Explore the vast range of titles available.

The aim of this work is to study the feasibility of preparation of fly ash based geopolymer using sodium water glass from agricultural waste as alternative activators. Rice husk ash and bagasse ash were used as raw materials for producing sodium water glass solution. The sodium water glass were produced by mixing rice husk ash and bagasse ash with NaOH in ball mill and boiling. The prepared sodium water glass were analyzed and used in geopolymer preparation process. The geopolymer paste were prepared by adding the obtained water glass and NaOH with fly ash. After cured at ambient temperature for 7 days, mechanical properties were investigated. Bonding and phases of the geopolymer were also characterized. The geopolymer from rice husk ash presented highest compressive strength about 23 MPa while the greatest for bagasse ash was about 16 MPa.

Geopolymer recycled aggregate concrete (GRAC) was prepared by replacing cement with geopolymer and natural aggregate with waste concrete. The effect of the water-glass module on the mechanical properties of GRAC was studied. It was found that water-glass has a double-layer structure. The low module water-glass leads to a thicker diffusion layer and more Na+ and OH− in the solution, which activates more CaO, SiO2, and Al2O3 in the raw material, and improves the strength of GRAC. Moreover, two kinds of gel structures, namely layered C-A-S-H (calcium silicate hydrate) and networked N-A-S-H (zeolite), were found in the products of geopolymer. As the water-glass module changed, the phase of zeolite changed significantly, whereas the calcium silicate hydrate did not change, indicating that the decrease in the water-glass module contributes to the formation of more N-A-S-H gel. The compressive strengths of GRAC with the sizes of 200, 150, and 100 mm3 were in line with Bazant’s size effect theoretical curve. Through the segmented fitting method, the relationship of the size conversion coefficient of GRAC (α), the critical strength (fcr), the critical dimension (Dcr), and the water-glass module (ε) were determined. It was found that ε = 1.5 is the segmented point of the three equations. The elastic modulus and peak stress of GRAC are inversely proportional to the water-glass module, and the peak strain is proportional to the water-glass module, indicating that by reducing the water-glass module, the strength of GRAC can be improved, but the brittleness is increased. The constitutive equation of GRAC with only the water-glass module as a variable was also established. It was found that the polynomial mathematical model and rational fraction mathematical model are optimal for the rising-stage and falling-stage, respectively, and the relationship between the parameters of the rising-stage (a) and the falling-stage (b), and the water-glass module, is given.

Waste from construction and demolition (also known as CDW) is one of the most harmful environmental issues. This study's primary goal is to produce new mortar and brick materials from recycled concrete powder (RCP) and recycled brick powder (RBP), two of the most popular CDW. Geopolymeric mortar and brick samples were produced by passing RCP and RBP through sieve No. 50 (with sand filler if necessary) and combining them with an alkaline solution made of water glass (WG) and NaOH. In this study, the mixture was then cured for three days at 80 °C in an oven. The effects of filler, RBP amount, WG amount, and the concentration of NaOH alkaline solution on the samples’ strength were examined. Additionally, XRF and SEM/XRD tests were performed to verify the materials' composition and microstructure. The mechanical strength of the samples showed an increase with the increase of RCP values, so the brick sample with filler showed the highest compressive strength, measuring 59.53 MPa. The study's samples exhibited strong mechanical properties. Additionally, all of the bricks' water absorption fell within the standard range. In summary, according to different standards, both waste concrete and waste brick can be used to produce geopolymer materials especially bricks for construction and paving purposes.

Removal of Na + is a very important step in the SiO 2 aerogel preparation using water glass as precursor, which has a significant effect on the structure and properties of aerogel. In this study, three methods (Solution-crystallization, Water washing, and Ion exchange) were used to remove Na + from the system and investigated the effects of different methods on the aerogel properties. The results show that all three aerogels have low bulk density (<0.075 g/cm 3 ), low thermal conductivity (≤0.015 W/(m·K)), and well hydrophobicity ( θ  ≥ 137°). Among them, Na + exists in the sol in the sodium removal process by water washing and effects the uniformity of gel network. The samples for sodium removal by solution-crystallization show better hydrophobicity and poorer high-temperature stability, which is related to the presence of abundant hydrophobic groups (Si-OC 2 H 5 ) on the gel surface. The microstructure and the pore size distribution of the aerogels prepared by ion exchange are uniform, which makes them have optimal comprehensive performance. The mechanism of solution-crystallization effect in the process of sodium removal was explored, providing a workable idea for low-cost preparation of SiO 2 aerogel. Graphical Abstract Highlights Water glass was chosen as the inorganic silica source to prepare SiO 2 aerogel with good performance. The effects of different sodium removal methods on the properties of aerogels were explored. The mechanism of solution-crystallization effect in the process of sodium removal was explored.

Converter steel slag, currently underutilized crystalline metallurgical residue, was investigated for use as a precursor for alkali activation. Water glass solution with various moduli (0.5, 1.0, 1.5 and 2.0) was used at the same Na 2 O dosage of 4% in order to investigate effect of modulus on hydration. Pure cement paste with the same ratio of water to binder was selected as the control sample. Results show that modulus has a significant impact on the hydration and mechanical strength development of alkali-activated steel slag. Similar to pure cement paste, alkali-activated steel slag paste has C–S–H gel and Ca(OH) 2 as its main hydration products. However, alkali-activated steel slag pastes have lower hydration heat and fewer amounts of hydration products. Additional silicate has a retarding effect on the hydration of steel slag. Hydration heat, Ca(OH) 2 contents and non-evaporable water contents reduce with increasing modulus. In addition, high silicate modulus fines the pore structure and improves compressive strength of the hardened paste.

Currently, construction uses a vast array of materials that, while serving the same purpose, differ only slightly in their properties. This complicates the substitution of one material for another, significantly expanding the product range when considering operating conditions, necessitating expanded warehouse space. Therefore, preference should be given to universal materials that, while maintaining the same chemical composition, can change their properties by altering the ratio of their components. This study addresses this issue by evaluating the potential of glass composites containing powdered waste glass as alternatives to selected conventional construction materials. The results demonstrated that the rheological properties of the composites can be effectively controlled by adjusting the ratio of water glass to waste glass powder, enabling the achievement of viscosity values suitable for both plastering and installation mortars. In addition, the composites exhibited markedly higher adhesion strength than conventional gypsum mortars under high-humidity conditions, confirming their applicability as adaptable, substrate-specific materials with geopolymer-like characteristics.

To improve the performance of polyurethane grouting materials and reduce costs, polyurethane was modified with sodium silicate to prepare sodium silicate modified polyurethane grouting materials. The preparation process of the material was studied experimentally, and its main properties such as gel time, compressive strength, bonding strength and water resistance were systematically tested. The microstructure and chemical structure of the material were analyzed by combining microscopic testing methods such as SEM and FTIR. At the same time, indoor grouting simulation tests were carried out to evaluate its groutability in fissure media and the integrity of the stone body. The results showed that the introduction of water glass was involved in the curing reaction of polyurethane, altered the microstructure of the material, significantly increased the strength of polyurethane (compressive strength could reach more than 30 MPa), and also reduced its reaction temperature (the maximum reaction temperature was all below 100°C). Indoor grouting simulation tests and field engineering applications showed that the modified polyurethane material could effectively fill the fissures, form continuous and complete stone bodies, and had a good water-blocking effect. This study provides a theoretical basis and experimental support for the optimal design and engineering application of sodium silicate modified polyurethane grouting materials.

Silicic acid solution, which is prepared from water glass followed by extraction with tetrahydrofuran (THF), is focused on an environmentally friendly and inexpensive source of silica. In this study, we aimed the preparation of bulk porous silica with low environmental impact and cost, and desulfurization of its supported ZnO was investigated. Bulk porous silica was prepared by the condensation of silicic acid/THF in the presence of Pluronic P123. Suitable condition was investigated for the formation of crack-free bulk body with high surface area and reproducibility under the molar ratio of H 2 O/Si and Si/Pluronic P123 on 121 and 100, respectively. From nitrogen adsorption–desorption measurements, this bulk porous silica was categorized into micro–mesoporous silica. Moreover, Pluronic P123 was extracted and recycled. Bulk porous silica-supported 15 wt% ZnO was prepared by the impregnation of ZnCl 2 followed by calcination in air. The desulfurization ability was 8.7 mg/g. Graphical Abstract Highlights Micro–mesoporous silica bulk bodies were prepared using silicic acid derived from water glass. Pluronic P123 was recycled and micro–mesoporous silica could be prepared by using recycled Pluronic P123 with high reproducibility. Bulk micro–mesoporous silica-supported ZnO showed a desulfurization ability.

Calcium aluminate cement (CAC) is a suitable source of tetrahedral aluminum, which reacts with tetrahedral silicon from water glass (aqueous sodium or potassium silicate solution) in an exothermic reaction, forming inorganic polymer structures that are stable at high temperatures. All tetrahedrally configurated aluminum atoms of the various calcium aluminates tested, react with tetrahedral silicon groups to form –O–Si–O–Al–O– chains with an average Si/Al ratio near of 1. Octahedrally configurated aluminum, as in γ-Al 2 O 3 , does not react at room temperature. The sodium-to-silicate ratio of the silicate solution was measured to be 1:1, so most water glasses require activation with NaOH. The number of positive charges in the activated water glass (Na + or K + ions) corresponds to the negatively charged Al IV centers of the CACs, suggesting a sodium-to-aluminum ratio of 1:1. The polymer hardens at temperatures between 4 and 65 °C. The workability is identical to that of ordinary Portland cement (OPC) and enables concrete structures to be cast at room temperature without additional energy supply. The new polymer has the potential to completely replace OPC in all its applications, but can reduce annual CO 2 emissions from OPC production worldwide from the current 8% to less than 2%.

Despite cement’s superior performance and inexpensive cost compared to other industrial materials, crack development remains a persistent problem in concrete. Given the comparatively low tensile strength, when cracks emerge, a pathway is created for gas and water to enter the cementitious matrix, resulting in steel reinforcement corrosion which compromises the durability of concrete. Superabsorbent hydrogels have been developed as a novel material for enhancing the characteristics of cementitious materials in which they have been demonstrated to decrease autogenous shrinkage and encourage self-healing. This study will detail the design and application of polyelectrolyte hydrogel particles as internal curing agents in concrete and provide new findings on relevant hydrogel–ion interactions. When hydrogel particles are mixed into concrete, they generate their stored water to fuel the curing reaction that results in less cracking and shrinkage, thereby prolonging the service life of the concrete. The interaction of hydrogels with cementitious materials is addressed in this study; the effect of hydrogels on the characteristics and self-healing of cementitious materials was also studied. Incorporating hydrogel particles into cement decreased mixture shrinkage while increasing the production of particular inorganic phases within the vacuum region formerly supplied by the swollen particle. In addition, considering the control paste, cement pastes containing hydrogels exhibited less autogenous shrinkage. The influence of hydrogels on autogenous shrinkage was found to be chemically dependent; the hydrogel with a delayed desorption rate displayed significantly low shrinkage in cement paste.