Sodium Silicate Concentration Research Articles

Upcycling of pine and sodium silicate composites through pyrolysis: Effects of pyrolysis temperature and sodium silicate content

In 3D-printing, sodium silicate (SS) can be used as an inorganic binder for wood-based composites due to its better rheological properties, high strength, and affordability. Investigating the recyclability of 3D-printed composites is necessary to understand the reusability of demolished additively manufactured construction waste. In this work, the bio-oil through pyrolysis was produced using pine and SS composites and further characterized to observe the effects of the pyrolysis temperatures and the proportion of SS in composites. Pine and SS composites with 0, 33.33, 50, and 66.67 % of the SS on a mass basis were prepared and cured to mimic the 3D-printed composites. Then, pyrolysis of cured composites was performed in a bench-scale fixed bed pyrolysis reactor at four temperatures (450–600 °C). From the pyrolysis of composites with 66 % SS at 600 ℃, a maximum condensed liquid yield of 68 % (wt.%, dry basis) was obtained. Further, it was observed that the selectivity towards hydrocarbons and alkyl phenols increased by increasing the proportion of SS in the composite, but methoxy phenols decreased, which enhanced bio-fuel production. A maximum hydroxyl concentration of 6.54 mmol g−1 was observed for the bio-oil from pyrolysis of SS-based composite at 600 ℃. This study shows the feasibility of upcycling the 3D-printed wood composites through pyrolysis to generate bio-oil that can be used for bio-based resin synthesis and bio-fuel applications.

Effect of Data Augmentation Using Deep Learning on Predictive Models for Geopolymer Compressive Strength

In recent years, machine learning models have become a potential approach in accurately predicting the concrete compressive strength, which is essential for the real-world application of geopolymer concrete. However, the precursor system of geopolymer concrete is known to be more heterogeneous compared to Ordinary Portland Cement (OPC) concrete, adversely affecting the data generated and the performance of the models. To its advantage, data enrichment through deep learning can effectively enhance the performance of prediction models. Therefore, this study investigates the capability of tabular generative adversarial networks (TGANs) to generate data on mixtures and compressive strength of geopolymer concrete. It assesses the impact of using synthetic data with various models, including tree-based, support vector machines, and neural networks. For this purpose, 930 instances with 11 variables were collected from the open literature. In particular, 10 variables including content of fly ash, slag, sodium silicate, sodium hydroxide, superplasticizer, fine aggregate, coarse aggregate, added water, curing temperature, and specimen age are considered as inputs, while compressive strength is the output of the models. A TGAN was employed to generate an additional 1000 data points based on the original dataset for training new predictive models. These models were evaluated on real data test sets and compared with models trained on the original data. The results indicate that the developed models significantly improve performance, particularly neural networks, followed by tree-based models and support vector machines. Moreover, data characteristics greatly influence model performance, both before and after data augmentation.

Preparation and performance influencing factors of sludge-based non-sintering ceramsite foam concrete block

In this study, the preparation of ceramsite foam block using Sludge-based Non-sintering Ceramsite (SNSC) was investigated through orthogonal test and performance optimization test to investigate the effects of different coal fly ash addition, volume ratio of SNSC, water binder ratio and sodium silicate concentration on the performance of the concrete block, and the optimal material mixing ratios were obtained as follows: cement was 400 kg/m3, coal fly ash was 100 kg/m3, SNSC was 371 kg/m3, water binder ratio was 0.43, CaCl2 was 10 kg/m3, and Na2SO4 was 5 kg/m3. The performance of Sludge-based Non-sintering Ceramsite Foam Concrete Block under these conditions meets the specification requirements of GB/T 36534–2018 "Ceramsite Foam Concrete Block". Its compressive strength was 7.76 MPa, dry bulk density was 948.7 kg/m3, the water absorption was 20.75 %, and the softening coefficient was 0.861. XRD and SEM analyses revealed that the internal physical phase of the concrete blocks under the optimal conditions was tightly bonded, with fewer and uniformly distributed pores, and that the hydration generated C-S-H, C-A-H gel-like substances, calcium alumina (AFt), and hydrated calcium chloroaluminate generated by hydration could significantly improve the physical and mechanical properties of concrete blocks.

Research on the long-term strength development of Datça Pozzolan-based geopolymer

This study examined the influence of long-term curing duration on the properties of geopoly- mers produced through the geopolymerization reaction between Datça Pozzolan and sodium silicate and potassium hydroxide solutions. The specimens were heat cured at 90 °C, 95±5% RH for 24 h initially and then kept under ambient conditions until the tests were conducted at 7, 90, and 365 days. The results showed that applied initial heat curing was appropriate to achieve high early and long-term strength. Geopolymer mortars with 12.5 M and 2.5 activator ratios had the lowest porosity (20.90%) and the highest ultrasound pulse velocity (UPV) (3.10 km/s), compressive strength (10.57 MPa), and flexural strength (5.20 MPa) after seven days. While the porosity of the identical specimens decreased by up to 15.77%, the UPV, compres- sive strength and flexural strength increased by 3.37 km/s, 15.32 MPa, and 6.06 MPa, respectively, after 365 days. The physical and mechanical improvement in the first 90 days exceeded 90–365 days. A higher rate of improvement was obtained when the activator ratio was low, i.e., the improvement decreased inversely as the sodium silicate content of the mortar increased. An increasing trend was observed in the plot of compressive strength as a function of UPV, and the slope values presented a strongly related linear function relation.

Effects of elevated temperatures and cooling regimes on the waste andesite dust-based geopolymer mortars

In this study, the geopolymer mortar mixtures were manufactured by activating andesite stone cutting waste dust with sodium silicate. The sodium silicate content in the mixtures was determined to contain 6%, 8% and 10% Na2O by weight of waste andesite dust (WAD). The produced mixtures were subjected to thermal curing at three different temperatures (60 ºC, 75 ºC and 90 ºC), and in two different periods (8 hours and 24 hours). Flexural strength (fs) and compressive strength (fc) tests of 1, 28 and 56 days were carried out on the specimens obtained from the geopolymer mortar mixtures. The effects of Na2O content, thermal curing temperature and time on the strength values of the geopolymer mortars were investigated. Moreover, the geopolymer mortar samples produced with 8 hours of thermal curing were exposed separately to 400 ºC, 600 ºC and 800 ºC. The specimens, which were kept for 1 hour at 400 ºC, 600 ºC and 800 ºC, were exposed to three different cooling conditions (slow-cooled in air, fast-cooled in air and water-cooled). The fs and fc tests were carried out on the cooled geopolymer mortars, and the effects of high temperatures and cooling conditions on the strength properties of the geopolymer mortars were evaluated. In addition, the changes in the microstructures were examined by performing XRD and SEM/EDAX analyses on the selected geopolymer mortars. The fs and fc values of the water-cooled geopolymer mortars significantly decreased.

Analysis and prevention of copper pipe corrosion

The failure of the locomotive heat exchanger due to pitting and corrosion of the T2 heat exchange copper tube is used as the engineering application background. The pitting corrosion and influencing factors of T2 copper tu were studied by weight loss method, SEM, and EDS. The optimal ratio of compound corrosion inhibitors (borax, sodium nitrite, sodium silicate, and benzotriazol) of T2 copper tube was obtained. The results show that the main reason for the pitting corrosion of T2 copper pipe is the local rupture of cuprous oxide protective film on the copper surface, resulting in the copper at the bottom of the pit as the anode and the Cu2O oxide film on the surface as the cathode to form a corrosion cell so that copper dissolves and pitting in the pit. The rupture of the Cu2O oxide film is related to excessive carbon-containing residue and the deposition of dirt (foreign matter) on the surface, mechanical attack, and defects of the material itself. The optimal ratio of compound corrosion inhibitor in 2 L pure aqueous solution is as follows: Borax content is 4.4 g, sodium silicate content is 4.23 g, sodium nitrite content is 4 g, and benzotriazole content is 0.2 g.

Developing High-Performance and Low-Cost Paint Thermoelectric Materials for Low-Midtemperature Applications.

Most thermoelectric (TE) materials used to convert heat energy into electrical energy are expensive and, to a certain degree, toxic. Moreover, due to the chemical complexity in the synthesis process, some of the TE materials are not reproducible. Similarly, the scarcity of TE materials hampers their scalability. To address the above issues, this study presents an inexpensive, nontoxic, scalable, and highly reproducible paint-based TE module for the conversion of heat energy to electrical energy. Transport properties with structural analysis indicate that the electrical conductivity of the paint TE material is controlled by the concentration of graphite and sodium silicate, while the Seebeck coefficient is dominated by the ratio of n- and p-type Bi-Sb-Te. The results indicate that the as-developed TE module can withstand an operating temperature of up to 160 °C. At a temperature of 57 °C, the highest power factors of the as-synthesized n- and p-type TE paints are 1.34 and 1.42 μW/(cm K2), respectively. It is also found that the TE module can have a higher output voltage when the cold side of the TE module is allowed to float in the air in comparison to that when it is in contact with the human body. The performance of the paint-based TE module is measured on five parts of the body, namely, the chest, palm, leg, wrist, and neck; the wrist has the highest open-circuit voltage of 1.9 mV, indicating its suitability for wearable applications. Finally, at a temperature gradient of 30 °C, a maximum output power of 6.8 μW is attained.

Alleviating Cd Stress in Sunflower (Helianthus annuus) through the Sodium Silicate Application

Sunflower has substantial potential for the remediation of heavy metals in soil, but its efficiency in Cd-contaminated soil is limited, with high concentrations of Cd causing stress in plants. Exogenous Si enhances plant tolerance to heavy metals, but the mechanism for enhancing the tolerance of oil sunflower under Cd stress is not known. In potting experiments, sunflowers were grown in soil with a Cd concentration of 11.8 mg/kg soil (the maximum value in the Zhundong coal mining area of Xinjiang) and five Si treatment levels (0, 50, 250, 500, and 1500 mg/kg soil). Exogenous Si improved sunflower development, gas exchange characteristics, and antioxidant enzyme activities in sunflower compared with the Cd-only control; exogenous Si application increased Cd concentrations in sunflower roots, stems, and leaves, and Cd was mainly concentrated in sunflower roots. Sunflower biomass increased by 13.83–114.18%, and gas exchange parameters increased by 16.95–36.03%, 30.06–66.82%, and 9.77–14.71%, respectively, as compared to the control. With the increase in sodium silicate concentrations, sunflower antioxidant enzyme activities increased by 8.81–150.28%, 91.35–351.55%, and 35.11–54.69%, respectively, and MDA content decreased by 3.34–25.14% as compared to Si0. Moreover, exogenous Si increased Cd uptake and minimized Cd stress in sunflowers at the seedling and blooming stages, and it potentially facilitated the phytoremediation of Cd-contaminated soils through enriched plants such as sunflower, as well as contributing to the achievement of sustainable development of the soil environment.

Assessment of Bearing Capacity and Settlement Characteristics of Organic Soil Reinforced by Dune Sand and Sodium Silicate Columns: A Numerical Study

Organic soil is problematic soils in geotechnical engineering due to its properties, as it is characterized by high compressibility and low bearing capacity. Therefore, several geotechnical techniques tried to stabilize and improve this soil type. In this study, sodium silicate was used to stabilize sand dune columns. The best sodium silicate concentration (9%) was used, and the stabilized sand dune columns were cured for seven days. The results for this soil were extracted using a numerical analysis program (Plaxis 3D, 2020).In the case of studying the effect of (L/D) (where ‘’L” and ‘’D’’ length and diameter of sand dune columns) of a single column of sand dunes stabilized with sodium silicate with a different diameter, the results showed that the best effect was for L/D of (4) with D equal to (0.7m) in the end bearing columns type. In the case of studying a group of columns, the percentage of improvement in soil bearing ratio increased with increasing the number of columns in both floating and end bearing types. When using (8-columns) with a square distribution pattern, the optimum improvement was at the end bearing and at the ratio L/D of (6), where the improvement percentage was (666%) compared to the unimproved soil.

LABORATORY INVESTIGATION OF THE EFFECT OF SODIUM SILICATE AND BENTONITE ON THE MECHANICAL PROPERTIES OF THE GROUT BEHIND THE SEGMENT IN MECHANIZED EXCAVATION

Nowadays, the use of Tunnel Boring Machines (TBM) in tunnelling has increased in urban environments. One of the effective parameters in the excavation process is the use of grout behind the segments to prevent ground settlement and penetration into the tunnel. The investigation of the effects of two-component grout (bentonite and sodium silicate) on the mechanical properties of the grout plays a crucial role in mechanized excavation. Therefore, this article aims to investigate the effect of various parameters on the properties of the two-component grout. Eight different mixing designs were considered in this research. Gel-time tests, viscosity test, water bleeding test, uniaxial compressive strength tests (UCS), and direct shear tests were conducted for each mixing design. The UCS tests were performed for eight mixing designs and at four different ages of the grout, while the direct shear test was conducted for five mixing designs at the age of one day. The results showed that increasing the sodium silicate content from 4% to 9.4% reduced the Gel-time to 7 seconds, and increasing the bentonite content from 2.3% to 4.58%, increased the marsh funnel time to 12 seconds. The uniaxial compressive strength of the grout increased to 0.682 MPa at the age of 28 days. Finally, by conducting the direct shear test on the grout and obtaining the parameters of cohesion and internal friction angle, it was determined that these two parameters depend on the values of bentonite and sodium silicate, and they change with the increase or decrease of these grout components.

COMPOSITE MIXTURES OF LIGNOSULFONATE REAGENT SYSTEMS WITH SILICON COMPOUNDS

The relevance of the article is related to the study of the possibility of improving the quality of lignosulfonate systems used during the passage of intervals of swelling clay rocks. A feature of reagent systems based on lignosulfonates is their ability to inhibit the hydration processes of clay minerals and thereby reduce the risks of complications during the construction of oil and gas wells. The properties of the composition were studied on the basis of a mixture of lignosulfonate systems and silicon compounds using the example of ferrochromolignosulfonate (FHLS-M) and sodium silicate Na2SiO3 (SS). The objective of the study was to find optimal ratios of the components of the mixture by the method of experimental planning, as a means of constructing mathematical models and regression analysis to assess the magnitude and direction of the impact of various factors on the output parameters of the flushing fluid system. The research method consists in determining the stability of the solution parameters with varying temperatures from 20 to 190 °C in the aging cell for 5 h and conducting at least three parallel determinations for each ratio of reagents in the composition relative to the initial clay solution. The performed regression analysis of the composition of FHLS-M: SS showed that the greatest influence on the viscosity and filtration properties of the solution is exerted by the content of FHLS-M. However, in the temperature range of 80-190 °C, the ratio of FHLS-M: SS is justified, equal to 3%:5% (the addition of SS enhances the effect of the composition by more than 40%). In the temperature range of 20-120 °C, to maintain the conditional viscosity of the solution (CV) at least 60 s, a sodium silicate content of about 4 % is required, FHLS-M – within 3-5%. At temperatures of 80-120 °C and a value of CV = 60 s, the composition of the composition of FHLS-M: SS is 3%:4%, respectively; with an increase in temperature of more than 120 °C, there is a need to increase the consumption of FHLS-M. At the same time, in the temperature range of 80-190 °C, the ratio of FHLS-M: SS is justified at the level of 3%:4%, respectively. It was found that the optimal ratio in the temperature range of 20-190 °C, in the composition of FHLS-M: SS, is 0.75%:0.75 %, respectively, however, the conditional viscosity (CV) of the solution is no more than 35 s. A decrease in the filtration index (FI) of the solution at temperatures up to 80 °C is ensured by the use of less than 2% sodium silicate in the composition, and FHLS-M in the range of 2-5%.

Workability and durability analysis of waste based geopolymer concrete

GPC as a promising material, started gaining momentous attention from the researchers and construction specialists because of its advantages in using by-products from agriculture and industries to replace cement thereby reducing greenhouse gas emission. Workability and durability tests were carried out, so as ascertain the efficiency of the rice husk ash and rice husk as sodium silicate and super plasticizer, for solving efflorescence problem known with geopolymer concrete. The factory-made sodium silicate was also used and compared with laboratory-produced, before addition of other geopolymer binders such as kaolin clay and fly ash. Brunauer-Emmett-Teller (BET) scrutiny that delivers quantitative data on the specific surface area as well as porosity dispersal of solid materials revealed that correlation coefficient of RHA (0.994) was higher than that of cement (0.991). Besides, RHA has higher surface area (250.023 m3/g) than the cement utilized which stood at 211.49 m3/g. Though the c constant of cement exceeds the RHA values, RHA can serve as good pozzolanic material and cement substitute. It is seen that the workability of laboratory-produced sodium silicate and superplasticizer geopolymer concrete was enhanced significantly compared to that of prior geopolymer systems. It is observed that the workability of the geopolymer concrete was considerably enhanced compared to that of orthodox geopolymeric systems, especially at 2.5% rice-husk created superplasticizer and higher content of laboratory-produced sodium silicate.

Impact of Sodium Silicate Supplemented, IR-Treated Panax Ginseng on Extraction Optimization for Enhanced Anti-Tyrosinase and Antioxidant Activity: A Response Surface Methodology (RSM) Approach.

Ginseng has long been widely used for its therapeutic potential. In our current study, we investigated the impact of abiotic stress induced by infrared (IR) radiations and sodium silicate on the upregulation of antioxidant and anti-tyrosinase levels, as well as the total phenolic and total flavonoid contents of the Korean ginseng (Panax ginseng C.A. Meyer) variety Yeonpoong. The RSM-based design was used to optimize ultrasonic-assisted extraction time (1-3 h) and temperature (40-60 °C) for better anti-tyrosinase activity and improved antioxidant potential. The optimal extraction results were obtained with a one-hour extraction time, at a temperature of 40 °C, and with a 1.0 mM sodium silicate treatment. We recorded maximum anti-tyrosinase (53.69%) and antioxidant (40.39%) activities when RSM conditions were kept at 875.2 mg GAE/100 g TPC, and 3219.58 mg catechin/100 g. When 1.0 mM sodium silicate was added to the media and extracted at 40 °C for 1 h, the highest total ginsenoside content (368.09 mg/g) was recorded, with variations in individual ginsenosides. Ginsenosides Rb1, Rd, and F2 were significantly affected by extraction temperature, while Rb2 and Rc were influenced by the sodium silicate concentration. Moreover, ginsenoside F2 increased with the sodium silicate treatment, while the Rg3-S content decreased. Interestingly, higher temperatures favored greater ginsenoside diversity while sodium silicate impacted PPD-type ginsenosides. It was observed that the actual experimental values closely matched the predicted values, and this agreement was statistically significant at a 95% confidence level. Our findings suggest that the application of IR irradiation in hydroponic systems can help to improve the quality of ginseng sprouts when supplemented with sodium silicate in hydroponic media. Optimized extraction conditions using ultrasonication can be helpful in improving antioxidant and anti-tyrosinase activity.

Effects of metakaolin and sodium silicate treatment on highwater content dredged clay for improved construction fill performance

This study experimentally investigated the strength characteristics of metakaolin (MK) and sodium silicate (SS) treated dredged clay at high water content for use as construction fills. A series of laboratory tests including direct shear tests, unconfined compression tests, SEM and XRD tests were carried out to systematically evaluate the effects of water content, sodium silicate modulus, curing agent content, and curing time on the strength behavior of MK and SS treated dredged clay samples. The direct shear test results showed that the shear strength at a given vertical stress consistently increases with the increase of curing agent content and curing time while decreasing with the modulus of SS. Both cohesion and friction angle increase with increasing curing agent content and curing time, while reducing with the increasing modulus of SS. Unconfined compression test results showed that all samples tested exhibit a strain-softening behavior. The value of unconfined compressive strength increases with the increase of curing agent content and curing time but decreases with the increase of water content and modulus of SS. The optimal dosage combination is a sodium silicate modulus of 0.9, curing agent content of 12%, and curing time of 28d. SEM test confirmed the formation of gels in the treated soil sample, the dredged clay showed a more uniform and denser microstructure after treatment. Through XRD analysis, it is not easy to generate direct chemical reactions with no new mineral components generated in the sample. For high-water content dredged clay, it is recommended to use an optimum dosage combination of MK and SS to achieve a better treatment effect for use as construction fills.

Recycling Ash and Slag Waste from Thermal Power Plants to Produce Foamed Geopolymers

Ash and slag waste (ASW) from coal combustion creates significant environmental and economic challenges. A promising method of ASW recycling is alkali activation with geopolymer material formation. This study investigates the influence of activating solution components (sodium hydroxide and sodium silicate) on the formation of porous geopolymers using ASW of different origins. The sodium hydroxide content of 0–4 wt.% and the sodium silicate content of 17–25 wt.% were studied. An increase in sodium hydroxide resulted in decreased density, but it adversely affected the strength. An increase in sodium silicate led to a compromised porous structure with relatively high density and compressive strength. An optimal composition, S19N3, comprising 3 wt.% of sodium hydroxide and 19 wt.% of sodium silicate obtained porous geopolymers with uniformly distributed 1.4–2 mm pores and a corresponding density of 335 kg/m3, a compressive strength of 0.55 MPa, a porosity value of 85.6%, and a thermal conductivity value of 0.075 W/(m·K). A mechanism for porous geopolymer formation was developed, including the interaction of alkaline components with ASW and a foaming agent, foaming, curing, and densification. The mechanism was examined using ASW from the Severodvinsk CHPP-1. This study allows for the optimization of geopolymer mixtures with various waste sources and the utilization of waste materials in the construction industry.

Deeper Understanding of the Strength Evolution and Deformation Characteristics of Sodium Silicate–Cemented Paste Tailing Material

This research aims to examine the impact of sodium silicate (SS) on the mechanical and microstructural properties of cemented paste tailings or cemented paste backfill (CPB), a cementitious construction material extensively used in underground mining operations. The study involved various compositions and curing conditions of SS-CPB samples, and their uniaxial compressive strength (UCS), stress–strain behavior, microstructure, and modulus of elasticity were evaluated by conducting mechanical (UCS) and microstructural (DT/DTG, MIP) tests, as well as monitoring experiments. Findings indicate that SS improves the mechanical strength of CPB and enhances its microstructure. The development of UCS is affected by SS dosage, curing time, water chemistry, curing temperature, and curing stress. Higher SS dosage, curing time, temperature, and stress lead to higher UCS, while sulfates decrease UCS. SS also increases CPB’s resistance to sulfate attack, and field curing temperature improves the binder hydration enhancement induced by SS. The presence of SS affects the stress–strain properties of CPB, including the shape of the stress–strain curve, maximum stress and strain, and modulus of elasticity. The modulus of elasticity of CPB with SS is higher than that without SS under field thermal curing conditions. Moreover, UCS and the modulus of elasticity have a linear relationship in SS-CPB, regardless of SS content. A relationship is proposed to estimate the modulus of elasticity of SS-CPB from its UCS. The study has significant practical implications for the cost-effective design of mine CPB structures and for improving underground mine work safety and productivity.

Alkali Activation of Solid Waste from Cable Wire Manufacturing Industry for Building and Construction

Iron-laden tailings have received a lot of attention in recent years, especially for their potential use in civil engineering projects. Alkaline activation was studied as a method to use iron sludge from cable wire manufacturing industry (CWI). Two reagents, namely sodium silicate and sodium hydroxide concentrations of 1 M, 5 M, and 10 M were studied for alkaline activation. To make a paste, the solutions were combined with CWI waste. Using 50x50x50 mm3 molds, the paste was cast into triplicates and allowed to set. The molds were demolished once the paste had solidified, and the specimens were cured at increased temperatures and at room temperature. The specimens were cured for days, 7 days, and 14 days at ambient temperature. The specimens were subjected to geochemical and geotechnical testing after the curing period to determine the mechanism that contributed to unconfined compressive strength (UCS) development. The findings demonstrated that when the two reagents were compared, sodium hydroxide proved to be a better activator, resulting in a greater unconfined compressive strength, particularly when the specimen was cured at a high temperature. When cured at both elevated and ambient temperatures, the sodium silicate did not perform well as an activator, as the specimen were not durable.

Study on improvement of waterproofing performance of CCCW with silicone waterproof material and waterbased capillary inorganic waterproofer

The silicone waterproof material and waterbased capillary inorganic waterproofer possess the advantages of rapid film formation and significant hydrophobic effect. In this study, the material composition and mixing ratio of the silicone waterproofing material and waterbased capillary inorganic waterproofing were investigated by multiple performance tests. The results indicated that a white coating was formed on the surface when the mixing ratio of isobutyl-triethoxy-silane and isooctyl-triethoxy-silane was more than 69 %. When the content of sodium and potassium methyl silicate exceeded 0.5 %, respectively, there was an upward trend of contact angle while the reduction in water absorption gradually decreased. Meanwhile, the contact angle and water absorption height of silicone waterproof material were tested. The results showed that the coating performance and hydrophobicity were the best when the mixing ratio of isobutyl-triethoxy-silane, isooctyl-triethoxy-silane, sodium methyl silicate, and potassium methyl silicate was 1.5:0.2:1:0.5. When the matrix mortar specimen was made of Cementitious Capillary Crystalline Waterproofing Materials (CCCW), the lowest water absorption height and water absorption of the experimental group consisted of sodium silicate, sodium tetraborate, sodium phosphate, and sodium hydroxyethyl cellulose were 316.7 % and 39%, respectively. The lowest water absorption height and water absorption of the experimental group consisted of sodium silicate, sodium tetraborate, nano-silica, and sodium hydroxyethyl cellulose were 215.4 % and 28 %, respectively. The results showed that CCCW combined with the experimental group consisted of sodium silicate, sodium tetraborate, sodium phosphate, and sodium hydroxyethyl cellulose had better waterproofing effect.

The surface structure of nanosilica produced from sodium silicate by the carbonation process

CO2 was used to prepare nanosilica particles through a carbonization reaction in a Na2SiO3 solution, aiming to convert CO2 into value-added products. The relationship between the specific structure of the as-prepared nanosilica and the sodium silicate concentration, reaction temperature, reaction time, and aging time was explored by TEM, BET, and XRD analysis. The growth process of nanosilica particles was relatively slow with the increase in the Na2SiO3 concentration, which resulted in the formation of large primary particles, reducing the specific surface area. The decreasing temperature reduced the polymerization of Si(OH)4 and SiOSi(OH)3, reducing the specific surface area. Meanwhile, the effects of reaction time and aging time on the surface structure of silica nanoparticles were studied. Different surface structure of nanosilica particles were synthesized by controlling the carbonization process conditions, which expand the application of nanosilica products. At present, the research on the carbonization preparation of nanosilica mainly focused on the carbonization process conditions and modification technology, but the research of control mechanism of nanosilica surface structure and properties was insufficient. This study focused on the relationship between surface structure evolution and properties, and provided a theoretical basis for the mechanism of the influence factors of preparation process on the structure evolution of prepared nanosilica. And the process reduced CO2 emission, which had important environmental protection value.

Alkali-activated slag mortar molded by non-stirring molding: Compressive strength, hydration properties and microstructures

Alkali-activated slag (AAS) characterized by fast hardening and high early strength has potential application prospects in concrete canvas (CC), where a non-stirring molding method is required to prepare mortar. This paper provides a new method for the preparation of alkali-activated slag mortar (AASM) by non-stirring (sprinkling-molding), where mechanical properties, hydration properties, and microstructures were investigated. The results suggest that the compressive strength of the sprinkling-molding mortar was slightly lower than that of the conventional stirring-molding mortar, and the compressive strength with sodium silicate content of 15 % the slag mass at 28d can reach 44.5 MPa. The hydration products are dominated by amorphous C-A-S-H gels, with small amounts of hydrotalcite. There are differences in degree of hydration and microstructures of each layer in the sprinkling-molding mortar.