this approach seeks to facilitate the adoption of geopolymer concrete in practical construction applications. The proposed mix design guidelines have been validated through examples for concrete cured under different conditions, including outdoor and oven curing. Future research should focus on validating the proposed methodology through experimental studies and exploring cost-effective alternatives for alkali activation solutions to enhance the feasibility and scalability of geopolymer concrete production. Overall, the proposed simplified approach holds promise for advancing the utilization of geopolymer concrete as a sustainable alternative in the construction industry.

A Comprehensive Review on Red Mud-based Geo-polymerase a Sustainable Material

Effective waste management is crucial; every waste component can be systematically controlled to minimize its creation. The development of geo-polymer concrete offers a pathway towards achieving this objective. Methods: Geo-polymers are inorganic materials that result from the alkali activation of aluminosilicates. The alumino-silicates are sourced from naturally occurring materials and industrial waste such as fly ash, blast furnace slag, and rice husk ash. Red mud, a by-product from an alumina refining industry practically rich in alumina content, can be used as a geo-polymer material along with other calcium and silicate-rich by-products to create an excellent binding material like cement. Findings: This paper studies the properties of red mud-based geo-polymer concrete. Red mud is known for its high alkalinity; it contains significant amounts of aluminium, silicon, and iron oxides, making it a valuable material for polymerization. Incorporating red mud in the production of geopolymer concrete is anticipated to have a significant impact in the future. Studies show red mud-based geo-polymer concrete's mechanical and durability properties, drawing insights from past literature. The chemical properties of red mud were correlated with the mechanical properties of the geo-polymer concrete block. Strength comparison of red mud and fly ash-based geo-polymer and red mud-mud-metakaolin eco-polymer was made to know the optimum percentage of replacement of red mud in the geo-polymer mix. Novelty: The findings will serve as a technical framework for future experimental endeavours and a more environment-friendly construction approach, ultimately assessing its practical feasibility.

Utilisation of industrial waste materials in the production of geopolymer concrete

Utilisation of industrial waste materials in the production of geopolymer concrete

Mechanical and Microstructural Investigation of Geopolymer Concrete Incorporating Recycled Waste Plastic Aggregate.

The effective use of waste materials is one of the key drivers in ensuring sustainability within the construction industry. This paper investigates the viability and efficacy of sustainably incorporating a polylactic acid-type plastic (WP) as a 10 mm natural coarse aggregate (NA) replacement in geopolymer concrete. Two types of concrete (ordinary Portland cement-OPC and geopolymer) were produced for completeness using a concrete formulation ratio of 1:2:3. The ordinary concrete binder control was prepared using 100% OPC at a water/binder ratio of 0.55, while the geopolymer concrete control used an optimum alkaline activator/precursor-A/P ratio (0.5) and sodium silicate to sodium hydroxide-SS/SH volume ratio (1.2/0.8). Using the same binder quantity as the control, four concrete batches were developed by replacing 10 mm NA with WP at 30 and 70 wt% for ordinary and geopolymer concrete. The mechanical performance of the developed concrete was assessed according to their appropriate standards, while a microstructural investigation was employed after 28 days of curing to identify any morphological changes and hydrated phases. The results illustrate the viability of incorporating WP in geopolymer concrete production at up to 70 wt% replacement despite some negative impacts on concrete performance. From a mechanical perspective, geopolymer concrete indicated a 46.7-58.3% strength development superiority over ordinary concrete with or without WP. The sample composition and texture quantified using automated scanning electron microscopy indicated that adding WP reduced the presence of pores within the microstructure of both concrete types. However, this was detrimental to the ordinary concrete due to the low interfacial zone (ITZ) between calcium silicate hydrate (CSH) gel and WP, resulting in the formation of cracks.

A Comprehensive Performance Evaluation of GGBS-Based Geopolymer Concrete Activated by a Rice Husk Ash-Synthesised Sodium Silicate Solution and Sodium Hydroxide

Commercial sodium hydroxide (NaOH) and sodium silicate (SS) are commonly used as alkaline activators in geopolymer concrete production despite concerns about their availability and associated CO2 emissions. This study employs an alternative alkaline activator (AA) synthesized from a sodium silicate alternative (SSA) solution derived from rice husk ash (RHA) and a 10 M sodium hydroxide solution. The initial phase established an optimal water-to-binder (W/B) ratio of 0.50, balancing workability and structural performance. Subsequent investigations explored the influence of the alkali/precursor (A/P) ratio on geopolymer concrete properties. A control mix uses ordinary Portland cement (OPC), while ground granulated blast-furnace slag (GGBS)-based geopolymer concrete—GPC mixes (GPC1, GPC2, GPC3, GPC4) vary the A/P ratios (0.2, 0.4, 0.6, 0.8) with a 1:1 ratio of sodium silicate to sodium hydroxide (SS: SH). The engineering performance was evaluated through a slump test, and unconfined compressive strength (UCS) and tensile splitting (TS) tests in accordance with the appropriate standards. The geopolymer mixes, excluding GPC3, offer suitable workability; UCS and TS, though lower than the control mix, peak at an A/P ratio of 0.4. Despite lower mechanical strength than OPC, geopolymers’ environmental benefits make them a valuable alternative. GPC2, with a 0.4 A/P ratio and 0.5 W/B (water to binder) ratio, is recommended for balanced workability and structural performance. Future research should focus on enhancing the mechanical properties of geopolymer concrete for sustainable, high-performance mixtures.

Uma contribuição para o estudo de concreto geopolimérico leve com argila expandida: avaliação de seu desempenho térmico

Purpose: The objective of this work was to evaluate the thermal insulation performance of lightweight geopolymer concretes with expanded clay, considering their implications for energy consumption and construction efficiency. Theoretical framework: The urgent need for sustainable construction practices amid global concerns about climate change and environmental degradation has been increasingly discussed. With the cement industry being a major contributor to CO2 emissions, alternative materials like geopolymers offer a promising solution, once the consumption of concrete tends to grow bigger. The production of geopolymer concrete, known for its strength and low environmental impact, involves combining a precursor rich in aluminosilicates with an alkaline activator, usually sodium hydroxide and sodium silicate. Notably, geopolymer cement can cut up to 64% of greenhouse gas emissions. Expanded clay, as a lightweight aggregate, garners attention for its porous structure and ability to provide thermal and acoustic insulation to concrete. Its application in constructing vertical enclosures, such as concrete walls, enhances thermoacoustic comfort and aids in assembly and transportation on construction sites. Effective thermal insulation, achieved through materials with low thermal conductivity, plays a pivotal role in creating thermally suitable environments, impacting user satisfaction, productivity, and energy conservation. Method and materials: The materials used for concrete production, including metakaolin, sodium hydroxide, sodium silicate, expanded clay, crushed stone, and sand, were initially characterized. Subsequently, the dosage calculation for the production of test specimens was performed, involving mini concrete slabs with dimensions of 20x40x12 cm, compacted on a vibrating table. The concretes were produced with volume substitutions of crushed stone by expanded clay at 0% (GP) 30% (GP30%) and 70% (GP70%). For the thermal insulation test, the slabs were exposed to a heat source, and temperatures on the exposed and opposite faces were measured over 12 hours, at 30-minute intervals. After obtaining the experimental data, logarithmic equations with three parameters were fitted to achieve the stabilization temperature of the surfaces. Results and conclusion: Despite the expectation of stabilization in temperature after exposure to a heat source, it was not observed for the faces of the tested panels. A mathematical curve was derived through a curve-fitting process using logarithmic equations with three parameters. All curve fittings yielded R² values equal to or higher than 0.95, indicating satisfactory representativity and suggesting viability in analyzing panel thermal insulation through the adjusted equations. Considering the adjusted data, thermal insulation values for GP, GP30%, and GP70% were 31.82 °C, 35.30 °C, and 40.24 °C, respectively. Expanded clay's effect on increasing thermal insulation was evident, aligning with references indicating its insulating characteristics. Moreover, the substitution of crushed stone with expanded clay led to a noticeable reduction in specific mass, highlighting the lightweight nature of the compositions. Both 30% and 70% mixes fall under the lightweight category. Research implications: To produce a more environmentally friendly concrete using geopolymer cement, combined with expanded clay, aiming for a weight reduction in precast concrete wall structures and an improvement in the thermal insulation of these systems. Originality/value: To assess the feasibility of using lightweight geopolymer concretes with locally sourced materials through tests conducted in Brazilian studies, aiming to contribute to the existing gap in knowledge regarding the behavior of this alternative binder.

Enhancing the properties of geopolymer concrete using nano-silica and microstructure assessment: a sustainable approach

Nowadays low calcium fly ash-based geopolymer concrete can be replaced with cement-based concrete to avoid the adverse effect of manufacturing cement on the environment. Utilization of geopolymer concrete instead of traditional concrete using low calcium fly ash and nano silica reduces a significant amount of CO­2 emission towards the atmosphere. However, the performance of geopolymer concrete is less than that of Portland cement concrete. To improve the performance of geopolymer concrete nano silica was used in the present study. In this work, geopolymer concrete was made utilizing fly ash, ground granular blast furnace slag (GGBS), and sugarcane bagasse ash. In the first instance, binary combinations i.e. fly ash and GGBS were employed as cementitious materials for the production of geopolymer concrete. In the second instance, a ternary mixture of pozzolanic material was prepared by taking 25% GGBS, 65% Fly ash, and 10% bagasse ash. In the third instance, varying percentages of nanoparticles were used for the above ternary mixture. The mechanical and durability properties of the geopolymer composite that was made earlier were tested. The compressive strength and split tensile strength of geopolymer composites were assessed for mechanical properties and a rapid chloride permeability test, water absorption test, and acid attack test were done to know about the porosity of concrete. Results showed that, with a dose of 4% nanoparticles, the durability and strength properties of the concrete had improved the most. The GCBA-N4 mixture had the highest split tensile and compressive strength was measured to be 2.91 MPa and 41.33 MPa and the rapid chloride permeability test, water absorption rate, and percentage of mass loss due to sulfate attack were found as a minimum for GCBA-N4 specimen.

Geopolymer Concrete Production by Using Binder Nano Bauxite

Geopolymer Concrete Production by Using Binder Nano Bauxite

Potential utilization of natural zeolite, fly ash and rice husk ash for geopolymer concrete production

Purpose. The experimental research purpose is to study the potential use of natural zeolite, fly ash, and rice husk ash for geopolymer concrete production based on the effect of the Al/Si ratio on microstructure properties and compressive strength. Methods. The formulation process is based on the ratio of Al/Si contained in the raw material, the selection of raw material grain size, mixing and molding of the geopolymer concrete. The geopolymer concrete properties are analyzed in terms of compressive strength and microstructure properties. Findings. Fly ash, natural zeolite and rice husk ash can be used to produce new functional materials in the form of geopolymer concrete with a compressive strength of up to 16.74 MPa. The mixing formula is based on the ratio of Al/Si contained in the raw materials, and their ratio is 1:2; 1:2.5; 1:3; 1:3.5 and 1:4. Geopolymer concrete specimens showed the required physical and mechanical properties. Originality. The originality of this research lies in the utilization of natural zeolite, fly ash, and rice husk ash as raw materials for geopolymer concrete production. This approach offers a practical solution by utilizing these common and readily available materials, rich in silica and alumina, to produce functional and environmentally friendly building materials. Practical implications. This research can provide a practical solution to the problem of natural zeolite, fly ash, and rice husk ash rich in silica and alumina, which can be utilized for geopolymer concrete production. Thus, geopolymer concrete can mainly be utilized as a building material for laying walls and floors in pedestrian areas and parks or for other purposes.

Influence of sugarcane bagasse ash on mechanical properties of geopolymer concrete

Portland cement is a crucial component of building and construction projects; however, its production emits harmful pollutants and contributes to climate change. The indiscriminate disposal of waste materials can also negatively impact the environment. This study aims to utilize agricultural and industrial waste materials for the production of Geo Polymer Concrete (GPC). Sugarcane bagasse was burned at controlled conditions, obtaining Sugarcane Bagasse Ash (SCBA). Fly Ash (FA) was partially replaced with SCBA, ranging from 5% to 40%. These binary mixtures were mixed with 50% weight of Ground Granulated Blast Furnace Slag (GGBFS). A 10 M of Sodium hydroxide solution and sodium silicate gel was prepared as an activating solution. Mechanical properties were tested on cube, cylinder, and prism specimens at 3,7,14 and 28 days curing. The strength results were modelled and compared with Ordinary Portland Cement Concrete (OPCC). The prediction of mechanical properties using various models from international standards and literatures was compared with experimental results. The results demonstrated that cube compressive and flexural strengths, as well as cylinder compressive and split tensile strengths, are closely related.

AN INVESTIGATION ON THE PROPERTIES OF GEOPOLYMER LIGHT WEIGHT CONCRETE

The large-scale production of cement is posing environmental problems on one hand and unrestricted depletion of natural resources, on the other hand causing greenhouse effect and global warming. Each ton of Portland cement production results in loading about one ton of CO2 in to the environment. Environmental and economic reasons require the vision of present concrete making materials. Fortunately in such scenario a new material has emerged that can help in mitigating the problem and the material is Geopolymer Concrete. Hence, the present research work is focused on the production of geopolymer concrete using pozzolans. Geopolymer concrete donot use cement in its productive. Materials like fly ash, ground granulated blast furnace slag (GGBS), silica fume, etc may be used as pozzolanes. The parameters influencing strength of GPC are total combined aggregate, alkaline to binder ratio, mass of sodium silicate to sodium hydroxide, molarity of sodium hydroxide and curing conditions. The main objective of this experimental investigation is to produce geopolymer concrete using industrial wastes such as fly ash to reduce the global warming effect. The industrial waste foundry slag is used as partial replacement with coarse aggregate in various percentages such as 0%, 20%, 40%, 60%, 80% and 100% by weight. Specimens are prepared with 13 molarity, with alkaline to binder ratio as 0.35 and with mass of Na2SiO3 to NaOH as 2.0. The specimens are kept for ambient curing for required days. The workability tests such as slump test, vee-bee test and compaction factor test are conducted. The mechanical properties are studied by testing for compressive strength, tensile strength and flexural strength. Durability properties like water absorption, sorpitivity tests are carried out. The test results showed the ability of producing light weight geopolymer concrete with acceptable performance of strength and durability properties. Key Words: Geopolymer concrete, Light weight aggregate, waste foundry slag, alkaline solution, sorpitivity.

Fly-ash and GGBS based geo-polymer concrete with granite powder as partial replacement of M-Sand for sustainability

In the present scenario, the usage of sustainable developing materials in the construction industry is popular nowadays. The primary role in the production of ecologically friendly concrete is the creation of geopolymer concrete. Industrial by-products used as base material or replacements for cement are trending. In that manner, the utilization of industrial by-products was used as an admixture or replacement material in this geopolymer concrete production. This research attempted to make a green concrete of Geopolymer Concrete (GPC) using fly ash, Ground Granulated Blast Furnace Slag (GGBS), Manufactured Sand (M-Sand) and Granite powder (GP) used with alkaline solutions mixture of sodium hydroxide and sodium silicate with water was used. At 10, 12, 14, and 16 M molarity, the effect of granite waste powder on geopolymer fresh and mechanical qualities are studied. Embodied energy parameter performances of GPC are also shown in this study. When compared to regular concrete, the GPC series produces less carbon dioxide. In this work, 90% of fly ash and 10% of GGBS were used as a cementitious material, M- sand was used as a fine aggregate, and different proportions of 10, 15, and 20% of replacement were done by granite powder. The mechanical properties of compressive strength, Split tensile strength, and stress–strain behavior of geopolymer concrete were investigated. The test of the concrete was carried out at the age of 7 days, 14 days, and 28 days. The inference of the work is concluded that Fly ash, GGBS with GP as partial replacement to M Sand shall be used for construction application where the early gain of strength is recommended. Nevertheless, more studies have to be carried out for further conclusions in applications related to mixing at site, transportation and placement and compaction aspects of GPC mixes in the construction industries.

Evaluating the Influence of Palm Kernel Shell Ash on Ire Clay Geopolymer Concrete Cured at Ambient Temperature

There is an abundance of clay deposit in Ire Ekiti which can serve as geopolymer source material and Palm kernel shell exists as a massive agro waste in South Western Nigeria. This study evaluates the effect of palm kernel shell ash (PKSA) as an additive on the compressive strength of Ire clay geopolymer concrete. The objective of the study is to determine the selected properties of the obtained concrete at room temperature. Palm kernel shell was burned at 650oC for 2 hours in a furnace. Natural clay collected from Ire Ekiti was manually pulverized, air dried and calcined in a furnace at 750o for 2 hours. The geopolymer concrete was prepared at a mixing ratio of 1:2:3. The material constituents were calcined clay (source material), 12M of NaOH and Na2SiO3 (ratio of NaOH to Na2SiO3 was 2:5), river sand and 12.5mm granite were the fine and coarse aggregates respectively while PKSA of 0%,7.5% and 15% of the calcined Ire Clay content were used as additive in preparing the geopolymer concrete. geopolymer concrete specimens were cured at ambient temperature till testing at different maturity ages of 7, 14 and 28 days. It was generally observed that increasing the percentage of PKSA as additive strongly improved the compressive strength gain with maturity of the Ire clay geopolymer concrete. At 28 days maturity, 7.5% PKSA addition improved the compressive strength by 166% while 15% PKSA addition improved the strength by 181% increase. The highest compressive strength was 7.67N/mm2 at 15% PKSA addition on 28 day. Conclusively, Ire clay and PKSA are viable source material and additive respectively for geopolymer concrete production. The Ire clay geopolymer concrete can be practically applied like conventional concrete in structural work especially in a rural community like Ire Ekiti where cement needs to be transported over kilometers. Also, the concrete performing well at ambient temperature makes it cost effective compare to most geopolymers that require heating at high temperature. It is recommended that further study on the durability should be done.

Analytical Review of Geopolymer Concrete: Retrospective and Current Issues.

The concept of sustainable development provides for the search for environmentally friendly alternatives to traditional materials and technologies that would reduce the amount of CO2 emissions into the atmosphere, do not pollute the environment, and reduce energy costs and the cost of production processes. These technologies include the production of geopolymer concretes. The purpose of the study was a detailed in-depth analytical review of studies of the processes of structure formation and properties of geopolymer concretes in retrospect and the current state of the issue. Geopolymer concrete is a suitable, environmentally friendly and sustainable alternative to concrete based on ordinary Portland cement (OPC) with higher strength and deformation properties due to its more stable and denser aluminosilicate spatial microstructure. The properties and durability of geopolymer concretes depend on the composition of the mixture and the proportions of its components. A review of the mechanisms of structure formation, the main directions for the selection of compositions and processes of polymerization of geopolymer concretes has been made. The technologies of combined selection of the composition of geopolymer concrete, production of nanomodified geopolymer concrete, 3D printing of building structures from geopolymer concrete, and monitoring the state of structures using self-sensitive geopolymer concrete are considered. Geopolymer concrete with the optimal ratio of activator and binder has the best properties. Geopolymer concretes with partial replacement of OPC with aluminosilicate binder have a denser and more compact microstructure due to the formation of a large amount of calcium silicate hydrate, which provides improved strength, durability, less shrinkage, porosity and water absorption. An assessment of the potential reduction in greenhouse gas emissions from the production of geopolymer concrete compared to the production of OPC has been made. The potential of using geopolymer concretes in construction practice is assessed in detail.

Study on Mechanical and Durability Characteristics of Sustainable Geopolymer Concrete

Abstract: The concentration of greenhouse gases in the atmosphere has increased quickly as a result of anthropogenic activities that cause global warming. To solve this issue, Portland cement-free geopolymer concrete is created by using ground granulated blast furnace slag (GGBS) as the primary binder and micronized biomass silica (MBS) in varying proportions in composition of GGBS. The outcomes of this experimental investigation demonstrate the mechanical properties and robustness of geopolymer concrete. In the creation of MBS, rice husk is utilized. Besides from compression, flexural, split tensile strength, and elastic modulus testing, further measurements of water absorption, water sorptivity and rapid chloride permeability test were also carried out. It is found that a geopolymer concrete mix with 10% MBS and 90% GGBS as a binder had the best strength and durability. Also, the compressive strengths of each geopolymer concrete mixture exceeded the required design strength. This experimental investigation shows the possibility of employing MBS as a binder raw material in the production of geopolymer concrete.

Physico-Mechanical Evaluation of Geopolymer Concrete Activated by Sodium Hydroxide and Silica Fume-Synthesised Sodium Silicate Solution

Commercial sodium hydroxide (NaOH) and sodium silicate (SS) have remained two of the leading alkaline activators widely used in producing geopolymer concrete, despite some identified negatives regarding their availability and additional CO2 emissions relating to the overall manufacturing process. This study reports the viability of developing geopolymer concrete using a laboratory-synthesised silica fume (SF)-derived SS solution in combination with NaOH at a molarity of 10M as an alternative binary alkali-alkaline activator to Ground Granulated Blast Furnace slag (GGBS). The use of SF in the development of geoolymer activators will pave the way for the quality usage of other high-silica content by-products from nature, industry, and agriculture. In the currently reported proof of concept, four geopolymer concrete batches were produced using different alkaline activator/precursor-A/P ratios (0.5 and 0.9) and SS to NaOH-SS/SH volume ratios (0.8/1.2 and 1.2/0.8), to establish the impact on the engineering performance. Two controls were adopted for ordinary and geopolymer concrete mixes. The engineering performance was assessed using slump and compaction index (CI) tests, while the Unconfined Compressive Strength (UCS) and tensile splitting (TS) tests were measured at different curing ages in accordance with their appropriate standards. The results indicated a reduction in slump values as the A/P ratio decreased, while the CI values showed a reversal of the identified trend in slump. Consequently, mix GC2 attained the highest UCS strength gain (62.6 MPa), displaying the superiority of the alkali activation and polymerisation process over the CSH gel. Furthermore, the impact of A/P variation on the UCS was more pronounced than SS/SH due to its vital contribution to the overall geopolymerisation process.

Life cycle assessment of a new industrial process for sustainable construction materials

One of the key sectors for the green transition of European countries is construction, that is more and more asked to evolve towards innovative ecological binders and green cost-effective processes. The construction sector is highly energy intensive, and the cement production is one of the main sources of environmental pollution in the world. In this regard, GeoPolymers (GP) seem to be promising for a sustainable replacement of cementitious materials. Therefore, the Life Cycle Assessment (LCA) of the industrial production of different formulations of Geopolymer Concrete (GC) was performed in this study after scaling up the Life Cycle Inventory (LCI) from a laboratory scale to an industrial one. Based on LCA results, the Global Warming Potential (GWP) indicator demonstrated a lower greenhouse gas emission of the proposed GC production in respect to the CC manufacturing process, while no significant difference was observed in the GWP scores of the considered GC formulations when referring to the functional unit. Nevertheless, the usage of the innovative GC formulations, on an industrial scale, would avoid a significant reduction of sand and kaolin extracted, with a consequent decrease on the environmental impact. Finally, the economic assessment showed that the combined production of thermal and electrical energy by a cogeneration system could provide a significant cost reduction when the percentage of electricity fed into the public network is higher than 39%.