Alkali Dosage Research Articles

Selective ion channel adsorbents facilitate efficient and low environmental impact extraction of liquid lithium resources

As lithium is the cornerstone of green energy development, it is crucial to realize a low environmental impact and efficient lithium extraction process. Ion-sieve adsorption is the most widely used method to extract liquid lithium resources, but this method is only efficient under alkaline conditions for H+ and Mg2+ competing adsorption. Conventional methods are often accompanied by the consumption of quantities of alkali, the generation of solid waste, and the acidification of liquid lithium resources. To address these issues, a selective ion-channel adsorbent was constructed. The composition comprises an ion sieve adsorbent and an organic carrier with a zwitterionic quaternary ammonium base group. This group storages OH-in situ, hinders H+ diffusion, slows down Mg2+ diffusion, and accelerates Li+ diffusion by relying on the difference in binding energies, which reduces the competing adsorption and avoids acidification and solid waste generation. The saturated adsorption capacity (21.38mg/g) and selectivity of the adsorbent are 4.7 and 24 times higher than that of conventional ion-sieve adsorbent under neutral conditions respectively. The dosage of alkali is 1/256 of the traditional method, the effluent remains neutral and no solid waste is generated. This study presents an environmental and effective adsorbent for lithium extraction.

Effect of alkali dosage and silicate modulus on the deterioration of alkali-activated concrete properties subjected to sodium chloride attack and freeze thaw cycles

The deterioration mechanism of alkali-activated slag-fly ash-steel slag concrete (AAC) under sodium chloride attack and freeze-thaw (SF-T) cycles was investigated through a multi-scale methodology. Results showed that appropriate water glass modulus and higher Na2O dosage increased the compressive strength and salt-frost resistance of AAC. The mass loss in AAC was concentrated in the first 100 SF-T cycles, but PCC increases linearly with the SF-T cycles. The salt-frost resistance of PCC was similar to that of AAC samples Na2O dosage of 5 %. Higher Na2O dosage reduces the amount of unreacted precursor, thus reducing the porosity and improving the pore structure of concrete. However, increasing Na2O dosage has not limited the crack development, and the crack width in AAC was greater than in PCC after SF-T cycles. The porosity and average pore size of the concrete increased after SF-T cycles. Friedel's salt was only present in PCC, and NaCl crystals were observed in AAC.

Preparation and characterization of alkali-activated Pisha sandstone-slag composite cement

This study explores the development of a novel alkali-activated cementitious material (APKC) using Pisha sandstone and slag as the main raw materials, offering a sustainable alternative to traditional cement. The APKC's flowability and mechanical properties are comparable to those of ordinary Portland cement (OPC), but it is significantly more cost-effective, with lower carbon emissions and energy consumption. Specifically, at a water-to-binder (w/b) ratio of 0.3, with an optimal activator content of 17.5 % and a Pisha sandstone-to-slag ratio of 1:1, APKC achieves excellent performance: a flowability of 195 mm, and 28-day compressive and flexural strengths of 59.1 MPa and 9.96 MPa, respectively. Moreover, the production of one ton of APKC reduces costs to 64.01 %, carbon emissions to 22.76 %, and energy consumption to 28.56 % of those associated with one ton of OPC, highlighting its potential as a viable replacement in engineering applications. The primary hydration products of APKC include hydrotalcite, C,N-A-S-H gels, C-S-H gels, and natrolines. It is crucial to maintain the alkali activator content and Pisha sandstone-to-slag ratio within optimal ranges, as insufficient alkali dosage or an excessive Pisha sandstone-to-slag ratio can diminish the mechanical properties by reducing hydration product content. Conversely, too much alkali activator can lead to high-porosity hydration products due to the dissolution of Al in C,N-A-S-H gels.

Regulating pore structure of diatomite with alkali dissolution and its influence on humidity control performance

Alkali dissolution is an effective method to regulate the pore structure of porous mineral material. The main chemical composition of diatomite is amorphous SiO2, which can be dissolved in alkali dissolution. The diatomite samples with alkali dissolution treatment were systematacially characterized by the particle size analysis, low temperature nitrogen adsorption, MIP, fractal theory, SEM, TEM, XRD, FTIR and surface hydroxyl density to analyze the pore structure and surface properties. And the humidity control performance of diatomite was tested under different temperatures and relative humidities. The relationship among pore structure, surface properties and humidity control performance were analyzed. The results show that alkali dissolution can regulate the mesoporous and macroporous of diatomite, and some new microporous can generate at high alkali dosage. The specific surface area, mesoporous pore volume, proportion of macroporous volume, surface roughness, heterogeneity of pore structure and number of hydroxyl groups on the surface of diatomite are important factors which determining the humidity control performance. The humidity control performance of diatomite is positively correlated with the specific surface area, mesoporous volume, surface roughness, heterogeneity of pore structure and number of hydroxyl groups on the surface, while is negatively correlated with the proportion of macroporous volume.

Effect of low-temperature thermal-alkali pre-treatment on waste activated sludge solubilisation

The study was aimed to examine the effects of alkaline and thermal-alkaline pre-treatment on sewage sludge solubilisation with different alkali and its doses ranging from 40 mg alkali/g TS to 120 mg alkali/g TS. Initially, the effect of alkali pre-treatment was monitored with four alkali at room temperature, to further enhance soluble chemical oxygen demand (sCOD) and reduce treatment time, thermal-alkaline pre-treatment was performed with varying temperature from 40 to 70 °C. To explore and optimise the effects of temperature, alkali, and alkali doses on COD solubilisation, response surface methodology was employed. Statistical analysis of the variance was conducted to identify the relationship between experimental data and the proposed model. The thermal-alkaline process was optimised for maximum COD solubilisation with optimal conditions achieved at 65.61 °C of 66.57 mg alkali /g TS for NaOH and 27 °C of 20 mg/g TS for KOH. The maximum COD solubilisation achieved at these optimised conditions for NaOH and KOH was 21.28 % and 16.13 %, respectively. The results demonstrated a significant improvement in protein and carbohydrate concentration and a 16–20 % reduction in sludge solid content after thermal-alkali pre-treatment.

Enhancing the mechanical strength of corrugated medium paper through instant catapult steam explosion pretreatment of tobacco stem

The decline in mechanical properties of secondary fiber upon multiple recycling iterations necessitates the incorporation of cost-effective and environmentally friendly fibers to counterbalance strength loss. In this study, an orthogonal experiment design was employed to optimize the SE process to acquire tabocco stem pulp (TSP). The study systematically investigated the influence of steam pressure, residence time, and alkali dosage employed during impregnation were investigated. Notably, the research identified alkali dosage as the most significant parameter impacting system performance. Under optimized conditions (1.2 MPa, 5 min, and 5 %), the prepared paper using 100 % TSP exhibited the capability to attain Grade C corrugated medium. TSP, subsequently, served as a compensatory material for mitigating the loss of strength observed in low-quality secondary fibers (LSF). Remarkably, the introduction of 20 wt% TSP resulted in the production of grade B products, showcasing exceptional enhancement in ring-crush strength. The breaking length of paper was increased with an additional 0.5 wt% PAE added, resulting in all criteria achieving the highest grade A. In conclusion, the study elucidated the synergistic and complementary effects of TSP and LSF, wherein stiff TSP fiber bundles formed a network that effectively supported LSF filling. This study identified the relationship between SE parameters and fiber properties, conclusively establishing waste tobacco stem as a quality fiber source conducive to producing high-quality paper.

A green binder for cold weather applications: enhancing mechanical performance of alkali-activated slag through modulus, alkali dosage, and Portland cement substitution

Below 5 °C, Portland cement (PC) experiences delayed hydration, slowing strength development, making it unsuitable for winter. Alkali-activated slag (AAS) emerges as a viable alternative with continuous hydration in low-temperature conditions. The effect of the activator nature on the performance of AAS cured at normal temperatures is well known, but further studies are required for low-temperature conditions. This study investigates the synergistic impact of activator modulus (1.2 and 1.5), alkali dosage (5, 7, and 9%), and PC substitution rates (0, 10, and 20%), on low-temperature cured AAS properties. Eighteen mixtures were prepared and cured at 2 °C. Compression and ultrasonic pulse velocity tests were conducted after 7, 28, and 90 days. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy analyses were performed to examine the microstructure of the samples. Elevating alkali dosage enhanced early age strength but resulted in a drop in 90-day strength. Simultaneous increases in modulus and PC substitution rate reduced strength due to shrinkage-induced crack formation. Optimal mixture design options included using 10% PC in the 1.2 modulus and omitting PC when the 1.5 modulus was selected. Despite low temperatures, the use of PC significantly accelerated the setting time. Altering modulus and alkali dosage caused a considerable change in the intensity of the peaks in the FTIR spectrum. The findings indicate that AAS shows promise when adjusting the mixture design for temperatures below 5 °C, which are unfavorable for the hydration of PC.

Effect of synthesis parameters on the alkali activation reaction degree and the relationship between reaction degree and microstructure of fly ash-based geopolymers

This study systematically explored the impact of various parameters on the alkali activation reaction degree of fly ash-based geopolymers (FABGs) using the acid solubility test method. Key parameters such as the alkali activator modulus (AAM), alkali dosage (AD), and water-to-fly ash ratio (W/FA) were considered. The micromorphology, phase composition, and pore characteristics of FABGs were also examined, and the relationship between the alkali activation reaction degree and these microstructural characteristics was analyzed. The alkali activation reaction was relatively rapid during the early curing stage but slowed down in the later stage. The influence of synthesis parameters on the alkali activation reaction degree ranked from highest to lowest as AAM, W/FA, and AD. According to Spearman correlation analysis, the alkali activation reaction degree of FABGs is positively correlated with AAM and AD, and negatively correlated with W/FA. As the alkali activation reaction degree increases, the number of pores, cracks, and partially reacted FA particles decreases, and the bonding between FA particles and the matrix becomes denser. FABGs with higher alkali activation reaction degrees exhibit greater mass loss at 100–700 °C, indicating higher production of gel phases. Additionally, the pores in FABGs are predominantly gel pores and transition pores. Notably, there is a negative correlation between porosity and the alkali activation reaction degree of FABGs.

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.

Optimization of biogas production from thermal-alkali pre-treated sludge using response surface methodology and random forest regressor model

BackgroundUnderstanding the intricate relationships between input variables and methane potential is crucial for optimizing anaerobic digestion process after thermal-alkali pre-treatment. This study aimed to optimize low-temperature thermal alkali pre-treatment, focusing on dosage based on the total solids (TS) content of raw sludge. A comparative analysis was conducted to optimize input parameters related to biogas generation potential as the primary response. MethodsBiomethane potential data were collected following the pre-treatment of sludge within the temperature range of 40–70 °C, using various doses of NaOH, KOH, Mg(OH)2, and Ca(OH)2 ranging from 40 mg alkali/g TS to 120 mg alkali/g TS. The optimization of biogas and methane production was conducted through Response Surface Methodology (RSM) and the Random Forest Regressor (RFR) model considering dosage and temperature as input variables. Additionally, sensitivity analysis was performed using the permutation feature importance function to gain insights into the influence of alkali types on biogas and methane production. FindingsThe results obtained from the RFR model showcased a notably high accuracy in predicting optimal solutions. NaOH addition was the most effective pre-treatment with an optimal dose of 65 mg/g TS and at a temperature of 56 °C. NaOH pre-treatment increased methane yield to 414.40 mL/g VS, compared to 117.08 mL/g VS for the untreated sludge. The sensitivity analysis results indicated that the temperature had a more significant effect on biogas potential than the alkali dosage.

Combining thermal–alkaline hydrolysis pretreatment with catalytic supercritical water gasification for hydrogen production from sewage sludge

An integrated process consisting of a thermal–alkaline hydrolysis pretreatment (TAHP) combined with catalytic supercritical water gasification (CSCWG) was developed to treat sewage sludge to produce H2. TAHP facilitated the transfer of organics from sludge into liquid products for subsequent CSCWG to produce H2. Upon increasing the hydrolysis temperature, time, and alkali dosage, the continuous transfer of organics to liquid products was observed, wherein the hydrolysis temperature had the greatest effect. Under the optimal pretreatment conditions (180 °C, 1 h, and mNaOH/mOM = 25 %), approximately 70 % of proteins, carbohydrates, and 50 % of humus in sludge, i.e., easily gasified organic species, were transferred. Using this process, the TOC concentration in the liquid products reached about 17,000 mg/L, and the polysaccharide and soluble protein concentrations reached 2400 and 15,000 mg/L, respectively. With this integrated process, the H2 yield and selectivity increased by 3.7–7.6 times and 5.94–52.92 times, respectively, compared with the directly catalyzed gasification of sludge. This improvement occurred because TAHP promoted the transfer of easily gasified organic species into the liquid products, while the difficult-to-gasify organics and inorganics in ash remained in the solid phase, which prevented them from inhibiting the catalyst.

Strength and microstructural analysis of geopolymer prepared with coal-based synthetic natural gas slag

PurposeThe coal-based synthetic natural gas slag (CSNGS) is a solid waste remaining from the incomplete combustion of raw coal to produce gas. With the continuous promotion of efficient and clean utilization of coal in recent years, the stockpiling of CSNGS would increase gradually, and it would have significant social and environmental benefits with reasonable utilization of CSNGS. This study prepared a new geopolymer by mixing CSNGS with PC42.5 cement in a certain mass ratio as the precursor, with sodium hydroxide and sodium silicate solution as the alkali activators.Design/methodology/approachThe formulation of coal-based synthetic natural gas slag geopolymer (CSNGSG) was determined by an orthogonal test, and then the strength mechanism and microstructure of CSNGSG were characterized by multi-scale tests.FindingsThe results show that the optimum ratio of CSNGSG was a sodium silicate modulus of 1.3, an alkali dosage of 21% and a water cement ratio of 0.36 and the maximum unconfined compressive strength of CSNGSG at 7 d was 26.88 MPa. The increase of curing temperature could significantly improve the compressive strength of CSNGSG, and the curing humidity had little effect on the compressive strength of CSNGSG. The development of the internal strength of CSNSG at high temperatures consumed SiO2, Al2O3 and CaO and the intensity of corresponding crystalline peaks decreased.Originality/valueMoreover, the vibration of chemical bonds in different wavenumbers also revealed the reaction mechanism of CSNSG from another perspective. Finally, the relevant test results indicated that CSNGS had practical application value as a raw material for the preparation of geopolymer cementing materials.

Optimizing The Na2O Dosage to Develop Mechanical Properties of Ferrochrome Slag-Based Alkali-Activated Mortar

The purpose of this study is to investigate the effect of alkali dosage on the compressive strength and ultrasonic pulse velocity of alkali-activated ferrochrome slag/Portland mortar. A total of eight mortar mixtures were produced. While four of the mixtures contain 15% Portland cement, the binder material of the other four mixtures consists entirely of ferrochrome slag. These alkali-activated mortar mixtures were prepared with four alkali dosages (4, 6, 8, and 10). The alkali modulus of all mixtures was kept constant at 1.4. Compressive strength and ultrasonic pulse velocity tests were performed to examine the effect of alkali dosage on both PC-substituted and PC-free mortars. As the alkali dosage increased, the compressive strengths of both PC-substituted and unsubstituted mortar specimens increased. It was seen that the critical alkali dosage of the alkali-activated mortar was 6%. Compressive strength and UPV values of the mortar specimens increased significantly with PC substitution

Preparation of alkali-activated nickel slag-based cemented tailings backfill: Workability, strength characteristics, localized deformation and hydration mechanism

To solve the problems of high magnesium nickel slag (HMNS) and tailing stacks with large storage and environmental pollution, alkali-activated HMNS-based cementitious materials were prepared by using NaOH, phosphogypsum (PG), HMNS and ground granulated blast furnace slag (GGBFS), and cemented tailings backfill (CTB) was prepared using tailings as aggregates. The workability, strength characteristics, localized deformation and hydration mechanism of CTB were studied. Based on the digital speckle correlation method (DSCM), the localized deformation of CTB was analyzed. The hydration mechanism of CTB was analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential scanning calorimetry (TGDSC), mercury intrusion porosimetry (MIP) and scanning electron microscopy and energy dispersive spectroscopy (SEMEDS). The results showed that the optimal mix proportions for the cementitious material were 8%, 30%, 6%, and 0.38 for PG content, GGBFS content, alkali dosage, and water/binder ratio, respectively. The best performance of CTB was achieved when the bone glue ratio (BGR) and mass concentration (MC) were 5:1 and 79%, respectively; the slump, slump flow, and consistency of CTB decreased continuously with increasing BGR and MC; the layering degree, bleeding rate, and linear shrinkage of CTB continuously increased with increasing BGR, and decreased with increasing MC; the unconfined compressive strength of CTB increased with increasing maintenance age and MC and decreased with increasing BGR; when the BGR was small (3:1), CTB exhibited shear failure, and when the BGR was large (6:1), CTB exhibited tensile failure. The main hydration products of CTB were C-S-H gel, M-S-H gel, ettringite (AFt), Ca(OH)2 and CaCO3. In the early stage of curing, CTB has more pores, fewer hydration products and a relatively loose internal structure, flocculation, sheet, network and needle rod hydration products coated tailing particles, porosity decreased, and CTB became dense.

Understanding the impact of synthesis parameters on the pore structure properties of fly ash-based geopolymers

This paper systematically investigated the effects of alkali activator modulus (AM), alkali dosage (AD), and water-fly ash ratio (W/FA) on the pore volume, pore size distribution, pore volume fractal dimension (Dv), and pore surface fractal dimension (Ds) of fly ash-based geopolymer (FABGs) by orthogonal test and mercury intrusion porosimetry test. Dv and Ds of FABG can be calculated by the Menger sponge model and Zhang and Li's models, respectively. The relationship between multiple synthesis parameters and pore characteristics of FABGs was detailedly studied through range analysis and correlation detection analysis, which provides a basic understanding of the influence of multiple parameters on the pore characteristics of FABG, as well as the relationship between pore characteristics and mechanical properties. The results show that AM has the greatest effect on the volume proportion of gel pores and transition pores, and AD and W/FA have the greatest effect on the volume proportion of capillary pores and large pores, respectively. W/FA has the greatest effect on the porosity, and the porosity and the most probable aperture increase with the increment of W/FA and decrease with a rise in AD. It is worth noting that AM, AD, and W/FA have little effect on the Dv of larger pores, but have a greater on the Dv of smaller pores, with the influence order of AD-W/FA-AM. Ds of the large pores and capillary pores range between 2.70–2.90, and the Ds of the transition pores and gel pores are mostly greater than 3.00, which suggests that there may be more ink-bottle pores in transition pores and gel pores. In addition, there was a strong linear relationship between the porosity and compressive strength of FABGs, and the compressive strength of FABGs showed a decreasing trend with the increase of porosity. Compared with Dv, there is a stronger correlation between Ds and compressive strength, indicating that the roughness of the pore surface and the pore size distribution have a greater influence on the compressive strength of FABGs.

Effect of retarders on the properties of ultra-high strength alkali-activated concrete

Alkali-activated slag-fly ash-silica fume cement (AA-SFSC) is suitable for the production of clinkerless alkali-activated binder-based ultra-high strength concrete (AAB-UHSC). However, using a relatively low water-to-binder ratio and a high alkali dosage to prepare AAB-UHSC leads to rapid setting and a loss of flowability. Thus, the setting time of the AA-SFSC needs to be controlled. In our study, the effect of various retarders (single retarder borax and hybrid retarder a combination of zinc nitrate hexahydrate and sodium gluconate) on the AA-SFSC was investigated. The setting characteristics, reaction kinetics, mechanical performance, pore structure alteration, mineralogical and molecular transformations, and microstructure of the AA-SFSC were systematically examined. The results showed that both borax and a combination of zinc nitrate hexahydrate and sodium gluconate had a remarkable retarding effect on AA-SFSC with a low water-to-binder ratio and high alkali dosage. However, borax had a detrimental effect on the compressive strength, and the effect of adding zinc nitrate hexahydrate and sodium gluconate as the hybrid retarders on the compressive strength depended on the dosage; and a dosage of 1% zinc nitrate hexahydrate and 2% sodium gluconate was recommended for prolonging the setting time of AA-SFSC without compromising the mechanical performance.

Flow-through electrochemically assisted reverse-osmosis: A new process towards low-chemical desalination

Two-pass reverse osmosis (RO) process is prevailing in seawater desalination, but each process must consume considerable amounts of chemicals to secure product water quality. Caustic soda is used to raise the pH of the first-pass RO permeate (also the second-pass RO feed) to ensure adequate removal of boron in the subsequent second-pass RO, while antiscalants and disinfectants such as hypochlorite are added in the feed seawater for scaling and biofouling control of the first-pass RO membranes. Here, we report for the first time a flow-through electrochemically assisted reverse osmosis (FT-EARO) module system used in the first-pass RO, aiming to dramatically reduce or even eliminate chemical usage for the current RO desalination. This novel system integrated an electroconductive permeate carrier as cathode and an electroconductive feed spacer as anode on each side of the first-pass RO membrane. Upon applying an extremely low-energy (< 0.005 kWh/m3) electrical field, the FT-EARO module could (1) produce a permeate with pH >10 with no alkali dosage, ensuring sufficient boron removal in the second-pass RO, and (2) generate protons and low-concentration free chlorine near the membrane surface, potentially discouraging membrane scaling and biofouling while maintaining satisfactory desalination performance. The current study further elucidated the high scalability of this novel electrified high-pressure RO module design. The low-chemical manner of FT-EARO presents an attractive practical option towards green and sustainable seawater desalination.

Relationship of electrical resistivity and corrosion rate in alkali-activated mortars with varying alkalinity and nitrite inhibitor

The quantitative relationship between electrical resistivity and corrosion rate of steel (noted as R-C relationships) is empirical but informative in indicating corrosion risk of reinforced concrete in complex environments. However, it remains unclear how the R-C relationship line is affected by the chemistry and microstructure of cementitious binders. In this work, the corrosion behaviors of steel embedded in alkali-activated slag (AAS) mortars with varying alkali dosages were investigated to uncover the role of hydroxide ion concentration (pH) of pore solution in R-C relationship lines. Additionally, the effectiveness of sodium nitrite as a corrosion inhibitor in AAS was evaluated under high pH and chloride-rich conditions, as well as its effect on the R-C relationships. The results show that the intercept of R-C relationship lines increases with the decrease of alkali dosage in activators, which is mainly attributed to the pH drop in cementitious materials. Moreover, the slope of R-C relationship lines is a parameter related to pore structure and has a linear correlation with the average pore diameter measured by mercury intrusion porosimetry. Additionally, the efficacy of sodium nitrite as a corrosion inhibitor in AAS is insignificant, likely due to its detrimental effect on pore structure and enhanced water absorption.

Monitoring early age elastic and viscoelastic properties of alkali-activated slag mortar by means of repeated minute-long loadings

This study investigates the development of elastic and creep properties of sodium hydroxide-activated blast furnace slag mortar, utilizing three different molarities of the activator solution and two solution-to-binder ratio and a reference OPC-based mixture, since the earliest age. The experimental phase involves a series of hourly-repeated 5-min long creep tests on the aging material. This approach enables continuous monitoring, facilitating the characterization of early-age elastic stiffness and creep properties. Linear regression is employed to calculate the tangent unloading (elastic) modulus and Poisson's ratio. To model short-term creep behaviour, a power-law creep function is utilized. The integration of these findings with calorimetry-derived evolutions of cumulative heat release establishes linear correlation between (compressive) strength and heat release, along with a power function relationship between unloading (elastic) modulus and heat release. An optimal alkali dosage (Na2O content) appears to be vital for long-term strength development. Additionally, the creep parameters, namely amplitude (A) and kinetic (K), demonstrate a gradual decrease, although they maintain values higher than those of the corresponding OPC mixture, as the heat release progresses.

Synthesis of Porous Materials Using Magnesium Slag and Their Adsorption Performance for Lead Ions in Aqueous Solution.

Magnesium slag-based porous materials (MSBPM) were successfully synthesized using alkali activation and foaming methods as an effective adsorbent for Pb2+ in solution. The effects of foaming agent type, foaming agent dosage, alkali dosage, and water glass modulus on the properties of the MSBPM were studied, and the micromorphology and porosity of the MSBPM were observed using microscopy. The influence of pH value, initial concentration, and adsorbent dosage on the Pb2+ adsorption was investigated. The results showed that a porous material (MSBPM-H2O2) with high compressive strength (8.46 MPa) and excellent Pb2+ adsorption capacity (396.11 mg·g-1) was obtained under the optimal conditions: a H2O2 dosage of 3%, an alkali dosage of 9%, a water glass modulus of 1.3, and a liquid-solid ratio of 0.5. Another porous material (MSBPM-Al) with a compressive strength of 5.27 MPa and the Pb2+ adsorption capacity of 424.89 mg·g-1 was obtained under the optimal conditions: an aluminum powder dosage of 1.5‱, an alkali dosage of 8%, a water glass modulus of 1.0, and a liquid-solid ratio of 0.5. When the pH of the aqueous solution is 6 and the initial Pb2+ concentrations are 200~500 mg·L-1, the MSBPM-H2O2 and MSBPM-Al can remove more than 99% of Pb2+ in the solution. The adsorption process of both materials followed the Langmuir isotherm model and pseudo-second-order kinetic model, indicating that the adsorption process was a single-molecule layer chemical adsorption.