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The following study presents the results of research in the field of the performance of geopolymers consisting of Class F fly ash with an alkaline activator solution consisting only of sodium metasilicate (Na2SiO3) and water. The performances of this geopolymer are compared to the those of American Petroleum Institute (API) Class G cement. This comparison is to evaluate the potential of the geopolymer as an alternative to cement in cementing hydrocarbon wells in the oil and gas industry. The gap in the research is determining the performance properties that restrict the use of fly ash in the oil and gas industry. Using only sodium metasilicate as an activator with water, the solution creates a strong binding gel for the geopolymer and activates the aluminosilicate properties of the fly ash. This geopolymer is compared with Class G cement without additives to determine their base performances in high pressure and high temperature conditions, as well as note any properties that are affected in the process. This commences by formulating recipes of these two materials from workable ratios and concentrations. The ratios are narrowed down to the best working models to proceed to comparative performance testing. The tests included exploring their vital performances in fluid loss and thickening time. The results produced suggest that Class G cement generally has less fluid loss at low temperature than the geopolymer but could not maintain its integrity and structure as temperatures increased. Class G cement exhibited stability, consistencies of 100 Bcs (Bearden Consistency Units), and a faster thickening time of 1 h and 48 min when placed under high temperature and high-pressure conditions, respectively. However, the geopolymer showed more consistency regarding fluid loss with respect to rising pressure and temperature, and smoother, less fractured samples emerging from both tests. Though the geopolymer showed stronger performances in thickening and water retention, the experiments showed that it is not a uniform and consistent material like Class G cement. Through the use of different additives and intricate design, the sample may show success, but may prove more difficult and complex to apply than the industry standard and uniform content of Class G cement. [ABSTRACT FROM AUTHOR]

Masonry units have been fundamental to building construction for over 6000 years, making them one of the oldest and most widely used materials in the industry. However, their production using ordinary Portland cement has significant environmental impacts, including high carbon dioxide emissions and depletion of natural resources. This highlights the need for more sustainable alternatives. One promising option is the use of recycled aggregates from construction and demolition waste in masonry unit manufacturing. This paper investigates the use of chipped waste timber as aggregates, bound together with geopolymer cement made from industrial by-products such as fly ash and slag. The result is a new type of masonry units, referred to as wood geopolymer masonry units (WGMUs), which were evaluated against established standards and compared with conventional masonry units (CMUs). The innovative WGMUs demonstrated improved ductility and reduced density compared to CMUs, making them easier to handle and lighter in construction. They also have a distinctive, rustic texture and consistent dimensions that meet Australian standards. Although WGMUs exhibited higher water absorption and drying contraction due to their wood content, these characteristics generally remain within acceptable limits, supporting their potential as eco-friendly construction materials.

The following study presents the results of research in the field of the performance of geopolymers consisting of Class F fly ash with an alkaline activator solution consisting only of sodium metasilicate (Na2SiO3) and water. The performances of this geopolymer are compared to the those of American Petroleum Institute (API) Class G cement. This comparison is to evaluate the potential of the geopolymer as an alternative to cement in cementing hydrocarbon wells in the oil and gas industry. The gap in the research is determining the performance properties that restrict the use of fly ash in the oil and gas industry. Using only sodium metasilicate as an activator with water, the solution creates a strong binding gel for the geopolymer and activates the aluminosilicate properties of the fly ash. This geopolymer is compared with Class G cement without additives to determine their base performances in high pressure and high temperature conditions, as well as note any properties that are affected in the process. This commences by formulating recipes of these two materials from workable ratios and concentrations. The ratios are narrowed down to the best working models to proceed to comparative performance testing. The tests included exploring their vital performances in fluid loss and thickening time. The results produced suggest that Class G cement generally has less fluid loss at low temperature than the geopolymer but could not maintain its integrity and structure as temperatures increased. Class G cement exhibited stability, consistencies of 100 Bcs (Bearden Consistency Units), and a faster thickening time of 1 h and 48 min when placed under high temperature and high-pressure conditions, respectively. However, the geopolymer showed more consistency regarding fluid loss with respect to rising pressure and temperature, and smoother, less fractured samples emerging from both tests. Though the geopolymer showed stronger performances in thickening and water retention, the experiments showed that it is not a uniform and consistent material like Class G cement. Through the use of different additives and intricate design, the sample may show success, but may prove more difficult and complex to apply than the industry standard and uniform content of Class G cement.

Untreated wastewater pollution causes environmental degradation, health issues, and ecosystem disruption. Geopolymers offer sustainable, eco-friendly alternatives to traditional cement-based materials for wastewater solidification and removal. In this study, we investigate how wastewater containing organic and inorganic pollutants can be removed using geopolymer mixes based on metakaolin incorporation with cement kiln dust as an eco-friendly material. The present investigation compares the efficacy of two different techniques (solidification and adsorption) for reducing dye contaminants and heavy metals from wastewater using a geopolymer based on metakaolin incorporation with cement kiln dust. This study investigated the adsorption capacity of a geopolymer based on metakaolin incorporating two different ratios (20% and 40% by weight) of cement kiln dust (MC1 and MC2) for the reactive black 5 dyeing bath effluent (RBD) only and in a combination of 1200 mg/L of Pb2+ and Cd2+, each separately, in aqueous solutions under different adsorption parameters. The results of the adsorption technique for the two prepared geopolymer mixes, MC1 and MC2, show that MC1 has a higher adsorption activity than MC2 toward the reactive black 5 dyeing bath effluent both alone and in combination with Pb2+ and Cd2+ ions separately. The study also looked at using MC1 mix to stabilize and solidify both the dyeing bath effluent alone and its combination with 1200 mg/L of each heavy metal individually inside the geopolymer matrix for different time intervals up to 60 days of water curing at room temperature. The geopolymer matrix formed during the process was analyzed using FTIR, SEM, and XRD techniques to examine the phases of hydration products formed. The results showed that MC1 effectively adsorbs, stabilizes, and solidifies the dying bath effluent for up to 60 days, even with high heavy metal concentrations. On the other hand, geopolymer mixes showed an increase in mechanical properties when hydration time was increased to 60 days. According to our findings, the type of geopolymer developed from metakaolin and 20 wt.% cement kiln dust has the potential to be employed in the treatment of wastewater because it has good adsorption and solidification activity for the reactive black 5 dye effluent alone and for a mixture of dye pollutants with both Pb2+ and Cd2+ ions separately. Our results have significant implications for wastewater treatment and environmental remediation efforts, as they offer a sustainable solution for managing hazardous waste materials. [ABSTRACT FROM AUTHOR]

In this study, simulated lunar rock sand was converted into geopolymer cement by alkali fusion with sodium hydroxide, and its radiation shielding ability was estimated. Space development is currently being conducted in various countries. For construction on the moon, it is difficult to bring all the construction materials from the earth, and construction materials prepared from lunar resources are required. In addition, it is necessary to develop construction materials with radiation shielding ability since the lunar surface is directly affected by space radiation. In a previous study, it has succeeded in making geopolymer cement from simulated lunar rock sand using alkali fusion. Therefore, there is a possibility that geopolymer cement used for construction material can be prepared from lunar rock sand, abundantly present on the lunar surface. In this experiment, geopolymer cement was prepared from simulated lunar rock sand by changing the mixing ratio of the sand, sodium hydroxide and water, and strength of the cement was examined to obtain high-strength geopolymer. In addition, the resulting high-strength geopolymer cement was subjected to radiation shielding tests to confirm its radiation shielding ability. As a result, it was found that the high-strength geopolymer cement with radiation shielding ability can be prepared from simulated lunar rock sand using alkali fusion with sodium hydroxide. [ABSTRACT FROM AUTHOR]

Water is a resource that is essential to almost all phases of industrial and manufacturing operations globally. It is important to handle the wastewater generated professionally. The textile industry is one of the major global polluters, with textile producers responsible for one-fifth of all industrial water pollution worldwide. In contrast, heavy metal contamination has developed into a critical, expanding global environmental problem. Geopolymer is a cementitious constituent of amorphous aluminosilicates derived from natural or industrial wastes. It is produced using the polymerization of aluminosilicate raw ingredients in an alkaline atmosphere. The aim of this study is to evaluate the application of eco-friendly geopolymer cement in the immobilization technique for the treatment of wastewater including heavy metals and dyes. Geopolymer cement pastes were organized using slag and fly ash as an aluminosilicate source, (1:1) sodium silicate and sodium hydroxide 15 wt.% as an alkali activator in the presence of organic dye pollutant reactive red 195, and Cu2+ ions (700 ppm) at different hydration times for up to 28 days. The physicochemical and mechanical properties of the prepared geopolymer cement mixes were further examined in relation to reactive dye pollutant and Cu2+ ions. The hydration characteristic was examined using the compressive strength and % of total porosity tests, as well as FTIR and XRD studies. Our findings support the 100% immobilization of both Cu2+ ions and organic dye pollutants in prepared geopolymer pastes for up to 28 days of hydration. Additionally, adding both Cu2+ ions and dye pollutants to the prepared geopolymer paste improves its mechanical properties, which is also supported by FTIR data. XRD and FTIR studies showed that the Cu2+ ions and dying bath effluent addition have no influence on the kind of hydration products that are produced. On the other hand, the geopolymerization process is negatively impacted by the presence of Cu2+ ions alone in the geopolymer paste. [ABSTRACT FROM AUTHOR]

These days, good quality road construction materials are scarce and their haulage to the construction site is expensive. When unsuitable materials are encountered during flexible pavement construction, the most technical and economical option is always to improve them to meet design standards. One of these deficient materials mostly encountered in tropical regions is kaolin clay soils. Cement and lime that are traditional deficient soil improvement agents are on high demand therefore have kept the cost of engineering construction financially high. Thus, the use of agricultural wastes such as sawdust and rice husk as alternative construction materials will considerably reduce the cost of construction and as well mitigate the environmental hazards caused by the wastes and cement production. This study investigated and compared the performance of rice husk ash (RHA) and sawdust ash (SDA) geopolymer cements in improving the geotechnical properties of kaolin clay soil used for flexible pavement construction. All laboratory experimental tests were carried out in accordance with British Standard (BS) 1377 and BS 1924 for natural and modified kaolin clay soil samples respectively. Soil samples were mixed with geopolymer cement at stepped concentrations of 0, 4, 8, 12, 16 and 20% by dry weight of soil. Results indicated that the plasticity index value of the natural kaolin clay of 18.52% was reduced to 7.24% at 20% RHA geopolymer cement content. The unconfined compressive strength of the natural soil was improved by 600 and 400 % by RHA and SDA geopolymer cements respectively. It was concluded that the use of up to 20% RHA and SDA geopolymer cements can efficiently and eco-friendly improve kaolin clay for flexible pavement foundation purpose

[Display omitted] The influence of different alkali and alkaline earth cations (Na+, K+, Ca2+, and Mg2+), and of solution pH, on surface interactions of metakaolin particles with a sodium naphthalene sulfonate formaldehyde polymer (SNSFP) (a commercial superplasticizer for concretes) was investigated in aqueous systems relevant to alkali-activated and blended Portland cements. This study used zeta potential measurements, adsorption experiments, and both in situ and ex situ Fourier transform infrared spectroscopy measurements of the suspensions to gain a fundamental understanding of colloidal interactions and physicochemical mechanisms governing dispersion in this system. SNSFP was most effective in dispersing metakaolin suspensions in Ca2+-modified aqueous NaOH systems (CaCl 2 -NaOH) at dosages of 5 wt.%. Additionally, Ca2+ was the most effective alkaline earth cation mediator in providing a dispersion effect in metakaolin dispersed in aqueous NaOH and SNSFP mixtures, while Mg2+ was the most effective in aqueous KOH and SNSFP mixtures. The colloidal dispersion remained stable in the highly alkaline environment, and therefore SNSFP could be utilized to improve dispersion of metakaolin-based alkali-activated systems. The suggested mechanism for colloidal stability and fluidity of metakaolin-based cements (e.g. Portland cement blends and alkali-activated cements) is explained by changes in the distribution and structure of the electric double-layer, as well as structural forces, due to alteration in surface charge density and hydrated shell, facilitating competitive adsorption of the polymer. [ABSTRACT FROM AUTHOR]

Geopolymer cement (GPC) is a sustainable alternative to ordinary Portland cement (OPC) that considerably cuts the emission of carbon dioxide linked to the building of concrete structures. Over the last few decades, while a large number of papers have been written concerning the use of GPC with natural aggregates and OPC with recycled aggregates, few papers have been devoted to investigating the use of Geopolymer Recycled Aggregate Concrete (GRAC) in structural members. Most of them show more interest in the mechanical strength of the material, rather than the structural behavior of RC members. This review critically compiles the present and past research on the behavior of structural members cast with different types and compositions of GRAC. The focus is on the few research studies investigating the structural behavior of GRAC elements, with an analysis of the load-bearing capacity, the load-deflection mechanism, shear behavior, tensile and flexural strength, and ductility of GRAC structural members. This review aims to indicate the research and experimental tests needed in the future for characterizing the behavior of structural members made up of GRAC. [ABSTRACT FROM AUTHOR]

The most effective approach to enhance the strength of cementitious materials is by manipulating their structure at the nano and microscale levels. However, although long-pursued, current nano-engineering methods are still challenging or impractical for large-scale applications. Here, we introduce a facile method to nano-engineer geopolymer cement materials with microstructure resembling that of nacre, thereby possessing superior tensile/flexural properties. The pivotal step in our approach was meticulously employing mica microplates and cellulose nano-fibers to guide the layer-by-layer, nacre-like assembly of metakaolin, the raw material of geopolymer cement. Then, through straightforward alkali-activation and lamination techniques, we successfully created nacre-like geopolymer cement composites at the centimeter scale, as extensively validated by microscopy, spectroscopy, and thermogravimetric characterization. Mechanical testing showed that the developed nacre-like geopolymer composites possessed a flexural strength of ∼38 MPa—10–20 times higher than that of conventional cementitious materials—while maintaining similar stiffness and hardness to conventional geopolymer cement. Further microscopy analysis demonstrated that the superior strength of the composites stemmed from the ordered assembly of clay and cellulose building blocks within the geopolymer matrix, endowing a dense microstructure with crack bridging and deflection capabilities. Given the outstanding mechanical performance of the nano-engineered composites and the feasibility of scaling up the method, these findings represent a significant advancement in crafting novel cement-based materials with unparalleled performance. [ABSTRACT FROM AUTHOR]

Natural material like metakaolin, along with industrial wastes such as fly ash (FA), cement kiln dust (CKD), and ground granulated blast furnace slag (GGBFS), are being used to develop new affordable and environmentally friendly construction materials (Geopolymers) that result in reduced carbon dioxide emissions. Geopolymers are gaining attention for their ability to effectively remove organic and inorganic contaminants from wastewater, including dyes and heavy metals. However, the study of the radiation properties of eco-friendly geopolymer cement materials has received little attention. To address this gap, conducted a previous study to examine the radiation properties of different geopolymer cement samples. In this study, the analyzed the radon concentration, radium concentration, and annual effective dose of various pre-treated geopolymer cement samples that contained industrial wastes from dyes and heavy metals. By using the CR-39 detector as a passive technique for this examination. In the pretreated geopolymer cement samples, we used three types of reactive dye effluents - reactive black 5 (BD), reactive red 195 (RD), and reactive yellow 145 (YD) in the presence of heavy metals (Cu2+, Cd2+, and Pb2+). Based on our research, the concentration of radon ranged from 2.69 to 212.42 Bq m-3. The sample with the lowest value of radium concentration was labeled as (10) (GGBFS), while sample (9) (SF 10 -YD-Cu2+) had the highest value. Found that the annual effective doses were within the range of the world average for indoor and outdoor 1.55 and 0.58 mSv y − 1 respectively, except for sample 9 (SF 10 -YD-Cu2+) which had the highest radium concentration. The pretreated geopolymer cement mixes containing different dye effluents and heavy metals were found to be safe for use in construction areas, except for sample 9 (SF 10 -YD-Cu2+). Recommend using sample 9 (SF 10 -YD-Cu2+) only for public highways, bridges, and other well-ventilated buildings. • Determine the radon and radium concentrations for the samples using CR-39 detector. • Analyze the annual effective dose of the samples that contain industrial waste. • Study the radiation properties of eco-friendly geopolymer cement materials. • Pretreated geopolymer cement mixes contain different dye effluents & heavy metals. • The results show the effects of using geopolymer samples in construction materials. [ABSTRACT FROM AUTHOR]

In this article we studied the effects of sodium hydroxide pellets (SH) and sodium silicate liquid (SSL) as an activator on the physico chemical and mechanical Properties of ground granulated blast furnace slag (GGBFS) geopolymer pastes. Various mixes are prepared using different liquid/solid ratios (L/S) by weight. The hydration characteristics of the various mixes have been tested through determination of total porosity, compressive strength, bulk density, chemically combined water, and XRD analysis at different time intervals from 2 days up to 90 days under relative humidity 100%. The results elucidated that as the quantity of alkali activator increases up to (15% SSL, and 15% SH), the compressive strength increases up to 90 days. The combined water content of all mixes increases up to 90 days. Also the bulk density raises and the total porosity minimizes, this is due to the addition of the pozzolanic materials. All mixes showed good stability of its compressive strength values in 5 % MgSO4 solution. The data showed that mix S6 (100% GGBFS) activated by (15% SSL, and 15% SH) is the most appropriate binding material (geopolymer cement) that has good properties so it can be used as alternative binding materials to the ordinary Portland cement.

Untreated wastewater pollution causes environmental degradation, health issues, and ecosystem disruption. Geopolymers offer sustainable, eco-friendly alternatives to traditional cement-based materials for wastewater solidification and removal. In this study, we investigate how wastewater containing organic and inorganic pollutants can be removed using geopolymer mixes based on metakaolin incorporation with cement kiln dust as an eco-friendly material. The present investigation compares the efficacy of two different techniques (solidification and adsorption) for reducing dye contaminants and heavy metals from wastewater using a geopolymer based on metakaolin incorporation with cement kiln dust. This study investigated the adsorption capacity of a geopolymer based on metakaolin incorporating two different ratios (20% and 40% by weight) of cement kiln dust (MC1 and MC2) for the reactive black 5 dyeing bath effluent (RBD) only and in a combination of 1200 mg/L of Pb2+ and Cd2+, each separately, in aqueous solutions under different adsorption parameters. The results of the adsorption technique for the two prepared geopolymer mixes, MC1 and MC2, show that MC1 has a higher adsorption activity than MC2 toward the reactive black 5 dyeing bath effluent both alone and in combination with Pb2+ and Cd2+ ions separately. The study also looked at using MC1 mix to stabilize and solidify both the dyeing bath effluent alone and its combination with 1200 mg/L of each heavy metal individually inside the geopolymer matrix for different time intervals up to 60 days of water curing at room temperature. The geopolymer matrix formed during the process was analyzed using FTIR, SEM, and XRD techniques to examine the phases of hydration products formed. The results showed that MC1 effectively adsorbs, stabilizes, and solidifies the dying bath effluent for up to 60 days, even with high heavy metal concentrations. On the other hand, geopolymer mixes showed an increase in mechanical properties when hydration time was increased to 60 days. According to our findings, the type of geopolymer developed from metakaolin and 20 wt.% cement kiln dust has the potential to be employed in the treatment of wastewater because it has good adsorption and solidification activity for the reactive black 5 dye effluent alone and for a mixture of dye pollutants with both Pb2+ and Cd2+ ions separately. Our results have significant implications for wastewater treatment and environmental remediation efforts, as they offer a sustainable solution for managing hazardous waste materials.

Sodium silicate is a commonly used activator in geopolymer that is produced commercially. In this study, rice husk ash (RHA) from agricultural waste was used to synthesize sodium silicate as an activator for geopolymer cement. This white ash was applied for producing sodium silicate with different molarities (8, 10, and 12) and then used to synthesize fly ash-based geopolymer cement. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were applied to investigate the micro-characteristics of the geopolymerization products. Bulk density, water absorption, compressive strength, flexural strength, and fracture toughness were carried out to measure and evaluate the geopolymers with sodium silicate. The combination of 10 M NaOH with sodium silicate increased the compressive strength by 16.21% and the flexural strength and fracture toughness by 81.6%. However, sodium silicate combined with 12 M NaOH decreased compressive strengths by 13.23% and flexural strength and fracture toughness by 61.94%. The lowest water absorption value of 12.3% was obtained in a geopolymer paste using sodium silicate combined with 10 M NaOH, and the largest was 13.3% for sodium silicate combined with 8 M NaOH. The microstructure analysis showed the hydrated calcium alumina silicate gel (C–A–S–H) and the SEM image also revealed a compact geopolymer matrix. Thus, it can be concluded that sodium silicate from rice husk ash can be utilized as an activator or reactive material to produce geopolymer cement with a good geopolymer network. [ABSTRACT FROM AUTHOR]

India is the second-leading cement producer in the world after China. Cement causes huge carbon footprint during the production and transportation of materials. Various efforts are being made to reduce the environmental impacts. Among the notable developments are the use of by-product or secondary material to develop new binders such as geopolymer cement. This paper contains a cradle-to-gate life cycle impact assessment of two types of geopolymer cement produced from blending fly ash and slag, and blending fly ash and cement in an Indian scenario. As there is no standard data available for geopolymer cement production, the primary data used were collected by producing geopolymer cement at pilot scale (5 t/d). In an Indian context, the geopolymer cement significantly reduces the global warming potential (267 kg CO2-Equiv.), abiotic depletion potential fossil (3092 MJ), abiotic depletion potential element (1.18 e−3 kg Sb-Equiv.), human toxicity potential (249 kg DCB-Equiv.), and terrestrial ecotoxicity potential (0.438 kg DCB-Equiv.) with blending fly ash and slag. The geopolymer cement produced from fly ash and slag reduces the global warming potential by 70%, abiotic depletion potential fossil by 49%, abiotic depletion potential element by 34%, and terrestrial ecotoxicity potential by 77% when compared with ordinary Portland cement of the building and construction industries. In case of geopolymer cement, the maximum impact on the environment is due to the use of an alkali solution. Based on the analysis, geopolymer cement appears more sustainable than traditional cement and thus has good potential as an alternate binder. [ABSTRACT FROM AUTHOR]

This study investigates the effect of modifying ambient-cured geopolymer-bonded composites of coir fibre and wood particles with γ-aminopropyltriethoxysilane (APTES, 0.10 wt%) and colloidal nano-silica (CNS, 1.45 wt%). APTES-modified binders had lower workability (200.7 ± 11.5 mm spread diameter) than unmodified (255.3 ± 12.5 mm) and CNS (248.5 ± 8.9 mm) counterparts. Setting times were similar, with the APTES variant setting faster. CNS-modified binders showed the highest reactivity, reaching peak temperature at 39.5 min. Physicochemical, mechanical, and microstructural analyses were conducted on the composites. CNS-modified composites had the highest internal bond strength (1.52 ± 0.11 N mm−2), flexural modulus (5416.3 ± 222.8 N mm−2), flexural strength (10.2 ± 0.7 N mm−2), and work to maximum force (670.4 ± 23.3 Nmm). APTES-modified composites exhibited superior water resistance, with the lowest water absorption (18.1 ± 0.5 %) and thickness swelling (0.10 ± 0.03 %) after three 24 h-cycles of water soaking. The pH value remained at 11 over 28 days. Microstructural analysis revealed improved adhesion and reduced voids and cracks in modified composites, which increased performance and water resistance. Coir fibre-reinforced composites exhibited higher strength than those with wood particles. These findings highlight the feasibility of producing ambient-cured geopolymer-bonded lignocellulosic composites for building applications. • Ambient-cured geopolymer-bonded lignocellulosic composites are feasible. • Aminosilane and nano-silica modifications enhance strength and water resistance. • Aminosilane and nano-silica modifications result in a densified microstructure. • Nano-silica modification results in the highest strength and improved water resistance. • Aminosilane modification enhances water resistance and interfacial connectivity. [ABSTRACT FROM AUTHOR]

Water is a resource that is essential to almost all phases of industrial and manufacturing operations globally. It is important to handle the wastewater generated professionally. The textile industry is one of the major global polluters, with textile producers responsible for one-fifth of all industrial water pollution worldwide. In contrast, heavy metal contamination has developed into a critical, expanding global environmental problem. Geopolymer is a cementitious constituent of amorphous aluminosilicates derived from natural or industrial wastes. It is produced using the polymerization of aluminosilicate raw ingredients in an alkaline atmosphere. The aim of this study is to evaluate the application of eco-friendly geopolymer cement in the immobilization technique for the treatment of wastewater including heavy metals and dyes. Geopolymer cement pastes were organized using slag and fly ash as an aluminosilicate source, (1:1) sodium silicate and sodium hydroxide 15 wt.% as an alkali activator in the presence of organic dye pollutant reactive red 195, and Cu2+ ions (700 ppm) at different hydration times for up to 28 days. The physicochemical and mechanical properties of the prepared geopolymer cement mixes were further examined in relation to reactive dye pollutant and Cu2+ ions. The hydration characteristic was examined using the compressive strength and % of total porosity tests, as well as FTIR and XRD studies. Our findings support the 100% immobilization of both Cu2+ ions and organic dye pollutants in prepared geopolymer pastes for up to 28 days of hydration. Additionally, adding both Cu2+ ions and dye pollutants to the prepared geopolymer paste improves its mechanical properties, which is also supported by FTIR data. XRD and FTIR studies showed that the Cu2+ ions and dying bath effluent addition have no influence on the kind of hydration products that are produced. On the other hand, the geopolymerization process is negatively impacted by the presence of Cu2+ ions alone in the geopolymer paste.

The present study aimed to investigate the effect of an expandable additive on the compressive strength and linear expansion of geopolymer cement, which is an alternative to ordinary Portland cement, for oil-well cementing. Fly-ash-based geopolymer cement samples, with the addition of slag cement as a strength enhancer, were prepared by using an elastomeric expandable additive (R-additive), which consists of styrene–butadiene rubber with a specific gravity of 0.945, at concentrations of 10%, 15%, 20% and 25% by weight of the solid blend, and cured in a water bath at 60 °C and atmospheric pressure, and a curing chamber at 90 °C and 3000 psi, or approximately 20.68 MPa. Mixability, amount of free water and slurry density were studied, and the effects of the concentration of R-additive on the compressive strength (F) and linear expansion (∆l/l0) of the samples were analyzed. When cured at 60 °C and atmospheric pressure, the highest F of 15.01 MPa was obtained when the concentration of R-additive was 10%, while the highest ∆l/l0 of 0.9985% was obtained when the concentration of R-additive was 25%. An increase in the curing temperature and pressure to 90 °C and 3000 psi (≈20.68 MPa) resulted in the reduction of F from 15.01 to 14.62 MPa and from 10.33 to 9.61 MPa, and the increase in ∆l/l0 from 0.52% to 0.63%, and from 0.99% to 1.32%, when the concentrations of R-additive were 10% and 25%, respectively. The findings suggest that the formulations adopted, which contain R-additive at concentrations ranging from 10% to 25%, fulfilled the requirements of the oil and gas industry. [ABSTRACT FROM AUTHOR]

In this study, the Palm Oil Fuel Ash (POFA) was used as a raw material for making geopolymer mortars that uses a combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The purpose of this study was to determine the effect of various parameters on the compressive strength of mortars. The parameters involved were namely modulus of activator ratio (Ms 1-3), the molarity of NaOH (10-16M), curing temperature (28-110ºC), type of POFA particle processing (oven-dried, passed the #200 sieve, burned in a brick kiln, burned at 800ºC), rest periods of 3 and 5 days. Based on the parametric study, it was found the optimum mixture with the highest compressive strength consisted of NaOH 14M, Ms ratio of 2.5, curing temperature of 100OC, a rest period of 5 days, particles sieved using #200 sieve and had 15% PCC content.

Geopolymer cement (GPC) is a sustainable alternative to ordinary Portland cement (OPC) that considerably cuts the emission of carbon dioxide linked to the building of concrete structures. Over the last few decades, while a large number of papers have been written concerning the use of GPC with natural aggregates and OPC with recycled aggregates, few papers have been devoted to investigating the use of Geopolymer Recycled Aggregate Concrete (GRAC) in structural members. Most of them show more interest in the mechanical strength of the material, rather than the structural behavior of RC members. This review critically compiles the present and past research on the behavior of structural members cast with different types and compositions of GRAC. The focus is on the few research studies investigating the structural behavior of GRAC elements, with an analysis of the load-bearing capacity, the load-deflection mechanism, shear behavior, tensile and flexural strength, and ductility of GRAC structural members. This review aims to indicate the research and experimental tests needed in the future for characterizing the behavior of structural members made up of GRAC.

The use of wastes for new binders aims to reduce the environmental impact caused by the manufacture of Portland cement (PC) given the advance of urbanization. In this work, the main effects of the use of Geopolymer Cement (GC) in partial replacement to PC in mortars for coating were investigated. The GC was obtained from mixtures of industrial wastes, fly ash (FA), granulated blast furnace slag (GBFS), and metakaolin (MK), activated by a solution composed of alkaline sodium silicate (SS) and potassium hydroxide (KOH). The factors used for the experimental planning were the cement replacement content, T (10, 30, and 50%, by weight) and the aggregate-cement ratio, A/C (6.11, 6.90, and 7.69, by weight). Some properties were evaluated initially: consistency, compressive strength, durability (sulfate attack) and microstructural analysis (SEM, XRD, DSC, and TG). For optimized mixture and reference were tested: consistency, setting time, the heat of hydration, water retention, compressive strength, flexural tensile strength, tensile bond strength, dimensional variation, water absorption, voids content, elastic modulus, and thermal conductivity. The results are promising for the use of GC in mortars. The optimized mortar reached values of compressive strength and flexural tensile strength of 5.65 MPa and 1.73 MPa, respectively. The results showed the feasibility of using as eco-friendly mortar for internal and external coating, or as a mortar to repair degraded coatings. Hybrid mortars did not show good performance for attack by sulfates.

The results of a preliminary case study of the effects of silica fume and additional calcium oxide (CaO) on the compressive strength of a metakaolin-based geopolymer binder developed to exhibit appropriate properties for use in recycled aggregate concrete (RAC) are presented. Using recycled aggregates in new concrete has significant environmental benefits but also presents significant challenges to the applicability of the technology, and using geopolymer binders in place of ordinary Portland cement (OPC) has the potential to solve some of these challenges. The study presented in this paper suggests that partial replacement of metakaolin with silica fume results in increased strength while additional CaO may only have limited effectiveness in certain applications. Additionally, it was observed that the activator-to-binder ratio has a much more significant effect on the strength than the water-to-binder ratio. It is concluded that, with some optimization, a geopolymer binder with appropriate strength can be developed for use in RAC applications.

Ensuring the integrity of oil and gas wellbores critically hinges on cement binding. This paper presents findings of the untapped potential of Tanzanian natural pozzolans, namely, kaolin and pumice, as a feasible option for geopolymer cement, specifically tailored to enhance the structural integrity of oil and gas wellbores. Results from XRF, XRD and FTIR analyses confirmed that kaolin, modified kaolin (metakaolin), and pumice powder are composed mainly of SiO 2 and Al 2 O 3 , while modified quartz with NaOH (metasilicate) is primarily composed of SiO 2 and Na 2 O. The results revealed that 21% of metasilicate in a mixture of kaolin activated at 800 °C and pumice resulted in geopolymer pastes with the best compressive strengths. Compressive strengths of 35.94 ± 0.93 and 33.71 ± 0.37 MPa were obtained at 70 and 90 °C respectively, after 28 days of curing in brine baths (40 g/L NaCl and 40 g/L Na 2 SO 4). XRD results on crystallinity showed that the formulated geopolymer pastes had amorphous phases (70.73%), indicating the presence of irregular, non-repeating atomic structure. The AFM results strongly supported the presence of amorphous phases and further revealed that the geopolymer pastes have few pores and no cracks. TGA results revealed that the formulated pastes were thermally stable up to 900 °C. MP-AES results showed an increase in the concentration of dissolved metal ions from the geopolymer pastes from the 7th to 21st days of curing that remained relatively constant until the 28th day. This observation suggests that the chemical stability of geopolymer paste increased with curing time due to the formation of more geopolymerization chains facilitated by the consumption of unreacted metal ions during curing. These results concurred with the compressive strength findings of this study. The water absorption result was 0.81%, implying that the geopolymer pastes were water-resistant. The overall results contribute to developing sustainable and eco-friendly cement options for the oil and gas industry, ensuring the integrity and longevity of wellbores. • Utilizing kaolin and pumice significantly improves structural stability. • A 21% metasilicate geopolymer cement mix exhibits superior compressive strength, ideal for challenging wellbore environments. • Developed pastes demonstrate amorphous structure, minimal porosity, and crack resistance, indicating high durability. • The pastes show outstanding thermal stability up to 900 °C and increased chemical resilience over time. • The water-resistant nature of these geopolymer pastes aligns with sustainable oil and gas wellbore applications. [ABSTRACT FROM AUTHOR]

Radon is a naturally occurring radioactive gas that is known to cause lung cancer. Therefore, it is essential to measure and determine the concentration of radon in different materials. The purpose of this research is to measure and analyze the levels of radon concentration, radium concentration, and radon exhalation rates in various geopolymer cement mixes. These mixes are made from slag or metakaolin blended with different ratios of fly ash, silica fume, and cement kiln dust. The main goal is to determine the potential risks associated with using geopolymer cement materials in construction and how they may impact indoor air quality. To achieve this, the study will monitor the amounts of radon released from different geopolymer cement mixes and compare them to traditional cement samples. A CR-39 solid-state nuclear track detector will be used for monitoring purposes. Results of this study have revealed that the radon concentration varies from 4.03 to 348.21 Bq m − 3 with an average value 62.01 Bq m − 3 . Radium concentration also changes from 15.18 to 926.47 Bq kg − 1 with an average value 174.23 Bq kg − 1 . The value of the dissolved radon concentration in the collected samples alters from 4.57 to 394.87 Bq m − 3 with an average value 70.32 Bq m − 3 . The mass exhalation rates are found to vary from 0.04 to 2.28 Bq kg − 1 h − 1 with an average value 0.43 Bq kg − 1 h − 1 , while the surface exhalation rates vary from 0.91 to 78.92 Bq m − 2 h − 1 with an average value 14.06 Bq m − 2 h − 1 . The Annual Effective Dose (AED), due to conducting the experiment indoors, has varied from 0.102 to 8.785 mSv y − 1 with an average value 1.564 mSv y − 1 , where AED in the outdoor experiment has varied from 0.038 to 3.294 mSv y − 1 with an average value 0.587 mSv y − 1 . According to the results, the geopolymer mixes labeled as (S) and (SS) containing 100% GGBFS and 85% GGBFS with 15% SF respectively has had the highest levels of radium concentration, radon concentration, dissolved radon concentration, radon exhalation rates, and AED. The investigation results indicate that, with the exception of samples (S) and (SS), the analyzed samples fall within the suggested range of acceptable values. Based on our results, it seems that all geopolymer samples except for (S) and (SS) are safe for being used in building materials production. We recommend utilizing these samples (S, SS) for public highways, bridges, and other buildings that have good ventilation. • Study the radium and radon concentration for the collected samples. • Measure the radon exhalation rates for the collected samples. • This technique based on using SSNTD such as CR-39 nuclear track detector. • The results clarifying the risks of using geopolymer material in construction. • The results show effects of using geopolymer mixes on indoor air quality. [ABSTRACT FROM AUTHOR]

Abstract Ensuring oil-well-integrity is one of the challenging tasks when cementing is designed. It has been well established that cement tends to degrade when exposed to a corrosive environment and at elevated temperatures. This paper presents the results of the uniaxial compressive strength of the qualified mixes of geopolymer cement containing fly ash as the precursor. Geopolymer cement samples were cured in the potable water heated at 60 °C and 90 °C for 24 h before testing for uniaxial compressive strength. Uniaxial confined compressive strength test was performed for samples cured at a 60 °C, and results of the samples bearing density of 13, 15, and 17 ppg were obtained as 4.12, 9.21 and 17.68 kPa, respectively. For 90 °C, the compressive strengths were 4.43, 15.34 and 78.14 kPa, respectively, for the samples bearing the same density. Samples cured at 90 °C showed the higher value of UCS as compared to the samples cured at 60 °C, and it was because heat is required to stimulate the polymeric reaction.

Sodium silicate is a commonly used activator in geopolymer that is produced commercially. In this study, rice husk ash (RHA) from agricultural waste was used to synthesize sodium silicate as an activator for geopolymer cement. This white ash was applied for producing sodium silicate with different molarities (8, 10, and 12) and then used to synthesize fly ash-based geopolymer cement. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were applied to investigate the micro-characteristics of the geopolymerization products. Bulk density, water absorption, compressive strength, flexural strength, and fracture toughness were carried out to measure and evaluate the geopolymers with sodium silicate. The combination of 10 M NaOH with sodium silicate increased the compressive strength by 16.21% and the flexural strength and fracture toughness by 81.6%. However, sodium silicate combined with 12 M NaOH decreased compressive strengths by 13.23% and flexural strength and fracture toughness by 61.94%. The lowest water absorption value of 12.3% was obtained in a geopolymer paste using sodium silicate combined with 10 M NaOH, and the largest was 13.3% for sodium silicate combined with 8 M NaOH. The microstructure analysis showed the hydrated calcium alumina silicate gel (C–A–S–H) and the SEM image also revealed a compact geopolymer matrix. Thus, it can be concluded that sodium silicate from rice husk ash can be utilized as an activator or reactive material to produce geopolymer cement with a good geopolymer network.

Pb2+ ions were detected on a carbon paste electrode modified with a geopolymer cement. The X-ray pattern and the infrared spectrum of the geopolymer synthesized from metakaolin and phosphoric acid showed a three-dimensional semi-crystalline structure. The obtained geopolymer cement indicates the formation of a broad hump structure between 17 and 40° (2θ) ascribed to the poly(phospho-siloxo) network. The electroanalysis of Pb2+ ions was done in three steps by stripping voltammetry: accumulation of Pb2+ ions in open circuit at pH 4, detection in NaNO3 medium, and desorption. The peak current of Pb2+ ions obtained after 5-min accumulation on the geopolymer cement–modified carbon paste electrode was found to be four times higher than that from the bare carbon paste electrode. After optimization of some parameters related to the detection process (geopolymer cement content in paste, accumulation time, pH of detection medium, detection medium, electrolysis time, potential electrode), a calibration line was drawn in the concentration range from 0.2 × 10−6 M to 1.4 × 10−6 M. The detection limit obtained from a signal-to-noise ratio equal to 3 is 2.3 × 10−9 M. The interferences of some heavy metal ions, such as Hg2+, Cd2+, and Cu2+, and some inorganic ions Al3+, Fe2+, Zn2+, Na+, K+, Ca2+, Mg2+, Cl−, SO42−, and NO3− on CPE/GP-Dib2 sensor were examined. The results obtained shows that these inorganic ions did not interfere with the determination of Pb2+ ions. It indicated that the prepared sensor possessed high selectivity for Pb2+. [ABSTRACT FROM AUTHOR]

The emissions of greenhouse gases such as carbon dioxide from the production of Ordinary Portland Cement and Blended Portland Cement have widely affected the environment with increase in infrastructure development worldwide. Secondly, due to the continuous mining of limestone for the production of cement there is also simultaneous depletion of natural resources and hardly will it last up to maximum 40 years. Hence we need to switch over to some other alternate binders for constructions purpose in future. Geopolymer Cement is one of the inventions which is produced by a polymeric chain reaction of alkali-activated alumino-silicate materials better known as alkali activator (NaOH/Na2SiO3) binders with the industrial by-product materials such as Fly Ash, Rice Husk Ash, Slag, Crusher Dust etc. and provides high compressive strength which is comparable to BPC and reduces the carbon foot print. The objective of our study is to prepare the low CO2 foot print green Geopolymer Cement which may substitute the Ordinary Portland Cement and Blended Portland Cement in future and will helpful to reduce the greenhouse effect up to some extent and takes an initiative towards the green revolution movement.

Due to the scarcity of well-graded gravel materials, lateritic soils are widely used for road construction in tropic areas. However, lateritic soils often do not meet the strict requirement for subgrade and need to be improved to be used as construction material. Among several approaches used to enhance the engineering properties of lateritic soils, the use of industrial waste materials, such as fly ash, granulated blast furnace slag, is of particular interest to the construction industry as a potential replacement material for Portland cement in soil stabilization. Meanwhile, some effort has been made to study the use of quarry dust in stabilizing lateritic soils. The present work aims at assessing the compaction characteristics of three different types of lateritic soils, treated with quarry dust based geopolymer cement. A systematic study by varying the proportion of geopolymer cement was carried out. Test results show that the soil dry density substantially increased while the corresponding optimal moisture content decreased with the amount of geopolymer cement under varying compactive effort. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate the effect of an expandable additive on the compressive strength and linear expansion of geopolymer cement, which is an alternative to ordinary Portland cement, for oil-well cementing. Fly-ash-based geopolymer cement samples, with the addition of slag cement as a strength enhancer, were prepared by using an elastomeric expandable additive (R-additive), which consists of styrene–butadiene rubber with a specific gravity of 0.945, at concentrations of 10%, 15%, 20% and 25% by weight of the solid blend, and cured in a water bath at 60 °C and atmospheric pressure, and a curing chamber at 90 °C and 3000 psi, or approximately 20.68 MPa. Mixability, amount of free water and slurry density were studied, and the effects of the concentration of R-additive on the compressive strength (F) and linear expansion (∆l/l0) of the samples were analyzed. When cured at 60 °C and atmospheric pressure, the highest F of 15.01 MPa was obtained when the concentration of R-additive was 10%, while the highest ∆l/l0 of 0.9985% was obtained when the concentration of R-additive was 25%. An increase in the curing temperature and pressure to 90 °C and 3000 psi (≈20.68 MPa) resulted in the reduction of F from 15.01 to 14.62 MPa and from 10.33 to 9.61 MPa, and the increase in ∆l/l0 from 0.52% to 0.63%, and from 0.99% to 1.32%, when the concentrations of R-additive were 10% and 25%, respectively. The findings suggest that the formulations adopted, which contain R-additive at concentrations ranging from 10% to 25%, fulfilled the requirements of the oil and gas industry.

The effect of quarry dust based geopolymer cement (QDbGPC) and ordinary Portland cement (OPC) replaced in the ratios of 0:0, 0:40, 5:35, 10:30, 15:25, 20:20, 25:15, 30:10, 35:5, and 40:0% by weight respectively was investigated. This was carried out under the influence of 4%, 8%, 12%, 16% and 20% by weight crushed waste glasses. This was conducted to study the effect of these materials on the consistency and strength characteristics of representative test soil in the laboratory. Preliminary test on the test soil shows that the soil is expansive, highly plastic with high clay content and classified as an A-7-6 soil group according to AASHTO classification system. It is also classified as poorly graded according to USCS. The treated exercise presented an improvement in the California bearing ratio, compaction and consistency characteristics in a steady and substantial pattern. The increased addition of the proportions of geopolymer cement caused increased values of CBR, Gs and decreased values of plasticity index. The unsuitable and problematic soft soil was improved to meet the requirements for a soil material to be used as a subgrade construction material. This is due to the composite blend of materials with high silicate contents responsible for strength gain. However, the replacement of ordinary Portland cement with silicate-based geopolymer cement will remove the dangers of CO2 emission during construction works and present an environmentally friendly practice of soil re-engineering. [ABSTRACT FROM AUTHOR]

In this study, it was tried to convert simulated lunar rock sand into geopolymer cement by alkali fusion with sodium hydroxide. Space development is currently being conducted in various countries. For construction on the moon, it is difficult to bring all the construction materials from the earth, and development of construction materials made from lunar resources is required. The authors have succeeded in making geopolymer cement from crushed stone dust using alkali fusion. Therefore, there is a possibility that geopolymer cement used for construction material can be made from lunar rock sand, abundantly present on the lunar surface, using the same method. In this experiment, simulated lunar rock sand was fused with NaOH by changing the mixing ratio of the sand and sodium hydroxide, heating temperature, heating time in vacuum or air atmosphere, and the reaction in vacuum and air was compared and examined. As a result, it was found that the elution contents of Si and Al in the fused sand into acid solution increased with increasing the temperature, NaOH addition and heating time of alkali fusion, and the fused reaction in vacuum atmosphere is different from that in air atmosphere. [ABSTRACT FROM AUTHOR]

The effect of quarry dust based geopolymer cement on the index and compaction characteristics of soft problematic soils has been studied in the laboratory. The particular interest was on the geopolymer cement treatment of test problematic soils subgrade as hydraulically bound materials. In pavement foundation constructions, particular emphasis is always placed on how moisture suction and capillary actions affect the performance of the subgrade layer. Lateritic soils, which form the compacted foundation of pavements have the tendency to behave like plastics or liquids when in contact with moisture. These factors affect substantially the behavior and overtime performance, which is the durability of pavement subgrades. The primary aim of this research work was to adapt geopolymer cement synthesized from valorized solid waste materials (quarry dust and metallurgical slag). Laboratory experiments were used in this study. The test soils were observed to belong to A-2-6, A-2-7 and A-7 soils according to AASHTO classification, which are highly plastic and expansive. They are also of high clay content, a property which makes them unsuitable as moisture bound materials in foundations. The quarry dust based geopolymer cement was utilized at the rate of 10 to 150% by weight of dry soil in an increment of 10%. The test soils treatment protocol shows that the additive consistently improved the plasticity index and maximum dry density of the treated soils obtained at optimum moisture condition. The results have shown that the environmentally friendly cement derived from the valorization of solid waste has improved the properties of the compacted earth utilized under moisture bound environment. So, it stands as a good replacement for ordinary cement. [ABSTRACT FROM AUTHOR]

Ensuring oil-well-integrity is one of the challenging tasks when cementing is designed. It has been well established that cement tends to degrade when exposed to a corrosive environment and at elevated temperatures. This paper presents the results of the uniaxial compressive strength of the qualified mixes of geopolymer cement containing fly ash as the precursor. Geopolymer cement samples were cured in the potable water heated at 60 °C and 90 °C for 24 h before testing for uniaxial compressive strength. Uniaxial confined compressive strength test was performed for samples cured at a 60 °C, and results of the samples bearing density of 13, 15, and 17 ppg were obtained as 4.12, 9.21 and 17.68 kPa, respectively. For 90 °C, the compressive strengths were 4.43, 15.34 and 78.14 kPa, respectively, for the samples bearing the same density. Samples cured at 90 °C showed the higher value of UCS as compared to the samples cured at 60 °C, and it was because heat is required to stimulate the polymeric reaction. [ABSTRACT FROM AUTHOR]

In the crushed stone production process, crushed stone fines, such as dust and slurry cake, are generated as by-products, and most of them are landfilled. Recently, it is becoming difficult to secure landfill sites, and effective utilization of by-products is desired. On the other hand, geopolymer cement has attracted attention due to the higher acid resistance than that of ordinary Portland cement. In this study, we attempted to prepare geopolymer cement from crushed stone by-products using alkali fusion. In the experiment, crushed stone dust, discharged from one of the quarries in Japan, the fused dust, which prepared from the dust by heating at 500 of with NaOH addition (weight ratio of addition is 1:1.6) for 0.5 h using rotary kiln, tap water and coal fly ash were used as raw materials. Crushed stone dust, fused dust, and tap water are mixed on various mixed ratio, with or without the addition of coal fly ash, heat at 30 of or 80 C for 24 h, and then stand at room temperature, in the air or distilled water to prepare geopolymer cement. Acid resistances for the obtained product and ordinary Portland cement was also investigated. As a result, 7 g of mixture of crushed stone dust, water and fused dust (mix ratio is 1: 1: 2) with 3 g of coal fly ash, heated at 80 oC, and cured in water to obtain the geopolymer cement with hard structure, and the obtained geopolymer cement indicates higher acid resistance than ordinary Portland cement. [ABSTRACT FROM AUTHOR]

Abstract Oil well cementing is one of the most important steps in drilling and completion processes and providing a full zonal isolation which is the most important features in the oil cementing. Traditionally, Portland cement is used for oil cementing operations, however, a few years ago, a new cost-effective material came to light called geopolymer. In this research, a fly ash class C based geopolymer was used. This research investigates the effect of drilling fluid contamination with geopolymer cement to understand its impact on geopolymer rheological and mechanical performance. Initially, the optimized geopolymer was prepared and mixed with different drilling fluid ratios, including 0%, 5%, and 10% by weight of cement at atmospheric pressure and ambient temperature (24 °C). Same percentages were added to Portland cement to compare it with the geopolymer. Four tests were conducted to determine the effects of drilling fluids including: rheology, density, fluid-loss, and compressive strength for different curing time (1 day, 3 days, and 7 days). Results showed that drilling fluids enhanced the geopolymer rheological behavior by improving geopolymer viscosity and reducing the fluid loss. Drilling fluids reduced the geopolymer viscosity which facilitates the pumping operation during the cementing. In contrast, mixing the drilling fluid with Portland cement had a negative effect on rheological behavior as well as fluid loss. Mixing the drilling fluid with Portland cement increased the fluid loss significantly. In term of compressive strength, as the amount of drilling fluids increased, the compressive strength of geopolymer was not significantly affected. After 3 days curing time, geopolymer lost about 8.5% of its strength when 5% of drilling fluids weight percent was added. Whereas, Portland cement has lost 38.4% of its strength when 5% of drilling fluids weight percent was added. After 7 days curing time, geopolymer lost about 23% of its strength when 5% of drilling fluid by weight of cement was added. However, Portland cement lost 49% of compressive strength in the same conditions. These obtained results indicates that geopolymer has the ability to withstand the drilling fluids contamination. Highlights • Drilling fluids enhanced the geopolymer rheological behavior. • Geopolymer showed higher compressive strength when exposed to drilling fluids compared to Portland cement. • Mixing drilling fluids with geopolymer reduced the fluid loss. • Geopolymer has early strength compared to Portland cement. [ABSTRACT FROM AUTHOR]

A metakaolin (Mk)-based geopolymer cement from Tunisian Mk mixed with different amounts of silica fume (SiO2/Al2O3 molar ratio varying between 3.61 and 4.09) and sodium hydroxide (10 M) and without any alkali silicate solution, is developed in this work. After the samples were cured at room temperature under air for 28 d, they were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, environmental scanning electron microscopy, mercury intrusion porosimetry, 27Al and 29Si nuclear magnetic resonance (NMR) spectroscopy, and compression testing to establish the relationship between microstructure and compressive strength. The XRD, FTIR, and 27Al and 29Si NMR analyses showed that the use of silica fume instead of alkali silicate solutions was feasible for manufacturing geopolymer cement. The Mk-based geopolymer with a silica fume content of 6wt% (compared with those with 2% and 10%), corresponding to an SiO2/Al2O3 molar ratio of 3.84, resulted in the highest compressive strength, which was explained on the basis of its high compactness with the smallest porosity. Silica fume improved the compressive strength by filling interstitial voids of the microstructure because of its fine particle size. In addition, an increase in the SiO2/Al2O3 molar ratio, which is controlled by the addition of silica fume, to 4.09 led to a geopolymer with low compressive strength, accompanied by microstructures with high porosity. This high porosity, which is responsible for weaknesses in the specimen, is related to the amount of unreacted silica fume. [ABSTRACT FROM AUTHOR]

Highlights • Alkali activated binders cured at room temperature exhibit larger drying shrinkage compared to Portland cement binder. • The use of additives to refine the alkali activated binder formulation lower the total drying shrinkage. • The addition of polyethylene glycol to alkali activated binder significantly reduced the total drying shrinkage. Abstract Alkali activated binders tend to exhibit higher drying shrinkage movements when compared with Portland cement. An experimental investigation was undertaken in order to assess the drying shrinkage of a basic alkali activated binder versus Portland cement, and to evaluate the effectiveness of different additives in reducing the drying shrinkage of the alkali activated binder. The results indicated that the drying shrinkage of the basic alkali activated binder was about twice that of Type I Portland cement. Some of the additives used to refine the alkali activated binder formulation were found to lower the drying shrinkage of the alkali activated binder to levels that were comparable with that of Portland cement. Explanations were presented for the mechanisms through which these additives enhance the dimensional stability of the alkali activated binder. SEM, TG/DTG and heat of hydration techniques were used to gain more insight into the mechanisms of action of different additives in alkali activated binders. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recycling decontaminated CCA treated wood and general timber waste into a wood geopolymer cement (WGC) composites. • The WGC with the decontaminated wood chips showed higher mechanical properties than both the samples with CCA-treated and non-CCA-treated wood chips. • The compressive strength and MOE decreased as the wood content increased, while the MOR increased with the wood content peaking at WC/B ratio of 0.25. • The WGC with WC/B ratio of 0.1 to 0.25 meets the minimum requirement for making load bearing cinderblocks, while all the samples satisfy the minimum requirement for non-load bearing cinder blocks. • The compressive strength of the WGC generally showed a higher value when compared to similar purpose wood-Portland cement composites. Addressing critical societal challenges, such as climate change, resource depletion, and environmental protection, requires sustainable management of resources. This study reports on the results of an experimental program using waste wood, including chromium copper arsenic (CCA) treated wood, to produce ambiently cured geopolymer cement bonded wood composites (WGC), and the results are very encouraging. The composite exhibited a reasonable compressive strength, which ranged between 7 and 27 MPa inversely corresponding to the amount of wood per binder ratio ranging between 0.1 and 0.4, conferring it the possibility of being used as a building material. The compressive strength of the composite with 40% wood chips showed the lowest compressive strength with values of 9.79, 7.29, and 7.92 MPa for decontaminated, CCA-treated, and non-CCA-treated wood chips, respectively. The results indicated that for all the wood per binder ratios, the use of decontaminated wood chips significantly improves the compressive, flexural, and specific strength of the composites, as well as their ductility, compared to non-decontaminated CCA-treated and non-CCA-treated wood chips. This paves the way for using wood waste in sustainability oriented product development and manufacturing. [ABSTRACT FROM AUTHOR]