Lightweight Geopolymer Concrete Research Articles

Optimisation of mechanical properties and pore structure of lightweight geopolymer concrete

Lightweight geopolymer has good physical and mechanical properties, thermal and chemical stability and low carbon dioxide emissions. The development of high-strength lightweight geopolymer concrete (LGC) for load-bearing structures can expand geopolymer applications. The use of ground granulated blast-furnace slag (GGBFS) to improve the mechanical properties and pore structure of LGC was investigated. The ultimate compressive stress of LGC containing GGBFS were analysed, as well as the variation in microscopic pore structure. Specimens of LGCs with different strengths (LC20, LC30 and LC40) were investigated. As the GGBFS content increases, the ultimate compressive stress and specific strength of LGC increases, while the strain corresponding to the peak stress decreases, indicating that the mechanical properties and deformation resistance of LGC are improved. The carbon dioxide emissions of LGC are less than those of cement-based lightweight concrete, indicating that LGC has good sustainability. Moreover, the addition of GGBFS can produce more gel and reduce the volume proportion of capillary pores and air pores, resulting in LGC densification. Recommended GGBFS contents for strength grades LC20, LC30 and LC40 are 0–12.7%, 12.7–24.6% and 24.6–30%, respectively. The LGC is lightweight and has high strength, and has potential for application in civil engineering.

Investigating the mechanical and physical properties of lightweight geopolymer concrete

Using waste materials and by-products from various building sectors is gaining popularity because natural resources are quickly depleting. Geopolymer concrete is made from by-product material and is a relatively new environmental material that does not require the presence of ordinary Portland cement as a binder. This study involves producing lightweight geopolymer concretes using a slag binder and replacing the conventional fine and coarse aggregates with two types of locally available lightweight aggregate (thermostone and montmorillonite). Several sequential steps were used to process the aggregates, along with a series of tests conducted to evaluate the concrete properties in different states. The fresh state test includes the slump test, while the hardened concrete tests involve compressive strength, flexural strength, density, thermal conductivity, and water absorption. This study reveals the suitability of lightweight concrete mixtures for various constructional applications. The most reliable mixture was the GMM, which consisted of coarse montmorillonite (5–25 mm) and fine montmorillonite aggregates. This mixture exhibited the highest compressive strength of 23.3 MPa, a flexural strength of 3.25 MPa compared to other LWGC mixtures, and a low density of 1785 kg/m3. The GMM density was 23.97% lower than the reference mixture, whereas the thermal insulation significantly improved by 65.58%. Consequently, this improvement was evident in the thermal conductivity coefficient, which measured as approximately 0.349 W/m.K. In addition, the GTT mixture containing thermostone aggregate (5-25 mm) yielded the most optimal thermal insulation and lowest density of 0.267 W/m.K and 1552 kg/m3, respectively. In general, the strength and density of the LWGC mixtures in this study meet the requirements of lightweight structural applications.

The effect of lightweight geopolymer concrete containing air agent on building envelope performance and internal thermal comfort

Innovative building materials are the primary focus for researchers seeking to reduce energy consumption and advance global sustainability initiatives. This target could accomplished by addressing environmental issues and confronting the adverse impact of climate change. In this regard, this paper used a combined experimental and simulation approach to evaluate the effectiveness of lightweight geopolymer concrete (LWGC) incorporating industrial waste of aluminum powder (AP) and ferrosilicon waste powder (FWP) for reducing the energy consumption in the building envelop. Seven concrete mixes for LWGC were prepared using an air operator. Three mixtures contain 0.1 %, 0.2 %, and 0.3 % AP (FA), and three mixtures contain 0.1 %, 0.2 %, and 0.3 % FWP by weight of fly ash. The workability, unit volume weight, compressive strength, thermal conductivity, and microstructure analysis of the LWGC were examined. In addition, energy simulations were performed to evaluate their ability to reduce energy use in residential buildings. The inclusion of AP and FWP in LWGC resulted in a significant decrease in the density of the material, which amounts to 55 % for AP0.3 and 35 % for FWP0.3. The diameter of the LWGC pore structure increased as the Ca/Si ratio was reduced. The AP and FWP materials reduced energy consumption for building envelope elements such as external walls and roof insulation by 14.5 %, resulting in a 9.2 % overall reduction compared to the traditional concrete mix as a control sample.

Mix design of FA-GGBS based lightweight geopolymer concrete incorporating sintered fly ash aggregate as coarse aggregate

Geopolymer concrete (GPC) is emerging as a sustainable alternative to conventional Portland cement-based concrete due to its significantly reduced carbon footprint and enhanced durability. To mitigate the environmental hazard posed by the disposal of fly ash (FA) and ground granulated blast furnace slag (GGBS) waste and reduce cement consumption, effective promotion of the geopolymerization technique is necessary. Incorporating sintered fly ash coarse aggregate (SFA) in GPC makes the concrete light in weight. This study involves the synthesis of geopolymer technology using FA and GGBS, as the primary source material. Due to the lack of an appropriate mix design method for using SFA in GPC, their application as a structural concrete is scanty. By using FA and GGBS with 100% SFA, a novel mix design methodology that offers greater simplicity and consistency is established in the present study. The proposed method is further verified by developing different concretes with alkali content to binder (AC/B) ratios ranging from 0.3 to 0.8. Fresh densities range between 1860 and 1930 kg/m3 and maximum compressive strength of nearly 50 MPa was attained after 28 days of ambient curing. The binder penetration and internal curing in SFA indicate that GGBS and FA have a superior synergistic effect on the efficacy of lightweight GPC using SFA.

Use of Alkaline-Activated Energy Waste Raw Materials in Geopolymer Concrete.

Silica fly ash, Certyd aggregate, and an alkaline solution were used to produce lightweight geopolymer concretes. The compressive strength, water absorption, and bulk density results, along with SEM photos showing the structure of the obtained composite, were obtained. Tests conducted on the specifications of lightweight geopolymer concretes have revealed significant chemical interactions between the ash aggregate and the geopolymer mortar, particularly when the coarse aggregate surface has been pre-treated with an alkaline solution. A statistical analysis of the experimental data, which investigated the influence of three key variables on the compressive strength, water absorption, and bulk density of lightweight geopolymer concrete (LBG), identified the following factors as having the most substantial impact: the quantity of alkali used, the curing temperature, and the concentration of alkali in the mixture. The optimal test series exhibited a commendable compressive strength of 20.14 megapascals (MPa), accompanied by a water absorption rate of 14.72%, and a bulk density of 1486.6 kg per cubic meter (kg/m³). These findings underscore the importance of alkali content, curing temperature, and alkali concentration in tailoring the properties of lightweight geopolymer concrete to meet specific performance requirements.

Renewable Energy for Carbon Footprint Reduction of Production of Lightweight Geopolymer Concrete

In the present world, researchers have been keenly interested in developing special concrete like Geo polymer concrete in recent years due to its lower global warming impact, better serviceability, higher durability, and overall economy compared to conventional concrete. Geo polymer is a comparatively new substitute binder for making concrete. The geopolymer binders are produced using industrial by-products such as fly ash and blast furnace slag instead of ordinary Portland cement. Using Geo polymer can reduce CO2 emissions and lower the global warming impact. The major issue before the present community is to minimize the CO2 emission, which is also the lead source of global warming. In the present research, an attempt has been made to predict that the CO2 emission rate has either increased or declined in preparing the concrete by using Hand-mixing concrete. The calculations of CO2 emission during manufacturing have been devised based on the collected data. It has also been proposed that how CO2 emission can be reduced by varying the concrete mix proportions or by replacing the ingredients of concrete.

Behaviour of sewage sludge based lightweight aggregate in geopolymer concrete

The global challenge of sewage sludge disposal has encouraged innovative solutions aimed at reducing environmental impact while simultaneously addressing the growing demand for sustainable construction materials. This study aimed to develop treated raw sewage sludge-based lightweight aggregates with strength comparable to commercially available aggregates. Two methods, namely cold bonding and sintering, were employed for the formation of aggregates. The sintering method produced well-formed and hard aggregates, while the cold bonded aggregates exhibited weakness and disintegrated under the slightest pressure. The optimal mix for quality aggregates was found to be 10%–20% sewage sludge, 70%–80% fly ash, and 10% lime using the sintering method. In the sintering method, an increase in sewage sludge content resulted in the reduction of bulk density and specific gravity by 13% and 4% respectively due to the high organic content in sewage sludge, volatile gas release, and porous structure formation. When 10% to 20% sewage sludge content was added, water absorption of the aggregates also increased by approximately 2%. Physical properties such as individual pellet strength. aggregate crushing value reduced by 18%, 20% respectively and the aggregate impact value increased by about 9%. These aggregates were then used to produce lightweight geopolymer concrete, which exceeded the design strength by 7% for the aggregate containing 20% sewage sludge and demonstrated excellent physical properties. The use of waste-based aggregates offers advantages including savings in cost, sustainability, resource conservation, waste reduction, and reduced environmental impact, making them a valuable alternative to natural crushed stone aggregates in specific applications.

Development of low carbon concrete and prospective of geopolymer concrete using lightweight coarse aggregate and cement replacement materials

The use of Ground Granulated Blast-furnace Slag (GGBS) as an alternative cement replacement material in combination with conventional coarse aggregate have been successful in the production of near green concrete. Undoubtedly, GGBS has exhibited good cementitious attributes, however, there are concerns with slow strength development and workability owing to its non-pozzolanic activities as well as some degree of porosity notwithstanding the sustainability potential. Therefore, this study presents a lytag based geopolymer lightweight concrete with high strength development, improved mechanical properties and reduced embodied carbon. To further improve and enhance the potential production of green concrete, complete replacement of conventional coarse aggregate with a recycled lightweight aggregate from industrial waste was carried out. The geopolymer precursors consisted of sodium hydroxide, sodium silicate, GGBS and silica fume to optimize the performance of the concrete at 60–80% cement replacement for a target design mix of 20, 30, 40, and 50 MPa. The performance of lytag based geopolymer concrete was compared with that of non-geopolymer lytag based concrete (control samples). The results show a 42% increase in compressive strength for the geopolymer lightweight concrete and a 22% increase in ultimate compressive strain which is an indication of improved moment of resistance in structural design. The results also show a 46–61% reduction in embodied carbon for the use of non-geopolymer lytag based concrete and 69–77% reduction for lytag based geopolymer concrete. The geopolymer concrete between 7 and 63 days of loading increases by 0.55% in creep strain compared with increases of 2.81% for non-geopolymer lytag based concrete and reduction to 27.96% for the normal weight concrete. Modulus of Elasticity reduces with age of loading for the geopolymer concrete during creep at 0.39% compared to reduction of 1.93% for non-geopolymer lytag based concrete and increase of 12% for the normal weight concrete.

Assessment of mechanical and durability properties of FA-GGBS based lightweight geopolymer concrete

The relentless consumption of natural aggregates and cement in concrete due to rapid construction has resulted in the exhaustion of natural resources; consequently, it's vital to create environment friendly building materials and implement sustainable construction methods. The development of geopolymer concrete (GPC) is a step towards the utilization of by-products. This study aims to prepare and assess the durability and mechanical characteristics of fly ash (FA) and ground-granulated blast furnace slag (GGBS)-based lightweight geopolymer concrete (LWGC). Utilizing sintered fly ash aggregate (SFA) in GPC is one such approach that can lower the usage of regular cement and natural aggregates. In the present investigation a total of six GPC mixes were prepared with varying alkaline activator to binder (AA/B) ratios of 0.3–0.8. The results shows that the AA/B ratio and the mechanical characteristics of LWGC samples are inversely related. The mechanical properties exhibits maximum strength at the lowest AA/B ratio. The LWGC achieved the highest compressive strength (CS) of 48.9 MPa, modulus of elasticity (EM) of 27.3 GPa, split tensile strength (STS) of 3.9 MPa, and direct shear strength of 5.4 MPa after 28 days of ambient curing. The oven dry density (OD) ranged from 1722–1805 kg/m3, satisfying the various codal provisions to be considered a lightweight concrete (LWC). The durability study indicates that for structural applications, the performance is satisfactory, especially in acidic conditions. SEM and EDS analyses also infer strong mechanical and durability characteristics. The obtained results suggests that LWGC is a possible material for structural concrete applications.

Impact of coconut husk microcrystalline cellulose on the properties of geopolymer lightweight concrete

Geopolymer composite is an alternative to ordinary Portland cement. It has potential to avoid CO2 emissions to the atmosphere and to save raw materials during its manufacture. Flyash-based geopolymer concrete is altered by adding ground granulated bast-furnace slag (GGBS) to improve its fresh and hardened properties. Thermal ash aggregate is used as coarse aggregate to reduce geopolymer concrete density, improve strength, and conserve natural aggregate. Along with this matrix, coconut husk microcrystalline cellulose (MCC) is added to enhance its performance. In a M40 grade flyash and GGBS-based geopolymer concrete, MCC was used to replace fly ash at 1% to 5% levels. The geopolymer composites were tested for slump, compression, split tensile, water absorption, and acid resistance to determine the way coconut husk MCC interacts with lightweight concrete. An inclusion of 3% MCC with geopolymer composites improved 2% slump, 6% of compressive and split tensile strength. About 1.6% of water absorption was reduced in GPC matrix with 3% of MCC. Meanwhile 3% of MCC in geopolymer concrete improved, 4% of weight and 7% of strength under acid exposure. The research strongly supported utilizing MCC in geopolymer concrete to render it more sustainable and eco-friendlier.

Mixture Design for Lightweight Geopolymer Concrete

Mixture Design for Lightweight Geopolymer Concrete

A Review of Lightweight Geopolymer Concrete Based on Slag

Abstract: The studies on Lightweight Geopolymer concrete (LGC) are leading-edge in the development of sustainable and ecofriendly concrete. Attempts were being made to develop LGC by various methods of production. This paper reviews about previously published research work on lightweight geopolymer concrete and the observations to the material binders - an alternate to the Ordinary Portland Cement (OPC) by the utilization of industrial by-products, alkaline activator solution, foaming agents, chemical expansive agents, lightweight aggregate, production methods, and their physical and mechanical properties. The main focus is to investigate pore size formation, density, compressive strength and curing conditions. From the review it is found that the stabilization of foam and the control of efflorescence are the two challenging problems faced by the industry for the mass production of lightweight geopolymer foam concrete. Furthermore, topics for future work in this field were suggested.

Investigating the fracture parameters of lightweight geopolymer concrete reinforced with steel and polypropylene fibers

In this current paper, the effects of different percentages of scoria (70, 80, and 90) replacing coarse aggregates, steel fiber volume fractions (Vsf = 0.5 %, 1 %, and 1.5 %) merely and in combination with polypropylene fiber volume fractions (Vppf = 0.1 %) on fracture parameters of lightweight geopolymer concrete(LWGC) have been studied using WFM(Work of Fracture Method) and SIZEM(Size Effect Method). The results indicate that: (a) increasing the content of Vsf and Vppf increases the fracture energy and fracture toughness. (b) The content of polypropylene and steel fibers has remarkable effects on fracture parameters in compositions containing 70 % scoria. (c)The composition of 70 % scoria instead of coarse aggregates, containing (Vsf = 1.5 %) and (Vppf = 0.1 %) is more significant in the analysis of fracture parameters than other samples in this research. In general, it can be said that the increase of fracture parameters like Gf, GF, KIC, and Cf is more noticeable in samples containing 70 % scoria. Also, in the samples containing 70 % scoria, containing (Vsf = 1.5 %) and (Vppf = 0.1 %), the Gf, KIC, and GF are almost 1.84, 1.44, and 2.08 times the control samples, respectively. It is also to see an increase in parameters such as Gf, GF, and KIC in samples containing (Vsf + Vppf) compared to (Vsf). This shows the positive effect of adding polypropylene fibers (Vppf = 0.1 %) to the samples. When the content of steel fibers increases by 0.5 %, 1 %, and 1.5 %, the increase in the mentioned parameters can also be observed. The positive effect of increasing the content of steel fibers in increasing the fracture energy obtained from the results is determined.

Thermal and mechanical performance of lightweight geopolymer concrete with pumice aggregate

AbstractThis study aims to prepare and assess the mechanical characteristics of fly ash (FA)‐based lightweight geopolymer concrete (LWGPC) utilizing pumice as a coarse aggregate. A comprehensive set of 16 LWGPC mixtures were synthesized. The first twelve mixtures produced with varying alkaline to FA ratio and varying proportions of coarse aggregates. The mixture proportion that has given the highest compressive strength (CS), was selected to create four other LWGPC mixes with water‐to‐solid ratios (w/s) ranging from 0.17 to 0.23. Fresh and mechanical properties as well as thermal conductivity (TC) of the LWGPC samples were examined. The experimental findings indicate an inverse relationship between the w/s ratio and mechanical properties of LWGPC samples. Notably, the mechanical properties attain their highest values at the lowest w/s ratio, primarily attributed to reduced porosity and higher concentration of alkali solution in the mixtures with lesser water content. The LWGPC achieved highest CS of 13 MPa, modulus of elasticity (ME) of 8.8 GPa, flexural strength (FS) of 2.2 MPa, and tensile splitting strength (TSS) of 1.64 MPa. The oven dry density (ODD) and TC values ranged from 1746 to 1815 kg/m3 and 0.119 to 0.131 W/m K, respectively. A low‐cost and eco‐friendly novel lightweight concrete composition with low TC was developed.

Assessment of sustainable eco-processed pozzolan (EPP) from palm oil industry as a fly ash replacement in geopolymer concrete

This research focusses on the feasibility of using eco-processed pozzolan (EPP), a palm oil industrial by-product, as partial replacement for fly ash (FA) in the geopolymer concrete (GPC); in addition, the effect of another palm oil industrial by-product, palm oil clinker (POC) as the lightweight coarse aggregate in the EPP-based GPC was also investigated. The ratios of alkaline activator to binder and sodium silicate to sodium hydroxide were kept constant, and the specimens were cured at 60 °C for 24 h. The mechanical properties, namely compressive, splitting tensile and flexural strengths, and modulus of elasticity (MOE) were investigated; further, microstructural analyses such as SEM, XRD and EDX were conducted. The test results show that the utilisation of 10–30% of EPP as FA replacement produced the compressive strengths in the range of 28–39 MPa. The splitting tensile strength of both the lightweight (LW) and normal weight (NW) GPC, except for M6 containing 30% of EPP substitution, fulfilled the minimum requirement of 2.0 MPa. In addition, the flexural strength of GPC produced about 12% of the respective compressive strength. The lower MOE of LW GPC compared to the NW GPC is attributed to the lower stiffness and specific gravity of POC aggregates. The XRD analysis shows the evidence of geopolymerization products of quartz, sillimanite, magnetite, and almandine.

Influence of elevated temperatures on the mechanical properties of foamed geopolymer materials

AbstractCurrent research focuses heavily on geopolymer concrete as possible applications for insulation materials. The aim of the research is to test the strength properties of lightweight geopolymer concrete after exposure to high temperatures. Waste material from the Wieczorek mine (Poland) was used to produce the foamed geopolymers. Alkaline activation took place by mixing the mine powder with an aqueous solution of sodium hydroxide combined with an aqueous sodium silicate with a concentration of 10 M. Prepared geopolymer samples after temperature curing at 75 °C for 24 hours in a laboratory dryer, they were seasoned for 28 days, after which the strength properties were determined. Mechanical tests: compressive strength and bending strength were carried out at temperatures: 20 °C, 200 °C, 600 °C, 800 °C, 1100 °C. Research has shown the precursor activation with the presence of hydrogen peroxide enabled the manufacturing of foamed geopolymers. Heating in the temperature range up to 1100 °C influenced, to some extent, the total porosity of the tested foams. The geopolymer foams based on coal gangue present stable mechanical properties in the range up to 800 °C. No sharp mechanical performances decrease or material chipping was observed. Only colour change of heated samples occurred.

A Review on Fresh, Hardened, and Microstructural Properties of Fibre-Reinforced Geopolymer Concrete

Alternative eco-friendly and sustainable construction methods are being developed to address growing infrastructure demands, which is a promising field of study. The development of substitute concrete binders is required to alleviate the environmental consequences of Portland cement. Geopolymers are very promising low-carbon, cement-free composite materials with superior mechanical and serviceability properties, compared to Ordinary Portland Cement (OPC) based construction materials. These quasi-brittle inorganic composites, which employ an "alkali activating solution" as a binder agent and industrial waste with greater alumina and silica content as its base material, can have their ductility enhanced by utilising the proper reinforcing elements, ideally "fibres". By analysing prior investigations, this paper explains and shows that Fibre Reinforced Geopolymer Concrete (FRGPC) possesses excellent thermal stability, low weight, and decreased shrinking properties. Thus, it is strongly predicted that fibre-reinforced geopolymers will innovate quickly. This research also discusses the history of FRGPC and its fresh and hardened properties. Lightweight Geopolymer Concrete (GPC) absorption of moisture content and thermomechanical properties formed from Fly ash (FA), Sodium Hydroxide (NaOH), and Sodium Silicate (Na2SiO3) solutions, as well as fibres, are evaluated experimentally and discussed. Additionally, extending fibre measures become advantageous by enhancing the instance's long-term shrinking performance. Compared to non-fibrous composites, adding more fibre to the composite often strengthens its mechanical properties. The outcome of this review study demonstrates the mechanical features of FRGPC, including density, compressive strength, split tensile strength, and flexural strength, as well as its microstructural properties.

Investigating the fresh and mechanical properties of wood sawdust-modified lightweight geopolymer concrete

Geopolymer concrete has developed as a potential alternative to ordinary Portland cement-based concrete, wherein various industrial by-products have been converted as beneficial spin-offs. Apart from appropriate compressive strength in the construction sector worldwide, the durability, sound absorption, thermal conductivity, and weight of concrete are also major concerns. Lightweight geopolymer concretes have gained attention because of their superior strength, durability, lower environmental impact, and sustainable characteristics. In this view, the current study examined the feasibility of using sawdust as a natural fine and coarse aggregate substitution in fly ash (FA)-granulated blast furnace slag (GBFS) based geopolymer concrete. Four mixes with a different percentage of sawdust (25, 50, 75, and 100) substituting natural aggregate were designed to examine the effects of sawdust on fresh and hardened features of geopolymer concrete compared to those conventional FA-GBFS-based geopolymer concrete with natural aggregate. Sodium silicate (NS) and sodium hydroxide (NH) (with NS/NH ratio of 0.75) were utilized to dissolve the alumina silicate from FA and GBFS. Informational models were developed using an experimental dataset to estimate the compressive strength of geopolymer concrete mix designs. Besides, using the weight of the developed network, a global sensitivity (GS) analysis was developed to identify the sensitivity of compressive strength to the waste sawdust content. Test results confirmed that by substituting natural aggregate with 100% sawdust, there was around a 35% decrease in compressive strength. Nevertheless, the sound absorption coefficient was increased by an average of 38% in frequencies range between 1800 and 2500 HZ, and thermal conductivity decreased by around 4.5 times once the natural aggregate was substituted by 100% sawdust.

Studies on Lightweight Geopolymer Concrete

The studies on Lightweight Geopolymer concrete (LGC) are leading-edge in the development of sustainable and eco-friendly concrete. Attempts were being made to develop LGC by various methods of production. This paper reviews about previously published research work on lightweight geopolymer concrete and the observations to the material binders - an alternate to the Ordinary Portland Cement (OPC) by the utilization of industrial by-products, alkaline activator solution, foaming agents, chemical expansive agents, lightweight aggregate, production methods, and their physical and mechanical properties. The main focus is to investigate pore size formation, density, compressive strength and curing conditions. From the review it is found that the stabilization of foam and the control of efflorescence are the two challenging problems faced by the industry for the mass production of lightweight geopolymer foam concrete. Furthermore, topics for future work in this field were suggested.

Experimental investigation on mechanical behavior of geopolymer light weight concrete

Experimental investigation on mechanical behavior of geopolymer light weight concrete