A comprehensive review of nano materials in geopolymer concrete: Impact on properties and performance

PurposeThe purpose of this paper is to investigate the effect of the replacement of natural coarse aggregate (NCA) with different percentages of recycled coarse aggregate (RCA) on properties of low calcium fly ash (FA)-based geopolymer concrete (GPC) cured at oven temperature. Further, this paper aims to study the effect of partial replacement of FA by ground granulated blast slag (GGBS) in GPC made with both NCA and RCA cured under ambient temperature curing.Design/methodology/approachM25 grade of ordinary Portland cement (OPC) concrete was designed according to IS: 10262-2019 with 100% NCA as control concrete. Since no standard guidelines are available in the literature for GPC, the same mix proportion was adopted for the GPC by replacing the OPC with 100% FA and W/C ratio by alkalinity/binder ratio. All FA-based GPC mixes were prepared with 12 M of sodium hydroxide (NaOH) and an alkalinity ratio, i.e. sodium hydroxide to sodium silicate (NaOH:Na2SiO3) of 1:1.5, subjected to 90°C temperature for 48 h of curing. The NCA were replaced with 50% and 100% RCA in both OPC and GPC mixes. Further, FA was partially replaced with 15% GGBS in GPC made with the above percentages of NCA and RCA, and they were given ambient temperature curing with the same molarity of NaOH and alkalinity ratio.FindingsThe workability, compressive strength, split tensile strength, flexural strength, water absorption, density, volume of voids and rebound hammer value of all the mixes were studied. Further, the relationship between compressive strength and other mechanical properties of GPC mixes were established and compared with the well-established relationships available for conventional concrete. From the experimental results, it is found that the compressive strength of GPC under ambient curing condition at 28 days with 100% NCA, 50% RCA and 100% RCA were, respectively, 14.8%, 12.85% and 17.76% higher than those of OPC concrete. Further, it is found that 85% FA and 15% GGBS-based GPC with RCA under ambient curing shown superior performance than OPC concrete and FA-based GPC cured under oven curing.Research limitations/implicationsThe scope of the present paper is limited to replace the FA by 15% GGBS. Further, only 50% and 100% RCA are used in place of natural aggregate. However, in future study, the replacement of FA by different amounts of GGBS (20%, 25%, 30% and 35%) may be tried to decide the optimum utilisation of GGBS so that the applications of GPC can be widely used in cast in situ applications, i.e. under ambient curing condition. Further, in the present study, the natural aggregate is replaced with only 50% and 100% RCA in GPC. However, further investigations may be carried out by considering different percentages between 50 and 100 with the optimum compositions of FA and GGBS to enhance the use of RCA in GPC applications. The present study is further limited to only the mechanical properties and a few other properties of GPC. For wider use of GPC under ambient curing conditions, the structural performance of GPC needs to be understood. Therefore, the structural performance of GPC subjected to different loadings under ambient curing with RCA to be investigated in future study.Originality/valueThe replacement percentage of natural aggregate by RCA may be further enhanced to 50% in GPC under ambient curing condition without compromising on the mechanical properties of concrete. This may be a good alternative for OPC and natural aggregate to reduce pollution and leads sustainability in the construction.

This study explores the durability of green cementitious material of geopolymer concrete. Geopolymer concrete is produced from the polycondensation reaction of aluminosilicate materials (fly ash, Ground Granulated Blast furnace Slag (GGBS)) with alkaline activator solutions. Geopolymer concrete has excellent mechanical properties and its production requires low energy and results in low levels of CO2 emission. Due to the high demand for river sand, manufactured sand is used as a replacement material in geopolymer concrete under ambient curing conditions. In this study, the durability of G30 grade geopolymer concrete has been investigated using tests acid resistance, water absorption, sulphate resistance, Rapid Chloride Penetration Test (RCPT), and rate of absorption (Sorptivity) test. The sulphuric acid, sodium sulphate, and water absorption tests were carried out at 28 days, 56 days, and 90 days for both the geopolymer and the conventional concrete. The reduction percentage in water absorption and compressive strength loss was found to be better in geopolymer concrete than in conventional concrete. Geopolymer concrete’s chloride penetrability and rate of absorption were analogous to conventional concrete. Regression analysis for geopolymer and conventional concretes in the rate of absorption test showed a good relationship between absorption and the square root of time.

Influence of repeated heating–cooling cycles and exposure duration on mechanical, electrical, and durability properties of geopolymer concrete

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.

Environmental impact assessment of fly ash and silica fume based geopolymer concrete

Utilisation of persistent chemical pollutant incorporating with nanoparticles to modify the properties of geopolymer and cement concrete

Abstract. The manufacturing of cement for use in construction sites all over the world has resulted in tonnes of carbon dioxide being released. It is better to replace an alternative material such as geopolymer which contributes less carbon footprint than traditional Portland cement. Concrete is the most versatile building material, yet it has drawbacks in mechanical and physical properties, such as limited ductility, high water absorption, and low compressive strength. This study aims to determine the effect of the addition of composite fibers on the mechanical and physical properties of geopolymer concrete. In this research, the physical and mechanical properties of geopolymer concrete were investigated by mixing Class F fly ash with an alkaline activator consisting of sodium hydroxide and sodium silicate. Steel fiber and polypropylene cut into 2 mm fiber were added into the geopolymer concrete as reinforcement. Various volume percentages ranging from 0% to 2% are used. Density, water absorption, workability, and compression testing were performed on all geopolymer concrete reinforced with steel and polypropylene fiber with varying volume percentages. The density of geopolymer concrete is similar to that of Ordinary Portland Cement (OPC), which is around 2400 kg/m3, and it has gradually increased with the inclusion of steel fiber, while more polypropylene fiber causes lesser density. With an increment of steel fiber and a decrement of polypropylene fiber, the result of water absorption percentage shows a decrement. Besides, the inclusion of steel fibers reduces the workability of geopolymer concrete. However, the addition of polypropylene fibers shows a higher workability. Plus, the inclusion of steel fiber and the reduction of polypropylene fiber improve the compressive strength.

Engineering properties of geopolymer concrete incorporating hybrid nano-materials

The thermal performance (TP) of concrete structures is vital to the evaluation of the fire response. Thus, this study examined the thermal properties slag-based geopolymer concrete (GPC) incorporating corncob ash (CCA). Corncob was valorised and partially used as a substitution for slag under the ambient curing conditions. Sodium hydroxide (SH) solution and sodium silicate (SS) gel were used as alkaline activators at 12, 14, and 16 M concentrations. The TP of GPC was compared with that of Portland cement concrete (PCC). Thermal predictions were developed based on the thermal properties. Based on the findings, GPC exhibited lower thermal conductivity (TC) and thermal diffusivity (TD) with increasing specific heat capacity (SHC), indicating good thermal insulation properties (TIP) compared with PCC. The TIP increased with increasing CCA content in the mixture at all levels of alkaline activators. Thus, CCA improves the insulating capacity of the GPC. In addition, a good correlation exists between the GPC produced and thermal properties. These findings can be beneficial in the hot climate regions and utilised for structural insulating construction concrete. Finally, the proposed models can be used in the assessment of GPC structures incorporating supplementary cementitious materials (SCMs) to enhance the TIP of construction materials.

Performance of fly ash/GGBFS based geopolymer concrete with recycled fine and coarse aggregates at hot and ambient curing

Geopolymer concrete is an eco-friendly material that possesses properties comparable to those of traditional Portland cement concrete. This study aimed to explore how the ratio of fly ash to blast furnace slag impacts the mechanical properties of geopolymer concrete using coral sand and seawater. Fly ash and blast furnace slag were used as binders alongside alkaline activators such as liquid glass and sodium hydroxide solution. The characteristics were assessed based on measurements of bulk density, water absorption, workability, compressive strength, and flexural strength. The compressive and flexural strengths of the samples increased gradually with the rising ratio of fly ash to blast furnace slag. Moreover, no significant differences were observed when comparing geopolymer concrete's flexural and compressive strengths using coral sand and seawater with those using river sand and freshwater. On the other hand, the FTIR analysis results indicate that the characteristic Si-O-Si(Al) bond of the geopolymerization reaction in the wavenumber range 950 to 1005 cm-1 is present in both types of concrete, with no significant difference observed. These findings suggest that river sand and freshwater in geopolymer concrete production can replace coral sand and seawater for geopolymer concrete.

One of the most important challenges in developing the concrete industry is to use sustainable materials that are able to improve concrete properties. Magnetized water (MW) is a type of water that can replace tap water (TW) in conventional concrete and enhance its mechanical properties. However, the performance of MW in geopolymer concrete has not been well investigated up to now. The goal of this study is to measure the effect of using an alkaline activator (AA) made of MW on the mechanical properties and durability of fly ash (FA)-based geopolymer concrete. The AA was a mixture of sodium hydroxide (SH) solution and sodium silicate (SS) solution. Eighteen geopolymer concrete mixes were tested for several fresh, hardened, and durability properties. Of these mixes, nine were prepared with AA made of MW and the other nine were the same but prepared with AA made of TW. The preparation of MW was simply carried out by passing TW across permanent magnets of 1.6 Tesla, and then 1.4 Tesla intensities for 150 cycles. The MW-based AA properties were analyzed and compared to those of the conventional TW-based AA. Several mechanical and durability properties were measured. Scanning electronic microscopy (SEM) analysis was also conducted on selected mixes. The outcomes of the hardened concrete tests demonstrated that while using MW to prepare AA solution contained SH with a molarity of 16 M, an SS/SH ratio of 2, an AA/C ratio of 0.4, a W/C ratio of 10%, and a curing temperature of 115 °C could display the best outcomes in this study when used in geopolymer concrete. Using MW in a geopolymer concrete AA could increase its slump by up to 100% compared to that made of TW. Using MW in the AA enhanced the compressive strength by up to 193%, 192%, and 124% after 7, 28, and 56 days, respectively. The SEM analysis showed that using MW clearly enhanced the surface morphology of geopolymer concrete. The proposed geopolymer concrete made using the MW-based AA in this study sheds the light on a new class of eco-friendly concrete that could possibly be used in many structural applications.

Mechanical properties of fly ash and silica fume based geopolymer concrete made with magnetized water activator

Performance evaluation on engineering properties of sodium silicate binder as a precursor material for the development of cement-free concrete

Concrete is the basic building material in the world, and cement is the main material used in the production of concrete. However, there is an urgent need to reduce the consumption of cement, where cement production leads to 5–8% of global emissions of carbon dioxide. Geopolymer concrete is an innovative building material produced by alkaline activation of pozzolanic materials such as fly ash, granulated blast furnace slag, and kaolin clay. Geopolymers are widely used in the production of geopolymer concrete due to their ability to reduce carbon dioxide emissions and reduce high energy consumption. During the present study, the environmental impact of two strength grades (30 MPa and 40 MPa) of metakaolin geopolymer concrete (GPC) was evaluated to study its applicability in the construction sector. The kaolin clay extracted from the Aswan quarries was activated by a mixture of sodium hydroxide and sodium silicate solution. To introduce geopolymer concrete in the Egyptian industry sector, its environmental performance, together with its technical performance, should be competitive to the cement concrete used mainly for the time being. The cost of this new concrete system should also be evaluated. The environmental impact of GPC was evaluated and compared with cement concrete using life cycle assessment analysis and IMPACT 2002+ methodology. The cost of production was calculated for 1 m3 of geopolymer concrete and conventional cement concrete. Metakaolin geopolymer concrete achieved a high compressive strength of ~ 56 MPa, splitting tensile strength of 24 MPa, and modulus of elasticity of 8.5 MPa. The corrosion inhibition of metakaolin geopolymer concrete was ~ 80% better than that of conventional cement concrete. Geopolymer concrete achieved a reduction in global warming potential by 61% and improved the human health category by 9.4%. However, due to the heavy burdens of sodium silicate, the geopolymer concrete negatively affected the quality of the ecosystem by 68% and showed a slightly higher impact than cement concrete on the resource damage category for low strength grade of 30 MPa. The high cost of the basic ingredients of the geopolymer resulted in a high production cost of geopolymer concrete (~ 92 US$) that was three times that of cement concrete (~ 31 US$). Based on the environmental results, geopolymer concrete based on locally available metakaolin clay can be applied in the construction sector as a green alternative material for cement concrete.