Equivalent Of Alkali Research Articles

Synchronous vacuum hot pressing ultra-high performance geopolymer: Ultrafast polymerization and early strength development

To overcome the application bottleneck of geopolymer in high-end industries, this study aims to develop ultra-high performance geopolymer products. By employing Synchronous Vacuum Hot Pressing, we have significantly enhanced the rate of polymerization and mechanical properties of Geopolymer based on Metakaolin-Fly Ash. The influence of Si/Al ratio, alkali equivalent, and molding time on the geopolymerization process, mechanical properties, and microstructure of geopolymers was investigated, while elucidating the underlying mechanisms. The compressive strength of SVHP-MFG reaches 90.92 MPa when the Si/Al ratio is 2, alkali equivalent is 8 %, and molding time is 30 min, owing to increased production of aluminosilicate gels and matrix structure densification. The ongoing reaction of unreacted particles and the subsequent transformation from "alumina-rich gel" to "silica-rich gel" in later stages further enhance the mechanical properties of the material. Additionally, the mean pore diameter of Synchronous vacuum hot pressing of metakaolin-fly ash geopolymer measures below 13.24 nm, thereby significantly enhancing the pore structure of the geopolymer. The synchronous vacuum hot pressing metakaolin fly ash-based geopolymers synthesized in this study represents a novel category of ultra-high performance ceramic-like geopolymers, exhibiting exceptional early strength and early stability. The research aims to promote the application of geopolymer in high-end industry and provide technical and theoretical support for the development of ultra-high performance geopolymer based products.

Synchronous hot-pressed metakaolin-fly ash based geopolymer: Compressive strength and hydration products

The dense structure of geopolymers typically requires long curing times, resulting in excessively lengthy production cycles for related products. To address this issue, synchronous hot-pressed curing technology is employed to accelerate the preparation of geopolymers. A comparative experiment was contrived to analyze the impacts of high-temperature curing and synchronous hot-pressed curing of metakaolin-fly ash geopolymer, examining how the silicon-aluminum ratio, alkali equivalent, and curing time influence the compressive strength and hydration products of synchronous hot-pressed cured metakaolin-fly ash geopolymer (SHPMFG) through orthogonal experiments. The outcome indicate that the compressive strength of SHPMFG test specimens can reach 80 % of their final strength within 20 min, with a more complete hydration reaction observed in SHPMFG, resulting in a denser microstructure. The alkali equivalent emerged as the dominant factor affecting SHPMFG strength, with a sample exhibiting a denser matrix structure and lower porosity achieving a maximum compressive strength of 95.33 MPa at 28 days when the alkali equivalent was 8 wt%, the silica-to-alumina ratio was 2.0, and the curing time was 30 min.

An innovative sustainable solution: Recycling shield-discharge waste soil as fine aggregate to produce eco-friendly geopolymer-based flowable backfill materials

The disposal of Shield-Discharge Waste Soil (SDWS) is substantial, yet their recycling rate remains low, necessitating the exploration of new recycling methods for effective waste management. This study examines the potential use of SDWS as a fine aggregate in the production of Controlled Low-Strength Material (CLSM), incorporating slag and fly ash as precursors. Key properties such as strength, flowability, setting time, microstructure, chemical composition, CO2 emissions, energy consumption, and cost were assessed and analyzed. Additionally, the environmental impact and material-related strategies were discussed. The results reveal that the developed CLSM exhibits competitive performance, with compressive strengths ranging from 2.830 MPa to 4.121 MPa, achieving over 1.0 MPa strength within 24 hours. The material demonstrates high flowability, exceeding 200 mm within 30 minutes, and has a setting time between 2.10 and 4.23 hours, offering advantages in both setting time and early strength. SDWS contributes to extending the coagulation process and enhancing the flowability. Optimal strength is observed when SDWS constitutes approximately 30 % of the binders or when the alkali equivalent is around 7 %. Compared to traditional cement-based CLSMs, incorporating SDWS results in reduced CO2 emissions and lower energy consumption. When considering savings from reduced waste disposal costs, the overall material cost remains competitive. Furthermore, higher SDWS content leads to enhanced environmental benefits, and it is recommended to keep the alkali equivalent below 7 % for optimal performance. In conclusion, the developed CLSM presents significant potential for wide-scale applications and offers a sustainable solution for recycling SDWS.

Study on optimization of mixing ratio and shrinkage property of alkali-activated ultrafine fly ash-slag mortar

Alkali-activated cementitious materials have received widespread attention due to their favorable mechanical properties and environmental benefits. However, there are fewer studies on the optimal mixing ratio of alkali-activated ultrafine fly ash-slag (AAUS) mortar, and shrinkage cracking is a critical issue that hinders its further application. Based on this, the study used the response surface method (RSM) to optimize the mixing ratio of AAUS mortar, explored the effect of basalt fibers (BF) on the compressive strength and drying shrinkage of AAUS mortar, and finally analyzed the energy consumption and carbon emission of fiber-reinforced AAUS mortar. The experiment used X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques for microstructural characterization to research the microstructure and mineral phase changes of AAUS mortar. The results demonstrated that the 28d compressive strength of AAUS mortar reached its maximum when the substitution ratio of ultrafine fly ash (UFA) was 14.5%, the alkali equivalent was 10.34%, and the modulus of the activator was 1.6, based on the RSM; BF of appropriate length and volume fraction can productively improve the compressive strength of AAUS mortar and limit drying shrinkage; AAUS mortar with optimal mixing ratio can be sufficiently activated by alkali activator to construct a considerable number of C-(A)-S-H gels to establish a high-density microstructure; the carbon emission of the B124 test group was reduced by 61.1% compared with ordinary Portland cement (OPC) mortar.

Utilization of municipal solid waste incinerator fly ash under high temperature sintering and alkali excitation for use in cementitious material

It is crucial to have a secure and dependable approach to treat and reuse municipal solid waste incinerator (MSWI) fly ash to prevent potential hazards. High temperature sintering is regarded as an efficient method for solidifying heavy metals, and alkali excitation provides a practicable solution for utilizing MSWI fly ash. In this work, the activation mechanism of MSWI fly ash was figured out under high temperature sintering. Besides, the preparation and optimization of sintered MSWI fly ash with metakaolin for use in alkali–activated cementitious material were explored based on Box–Benhnken design (BBD), considering different modulus and alkali equivalent of alkaline activator, as well as different contents of sintered MSWI fly ash and metakaolin. The mechanical performance and alkali excitation mechanism of the cementitious material were investigated. The results showed that the pozzolanic activity of MSWI fly ash treated by high temperature sintering was increased by 81.7 %, which further was improved by alkali excitation. The optimal mix proportion of alkali–activated sintered MSWI fly ash–metakaolin cement mortar consisted of a modulus of 1.332, an alkali equivalent of 1 %, a sintered MSWI fly ash content of 20 %, and a metakaolin content of 10.5 %, whose flexural and compressive strength were 8.5 and 57.3 MPa, respectively. Moreover, SiO32− and OH− in alkaline activator and Al(OH)4–, SiO2(OH)22−, and SiO(OH)32− in metakaolin promoted Ca2+ in sintered MSWI fly ash to generate C–S–H and C–A–S–H. Finally, the alkali–activated mortar made from sintered MSWI fly ash demonstrated high safety and eco–friendliness, with a synthesis toxicity index (STI) of 25.59.

Preparation of geopolymers from thermally activated lithium slag as sole precursor: Mechanical properties and microstructure

Lithium slag (LS) is a waste residue generated during lithium extraction, posing significant environmental challenge due to its extensive accumulation. This study proposes a method of utilizing thermally activated LS as the sole precursor for geopolymer synthesis. The thermal activation mechanism of LS was investigated using XRD, FTIR, ICP, and SEM techniques, while exploring the optimal composition for LS geopolymers(LSG). The research revealed that heating at 700 °C increased the amorphous content of LS from 15.9 % to 48.1 %, altering the chemical structure of its aluminosilicates and enhancing its leaching capacity in alkaline environments, thereby boosting its reactivity. The activator modulus and alkali equivalent were found to significantly influence the strength and microstructure of LSG. As the modulus increased from 1.0 to 1.4, geopolymer strength initially rose before declining, whereas strength progressively increased with alkali equivalent from 0.10 to 0.16. The geopolymer synthesized with a modulus of 1.2 and alkali equivalent of 0.16 exhibited the highest compressive strength of 53.1 MPa after 28 days. Test results indicated that the internal structure of LSG primarily comprised unreacted particles, N(C)-A-S-H gel, and microcracks. The increased alkali equivalent facilitated the dissolution of Si4+ and Al3+ within LS, intensifying geopolymerization to produce more N(C)-A-S-H gel, thereby densifying the structure and significantly enhancing compressive strength. This study elucidates the mechanism by which high-temperature calcination enhances LS reactivity, as well as the impact of activator on compressive strength and microstructural properties of LSG, offering new insights into the engineering applications of LS in high-performance cementitious materials.

Investigation on the anti-carbonation properties of alkali-activated slag concrete: Effect of activator types and dosages

In this paper, three alkaline activators, namely sodium hydroxide (SH), calcium oxide and sodium carbonate (COSC), calcium hydroxide and sodium sulfate (CHSS), and the influence of different alkali equivalents on the carbonation resistance of alkali-activated slag concrete (AASC) were investigated. By testing the mechanical properties at different carbonation ages of AASC with three types of activators at varying alkali equivalents (4%, 6%, and 8%), along with the changes in carbonation depth, this study aims to characterize hydration products and porosity through microstructural analysis. The objective is to explain the mechanism by which carbonation affects the AASC structure. The findings showed that the carbonation rate (i.e., the growth rate of the carbonation depth) of AASC was CHSS > COSC > SH when the exciter dosages were the same, and the carbonation rate of all samples tended to slow down as the alkali components increased. Calcite and spherulite were the calcium carbonate morphologies after SH, COSC, and CHSS carbonation according to XRD, TG/DSC, and pore structure tests; the calcium carbonate content decreased with increasing alkali equivalent after carbonation. Since the pore-increasing effect of carbonation due to the destruction of C–S–H is weaker than the filling effect produced by calcium carbonate, the total pore volume of SH, COSC, and CHSS decreased due to the activator effect after carbonation. Specifically, the calcium carbonate created by carbonation repairs pores and cracks of matrix, but its presence also reduces the calcium hydroxide concentration, leading to a decrease in the alkalinity of the pore solution, which disrupts the structure of the hydration products and loosens the matrix. The focus is on which aspect is more decisive. Interestingly, small pores however decreased, while there was an increase in larger pore sizes resulting in a change in pore size distribution. However, this negative impact on pore distribution decreased with increasing alkali dosage.

Utilizing municipal solid waste incineration bottom ash and volcanic tuff to produce geopolymer materials

Large volumes of municipal solid waste incineration bottom ash (MSWIBA) are produced annually in China; however, their improper disposal causes serious ecological and environmental problems. This study investigated the feasibility of using MSWIBA and volcanic tuff to produce geopolymers. The effects of the MSWIBA content, silicon–sodium molar ratio, and alkali equivalent on the uniaxial compressive strength (UCS) and bulk density of the geopolymer samples were examined using single-factor and optimization tests. The test results showed that the UCS and bulk density of the geopolymer decreased as the MSWIBA content increased, whereas they increased as the alkali equivalent increased. As the silicon–sodium molar ratio increased, the UCS first increased and then decreased, and the change in bulk density was limited. In the final geopolymer preparation, the MSWIBA content was 17.85%, the silicon–sodium molar ratio was 1.71, and the alkali equivalent was 9.49%. According to X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive spectrometry, and nuclear magnetic resonance analyses, the main phases of the geopolymer under the final preparation parameters were quartz, sanidine, calcite, orthoclase, gismondine, and illite. During the geological polymerization process, a large amount of CNASH gel was generated and attached to the surface of the particles or filled the pores between the particles, resulting in a pore size of 0.01–1 μm. The heavy metals in the geopolymers exhibited a good stabilization effect owing to the CNASH gel. Except for Cd, which posed a medium risk, the remaining heavy metals posed low or no risk.

Effects of alkali equivalent and polypropylene fibres on performance of alkali-activated municipal waste incineration bottom ash-slag mortar

Slag demonstrate significant potential as an important cementitious material for alkali-activated systems; however, the increase in alkali-activated materials has resulted in a short supply of slag. Therefore, other industrial wastes must be identified urgently to replace slag as an alkali-activated material while considering the alkali equivalent (AE) as an important factor affecting alkali-activated materials and the modification of polypropylene fibre (PPF). Effect. In this study, the effects of the AE and PPF length on the fluidity, consistency, compressive strength, and flexural strength of municipal waste incineration bottom ash-slag mortar are investigated by partially replacing slag with bottom ash (BA) derived from waste incineration as an alkali-activated material. The mechanism is elucidated via X-ray diffraction analysis and scanning electron microscopy. Finally, studies were conducted on the freeze-thaw resistance and dry shrinkage of alkali-activated bottom ash-slag mortar (AABA-SM). The results show that the performance of an AABA-SM can be modified and enhanced by controlling the AE size and the PPF length. Consistency of AABA-SM increased with the AE. The fluidity and mechanical strength of the AABA-SM enhanced significantly when the AE is 6.5%. PPF length of 12 mm were more significant in increasing the flexural strength of AABA-SM. This is attributed to the denser microstructure formed by the appropriate AE and the superior reinforcing effect of the well-coated 12 mm PPFs.In particular, at an AE of 6.5% and a PPF length of 12 mm, the AABA-SM shows a similar change in terms of dry shrinkage as natural mortar and is better resistant to freezing and thawing. This research provides theoretical support to improve the performance of AABA-SM, enhance the utilization of BA, and reduce environmental pollution.

Properties, Microstructure Development and Life Cycle Assessment of Alkali-Activated Materials Containing Steel Slag under Different Alkali Equivalents.

To improve solid waste resource utilization and environmental sustainability, an alkali-activated material (AAM) was prepared using steel slag (SS), fly ash, blast furnace slag and alkali activators in this work. The evolutions of SS content (10-50%) and alkali equivalent (4.0-8.0%) on workability, mechanical strength and environmental indicators of the AAM were investigated. Furthermore, scanning electron microscopy, X-ray diffraction and nuclear magnetic resonance techniques were adopted to characterize micromorphology, reaction products and pore structure, and the reaction mechanism was summarized. Results showed that the paste fluidity and setting time gradually increased with the increase in SS content. The highest compressive strength was obtained for the paste at 8.0% alkali equivalent due to the improved reaction rate and process, but it also increased the risk of cracking. However, SS was able to exert a microaggregate filling effect, where SS particles filling the pores increased the structural compactness and hindered crack development. Based on the optimal compressive strength, global warming, abiotic resource depletion, acidification and eutrophication potential of the paste are reduced by 76.7%, 53.0%, 51.6%, and 48.9%, respectively, compared with cement. This work is beneficial to further improve the utilization of solid waste resources and expand the application of environmentally friendly AAMs in the field of construction engineering.

The impact of accelerated maintenance system on alkali-activated mortar incorporating ultra-fine dredged sand

Alkali-activated concrete mixed with waste dredged sand (DS) is a new type of green concrete. In addition to reducing resource consumption and CO2 emissions, this approach is also cost-effective. Therefore, the ongoing research on its application in real industrial production is of great importance. This study examined the impact of the steam curing system on the mechanical properties and microstructure of alkali-activated dredged-sand concrete (AADSC). Different alkali equivalents and DS contents were used to produce AADSCs, and such AADSCs were cured using different steam curing schemes. The results show that steam curing significantly improves the early strength and 28-day strength under low alkali equivalent. The curing promotes the 1-day strength at 3% alkali equivalent from 2.1 MPa to 27 MPa after steam curing, and the 28-day strength increase was 7.8%. It is also found that the rise in compressive strength does not have a direct correlation with the energy consumption of steam curing. Even though the energy consumed by steam curing at 40 °C was 67% more than that at 60 °C, the 1 d strength under 40 °C steam curing was 7.5% lower. However, low-temperature steam curing retains more room for concrete strength increase. These results indicate the importance of a reasonable steam curing regime for the strength of AADSC.

Reduction in Drying Shrinkage and Efflorescence of Recycled Brick and Concrete Fine Powder–Slag-Based Geopolymer

It is an effective method to prepare geopolymer with recycled brick and concrete fine powder (RP) and slag as main materials for the resource utilization of construction waste. However, its hydration products have large drying shrinkage and high efflorescence risk under normal curing conditions. Until now, the durability of recycled brick and concrete fine powder–slag-based geopolymer (RPSG) has not been well documented, such as drying shrinkage and efflorescence. In this study, the effects of slag content, alkali equivalent and modulus on the durability properties of RPSG were evaluated. The results show: (1) Slag can significantly reduce the drying shrinkage and efflorescence of RPSG. (2) The potential for the efflorescence of RPSG increases with increasing alkali equivalent. The drying shrinkage of RPSG increases with the increase of alkali equivalent in the case of a low alkali equivalent (6 wt.% in this paper) and decreases with the increase of alkali equivalent in the case of a high alkali equivalent. (3) The drying shrinkage of RPSG increases with increasing modulus. In contrast, the degree of efflorescence decreases with increasing modulus. In this study, RP-S45-M1.3N6 (slag content: 45 wt.%; alkali equivalent: 6 wt.%; modulus: 1.3) is the best proportional design for RPSG with excellent durability. Compared to RP-S0-M1.3N6, the drying shrinkage of RP-S45-M1.3N6 is reduced by 76.32%, the capillary porosity is reduced by 60.9%, the visual efflorescence is significantly alleviated, and the early pH value is reduced by approximately 2.0. This paper systematically analyzed the drying shrinkage pattern and the efflorescence pattern of RPSG, which has a positive significance for promoting the recycling of RP from construction waste.

Time-Varying Pattern and Prediction Model for Geopolymer Mortar Performance under Seawater Immersion.

In this study, immersion experiments were conducted on the geopolymer mortar (GPM) by using artificial seawater, and the effects of alkali equivalent (AE) and waterglass modulus (WGM) on the resistance of geopolymer mortar (GPM) to seawater immersion were analyzed. The test subjected 300 specimens to 270 days of artificial seawater immersion and periodic performance tests. Alkali equivalent (AE) (3-15%) and waterglass modulus (WGM) (1.0-1.8) were employed as influencing factors, and the mass loss and uniaxial compressive strength (UCS) were used as the performance evaluation indexes, combined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) to analyze the time-varying pattern of geopolymer mortar (GPM) performance with seawater immersion. The findings demonstrated a general trend of initially growing and then declining in the uniaxial compression strength (UCS) of geopolymer mortar (GPM) under seawater immersion. The resistance of geopolymer mortar (GPM) to seawater immersion decreased with both higher or lower alkali equivalent (AE), and the ideal range of alkali equivalent (AE) was 9-12%. The diffusion layer of the bilayer structure of the waterglass particle became thinner with an increase in waterglass modulus (WGM), which ultimately led to the reduction in the resistance of the geopolymer structure to seawater immersion. Additionally, a support vector regression (SVR) model was developed based on the experimental data to predict the uniaxial compression strength (UCS) of GPM under seawater immersion. The model performed better and was able to achieve accurate prediction within 1-2 months, and provided an accurate approach to predicting the strength of geopolymer materials in a practical offshore construction project.

Effect of Alkali Equivalent on Compressive Strength and Microstructure of Alkali-Activated Slag Cementitious Material

Effect of Alkali Equivalent on Compressive Strength and Microstructure of Alkali-Activated Slag Cementitious Material

Effects of Different Kinds of Defoamer on Properties of Geopolymer Mortar

As a new type of green inorganic material, geopolymers have excellent mechanical properties, durability, and less environmental pollution. It is considered a new building material that can replace cement, but it also has some disadvantages such as high viscosity, poor fluidity, and more apparent pores after hardening. In this study, the uniaxial compressive strength test of geopolymer mortar was carried out, and the effects of alkali equivalent, alkali activator modulus, bone glue ratio, and silica fume content on the mechanical properties of geopolymer mortar were analyzed. The test results show that when the alkali equivalent is 13%, the alkali activator modulus is 1.4, the bone glue ratio is 2.0, the silicon powder content is 8%, and the metakaolin-based geopolymer mortar has higher uniaxial compressive strength. Through the comparative test of adding different kinds of defoamers and dosage, the effect of defoamers on the compressive strength, fluidity, density, and water-absorption of geopolymer mortar was further studied. The fluidity, density, and water-absorption were improved, and the uniaxial compressive strength was reduced. The formation of cementitious material in the mortar was confirmed by scanning electron microscope (SEM) observation. It was found that the pore structure and pore distribution changed with the content of different defoaming agents, and the microstructure of mortar after defoaming agent material treatment was shown. The proportion and distribution of Na, Al, and Si atoms were analyzed by energy dispersive spectroscopy (EDS). This experimental study shows that the defoamer can be an effective additive for geopolymer mortar.

Energy Dissipation and Dynamic Fragmentation of Alkali-Activated Rubber Mortar under Multi-Factor Coupling Effect.

Recycled rubber aggregate (RRA) made from ground tire rubber has been promoted for its light weight and shock resistance. The high alkalinity of alkali-activated slag mortar has a modification effect on the surface of RRA. This paper studies the performance of alkali-activated slag mortar using RRA as aggregate (RASM), which has significance for applications in low-carbon building materials. The orthogonal test analysis method was used to analyze the significance and correlation of the main variables of the test. The dynamic energy absorption capacity and crushing state of RASM under the synergistic effect of various factors were studied using the separating Hopkinson pressure bar (SHPB) test system. The energy absorption characteristics and failure modes of RASM were analyzed by SEM and microscopic pore characterization. The results show that the increase of the alkali equivalent of the mix ratio will increase the peak value of the absorption energy of the specimen. When the size of the RRA is between 0.48 mm~0.3 mm, the dynamic energy absorption of the specimen will reach its peak value. Although the increase in the total volume of RRA will reduce the energy absorption capacity of RASM specimens, its crack resistance is enhanced.

Research on Recycling Various Wastes in Papermaking as Eco-Friendly Slurry

Waste recycling has always been a priority in the paper industry. In this study, the potential of translating various wastes in papermaking into building materials was separately evaluated. For the first time, the improvement of flexibility and sample texture after translating wastes into cementitious materials was analyzed. The results showed that 20% of the waste in alkali-activated slag slurry is the best proportion for papermaking. In addition, paper sludge and wood chips significantly improved the slurry flexibility while lime mud and bottom ash did not have this effect. Considering the effect of adding wood chips on the optimization of the sample texture, the most appropriate proportion of the paper sludge was 5% when the wood chips in the mixture were 15%. The most suitable alkali equivalent was 6%, with a silicate modulus of 0.9. According to the experimental results, wastes in papermaking had great potential for exploitation and application as circular materials.

Strength and microscopic mechanism analysis of CFBCA-based geopolymer-Pisha sandstone cement composite soil.

Solidification of soil mass by geopolymer is a novel technology that can be used to prevent soil and water loss in the Pisha sandstone area of the middle reaches of the Yellow River. In this paper, to realize the effective utilization of a large number of loose Pisha sandstone and circulating fluidized bed combustion fly ash by adding combustion fly ash into Pisha sandstone cement-soil by alkali excitation, we prepared CFBCA-based geopolymer-Pisha sandstone cement composite soil, which is often used in agricultural engineering. The results show that the content of (C, N)-A-S-H gel in composite soil is affected by alkali equivalent and alkali excitation temperature, while the content is the main factor affecting the strength of composite soil. However, (C, N)-A-S-H gel will gradually transform into chabazite (gmelinite) crystal in a high-alkali environment, which will eventually lead to expansion and cracking occurring in the samples. When the alkali excitation temperature is 20°C, and the alkali equivalent is 5%, the CFBCA-based geopolymer-Pisha sandstone cement composite soil is the optimal physicochemical reaction condition. At this time, the strength of the composite soil is 6.85MPa; the porosity is 23.88%; and the proportion of internal micro-pores is 16.32%. The results of this study can provide a theoretical basis for the practical application of CFBCA-based geopolymer-Pisha sandstone cement composite soil, and also provide a scientific basis for the local resource utilization of Pisha sandstone and bed combustion fly ash.

Mechanical Properties of Glass-Based Geopolymers Affected by Activator and Curing Conditions under Optimal Aging Conditions

Inorganic polymeric materials react slowly at room temperature and therefore, usually require high-temperature curing. This study determined the correlation between temperature and duration in high-temperature curing. The results revealed optimal values for each alkali equivalent of an activator (weight ratio of Na2O/glass powder), curing temperature, and curing duration. Increasing the curing duration and curing temperature had positive effects when the alkali equivalent was lower than the optimal percentage. However, over-curing resulted in the visible cracking of the specimens. Furthermore, despite being initially high, the compressive strength of specimens gradually diminished after standing in air. To ensure the durability of glass-based geopolymers, the curing temperature and duration should not exceed 70 °C, and 1 day, respectively.

Experiment Research on the Mechanical Performance of Alkali-activated Slag Cementitious Material

The influence of three different kinds of alkali (sodium hydroxide, sodium sulfate and water glass) excitation agents on the mechanical properties of slag cement materials has been studied by compressive test. The results show that the effect of excitation of sodium silicate is better than that of sodium hydroxide and sodium sulfate, with the increase of alkali equivalent excitation agent, compressive strength of mortar specimens remarkably, compared with alkali equivalent of 3.1% of the sodium sulfate, the 28d compressive strength of mortar specimens with alkali equivalent of 4.65% and 6.2%, has been increased by 140% and 31.5% respectively.