A 10 % phosphorus slag was used as a silicate and calcium raw material to produce Portland clinker, but this caused delays. The study found that when the designed content of C4A3$ was 7.5 % and the calcination temperature was 1350 degrees C, the clinker showed optimal performance. The XRD and petrographic analysis indicated excellent mineral development in the clinker, which could be due to the addition of sulfur and CaF2, lowering the liquid phase formation temperature and promoting mineral-forming reactions. Furthermore, its mechanical properties improved compared to clinkers made from the same raw materials without C4A3$, even slightly exceeding those of ordinary Portland clinker (OPC). Most importantly, with a designed 7.5 % C4A3$ in the mineral composition, the clinkers' setting time was shortened. This is because a large amount of ettringite (AFt) forms during the early hydration stage, which not only shortens the setting time, but also improves the early mechanical properties. The study also explained the formation mechanism of C4A3$-modified Portland clinker, providing a theoretical basis for the stable production of this clinker type using solid waste, particularly phosphorus slag.
To address the issues of shrinkage cracking and poor volume stability in steel slag-based UHPC (SS-UHPC), this study utilised temperature and humidity sensors along with a smart shrinkage and expansion monitoring device. The effects of expansive agents (EAs), shrinkage-reducing agents (SRAs), pre-wet ceramic aggregate (PW-CA), and their various combinations (EA with SRA, EA with PW-CA, SRA with PW-CA) on the shrinkage behaviour of SS-UHPC were investigated, resulting in an effective autogenous shrinkage control strategy with excellent shrinkage reduction. The results showed that the addition of EA and SRA reduced the expansion of SS-UHPC, while the incorporation of PW-CA significantly enhanced its expansion. The use of individual EA, SRA, and PW-CA resulted in a clear reduction in the total autogenous shrinkage of SS-UHPC. Notably, incorporating 6 % EA and 0.8 % SRA significantly reduced the autogenous shrinkage throughout the process. The shrinkage-reducing effect of SS-UHPC with PW-CA was relatively weak, but incorporating 10 % PW-CA showed the best shrinkage reduction. The combined use of EA, SRA, and PW-CA did not show significant reductions in the overall autogenous shrinkage of SS-UHPC. Overall, the combined shrinkage-reducing effect was less effective than using individual agents, with the combination of EA and PW-CA showing significantly better shrinkage reduction than other combinations. This study found that there is a proportional relationship between different shrinkage-reducing materials, and that an appropriate combination ratio significantly affects the autogenous shrinkage of SS-UHPC. The shrinkage-reduction methods developed in this study are comprehensive and effective, making a significant contribution to advancing the practical application of SS-UHPC in engineering.
Polymethyl methacrylate (PMMA) scaffolds were prepared through the granule casting method. The variables considered in the manufacturing of the scaffolds were the wet process, dry process, granule size (mesh), and sintering temperature. The novelty of this study: In the first stage, a solid cylindrical commercial PMMA was reduced in size using the Hot Cutting method (HCm) at different temperature variations. The products were then sieved with diversified mesh sizes, namely M 40-50, M 50-60, M 60-70, M 70-80, and M 80-100, to be treated with the granule casting method in aluminium moulds under the wet and the dry processes. The sintering process was established with a temperature of 130 degrees C, a holding time of 60 min, and a heating rate of 5 degrees C & centerdot;min-1. The best products were recommended to be treated in the next stage. In the second stage, PMMA scaffolds were made from the recommended products, namely the M 80-100 PMMA granules treated in the wet process. The sintering temperature was the variable that determined the scaffolds'physical and mechanical properties. The resulting PMMA scaffold was proven thus satisfying the quality criteria at the sintering temperatures of 125, 130, and 135 degrees C. The SEM images showed good interconnections between the pores in the PMMA scaffolds.
Supersulfated cement (SSC) is considered a promising low-carbon cement, but its low early strength largely limits its application. Compared with dihydrate gypsum, anhydrite shows a much higher dissolution rate, which could promote the formation of ettringite (AFt) and improve the early strength of SSC. In this study, fluorogypsum (FG), primarily composed of anhydrite, was used to prepare SSC. The influence of the FG fineness on the hydration and properties was investigated. The results show that increasing the FG fineness increases the water demand at normal consistency. However, the early-age dissolution rates of Ca2+, Al3+, and SO42-in SSC can be accelerated by an elevated FG fineness, thereby increasing the AFt saturation index (SI) and promoting AFt precipitation as the main hydration product of SSC. Therefore, increasing the FG fineness improves the 3-day compressive strength of SSC. At the hydration age of 28 days, with increased fineness, the amount of AFt also increases, while the amounts of mesopores and large pores decrease. Therefore, increasing the FG fineness improves the 28-day compressive strength of SSC. In addition, increasing the FG fineness could significantly reduce the drying shrinkage. This study provides practical guidelines for optimising the FG use in SSC and improving the early strength, thereby promoting its practical application.
Aluminosilicate refractories are not resistant to the alkaline corrosion that occurs during biofuel combustion. Therefore, the chemical corrosion of refractory materials significantly reduces the durability of the internal structures (lining), leading to unplanned shutdowns of biofuel production facilities and requiring additional repair costs. These risks increase even more when biofuel ash contains a higher amount of potassium and sodium, which can increase the impermissibly (more than 10 times) when preventive measures against biofuel freezing, such as alkaline salts, are used. This practically inevitably leads to the corrosion of aluminosilicate materials and the rapid disintegration of the lining made of such materials. A case of an accident in practice, due to the alkaline corrosion of the lining material, is presented in the work, along with laboratory tests to find out the cause. This article examines two different classes of refractory bricks and their resistance to alkaline corrosion. One is classified as a low Al2O3 refractory brick, the other as a premium highAl2O3 refractory brick. Two different reagents (potassium carbonate and sodium carbonate) and their mixture were used in the alkaline resistance tests performed by the crucible method. Furthermore, X-ray studies and thermodynamic calculations were performed using the FactSage program package.
Drinking water treatment sludge (DWTS) is a by-product generated during the purification of groundwater used for the drinking water supply in the municipality of Vilnius, Lithuania. A scientific work on the replacement of the binder (Portland cement CEMI42.5R), with drinking water treatment sludge (DWTS) in the mortar is presented in this research. DWTS was calcined at 850 degrees C for 4 hours and milled in a drum mill for 24 hours, before its incorporation into the mortar. The DWTS used in this study contains a high amount of Fe2O3 (seeking up to 68.2 %). The calcined DWTS was incorporated into the mortar by replacing up to 10 % of the binder by its weight (at increments of 2.5 %). The following mortar properties were tested: hydration time and temperature, density, ultrasonic pulse velocity, water absorption, porosity, compressive and flexural strengths. The predicted frost resistance was calculated according to the obtained research results. The results of the tests revealed that the calcined DWTS has a positive effect on the mortar properties. The closed porosity increased from 7.4 % to 8.4 %. The density of the concrete modified with 10 % DWTS decreased by 1.2 %. In all the cases, the replacement of Portland cement with DWTS resulted in a lower flexural strength, compared to the control com-position. However, the results of the compressive strength tests indicate that up to 5 % of the Portland cement can be replaced with DWTS without a loss of mechanical performance. In this study, the results of the compressive and flexural strengths were normalised and expressed in MPa & centerdot;kg(-1) to evaluate the strength achieved per unit weight of Portland cement. With the incorporation of DWTS into the mortar, the number of predicted freeze-thaw cycles increases thus extending the durability of the mortar.
The article analyses the effect of the crystalline chemical admixture content on the properties of self-healing concrete. The self-healing concrete properties and the effectiveness of crack sealing were tested. The effect of the crystalline chemical admixture content on the following properties of self-healing concrete were tested: the consistency, density, compressive strength, ultrasonic pulse velocity, water absorption, porosity and freeze-thaw resistance. The self-healing concrete was made of cement, a crystalline chemical admixture, sand, gravel, and water. The crystalline chemical admixture was added from 0 to 1.5 % by weight of cement. The test results showed that with the addition of the crystalline chemical admixture, the density, ultrasonic pulse velocity, compressive strength, and water absorption decrease, whereas the resistance to the freeze-thaw cycles increases. The analysis of the crack-sealing effectiveness revealed that the formation of crystals started at 14 days of curing, and, at 42 days, the cracks were totally sealed. Therefore, in the presence of the crystalline chemical admixture added at 1.5 % by weight of cement, the self-healing concrete can bridge the cracks as free cement particles hydrate in contact with water and fill the cracks. The obtained self-healing concrete with better durability properties can be used in concrete structures.
Chloride binding is a key factor affecting chloride-induced corrosion in reinforced concrete. Different types of chloride salts may exhibit distinct binding mechanisms. In this work, the influence of chloride salts (NaCl, MgCl2 , and CaCl2) on the chloride ion binding mechanism in alkali-activated slag (AAS) was investigated. The pH value, chloride ion binding capacity, and phase evolution of AAS were examined through various experimental and analytical methods. To compare the phase compositions of AAS after chemical equilibrium under exposure to different chloride solutions, thermodynamic modelling was employed to predict the phase assemblages in AAS. The study revealed that the type of chloride salt significantly influences the chloride-binding capacity and pore solution pH of AAS. The binding capacity followed the order: CaCl2 > MgCl2 > NaCl. Compared to CaCl(2 )and MgCl2 , exposure to the NaCl solution increased the pore solution pH of AAS, thereby reducing the solubility of Friedels' salt and MgAl-LDHs (layered double hydroxides) and releasing more bound chloride ions. The X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results demonstrated that AAS exposed to the CaCl(2 )solution exhibited the enhanced formation of C-A-S-H, which contributed to the higher physical adsorption of chloride ions. In the MgCl2 solution, magnesium plays a dual role: it reacts with C-A-S-H phases, leading to a reduction in the pore solution pH; it provides favourable conditions for the precipitation of MgAl-LDHs, thereby enhancing the chloride ion binding. Furthermore, within the water-to-binder ratio range of 0.35 - 0.45, increasing the ratio enhances the chloride-binding capacity of AAS, but has negligible effects on the pH of the pore solution.
Traditionally, increasing the modulus of water glass solution (soluble sodium silicate) requires increasing the silica content in batches, which are used to melt the binary Na2O-SiO2 glass precursor. This is only applicable for large-scale production and inevitably results in a high melting temperature and high energy consumption. Herein, porous silica powder was dissolved in a commercial water glass solution under moderate temperature heating condition. Thus, the modulus of the water glass solution was easily tuned from 3.06 to 3.87, providing a convenient way that is suitable for obtaining small quantities of water glass solution with a high modulus. The pH, density, viscosity and conductivity of the tuned solution were characterised in detail. The FTIR and 29Si NMR spectroscopy evidenced that the porous silica dissolved in the water glass solution, but its [SiO4] skeleton was largely preserved.
Sustainable ultra-high-performance concrete (UHPC) is an advanced cementitious composite known for its exceptional strength, ductility, and durability. However, its high cement content contributes significantly to the carbon footprint, and the addition of cementitious materials is recommended to address this. In this regard, research on metakaolin, a natural pozzolan, is important. However, metakaolin has been mainly used in combination with silica fume or with silica fume and other pozzolans like fly ash and slag. Studies on binary compositions of UHPCs with metakaolin are scarce in the literature. In the present study, compositions with varying cement contents, containing 15 - 25 % metakaolin, were investigated. The study also considered two other natural materials with some pozzolanic reactivity, zeolite and limestone powder, to understand their effectiveness. These mixtures are compared to pozzolan-free compositions and a conventional composition containing only silica fume. The main evaluations of the study focus on the mechanical strength performance, permeability properties, such as water absorption, pore permeability, sorptivity, acid resistance, chloride penetration, and carbonation. In addition, factors, such as the GWP, carbon footprint and cost, were analysed to assess the environmental sustainability of UHPFRC compositions incorporating metakaolin.
To minimise carbon emissions from cement production, high-belite cements are being increasingly used to optimise the fresh and hardened cement strength. However, the hydration kinetics and reactions of belite remain poorly understood. A systematic, time-resolved study of belite hydration behaviour was conducted, focusing on the hydrate morphology of 20nm to 2-mu m diameter belite particles using X-ray powder diffraction and scanning electron microscopy. Reactions were investigated at room temperature (21 degrees C), 80 degrees C and 200 degrees C, over periods from 6 hours to 42 days. The hydration rate was strongly influenced by the size and shape of the starting material, as well as the temperature. The predominant product in all the samples is a calcium silicate hydrate (C-S-H) of poor crystallinity which can be found in different morphological forms. The crystallisation of calcium hydroxide (CH) began when the solution became oversaturated with Ca2+ and OH- ions. When exposed to ambient air, calcium carbonate formed, in direct contrast to the hydration behaviour of Ordinary Portland cement, in which the formation of calcium carbonate was insignificant. Since the hydration of pure belite proceeds slowly in water at room temperature, the development of the strength in cements with a high belite content within a reasonable time requires the incorporation of specific additives and alloys that accelerate the hydration.
Hydroxyapatite (HA) is a bioceramic of considerable interest in orthopaedic and dental applications due to its compositional similarity to natural bone and teeth. However, achieving the precise control over its crystallinity and surface area remains a challenge for enhancing the bioactivity and clinical performance. In this study, HA was synthesised via controlled precipitation by titrating (NH4)2HPO4 into Ca(NO3)2 with syringe-assisted feeding, followed by calcination at 600 degrees C for 5 h. The influence of the polyethylene glycol (PEG), pH adjustment, phosphate feed rate, and syringe needle size was systematically examined. Among these parameters, the phosphate feed rate was identified as the most critical factor affecting both the crystallite size and specific surface area. A feed rate of1 mL/min produced the highest surface area (45.55 m2.g-1), compared to 37.85 m2.g-1 at 3 mL min-1, while also maintaining favourable alkaline conditions forHA nucleation and growth. These findings demonstrate that the careful regulation of feed parameters enables the reproducible tailoring ofHA structural features without complex synthesis routes. The approach provides a simple and scalable pathway for producing high-surface-area HA, offering new opportunities for the development of advanced biomaterials for medical and dental applications.
The poor surface metallurgical quality of machined graphite mould titanium alloy castings is one of the key issues limiting their application. A surface coating treatment was applied to the graphite mould, and its improvement effect was studied. Using small-batch titanium alloy nozzle shell castings as the subject, GSK fine-particle graphite was machined to prepare the mould, and an inert surface coating formulated from high-purity fused Y2O3 powder and zirconium acetate binder was applied. Comparative analysis experiments were conducted after casting. The focus was on exploring the coating's effects on the surface appearance, fluorescent defects, X-ray defects, and surface alpha layer of the titanium alloy castings. After surface coating the graphite mould, the surface roughness of the titanium castings decreased from 3.473 similar to 14.560 mu m to 2.116 similar to 6.153 mu m; the number of fluorescent defects decreased by 73.2%, with linear defects reduced by 91.8%; there was no significant difference in the internal defects of the castings; and the thickness of the surface alpha layer decreased from 185 mu m to 136 mu m. The surface coating can effectively improve the poor metallurgical quality of machined graphite mould titanium alloy castings and has good potential for promotion in engineering applications.
Isothermal calorimetry quantifies the heat flow of cementitious materials during hydration. The paper summarises the calorimetry results from 65 industrially produced cements manufactured between 2018-2025 in the central European region. The hydration proceeds under 20 degrees C, covering a wide range of Portland cements (CEM I), Portland-slag/limestone/composite cement (CEM II), blast furnace cement (CEM III), composite cements (CEM V), alkali-activated cement and sulfocalcic cement. The water/cement ratio was kept in a range of 0.40-0.50, the shortest measurement time took 237 h and the mean time was 421 h. Each cement is approximated with a four-parametric affinity hydration model with a standard deviation error as 4.11 J center dot g-1 and 11 selected cements are approximated with a simpler exponential model. The comprehensive database can serve for the prediction of the microstructure, mechanical properties, or temperature rise in massive concrete structures.
Adhesion is one of the key properties of unshaped refractories, such as repair, shotcrete, mortar mixtures and others. Several standard methods for measuring the adhesive properties are available in the field of polymer materials, while their number is almost zero in the case of refractory materials. The aim of the work is to develop a methodology for the adhesion measurement of fresh refractory mixtures during their setting based on a standard test used to evaluate the adhesion of paints, grouts, mortars, and concrete with a substrate. The principle of the method consists in cyclically tearing off the measuring probe from the tested mixture and recording the applied force. The results are compared with other methods used to evaluate the setting progress, such as the rotary viscometer and the Vicat needle. The applicability of the method is verified for the dependence of the adhesion on the temperature of the refractory mixture.
As the construction industry continuously develops, people increasingly require better building materials. Traditional concrete materials struggle to meet these demands due to their high brittleness, low compressive strength, and weak corrosion resistance. To solve these problems, this study optimises concretes' mechanical properties by introducing prepared nano--SiO2 and glass fibres. This approach aims to improve the compressive strength, flexural strength, and corrosion resistance of concrete. After analysing the various properties of the prepared nano-SiO2 glass fibre concrete, it was found that the permeability coefficient of the concrete decreased from 5x10-12 to 1x10-12 m center dot s-1, and the water absorption rate of the concrete decreased to 2.2 %. In addition, in testing the mechanical performance of concrete, the compressive strength of the nano-SiO2 glass fibre reinforced concrete increased by 18.3 MPa, and the flexural strength increased from 5.3 to 9.2 MPa. These results demonstrate that nano-SiO2 and glass fibres can significantly improve the mechanical properties, corrosion resistance, and permeability of concrete. This study offers the construction industry a high-performance and durable composite material that meets the requirements of modern engineering for building materials.
This study investigates the influence of the curing conditions on the mechanical performance of a geopolymer mortar synthesised from fly ash (FA) and ground granulated blast-furnace slag (GGBS). These industrial by-products serve as a low-carbon alternatives to conventional cement, enabling reduced CO2 emissions and efficient waste utilisation. Fourteen geopolymer mortar mixtures were prepared using different fly ash:ground granulated blast-furnace slag ratios (50:50, 30:70, and 70:30). They were activated using an alkaline solution composed of a sodium hydroxide (SHS) solution at different molarities (2.5 M, 5 M, 7.5 M, and 10 M), and a sodium silicate solution (SSS). The alkaline solution was formulated by combining sodium hydroxide flakes (SHFs) and a sodium silicate solution (SSS) in varying ratios from 1:1 to 1:3. The geopolymer mortars were subjected to four curing regimes: ambient curing, water curing, oven curing, and steam curing. The mechanical performance was assessed in terms of the compressive and flexural strength. The results show that the water curing notably enhanced the strength in the mortars with equal proportions of FA and GGBS (50:50), activated with high molarities of the sodium hydroxide solution (5 M to 10 M) compared to ambient conditions. The oven and steam curing facilitated a rapid early strength gain, though the later-age strength gain is limited. The study highlights the crucial role of the curing type and duration in influencing the strength development and structural integrity. The steam-and oven-cured GP mortars with equal FA and GGBS proportions achieved approximately 98 %, 80 %, and 79 % of their 28-day strength at the 14th day when activated with 5 M, 7.5 M, and 10 M SHS, respectively. These findings provide valuable guidance for optimising the curing strategies to enhance the performance and sustainability of geopolymer mortars in ecoconscious construction practices.
Ensuring the adequate workability of cementitious coatings presents significant challenges in increasingly complex service environments. This study systematically investigates the effects of the cement particle size, water reducers and silica fume content on the workability of cement-based coatings. The individual impacts of these factors on the rheological properties (apparent and plastic viscosity) and bleeding ratio were first analysed. Subsequently, orthogonal experiments were employed to identify the optimal formulation. The results indicate that: (1) finer cement particles increase the slurry stability, but also increase the viscosity (reducing flowability), (2) the water reducer addition enhances the flowability, but reduces the stability (3) and the silica fume incorporation decreases the flowability, but significantly improves the stability. Considering practical performance requirements, the optimal formulation comprises cement with particle size O1, a superplasticiser dosage of 0.6 %, and a silica fume content of ]0 %. This research provides fundamental insights for optimising cementitious coating formulations and contributes to the development of high-performance construction materials.
High-purity SiC-ZrC composite powders were successfully synthesised via a carbothermal reduction method using zirconium silicate (ZrSiO4), silica sol, and carbon black as the raw materials. The synthesis involved the systematic control of the calcination temperature (1450-1650 degrees C), holding time (1-4 h), and SiC/ZrC mass ratio (7/3, 5/5, 3/7). The effects of these parameters (SiC/ZrC ratio, calcination temperature, holding time) on the phase composition, weight loss rate, and microstructure of the SiC-ZrC composite powders were thoroughly investigated, and the underlying reaction mechanism was elucidated. The XRD analysis and weight loss measurements revealed that: ZrSiO4 begins to decompose, generating a small amount of SiC at 1450 degrees C; the reaction is essentially complete, yielding high-purity SiC and ZrC, by 1500 degrees C; temperatures of 1550 degrees C and above further enhance the crystallinity. Elevated temperatures significantly shorten the required reaction time, with the reaction completing within 1 h at 1550 degrees C, compared to 4 h at 1450 degrees C. The SEM observations demonstrated that the quantity and size of SiC whiskers are regulated by the calcination temperature, holding time, and SiC/ZrC ratio. Higher temperatures or prolonged holding times increase the whisker diameter, but reduce their number. The formation of the SiC-ZrC composite powder follows a multi-step reaction mechanism: ZrSiO4 completely decomposes into highly reactive ZrO2 and SiO2 at 1500 degrees C. Subsequently, SiO2 is converted to SiC via gas-solid or gas-gas reaction pathways, while ZrO2 is converted to ZrC either through direct carburisation or via an intermediate ZrO (g) species. This study provides both theoretical and experimental foundations for the precise synthesis of SiC-ZrC composite powders with controlled composition and morphology.
This study investigates the coloration mechanism of Lang red glaze by exploring the coupling among the microstructure, copper valence states, and optical properties under crystal nuclei induction. Using K-feldspar, kaolin, CuO, and SnO2, the glaze formulation was optimised through single-factor and L-9(3(4)) orthogonal experiments. The influence of the process parameters-such as the ball milling time, glaze thickness, and firing temperature-was also evaluated. The XRD analysis confirmed an amorphous glass matrix with minor anorthite crystallisation. The SEM and EDS revealed a worm-like phase-separated structure with nanoscale domains (similar to 28 nm) conducive to Mie scattering. The XPS indicated that the copper exists predominantly as Cu+ (80.94 %), with SnO2 assisting in its stabilisation and in the uniform formation of Cu2O colloids. These results support a ternary colouration mechanism driven by "crystal nucleation-valence control-optical scattering," where phase separation facilitates the spatial distribution and optical enhancement of copper colloids. This work provides a scientific basis for recreating stable red glazes and offers insights into traditional Chinese ceramic aesthetics from a materials science perspective.
