Stability Of Geopolymers Research Articles

Assessment on Effectiveness of Geopolymer Stabilization of Arunachal Pradesh’s Peat Soil Reinforced with Coir Fiber: An Experimental Study

Assessment on Effectiveness of Geopolymer Stabilization of Arunachal Pradesh’s Peat Soil Reinforced with Coir Fiber: An Experimental Study

High-temperature mechanical performance and damage behavior of molybdenum tailings modified fly ash-based geopolymers

Molybdenum tailings modified fly ash based geopolymers were an eco-friendly building material with excellent mechanical performance and fracture toughness. In this work, cubic compressive test and acoustic emission technique were used to evaluate the effect patterns of molybdenum tailings contents and thermal temperature conditions on the high-temperature mechanical performance and damage behaviors of molybdenum tailings modified fly ash-based geopolymers. The molybdenum tailings contents were 0 %, 10 %, 20 %, 30 % and 40 %, and the target temperatures were 300 °C, 600 °C and 900 °C, respectively. The results of compressive tests showed that the low contents of molybdenum tailings could limit the growth of macroscopic cracks during the loading process and improve the compressive strength of fly ash-based geopolymers when the heat treatment temperature did not exceed 600 °C. The acoustic emission results showed that 20 % molybdenum tailings contents could improve the structural stability and high-temperature mechanical performance of fly ash-based geopolymers, reduced the growth of microcracks in the specimen during the loading process, and delayed the formation and cracking of macrocracks, but did not change the specimen's compressive damage mode. The 40 % contents of molybdenum tailings changed the compressive damage mode of the fly ash-based geopolymers, delayed the cracking of the matrix structure under the peak loading, and significantly improved its resistance to plastic deformation.

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.

Low-carbon metakaolin precursor for one-part and two-part geopolymer activation of demolition wastes

A critical part of civil engineering infrastructure works is to develop innovative construction materials for a low-carbon future development. This study delved into the feasibility of using metakaolin (MK) as a low-carbon precursor for one-part and two-part geopolymer stabilization of recycled demolition wastes. In this research, the effects of MK precursor were evaluated in combination with construction and demolition (C&D) waste aggregates such as crushed brick (CB), reclaimed asphalt (RAP) and recycled concrete (RCA) using one-part and two-part geopolymer activation. Various geotechnical tests were performed including compaction tests, repeated triaxial loading tests (RLT), unconfined compressive strength tests (UCS) and microstructural analysis. Results from this study indicated significant strength development of MK mixtures for both one-part and two-part geopolymer options. Furthermore, one-part geopolymer also showed better activation than two-part geopolymer under 7 days and 20℃ curing condition. Additionally, 30 % MK mixtures were optimal for road construction applications based on the obtained results. At 28 days or 40 ℃, MK mixtures performed best with RCA and CB as main aggregates, showing strength improvement of up to 250 % compared to 7 days and 20 ℃ curing condition. Resilient modulus (Mr) results indicated that the optimal mixtures experienced good resilient behavior with average Mr values ranging from 150 MPa to 200 MPa. Overall, MK precursor was found to be a suitable material for stabilizing demolition aggregates using geopolymer under various curing conditions.

Thermal performance of MK/FA geopolymers: Unveiling the role of FA, equivalent Na2O and modulus

This paper investigates the thermal stability of metakaolin/fly ash (MK/FA) based geopolymers at elevated temperature of 500℃ and 800℃. The thermal stability of geopolymers is evaluated from the following aspects: apparent morphology, residual compressive strength, volumetric shrinkage, and microstructure. The results show that the incorporation of FA contributes to the reduction of specimen cracking while the increasing of equivalent Na2O leads to severe cracking. After experiencing 800°C, the compressive strength of all specimens remains above 70 % of that at room temperature, and the specimen with high equivalent Na2O exhibits higher compressive strength. The XRD and FTIR results indicate that the chemical component of most specimens remains stable at elevated temperatures without decomposition and formation of new crystalline phases. However, the MK/FA based geopolymer exhibit considerable volume shrinkage at elevated temperatures. The shrinkage ranges from 3.2 % to 4.9 % at 500°C and 5.1–14.2 % at 800°C for different specimens. The increase of equivalent Na2O from 8 % to 16 % results in a 174.8 % increase of shrinkage. Overall, MK/FA based geopolymers exhibit convincing thermal performance, and the specimens exhibit higher residual compressive strength and chemical stability after exposure to elevated temperatures.

Evaluation of the thermal stability of metakaolin-based geopolymers according to Si/Al ratio and sodium activator

The thermal stability of geopolymer pastes with different Si/Al ratios (1.5–3.0) and sodium activators (Na2SiO3 and/or NaOH) were evaluated in this study. The inclusion of Na2SiO3 induced an active geopolymer reaction, enhancing pre-heating compressive strength, but gradually reduced from 300 °C due to vapor pressure and microstructural deterioration caused by entrapped physically bound water. Conversely, the strength of geopolymers containing only NaOH remained stable or increased up to 600 °C, owing to additional geopolymerization from unreacted raw materials and compact matrix induced by thermal shrinkage. The aluminosilicate networks of all geopolymers remained relatively stable until crystalline nepheline formed above 800 °C; larger crystalline particles were formed in geopolymers with Na2SiO3 owing to its denser geopolymer matrix, whereas smaller crystalline particles were formed in geopolymers with smaller Si/Al and only with NaOH, resulting in fewer voids and stable mechanical strength. Swelling of silica was notable in Na2SiO3-activated geopolymer, resulting in greater strength loss upon heating, indicating that Na2SiO3 hinders the thermal stability of geopolymers at extreme temperatures.

Feasibility of using building-related construction and demolition waste-derived geopolymer for subgrade soil stabilization

A high-value utilization approach is essential to improve the utilization rate of building-related construction and demolition waste (brCDW). This study developed a novel approach by synthesizing a brCDW-derived geopolymer to stabilize high liquid limit subgrade soil. The unconfined compressive strength (UCS) test, shear strength test, resilient modulus test, and permanent strain test were conducted to investigate the effects of brCDW-derived geopolymer dosage, curing time, stress state, and moisture condition on the engineering properties of geopolymer stabilized soil. These test results demonstrated that increasing the geopolymer dosage effectively improved the UCS, shear strength and resilient modulus of stabilized soil and reduced the permanent strain of stabilized soil. The 8% brCDW-derived geopolymer provided adequate UCS, shear strength, resilient modulus, and resistance to permanent strain for stabilized soil, which showed the most economical improvement. Mechanistic-empirical models were employed to accurately estimate the stress-dependent resilient modulus and permanent strain of geopolymer stabilized soil at any given stress state. The Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) test were performed to investigate the strengthening mechanism of brCDW-derived geopolymer stabilization of subgrade soil. The SEM test results indicated that the porosity of stabilized soil was significantly decreased when the geopolymer dosage increased to 8%. The EDS test results demonstrated that the predominant gel types generated from the geopolymer stabilization might be Calcium–Aluminum-Silicate-Hydrate (C-A-S-H), Calcium-Silicate-Hydrate (C–S–H), and Calcium-Aluminate-Hydrate (C-A-H) gels. There was also a small amount of Sodium-Alumino-Silicate-Hydrate (N-A-S-H) gel detected in the geopolymer stabilized soil. Finally, the sustainability of brCDW-derived geopolymer stabilization approach was assessed in terms of material production cost, carbon dioxide emission, and energy consumption. The brCDW-derived geopolymer was proven as a sustainable stabilizer for subgrade soil.

Silica Fume-Red Mud Based Geopolymer Stabilized Organic Soil

Organic soil presents significant challenges for construction due to its unsuitability as a soil type, often necessitating stabilization using conventional agents like cement. The Silica Fume (SF)-Red Mud (RM) binder mix emerges as a promising alternative stabilizer due to its low carbon footprint coupled with its superior strength-enhancing properties. In this study,we explore the feasibility of employing SF-RM based geopolymer to stabilize organic soil. To activate the collected samples, a solution of sodium hydroxide (NaOH) with molarity (M) of 6, 9, and 12 were utilized, as well as binder (SF + RM) proportions of 10%, 20%, 30%, and 40% relative to dried organic soil and alkali-to-binder (A/B) proportions of 0.5, 0.7, and 0.9, respectively. The experimental results reveal that a variety of factors, including NaOH molarity, A/B proportions, pH, and curing duration, have an effect on the unconfined compressive strength (UCS) of treated organic soil. The best combination was obtained with a binder concentration of 30%, a NaOH molarity of 9M, and an A/B proportion of 0.7. After 28 days of curing, the UCS of the treated organic soil (1714 kPa) was found to be 168 times that of the untreated organic soil (10.2kPa). Further, the production of compounds such as aluminium silicate, sodium aluminosilicate, and potassium aluminosilicate, which have been found by X-ray diffraction (XRD) research, can be ascribed to the increase in strength. Furthermore, when subjected to analysis through Field Emission Scanning Electron Microscopy (FESEM), it becomes evident that these items play a pivotal role in filling the voids within the soil-binder composite. As a consequence, they facilitate the creation of a more smoother, compact and denser structure.

Microstructure Behaviour of the Marine Clay Treated with Geopolymer

Marine clay usually related with poor soil properties, high settlement and instability that are not suitable for engineering requirements and low compressive strength. To solve this problem, chemical stabilizer is one of the soil stabilization method in construction industry which one of them are geopolymer stabilizer to increase the strength of marine clay soil. However, the study regarding of microstructure treated marine clay using geopolymer are less study. Hence, this study focus on the microstructure behaviour of treated marine clay using geopolymer stabilizer. The approach employed in this investigation was the preparation of the sample by the incorporation of marine clay soil and geopolymer (addition of 6% Magnesium Chloride (MgCl2)). The sample was then subjected to several microstructure tests, including X-Ray Diffraction (XRD), Particle Size Analysis, and Scanning Electron Microscopic (SEM). The findings demonstrate the alterations in the microstructural characteristics of marine clay following the application of geopolymer stabilization. According to the results of the XRD analysis, no further peaks were observed. Conversely, the SEM examination revealed a reduction in the voids within the marine clay soil, leading to increased density as the curing period increased. Furthermore, the Particle Size Analysis reveals that the use of a stabilizer results in a notable augmentation in the soil particle sizes. Consequently, This study may be utilized to examine the relationship between the microstructure and mechanical properties of treated soil.

Factors Affecting the Strength Formation Mechanism and Water Stability of Geopolymer Stabilized Phosphogypsum in Road Construction

By adjusting the content of geopolymer in geopolymer stabilized phosphogypsum (GSP) as roadbed filler, along with the mixing ratio, this paper mainly explores tendencies in the mechanical properties and water stability of GSP. This research is based on macro-mechanical properties such as unconfined compressive strength, resilience modulus, California bearing ratio and shear strength. It is also based on water stability tests, such as the water soaking test, dry and wet cycle test and expansion test, to explore changes in water stability. As for the durability of GSP, this paper is mainly based on the realization of a long time observation of mechanical properties and water stability. In the existing research, most of the stabilized phosphogypsum (PG) base material or roadbed filler consists of cement, lime, etc. In this paper, a new exploration is carried out on the composition of stabilized PG material, realized without the participation of cement. The 28 d compressive strength of GSP reaches 2.5 MPa, and over time this strength grows, which prevents the phenomenon of strength inversion that may occur in conventional cement-stabilized PG. In addition, a long-term soaking experiment was designed in this study based on the material after the strength was stabilized for up to 90 d. After the strength was steady, the GSP with the best water stability still had a softening coefficient of 80% after experiencing water immersion for 7 d. After determining the feasibility of the mechanical properties and water stability of GSP as roadbed filler, we further explored the strength formation mechanism of GSP by microscopic tests (XRD and SEM). This shows that geopolymer can stabilize PG in two main ways: one is the hydration reaction with PG to generate C-S-H gel and ettringite, and the other is to connect PG not involved in the chemical reaction to form a dense whole through generated hydration products. Geopolymer, stabilizing a high amount of PG, not only provides a new method for the consumption of PG, but also has more stable performance than cement, and has certain advantages in economy. In addition, the advantage of this study is that good performance can be achieved by simply sieving PG and adjusting the geopolymer ratio in practical engineering projects.

Effect of seawater on the properties and microstructure of metakaolin/slag-based geopolymers

Metakaolin-based geopolymer has good resistance to seawater erosion, but it often requires more alkali activators, resulting in higher costs, and its curing time is far greater than that of alkali-activated slag materials. In this paper, geopolymers were prepared using metakaolin + slag as precursors and waterglass as activator to investigate the mechanisms of strength and microstructural deterioration over time of metakaolin/slag-based geopolymers under seawater conditions with different slag contents. It was found that the addition of an appropriate amount of slag could not only decrease the activator of metakaolin-based geopolymers, but also improve the pore solution pH and strength retention rate of metakaolin-based geopolymers. Different from alkali activated slag and silicate cements, the metakaolin/slag-based geopolymers will form a dense layer of brucite deposits in seawater after cured, which will significantly reduce the interaction between the metakaolin/slag-based geopolymer and seawater, combined with the good stability of metakaolin-based geopolymers itself in liquid environment, making metakaolin/slag-based geopolymers have very good resistance to seawater erosion.

The Synergistic Mechanism and Stability Evaluation of Phosphogypsum and Recycled Fine Powder-Based Multi-Source Solid Waste Geopolymer.

Geopolymer prepared from solid waste is a high value-added means. However, when used alone, the geopolymer produced by phosphogypsum has the risk of expansion cracking, while the geopolymer of recycled fine powder has high strength and good density, but its volume shrinkage and deformation are large. If the two are combined, the synergistic effect of the phosphogypsum geopolymer and recycled fine powder geopolymer can realize the complementarity of advantages and disadvantages, which provides a possibility for the preparation of stable geopolymers. In this study, the volume stability, water stability and mechanical stability of geopolymers were tested, and the stability synergy mechanism between phosphogypsum, recycled fine powder and slag was analyzed by micro experiments. The results show that the synergistic effect of phosphogypsum, recycled fine powder and slag can not only control the production of ettringite (AFt) but also control the capillary stress in the hydration product, thus improving the volume stability of the geopolymer. The synergistic effect can not only improve the pore structure of the hydration product but also reduce the negative impact of calcium sulfate dihydrate (CaSO4∙2H2O), thus improving the water stability of geopolymers. The softening coefficient of P15R45 with a 45 wt.% recycled fine powder content can reach 1.06, which is 26.2% higher than P35R25 with a 25 wt.% recycled fine powder content. The synergistic work reduces the negative impact of delayed AFt and improves the mechanical stability of the geopolymer.

Characteristic evaluation of geopolymer based lateritic soil stabilization enriched with eggshell ash and rice husk ash for road construction: An experimental investigation

In line with sustainable development, the road sector has initiated the use of agro-wastes in road construction to preserve natural resources, which have been commonly used in conventional construction. In that sense, this study investigates the merits and demerits of incorporating eggshell ash (ESA) and rice husk ash (RHA) into geopolymer based lateritic soil stabilization for roadbase construction. Atterberg limits, modified Proctor compaction, unconfined compressive strength (UCS) tests were conducted on lateritic soil samples stabilized with cement or geopolymer that comprises of the combination of ESA, RHA and sodium hydroxide solution (NaOH). Results from the experimental study revealed that an increase in ESA substitution level reduced the plasticity index of lateritic soil. Maximum dry density was slightly reduced in all soil mixes stabilized with ESA, RHA and NaOH. With reference to cement stabilization, UCS showed a marginal reduction of 8.2 and 13.2% in geopolymer combinations of 3E1R1N (3% ESA + 1% RHA + 1% NaOH) and 2E2R1N (2% ESA + 2% RHA + 1% NaOH), respectively. Notably, out of all mixes, the mix combination of 3E1R1N and 2E2R1N produced the lowest cost to strength and embodied energy to strength ratio, and relatively lower CO2 emission to strength ratio. The authors believe that the proposed geopolymer stabilization method would be a competitive alternative to cement based lateritic soil stabilization for roadbase construction.

Durability Deterioration of Geopolymer Stabilized Soft Soil under Sodium Sulfate and Magnesium Sulfate Attack: A Comparative Study

Sulfate attack is one of the non-negligible factors that induces deterioration in the performance and life cycle of soil stabilizers. In this paper, the degradation mechanism of the durability of slag–fly-ash-based geopolymer stabilized soft soil (hitherto referred to as SF-GSSS) under the sodium sulfate (Na2SO4) and magnesium sulfate (MgSO4) attack environment is comparatively investigated, and the slag/fly ash ratios are set to S10F0, S9F1, S8F2, and S7F3. The SF-GSSS was fully immersed in a 2.5% Na2SO4 solution and 2.5% MgSO4 solution, respectively, to characterize the deterioration rules via visual observations, an unconfined compressive strength (UCS) test, and by mass change. The effect of sulfate on the microstructural characteristics of the SF-GSSS were determined by different microanalytical means, such as by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the SF-GSSS immersed in a MgSO4 solution displayed significant physical deterioration, but not when in a Na2SO4 solution. The mass growth of the SF-GSSS when immersed in a Na2SO4 solution was significantly lower than when it was immersed in a MgSO4 solution at the same immersion age. The rate of strength loss was lowest for S9F1 and highest for S7F3 at the end of immersion, regardless of its immersion in Na2SO4 or MgSO4 solutions.

Effect of cement and geopolymer stabilization on the thermal comfort: case study of an earthen building in Burkina Faso

PurposeThe stabilization of earthen blocks improves their mechanical strength and avoids adobe construction erosion due to rainwater. However, the stabilization affects the thermal properties of the earthen blocks, and thus their capacity to provide adequate thermal comfort to occupants. This article examines the influence of cement and geopolymer binders on thermal comfort in compressed earthen buildings in hot and arid climates.Design/methodology/approachThe test cell is on the building platform in Burkina Faso. The building is made of compressed earth blocks (CEB) consisting of laterite, water and binder. The thermal models of the building were implemented in EnergyPlus v9.0.1 software. Empirical validation is used to check whether the model used for the thermal dynamic simulation can reproduce with accuracy the thermal behavior in a real situation. The adaptive thermal comfort model of ASHRAE 55–2010 was used to assess thermal comfort in long-term hot and dry tropical conditions.FindingsThe results show that the CEB buildings remain hot despite the use of cement or geopolymer binder. Indeed, with both cement and geopolymer binders, on a daily basis, 19 h and 15 h are uncomfortable during, respectively, the hot and cold seasons. An increase of 1% in cement content raises the comfort hours by 9.2 h during the hot season and 11.7 h during the cold season. Hence, the comfort time varies linearly with the cement content in the building material. Moreover, there is no linear relationship between comfort time and geopolymer rate.Research limitations/implicationsComplementary work should also assess the influence of stabilization on building humidity levels. In fact, earthen materials are very sensitive to outdoor humidity and indoor humidity affects thermal comfort even if it is not taken into account in the ASHRAE adaptive thermal comfort model.Practical implicationsThe present study will certainly contribute to a better valorization of clay potential in countries with similar climatic conditions.Social implicationsThe use of geopolymer binder is a suitable ecological option to replace the cement binder. It is important to mention that nighttime comfort can be increased through passive strategies such as natural ventilation.Originality/valueMost CEB material stabilization analyses including cement and geopolymer ones were mostly investigated at the laboratory scale and less at the building scale. Also, the influence of the binder rate on the thermal performance of buildings made of cement and geopolymer has not yet been assessed. This paper fills this gap of knowledge by assessing the impact of cement and geopolymer binder rates on the thermal comfort of CEB dwellings.

Strength and stiffness performance of geopolymer stabilized washed recycled sands derived from demolition wastes in pavement subgrades

In this research study, geopolymer stabilized washed recycled sand (RS) derived from construction and demolition (C&D) waste was evaluated to effectively address issues related to the landfilling of wastes and the unsustainable usage of virgin sand quarry materials. This study evaluated the feasibilities of stabilizing washed RS with geopolymers and their subsequent usage as pavement subgrade materials. Industrial by-products comprising of fly ash (FA), granulated blast furnace slag (S), and the combination of (FA + S) were considered as three different precursors in the geopolymer stabilization of RS. The strength performance of geopolymers stabilized RS for each precursor was investigated through the unconfined compressive strength (UCS) and scanning electron microscopy (SEM) tests. Geopolymer stabilized samples with S were found to exhibit a generally higher UCS strength than FA-based samples. Yet the curing time was found to be important in geopolymerization process, that commonly longer the curing periods, higher the UCS strength. The chemical reaction of S-based geopolymer required a considerable amount of water to take place. A strength drop was therefore noticed in S-related instances at longer curing period due consideration of the water consumption during the geopolymerization process. As such, under cases of when an excess amount of S was added to the sample, when a high curing temperature was used or when longer curing durations were implemented. The highest UCS value attained among the tested samples was 22.024 MPa, when a precursor of 15 % FA + 15 % S was used and when cured for 7 days at 40 °C. A repeated load triaxial (RLT) test was carried out to further prove that the geopolymer stabilized washed RS could substitute the role of quarried sands in pavement. Under the curing condition of 7 days at 21 °C, samples stabilized with 30 % FA or 10 % S were found to be stiff enough to respond to the axial stress change under the same confining condition.

Random Forest Algorithm for the Strength Prediction of Geopolymer Stabilized Clayey Soil

Unconfined compressive strength (UCS) can be used to assess the applicability of geopolymer binders as ecologically friendly materials for geotechnical projects. Furthermore, soft computing technologies are necessary since experimental research is often challenging, expensive, and time-consuming. This article discusses the feasibility and the performance required to predict UCS using a Random Forest (RF) algorithm. The alkali activator studied was sodium hydroxide solution, and the considered geopolymer source material was ground-granulated blast-furnace slag and fly ash. A database with 283 clayey soil samples stabilized with geopolymer was considered to determine the UCS. The database was split into two sections for the development of the RF model: the training data set (80%) and the testing data set (20%). Several measures, including coefficient of determination (R), mean absolute error (MAE), and root mean square error (RMSE), were used to assess the effectiveness of the RF model. The statistical findings of this study demonstrated that the RF is a reliable model for predicting the UCS value of geopolymer-stabilized clayey soil. Furthermore, based on the obtained values of RMSE = 0.9815 and R2 = 0.9757 for the testing set, respectively, the RF approach showed to provide excellent results for predicting unknown data within the ranges of examined parameters. Finally, the SHapley Additive exPlanations (SHAP) analysis was implemented to identify the most influential inputs and to quantify their behavior of input variables on the UCS.

The effects of salt-loss soda residue and oxalate acid on property and structure of fly ash-based geopolymer

When industrial solid waste soda residue (SR) is subjected to water erosion, certain soluble salts are lost, which influences the reuse of SR in construction materials. This research studies the possibility of using salt-loss soda residue (SLSR) in fly ash (FA)-based geopolymers activated by sodium hydroxide solution (NS). To achieve a wider application, the SR and SLSR were proposed with an oxalic acid (OA) treatment. Fluidity, electrical conductivity, and densitywere assessed to examine the effects of SLSR and OA on fresh and hardened characteristics. In addition, flexural and compressive strengths, as well as drying shrinkages, were tested to investigate the role of SLSR and OA. Furthermore, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR) tests were carried out to evaluate the mineralogy, morphology, and products. Thermal stability was further evaluated using Thermo-Gravimetric and Differential Thermal Synchronous Thermal Analysis Spectrometer (TG-DSC) tests. The results show that SLSR and OA can be used to synthesize FA-based geopolymers at room temperature. When proper OA is introduced, SLSR contributes to higher compressive strength, improved drying shrinkage resistance, and increased thermal stability of FA-based geopolymers than SR due to the loss of soluble salts and the formation of calcium oxalate in the matrix. Furthermore, it is revealed that the structure of hardened paste (V4) prepared with SLSR, FA, and OA is composed of chemical CSH and (N, C)-ASH gels together with physically filled particles (such as calcite, calcium oxalate, sodium oxalate, and unreacted glass microsphere). The research findings give guidance for promoting the preparation of SLSR products and the utilization of organic calcium sources in geopolymer.

Synergetic effect of nano-silica fume for enhancing physico-mechanical properties and thermal behavior of MK-geopolymer composites

• The nano silica fume has a positive effect on the physico-mechanical and thermal properties of MK-geopolymer. • The mechanical strength of MK-geopolymer mixtures incorporating NSF increased with temperature up to 700 °C and increases with increasing NSF up to 5%. Thermal Stability of geopolymer at high temperatures has attracted great interest from several researchers. The use of nanosilica fumes gets more attention Because of its great influence on the mechanical properties and thermal stability of geopolymer composites. Therefore, this work reviewed the effect of Nano-silica fume on thermal stability and mechanical behaviors of geopolymers at high temperatures. The main geopolymer mixes made up of metakaolin having various nano-silica fume ratios in addition to kaolin and lime stone. The activators used are Na 2 SiO 3 and NaOH (5 M) in the ratio of (1:1). The geopolymer mix control has been composed of metakaolin (MK), kaolin (K) and lime stone (LS) in the ratio of (2:1:1). Nano-silica fume (NSF) was added in the ratios from 0 to 7 wt% from the metakaolin. To realization investigate the effect of Nano-silica fume on MK geopolymer binder, classical tests of bulk density and strength at various ages. The results were analyzed by using advanced devices. The thermo-physical, micro-structural and mechanical properties of the MK geopolymers binder after the exposure to elevated temperatures of 500, 700, 800 and 1000 °C have been investigated. The results indicated that the NSF has a positive effect on the physicomechanical properties of MK-geopolymer. The inclusion of 5 % NSF to MK geopolymer binder enhanced the properties in terms of strength and microstructure. The mechanical strength of MK-geopolymer mixtures incorporating NSF increased with temperature up to 700 °C and increases with increasing NSF up to 5 %. The inclusion of 5 % NSF enhanced the physico-mechanical properties and microstructure before and after exposure to high temperature.

Geopolymer Stabilization as Novel Technique of Reducing Carbon Dioxide Emissions

The paper discusses geopolymerisation which is a chemical reaction within an alkaline solution as well as a solid reaction of both aluminium and silicon. It highlights the origin of silicates, pozzolanic composite or alumino-silicates that could be melted within alkaline solution that may be utilized as a source of geopolymers creation. Materials that possess plenty aluminium, silicon and others such as metakaolin, microsilica, pozzolanas, ashes, red mud, kaolin clay and slags can be used as raw materials with the activators to create geopolymers. Also geopolymer end product after the exothermic procedure carried out via oligomers, as well as three stages of geopolymerisation which are suspension, when hard or solid alumino-silicates matter and stuff is dissolved because of the occurrence of water together with alkali activator. After jettisoning a small quantity of water, the reorientation outsets, and then the cluster atoms take their position in the structure. In the course of the solidification at 200C (twenty Celsius degree) or higher temperature of roughly 10000C, the water (H2O) is almost absolutely jettisoned and the material displays his final look.