Geopolymer Samples Research Articles

Phosphate's second life: Upcycling phosphogypsum and clay by-product through acid geopolymer technology

The present study explores the repurposing of large amounts of phosphoric acid by-products, specifically phosphogypsum (PG), by evaluating its effectiveness as a precursor in acid-activated geopolymer technology. Geopolymers were elaborated using PG and calcined clays, activated with phosphoric acid. The research focused on evaluating the mechanical properties and microstructure of these geopolymers after a 28-day curing period. X-ray diffraction (XRD) analysis revealed the formation of new crystalline phases, including brushite, newberite, and berlinite. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of P-O and Si-O-Al bonds, indicative of successful geopolymerization. Scanning electron microscopy (SEM) imaging demonstrated a dense, cohesive microstructure in optimized samples. Based on the response surface methodology, the study identified optimal conditions for maximum compressive strength: 28.83% PG content, 14.39mol/L phosphoric acid concentration, and a curing temperature of 72.45°C. This optimized formulation produced a dense, cohesive microstructure with a notable compressive strength of 21.46MPa. The leaching test confirmed that no harmful substances were released from the geopolymer samples. These results suggest that PG can be effectively recycled through geopolymer technology for use in the construction industry.

Physico-mechanical properties of geopolymers after thermal exposure: Influence of filler, temperature and dwell time

Geopolymers offer increasingly better physico-mechanical properties concerning thermal exposure at high temperatures compared to ordinary Portland cements (OPC). This paper aims to comprehensively study the use of different types of fillers with different particle size distributions in terms of type (silica sands and cordierites) and surface area, loaded at different temperatures and dwell times (30 min and 180 min). After thermal exposure in the temperature range of 100–1000 °C, geopolymer samples were evaluated regarding physico-mechanical properties compared to samples without thermal exposure, using OPC as a reference material. Geopolymer samples were found to have a denser microstructure than OPC, supporting their better resistance to elevated temperature conditions. In addition, the influence of different filler compositions on the resulting internal structure and porosity was demonstrated. Samples containing fillers in two particle size ranges showed better densification than samples with one particle size range.Conversely, OPC samples showed the least favourable results. In addition, the mechanical behaviour of the geopolymers under static loading, especially in bending and compression tests, showed that the prepared geopolymers exhibited better properties than Portland cement at elevated temperatures, especially in the range of 500–1000 °C. In conclusion, appropriately designed geopolymer compositions have the potential to be a sustainable material, a high-performance alternative to traditional building materials.

Strengthening of Masonry Structures by Sisal-Reinforced Geopolymers

The development of alternative environmentally friendly and sustainable materials in the construction industry has become a fundamental area of research. The current cementitious materials used in existing retrofitting techniques for masonry structures are unsustainable from an environmental point of view. The geopolymer, as a suitable alternative to ordinary Portland cement (OPC), has attracted interest in the last 20 years due to its environmental sustainability and improved properties compared to conventional concrete. To improve the ductile behavior of geopolymers, the adoption of fibers has been widely proposed in the scientific literature for a broad range of applications. The adoption of natural fibers can make geopolymers more advantageous based on their intrinsic environmental sustainability. The aim of this paper is to validate the performance of sisal fiber-reinforced geopolymer plaster as a strengthening material for masonry structures, which will be achieved by modeling the mechanical behavior of geopolymer samples in two different phases. The first phase accounts for the experimental results suitably obtained in the laboratory, while the second phase models the behavior of a masonry panel reinforced with geopolymer plaster using a suitable FEM model in Abaqus.

Production of lightweight geopolymer concrete with foam glass aggregate derived from cathode-ray glass waste

This work focused on producing an eco-friendly lightweight structure by recycling the cathode ray tube glass waste (CRT-GW)to prepare a foam glass aggregate (FGA) and using metakaolin to prepare a geopolymer binder (GP). The geopolymer binder replaces cement to decrease the release of gas generated during cement production. The silicon carbide (SiC) was used as a foaming agent at 1 wt% to prepare the FGA. The foaming temperature effect was investigated for the FGA characterization included: bulk density, volume expansion, apparent porosity, uniaxial compressive strength, and leaching tests for lead and barium. The foam glass aggregate was sintered at different temperatures 725 °C, 750 °C, 775 °C, and 800 °C. These temperatures were selected depending on heating microscopy analysis results, where the maximum expansion height was 119 % at 800 °C. The main characterization ranges of foam glass were: bulk density 0.58–1.26 g/cm3, volume expansion 8–77 (vol%), uniaxial compressive strengths 1.55–9.98 MPa, and thermal conductivity 0.063–0.097 W/m.K.The lightweight geopolymer (LWGP) was prepared with 30 vol% of FGA sintered at different temperatures and 70 vol% of GP. These samples hardened at room temperature. The bulk density and compressive strength were measured for the lightweight geopolymer samples after a curing time of 28 days. A higher compressive strength was 9.11 MPa with a bulk density of 1.21 g/cm3 for lightweight geopolymer-containing foam glass aggregate sintered at 775 °C.

Synthesis and characterization of metakaolin-based geopolymers doped with CRT waste glass for radiation shielding applications

This study presents the influence of CRT glass on the gamma-ray interaction processes in metakaolin-based geopolymers. Four batches of G-CRT composites (namely, G, G-10CRT, G-20CRT, and G-30CRT, which represent geopolymer (G) samples doped with 0, 10, 20, and 30 wt% of CRT glass) were prepared using the cold hydrostatic press method. The mass attenuation coefficients of the prepared C-xCRT samples were computed using XCOM and FLUKA simulations for photons within the energy range of 15 keV–15 MeV. The density of the pristine geopolymer increased from about 1.86 g/cm3 to 2.09, 2.26, and 2.34 g/cm3 for G-10CRT, G-20CRT, and G-30CRT, respectively. The photon mass and linear attenuation coefficients of the geopolymers increased with CRT glass concentration. The half-value layer and mean free path were within the ranges 0.070–18.079 cm and 0.101–26.083 cm for G; 0.036–15.110 cm and 0.052–21.799 cm for G-10CRT; 0.024–13.197 cm and 0.014–19.039 cm for G-20CRT; and 0.018–12.074 and 0.026–17.419 cm for G-30CRT. The G-30CRT had the best gamma attenuating prowess in contrast to other G-xCRT. CRT-rich G-xCRT had a higher effective atomic number. For 10 mm thick geopolymer, the absorbed dose rates were 0.211 μR/h, 0.66 μR/h, 1.11 μR/h, and 1.55 μR/h for G, G-10CRT, G-20CRT, and G-30CRT, respectively, for 100 keV photons. The introduction of CRT glass into the geopolymer matrix improved their photon interaction cross-section. The geopolymers showed outstanding photon interaction ability compared to ordinary concrete and some shielding glasses at low photon energies. The CRT glass-doped geopolymer samples are useful for preparing radiation shielding concrete.

Strength, durability, and toxicity characteristics of water treatment sludge based geopolymers for subgrade application

This study examined the strength, durability and toxicity characteristics of geopolymer made from water treatment sludge (WTS) using fly ash (FA) and ground granulated blast furnace slag (GGBS) as binding materials for the subgrade application. The mechanical properties of WTS-FA-GGBS geopolymers were assessed considering various parameters such as binder proportions, curing period, curing condition, Sodium silicate (SS) to Sodium hydroxide (SH) ratio (i.e. SS/SH), and Sodium hydroxide (NaOH) concentration. The results showed that increasing binder proportions, NaOH concentration, and curing period positively impacted the strength of the WTS-FA-GGBS geopolymer. The unconfined compressive strength (UCS) of the geopolymer samples with an SS/SH ratio of 2.5 showed higher compressive strength than those at an SS/SH ratio of 1. WTS-FA-GGBS geopolymers cured at 100°C showed increased UCS values after 1 to 3 days, but strength decreased after 7 days due to a faster geopolymerisation reaction, resulting in excessive moisture loss and microcracks in the geopolymerized samples. The study also found that all the geopolymer samples met the minimum strength criteria for cement-stabilized mix with a maximum mass loss of 8.17 % are well within the specified limits (<14 %) as per IRC:37–2018. The California Bearing Ratio (CBR) values of WTS-FA-GGBS geopolymers, which range from 41.11 % to 260.32 %, surpass the minimum criteria for cement stabilized subgrade or subbase material, as specified by IRC: SP:89–2010. Additionally, the changes during geopolymerization were confirmed by FESEM, EDS, and XRD analysis. The toxicity characteristic leaching procedure (TCLP) test results showed that the amounts of heavy metals in the geopolymer leachate were within the USEPA-mandated limits.

Study of the thermal stability of spent bleaching clay-based geopolymer with waste polypropylene plastic aggregates

This study incorporated polypropylene (PP) plastic waste into the spent bleaching clay (SBC)-based geopolymer as aggregates, aiming to address pollution from plastic and edible oil industry waste while promoting a transition into circular economy of repurposing waste. The geopolymer mixture paste, containing PP plastic aggregates in different mass ratios (SBC:PP = 1:0.4, 1:0.6, 1:0.8, and 1:1) is oven cured at 60 °C and 80 °C for 8 h followed by 7 days of room temperature curing. Thermal properties of PP-SBC-based geopolymer mortars with varying compositions of PP plastic were assessed using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The TGA results revealed that the geopolymer's thermal stability within the temperature range of 620 °C–700 °C improved with an increase in PP plastic aggregate content, up to an optimal amount of 1:08 PPSBCG sample ratio of SBC to PP cured at oven temperature of 80 °C has been chosen as the representative sample for further discussion based on analysis result of ATR-FTIR spectroscopy and BET analysis. Beyond this amount, a reverse trend was observed. The DSC analysis revealed that incorporating PP plastic aggregates reduced its thermal stability towards the melting reaction but improved its thermal insulation properties. However, this effect was observed only up to a composition of PP plastic relative to SBC of 0.6, beyond this threshold, a reverse trend was observed. In addition to TGA and DSC, the geopolymer samples were characterized using Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy and N2 Brunauer-Emmett-Teller (BET) analysis. This study proved that the addition of high heat-resistant PP plastic into the geopolymer system increased the thermal stability of geopolymers, but only up to a certain optimal quantity. Excessive PP plastic resulted in a reverse trend due to significant effect of weakened interfacial bonding between the geopolymer matrix.

Corrosion resistance of polymer-modified hardened cement paste and phosphoric acid-activated metakaolin geopolymer in carbonic acid solution

Corrosion resistance of hardened Portland cement paste (HCP), polymer-modified hardened cement paste (PHCP) and phosphoric acid-activated metakaolin (PMK) geopolymers in carbonic acid solution was comparatively evaluated by multiple techniques of thermogravimetry (TG), energy dispersive spectrometer (EDS), fourier transform infrared spectrometer (FTIR), inductively coupled plasma optical spectrometer (ICP), microindentation and compressive tests. The incorporated polymer kinetically slows down the corrosion process of Portland cement paste as the carbonation depth of PHCP is lower than those of HCP characterized by all techniques. Meanwhile, the addition of polymer slightly hinders leaching of substances from HCP by blocking the pores. Despite the increase of elastic modulus, decreases of compressive strength of both HCP and PHCP samples caused by carbonation are observed probably due to the generation of microcracks and uneven brittleness across the section. PHCP presents less mechanical loss after carbonation treatment than HCP. PMK geopolymer samples soaked in deionized water and carbonic acid solution have comparatively identical results of TG, EDS, FTIR and mechanical measurements, indicating that the PMK geopolymer is highly resistant to carbonic acid, thanks to its inherent acidic nature. In addition, the leaching amount of PMK geopolymer in carbonic acid solution is also much less than the HCP and PHCP.

The Effect of CaO in the Immobilization of Cd2+ and Pb2+ in Fly Ash-Based Geopolymer

The use of geopolymers for the solidification/stabilization (S/S) of municipal solid waste incineration fly ash (MSWI FA) is promising because the Cao in MSWI FA can provide an alkaline environment to facilitate geopolymer reactions and help to form the gel phase in the solidified body. This study investigated the role of CaO in MSWI FA in immobilizing common heavy metals, especially Cd2+ and Pb2+. Tests were performed to evaluate the effect of CaO on the unconfined compressive strength (UCS) of the polymer and the leaching of heavy metals. The findings revealed that as the CaO content increased, the UCS of the geopolymer samples also rose, reaching a maximum 28-day UCS of 24.8 MPa at a CaO content of 31.5%. Additionally, higher CaO levels resulted in lower leaching concentrations of heavy metals in the stabilized material. When the CaO level is 32%, the levels of heavy metals that leach out are very low, with Pb2+ at 0. 02 mg/L and Cd2+ at 0. 01 mg/L, achieving a stabilization rate of over 93.6% for these ions. Moreover, the geopolymer’s characteristics were analyzed by XRD, FTIR, and SEM, and the immobilization mechanisms of Cd2+ and Pb2+ were identified as gelation, physical encapsulation, and chemical substitution.

Optimization of geotechnical characteristics of clayey soils using fly ash and granulated blast furnace slag-based geopolymer

In this study, the effects of fly ash and granulated blast furnace slag based geopolymer on the mechanical properties of high plasticity clayey soils were investigated. For this purpose, experimental studies were carried out using the Taguchi Method. The Taguchi L16 orthogonal array was used with various amounts of class F fly ash (12 %, 16 %, 20 %, and 24 %), granulated blast furnace slag (8 %, 10 %, 12 %, and 14 %), and alkaline hydroxide solution NaOH molarity (6, 8, 10, and 12). After 7 and 28 days of curing, unconfined compressive strength (UCS) and California bearing ratio (CBR) were carried out. Permeability test was carried out as well after 28 days of curing. The effects of the variables on the experimental results were determined using S/N and variance analyses (ANOVA). The microstructure and phase composition of geopolymer samples were identified via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The findings indicate that the strength of geopolymer-stabilized soil is significantly affected by the stabilizer content, fly ash–slag ratio, and molarity of alkaline activator (M). The optimal mix proportions for geopolymer-stabilized high plasticity clayey soil were found to be as follow: 38 % geopolymer content (24 % fly ash, 14 % slag) and an alkaline activator content of 25.75 % with a molarity of 12 M.This study concluded that fly ash and granulated blast furnace slag based geopolymer can serve as a feasible alternative material to cement, being sustainable and applicable. It could be utilized to enhance the strength characteristics of high-plasticity clay soil, while simultaneously, reducing permeability.

Physical, chemical and radiation shielding properties of metakaolin-based geopolymers containing borosilicate waste glass

Upcycling waste borosilicate glass (BS) is a viable and sustainable way of preserving the natural resources required for the production of new materials and ensuring environmental sanitation and safety. This study was aimed at investigating how the addition of BS influences the physical, chemical, and mechanical properties and shielding performance against neutrons and charged particles on metakaolin-based geopolymer G. Four batches of G infused with 10%, 20%, and 30% wt BS samples and coded as G, G-10BS, G-20BS, and G-30BS, respectively, were fabricated based on the solid-state reaction method. The samples were characterized accordingly using experimental and theoretical procedures. X-ray diffraction analysis of the materials showed that the addition of BS suppressed crystal peaks in the geopolymers. The Vickers hardness values were calculated as 554, 503, 517, and 528 HV under a 0.1 kg load. The values of fast neutron macroscopic cross-section increased from 0.0601 cm−1 to 0.0706 cm−1 as BS content increased from 0 to 30 wt%. The coherent, incoherent, absorption, and total interaction probabilities of thermal neutrons increased in the geopolymer samples. For electrons, the stopping powers were in the range of 1.575–13.17 cm2/g, 1.571–13.15 cm2/g, 1.571–13.16 cm2/g, and 1.571–13.18 cm2/g for G, G-10BS, G-20BS, and G-30BS, respectively. The projected ranges of carbon ions in G, G-10BS, G-20BS, and G-30BS are within the limits 0.069–17.87 μm, 0.064–16.99 μm, 0.064–16.99 μm, and 0.057–15.24 μm. The trend of the projected ranges of electrons, protons, α-particles, and C ions with kinetic energies within 15 keV and 15 MeV was mostly in the sequence G > G-10BS > G-20BS > G-30BS. This order was consistent with the density and BS content of the geopolymer samples. The addition of BS to the metakaolin-based geopolymer improved the fast neutron moderating capacity and thermal neutron cross-sections and reduced the range of charged particle radiation in the geopolymers. The neutron shielding ability of G-30BS was found to be better than that of some existing shielding materials. The BS-infused concrete can be useful for the production of concrete used for radiation control.

In-depth analysis of macro-properties and micro-mechanism of eco-friendly geopolymer based on typical circulating fluidized bed fly ash

Geopolymer is an eco-friendly building material that significantly reduces energy consumption and CO2 emissions. The increase in circulating fluidized bed fly ash (CFBFA) production presents an opportunity to use CFBFA in geopolymer synthesis, mitigating environmental hazards and promoting a sustainable, low-carbon cement industry. However, the complex transformation of amorphous aluminosilicates in CFBFA into geopolymer gels and the impact of calcium (Ca) composition on the macro-properties and micro-mechanism of geopolymers are not well understood, hindering large-scale utilization of the CFBFA-based geopolymer. In this study, low-Ca CFBFA (LCFA) and high-Ca CFBFA (HCFA) were used as precursors, with NaOH as the activator. The workability, mechanical properties, and microstructure evolution of the geopolymer samples were systematically compared. The LCFA-based geopolymer slurry exhibited ideal workability. The high Ca content in HCFA increased the water demand of the slurry, thereby reducing its workability. Compared to LCFA-based geopolymer samples, although Ca-containing components in HCFA accelerated the geopolymerization processes, some gels transformed into irregular crystalline phases during the later stages of curing, compromising the dense structure and slowing the development of mechanical properties. The evolution of the Si–Al coordination structure showed that LCFA-based geopolymers favored the development of Si-rich gels (Q4(1Al) and Q4(2Al)), whereas HCFA-based geopolymers exhibited a preference for Al-rich gels (Q4(3Al) and Q4(4Al)). The results of this research can provide valuable insights for the synthesis of CFBFA-based geopolymers.

Silica-based geopolymers admixture of borosilicate waste glasses: A green material for gamma radiation shielding applications

The gamma shielding parameters of an admixture of waste borosilicate glass (BS) and geopolymer (GP) made from activated metakaolin are presented in the present study. The influence of the BS quantity on the density and different gamma shielding quantities is investigated over a wide gamma energy range. Four batches of the G-BS composite were prepared using the solid-state diffusion method, containing 0 (G), 10 % (G-10BS), 20 % (G-20BS), and 30 % (G-30BS) by weight of BS, respectively. The chemical compositions of the G-xBS samples were determined through X-ray fluorescence spectrometry. In addition, the density of the BS-doped geopolymers was determined using the liquid displacement method using deionized water as the displacement fluid. The theoretical determination of estimating shielding parameters began by estimating the mass (μρ) and linear (μ) attenuation coefficients of the geopolymers for photon energies in the range of 15 keV to 15 MeV using the XCOM data library. The B and Si content and density of the geopolymer samples increased as the BS weight proportion increased in the geopolymer. The values of the attenuation coefficients (ACs) decreased with energy. For μ, the decrease was from 9.1533 to 0.0355 cm−1, 6.7486 to 0.0374 cm−1, 10.2964 to 0.0396 cm−1, and 10.7722 to 0.0414 cm−1, while for μρ, it was 5.3217 to 0.0206 cm2 g-1, 5.3860 to 0.0206 cm2 g-1, 5.3627 to 0.0206 cm2 g-1, and 5.3594 to 0.0206 cm2 g-1, for G, G-10BS, G-20BS, and G-30BS, respectively. There are no significant differences between the photon energy absorption capacity of the geopolymers, especially at energies greater than 1 MeV. The photon buildup factors of the G-xBS samples have very close relative values with no clear order. The introduction of waste borosilicate glass is therefore a way of improving the photon attenuation capacity of geopolymer and, therefore, the potential of shielding applications of geopolymer-based concrete.

Mechanical, durability and microstructural characterization of cost-effective polyethylene fiber-reinforced geopolymer concrete

Portland cement is widely used in the construction industry. Its production contributes to carbon dioxide emissions, urging the need for sustainable alternatives. The present study aims to evaluate the strength, durability, microstructural properties, and cost-effectivity of geopolymer (GP) concrete containing polyethylene (PE) fibers, with fly ash (FA), ground-granulated blast furnace slag (GGBFS), and calcium magnesium carbonate (CaMg(CO3)2 known as dolomite) as binders. PE fiber used has an ultra-high molecular weight. Six different mixtures were produced with FA, GGBFS, dolomite, and/or PE fiber. The control mix used only FA as a binder without PE fiber. Fresh and mechanical properties, including slump value, compressive strength, and split tensile strength, were determined, and non-destructive tests, such as electrical resistivity and ultrasonic pulse velocity, were conducted. The durability of GP was evaluated through initial surface absorption and capillary suction absorption tests at different curing ages. Microstructural and mineralogical characteristics were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The results revealed that the addition of PE fibers and CaMg(CO3)2 reduced the workability of GP by 30.22% in comparison with that of PE fiber along with GGBFS. Compared to the reference mix at 28 days, incorporating 20% GGBFS resulted in the highest improvement of 76.89% and 104.86% in compressive and split tensile strength, respectively. GP sample with 20% GGBFS replacement of FA presented the highest reduction of 44.4–41.63% for initial and secondary rate of absorption. SEM analysis showed that the addition of GGBFS and CaMg(CO3)2 to fiber-reinforced FA-based geopolymer mixes developed a denser and more homogenous matrix with improved mechanical behavior due to the co-existence of C−S−H and aluminosilicate gel. PE fibers improve the toughness properties by helping to absorb energy and bridging cracks. The development of a stronger matrix was characterized by C−S−H, calcium aluminate oxide (carbonate) hydroxide (C4AHx) and quartz. A one-way ANOVA analysis and cost analysis demonstrate the cost-effectiveness of partially replacing FA with CaMg(CO3)2 and GGBFS in PE fiber-reinforced GP concrete.

Martian Regolith Simulant-Based Geopolymers with Lithium Hydroxide Alkaline Activator

As humanity envisions the possibility of inhabiting Mars in the future, the imperative for survival in the face of its challenging conditions necessitates the construction of protective shelters to mitigate the effects of radiation exposure and the absence of atmospheric pressure. The feasibility of producing geopolymers using the Martian regolith simulant MGS-1 (as precursor) for potential building and infrastructure projects on Mars in the future is investigated in this paper. Various alkaline activators, such as sodium hydroxide (NaOH), lithium hydroxide (LiOH·H2O) and sodium silicate (Na2SiO3), are employed to investigate their efficiency in activating the precursor. The influence of alkali type and concentration on the mechanical performance of the synthesized geopolymers is examined. Geopolymer samples are oven-cured for 7 days at 70 °C before a compressive strength test. It is found that through the hybrid use of LiOH·H2O and NaOH with optimal concentrations, metakaolin and milled MGS-1 as precursors, geopolymer mixtures with a compressive strength of 30 ± 2 MPa can be developed. The present test results preliminarily demonstrate the potential of Martian regolith simulant-based geopolymers as suitable construction and building materials for use on Mars.

Use of natural dyes to color metakaolin-based geopolymer materials

Over the years several colored ceramic-like materials have been prepared by using many synthetic dyes, which are toxic and polluting. Up to date, no studies have been reported on the combination of natural dyes within the geopolymers (also known as amorphous aluminosilicate polymers). In this scenario, natural dyes such as curcumin, chlorophyll, and a freeze-dried grape marc from the wine agrifood supply chain have been employed to investigate their effectiveness ability to color metakaolin-based geopolymers. The colored geopolymers, cured at 25 or 40 °C for 24 h, are characterized after 56 days of ageing time at room temperature by the ionic conductivity and pH measurements, Fourier-Transform Infrared spectroscopy, compressive strength, and color assessment by the color space analysis before and after soaking the samples in water. Eventually, the control geopolymer samples are also characterized for their potential antimicrobial and cytotoxicity properties. The main findings revealed that employing natural dyes to color geopolymers offers a promising alternative to toxic synthetic dyes. The samples retained their color for brief time when exposed to water thus suggesting indoor application. Moreover, all the samples exhibited good geopolymerization as confirmed by FTIR analysis. Notably, samples cured at 25 °C showed better compressive strengths compared to those cured at 40°C. Finally, the bioimpact of these materials suggests that the synthesis in loco of geopolymers is safe for the operator.

Perlite incorporation for sedimentation reduction and improved properties of high-density geopolymer cement for oil well cementing

Portland cement (PC) is known for its environmental and technical concerns and massive energy consumption during manufacturing. Geopolymer cement is a promising technology to totally replace the use of PC in the oil and gas industry. Although geopolymers are widely used in the construction industry, it is yet to see a full-scale application in the petroleum industry. High-density geopolymer cement development is essential to substitute heavy-weight Portland cement slurries for high pressure well cementing applications. Sedimentation issue is associated with high-density cement slurries which use high specific gravity solids such as weighting materials. This problem causes heterogeneity and density variation along the cemented sections. The main target of this work is to evaluate the use of perlite powder to address the sedimentation issue in the heavy weight geopolymer systems. Hematite-based Class F fly ash (FFA) geopolymer cement slurries with perlite concentrations of 0, 1.5, and 3% by weight of binder (BWOB) were prepared. The sedimentation problem was investigated using three techniques: API method, nuclear magnetic resonance (NMR), and computed tomography (CT) scan. The perlite effects on different geopolymer properties such as unconfined compressive strength (UCS), porosity, elastic and rheological properties were assessed. The results proved that perlite incorporation in high-density hematite-based FFA geopolymer significantly reduced sedimentation issue by increasing yield point and gel strength. NMR and CT scan showed that perlite decreases porosity and density variation across the geopolymer samples. The UCS increased with increasing perlite percentage from 0 to 3%. The measured Young’s moduli (YM) and Poisson’s ratios (PR) showed that the developed perlite based geopolymer systems are considered more flexible than Class G cement systems. It was found that the optimum perlite concentration is 3% BWOB for tackling sedimentation and developing a slurry with acceptable mixability and rheological properties.

Investigation of geopolymer efflorescence durability problems: Causes and possible solutions

AbstractExperimental investigations were conducted to assess the impact of factors such as relative humidity (RH%) and the H2O molarity of waterglass on the efflorescence behavior of geopolymer composites. Samples with sodium (Na) and potassium (K) bases were prepared, having varying waterglass molarities (M) (at 11 and 13 moles of water). These samples were categorized into three groups exposed to different average RH ranges: (i) 0%–70% RH, (ii) 70%–90% RH, and (iii) 90%–100% RH. This study analyzed the occurrence of efflorescence and its stability, employing analytical techniques such as x‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy to examine the formation and characteristics of efflorescent deposits. Additionally, mechanical testing was conducted to evaluate the compressive and flexural strengths of the geopolymer samples, considering the impact of efflorescence on their durability. For instance, in the composite geopolymer specimen containing 11 M water, at a RH of 80%, the compressive strength is decreased by approximately 25% from 56.4 to 42.3 MPa. The findings revealed that when the RH falls within the 70%–90% range, a decrease in water molar content from 13 M to 11 M leads to a more pronounced occurrence of efflorescence when compared to other conditions. Efflorescence may also occur in different RH ranges and water molarities, but its occurrence is significantly lower compared to the 70%–90% RH and 11 M water.

The effects of ZnO powder and different fiber types used in tuff/calcite-based geopolymers on electromagnetic shielding effectiveness

Electromagnetic (EM) shielding has become increasingly important in our modern world due to the growing use of electronic devices, which poses risks of EM pollution and its adverse effects on humans. Many studies have explored the incorporation of various additives into geopolymer mixes to enhance their EM shielding properties. This study investigates the impact of tuff/calcite-based geopolymers reinforced with three different types of fibers (Polypropylene, Steel, and Carbon) and varying percentages (2.5 %, 5 %, and 10 %) of ZnO powder on EM shielding effectiveness. Compressive strength, flexural strength, water absorption, length change tests, and EM shielding (900–6000 MHz at every 100MHz step) measurements were performed on geopolymer samples. Optimal shielding performance was achieved by the addition of 10 % ZnO by volume alongside carbon fiber. This combination resulted in a total shielding value of −78.92dB at a bandwidth of 2800MHz.

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

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