Improvement In Compressive Strength Research Articles

Microstructure and Phase Characterization of Alkali-Activated Slag–Fly Ash Materials with Tetrasodium of 1-Hydroxy Ethylidene-1, 1-Diphosphonic Acid (HEDP·4Na)

The effect of tetrasodium of 1-hydroxy ethylidene-1, 1-diphosphonic acid (HEDP·4Na) on the microstructure and phase characterization of alkali-activated fly ash–slag (AAFS) materials is not clear or well documented. In this study, XRD, DTG, TAM-air, and SEM analyses of AAFS were used to identify the microstructural changes in AAFS made with HEDP·4Na. Meanwhile, the workability and compressive strength of AAFS were evaluated. The results demonstrated that the early-age alkaline-activated reactions were retarded due to the addition of HEDP·4Na in the AAFS mixture. However, the degree of gel formation was relatively increased at a later age in the AAFS made with HEDP·4Na compared to the plain AAFS mixture. Additionally, in comparison to the control group, the incorporation of HEDP·4Na in AAFS specimens resulted in improved flowability, with increments of 5%, 15%, and 24% for concentrations of 0.1%, 0.2%, and 0.3%, respectively. The initial and final setting times were prolonged by 5% to 50%, indicating a beneficial impact on the rheological properties of the AAFS fresh mixture. Furthermore, the addition of HEDP·4Na led to an improvement in compressive strength in the AAFS mixtures, with enhancements ranging from 13% to 16% at 28 days compared to the control group. With the presence of HEDP·4Na, the increase in the degree of reactions shifted to the formation of gel phases, like C-S-H, through the combined measurement of TGA, XRD, and SEM, resulting in a denser microstructure in the AAFS matrix. This study presents novel insights into the intricate compatibility between the properties of AAFS mixtures and HEDP·4Na, facilitating a more profound comprehension of the potential improvements in the sustainable development of AAFS systems.

Scalable fabrication of collagen fiber-waterborne polyurethane foams with enhanced toughness and thermal insulation by constructing energy dissipation networks

Natural fiber-based foams demonstrate outstanding potential for energy-efficient building and personal protective equipment applications due to their lightweight, high porosity, and sustainability. However, the weak interfacial interaction among fibers, functional additives, and the matrix hampers effective stress dissipation, largely affecting the material performance. Herein, this paper demonstrates a facile strategy for fabricating high-performance collagen fiber-based foams by constructing efficient energy dissipation networks using tannin-modified leather collagen fibers (T-LCF) and waterborne polyurethane (WPU). Tannin acts as a coupling bridge, linking the fiber and polyurethane to create a hydrogen-bonded network, enhancing energy dissipation and imparting excellent mechanical properties. Compared to WPU foam (WPUF), the T-LCF-based foam (WPUF/T-LCF) showed 65%, 34 times, and 35% improvements in tensile strength, compressive strength, and ultimate oxygen index, respectively. This study provides new insights into the cleaner production of high-performance natural fiber-based foam composites and a new way for the high-value utilization of collagen solid waste.

Effect of titanium dioxide on fresh and mechanical properties of Mortar: A review

Nanotechnology-based engineering approaches are rapidly developing throughout the world. Modern, cutting-edge nanotechnology has proven useful in a variety of technical applications. In emerging and developed countries, increasing infrastructure needs a considerable amount of cement, which has a significantly impact on the environment and human health, resulting in greenhouse gas emissions and severe acute respiratory illnesses (asthma and silicosis, respectively). To overcome such difficulties, cement consumption in building materials must be reduced. Several novel extra materials have lately been introduced to improve the performance of mortar. Nano-titanium dioxide (NT) in cement mortar is widely used in green building construction because NT capable to the degradation of air pollution, self-cleaning, and enhancing mechanical, microstructural, and durability properties. In this paper, the effect of NT on fresh and hardened properties of cement mortar has been discussed. For the collection, screening and implementation of data for review paper PRISMA analysis and VOSviewer technique was used. Existing literature indicates that the reduction in workability 15% − 20% whereas improvement in compressive strength (CS) up to 15% and tensile strength up to 45% was noted with NT in mortar. Current research supports using NT as a cement replacement in mortar. Aside from the key findings, some identified gaps, problems, and future scope challenges have been presented in order to develop NT based mortar as a sustainable material in the building sector.

Examining Mechanical Property Differences in Concrete with Natural and Synthetic Fiber Additives

The rapid growth of Natural Fiber Laminate (NFL) innovation is a direct response to environmental challenges, positioning these materials as superior alternatives to synthetic fiber composites. This paper delved into the outcomes of an extensive experimental study investigating the influence of sisal fiber (SLF), banana fiber (BF), and glass fiber (GF) on the mechanical and microstructural characteristics of concrete. The water absorption curves were established for sisal fiber concrete (SLFC), banana fiber concrete (BFC), and glass fiber concrete (GFC). Furthermore, Scanning Electron Microscope (SEM) observations were conducted to perform microanalysis and failure analysis of the tested specimens. The results revealed significant improvements in the concrete containing fibers compared to its counterpart in fiber-free concrete. For mixtures with a water-to-binder (W/B) ratio of 0.3, the most optimal mix (GF-30-135) showed improvements in compressive strength, flexural strength, and splitting tensile strengths by 4.13%, 8.93%, and 10.10%, respectively. On the other hand, for W/B of 0.4, mix GF-30-135 showed improvements of 5.05%, 8.55%, and 11.60%, respectively. Furthermore, as the fiber content increased, microscopic analyses revealed a weakening of the bond between the fibers and the rest of the matrix, contributing to the deterioration of the mechanical properties.

Radiation shielding properties of heavy-weight concrete and heavy-weight geopolymer concrete incorporating nano-ZnS

The population growth and the subsequent increase in energy demand for buildings require the widespread use of sustainable materials in the construction industry. Therefore, geopolymer concretes (GPC) are expanding with the ability to emit less greenhouse gases (GHG) compared to conventional concrete. In this study, the effect of adding different content of Zinc sulfide nanoparticle (nano-ZnS) 0, 1.5, 3, 4.5, and 6 % by weight of cement on density (ρ), compressive strength, gamma ray radiation protection characteristics, and microstructure based on scanning electron microscope (SEM) is investigated in heavy-weight concrete (HWC) and heavy-weight geopolymer concrete (HGC). The results have shown that nano-ZnS nanoparticles improve the strength and gamma ray shielding properties of HWC and HGC by modifying the microstructure so that by adding the optimal amount of 6 % nano-ZnS, the maximum compressive strength for HWC and HGC was obtained by 57.4 and 41.5 %, respectively. In addition, the highest linear attenuation coefficient (µ)was obtained with the addition of 4.5 % nano-ZnS for HWC and HGC, 12.8 and 8.9 %, respectively.Furthermore, the life cycle assessment (LCA) of the three phases of raw material production, transportation and concrete production has revealed that HGC has emitted 41.5 % less CO2 compared to HWC. In general, HGC in the presence of the optimal amount of nanoparticles has shown a more visible improvement in compressive strength and gamma ray shielding properties. In addition, HGC as an environmentally friendly material, has significantly reduced the emission of CO2.

Effects of YSZ and CA6 additives on densification and thermal shock resistance of Al2O3-MgO-CaO-Y2O3 refractories

To achieve high-quality and stable production of modern clean steel, novel Al2O3-MgO-CaO-Y2O3 refractories with enhanced sintering properties and thermo-mechanical properties were synthesized by introducing YSZ and CA6 as the reinforcers. A sintering reaction mechanism involving the Al2O3-MgO-CaO-Y2O3 quaternary system is proposed. The results show that the sintering process in the Al2O3-MgO-CaO-Y2O3 quaternary system was characterized by the sequential formation of Al5Y3O12→YAlO3→Y4Al2O9→Y2O3 in three distinct stages, resulting in the predominant phases of Al5Y3O12 and MgAl2O4. The YSZ addition on Al2O3-MgO-CaO-Y2O3 refractories promotes the complete reaction between Y2O3 and CaAl4O7, fostering the formation of additional Al5Y3O12, which significantly enhances the densification, leading to improvements in both compressive strength and thermal shock resistance. The addition of CA6 promotes the generation of more Al5Y3O12, which forms numerous pores during the three stages of the sintering process, and the distribution of these pores is uncontrollable. Therefore, based on the sintering reaction mechanism of the Al2O3-MgO-CaO-Y2O3 quaternary system, a low-cost and enforceable reinforcement strategy for Al2O3-MgO-CaO-Y2O3 refractories is proposed, which is expected to focus on the application of YSZ in Al2O3-MgO-CaO-Y2O3 refractories for clean steel smelting.

Influence of basalt fiber and polypropylene fiber on the mechanical and durability properties of cement-based composite materials

To boost the mechanical strength and endurance quality of cement-based composites, basalt fiber and polypropylene fiber have been included cement-based composites in a single-doped and mixed manner, respectively. Through the tests of flexural strength, compressive strength, drying shrinkage and freeze-thaw cycle, the mechanics properties and endurance quality of cement-based composites with different fiber contents were analyzed. Scanning electron microscopy and a mercury intrusion test were used to compare and study the microstructure and pore structure properties of cement-based composites. The results indicate that the improvement of compressive strength for cement-based composites by single adding basalt, polypropylene fiber and mixed addition of two kinds of fibers is not obvious, but improving the flexural strength of composites by single addition of fiber and 1:1 mixing in a certain dosage range is effective. Among them, 1:1 mixed fiber shows a better advantage superposition effect, which shows better enhancement and toughening effect on composites. Fiber single doping and 1:1 mixing can reduce the Drying shrinkage and mass loss rate of the composites within a certain range, and enhance the composites' ability to resist Drying shrinkage and freezing. Based on the comprehensive mechanical properties and durability tests, it is recommended that the content range of the two fibers mixed with 1:1 is 0.4 %–0.6 %. Both basalt fiber and polypropylene fiber can be closely combined with the cement matrix, and randomly distributed in the composite material to form a network structure, which has the function of series skeleton, effectively inhibits the generation and expansion of cracks in the composite material, and improves the microstructure of the composite material. Both basalt fiber and polypropylene fiber can reduce the harmful pores and multi-harmful pores of the composite material, and transform them into harmless pores and less harmful pores, refine the internal pore structure of the composite material, and improve its compactness. The two kinds of fibers are randomly distributed to form a network structure, which refines the large pore size inside the composite material and blocks the connected pores, and the basalt fiber is refined to fill the interface between the polypropylene fiber and the cement matrix, so that the composite material is more compact, thereby significantly improving the mechanical properties and durability of the composite material.

Prediction improvement of compressive strength and strain of directionally solidified TiAl alloy based on training data size adjustment

Compressive strength and compressive strain, which are important mechanical properties of directionally solidified TiAl alloy, were predicted using machine learning algorithms, specifically Multiple Linear Regression (MLR), and Random Forest Regression (RFR). The input variables for the machine learning model were designated as the composition of the directionally solidified TiAl alloy, experimental parameters (pulling velocity, input power), and compression test parameters (strain rate, compression temperature). Compressive strength and compressive strain were designated as the output variables. Although the typical ratio of training and test data is 8:2, this study used different ratios of 9:1, 7:3, and 6:4 for machine learning, and excellent R2 values were obtained for all ratios. The feature importance, which can identify the factor that has the most influence on the output variables, was obtained through the RFR algorithm. According to the feature importance, temperature was found to have the greatest influence on compressive strength, while the Erbium (Er) element had the most significant influence on compressive strain. Through the results of feature importance, it was possible to quantitatively investigate the relationship between the Er element, a microalloying element that affects the microstructure of TiAl alloy, and the compressive properties. Furthermore, the study was conducted on which data ratio between training and test data is most suitable for predicting the compressive strength and strain of TiAl alloy.

Enhancing marine anti-washout concrete: Optimal silica fume usage for improved compressive strength and abrasion resistance

The anti-washout concrete (AWC) made with seawater and sea sand has a limited marine infrastructure application due to its unfavorable properties. Our study proposes an effective performance enhancement method for AWC using silica fume. A comprehensive examination was carried out to investigate the effects of silica fume on AWC's flowability, anti-washout ability, compressive strength, microstructure, permeability, and abrasion resistance, with the AWC prepared with seawater and sea sand, and molded in seawater. It was discovered that 10 % silica fume can most effectively improve the performance of AWC. This enhancement is due to the pore structure refinement realized with C-S-H gel generated from pozzolanic reaction. Exceeding 10 % silica fume content can have a detrimental effect on the slump-flow of mixtures, while only providing marginal improvements in impermeability and compressive strength. The study lays a fundamental groundwork for the wide use of sea-based resources and the application of AWC in marine engineering.

Enhancing Concrete Mechanical Properties through Basalt Fibers and Calcium Sulfate Whiskers: Optimizing Compressive Strength, Elasticity, and Pore Structure.

To study the effects of basalt fibers (BFs), calcium sulfate whiskers (CSWs), and modified calcium sulfate whiskers (MCSWs) on the compressive strength and dynamic modulus of elasticity of concrete, this paper utilizes Mercury Intrusion Porosimetry (MIP) to measure the microstructure of concrete and calculate the fractal dimension of pore surface area. The results indicate that both CSWs and BFs can increase the compressive strength of concrete. CSWs can enhance the dynamic modulus of elasticity of concrete, while the effect of BFs on the dynamic modulus of elasticity is not significant. The improvement in compressive strength and dynamic modulus of elasticity provided by MCSWs is significantly greater than that provided by CSWs. Both CSWs and BFs can effectively improve the pore structure of concrete and have a significant impact on the surface fractal dimension. CSWs inhibit the formation of ink-bottle pores, while BFs increase the number of ink-bottle pores. Due to the ink-bottle pore effect, the fractal dimension of the capillary pore surface is generally greater than three, lacking fractal characteristics. The compressive strength and dynamic modulus of elasticity of concrete have a good correlation with the fractal dimensions of large pores and transition pores.

Enhanced mechanical property of steel slag through glycine-assisted hydration and carbonation curing

Steel slag, an industrial by-product from the steelmaking process, has limited utilities primarily due to its low reactivity and grindability. This study proposed a new method to actively utilize steel slag as a cementless binder by adding glycine to enhance the reactivity of steel slag under CO2 curing condition. Employing glycine as an activator under 1 day of hydration followed by 7 days of carbonation curing resulted in noticeable densification of the microstructure and significant improvement in compressive strength. The compressive strength of seven-day carbonated steel slag with 3 wt% glycine reached 77.8 MPa. This improvement was due to the accelerated hydration of brownmillerite (C2F) and gradual carbonation during the carbonation period. While C2F was merely reactive without glycine, the hydration of C2F was significantly stimulated by glycine addition, producing hydrogarnet, CO32--bearing AFm phases, and amorphous phases. During the carbonation curing, AFm phases and hydrogarnet were carbonated and formed various polymorphs of CaCO3 and amorphous Al(OH)3. Adding 3 wt% and 5 wt% of glycine decreased the degree of carbonation, preserving the quantity of AFm phases and hydrogarnet. The use of glycine also made the pores finer and induced the reaction of RO phase to form pyroaurite.

Effect of olive waste ash on the properties of high‐strength geopolymer concrete

AbstractThis study examines the effect of incorporating olive waste ash (OWA) into high‐strength geopolymer concrete (HSGC) by partially replacing fly ash (FA) and/or granulated blast furnace slag (GBFS) in the presence of rice husk ash (RHA). A total of 18 different mixtures were prepared and divided into three groups: (1) Utilizing OWA as a partial replacement for FA at a weight ratio of 10%–50%. (2) Incorporating OWA as a partial substitute for GBFS, with a weight ratio of 10%–50%. (3) Incorporate OWA as a partial substitute for FA and GBFS, with a recommended weight ratio of 10%–50%. The slump flow test was used to analyze the fresh properties of the HSGC. The hardening properties were examined by measuring the compressive strength, tensile strength, flexural strength, and modulus of elasticity. Furthermore, an analysis was conducted on the water absorbency, sulfate attack, and chloride penetration depth. A scanning electron microscope was used for the microstructural analysis. The inclusion of OWA in HSGC mixtures resulted in a significant enhancement of the compressive strength. Specifically, adding 20% OWA to FA increased the compressive strength by 8.9% at 28 days. Similarly, 30% OWA for GGBS and 30% OWA for GGBS + FA led to compressive strength improvements of 20% and 17.8%, respectively. OWA application resulted in an enhanced microstructure density of the HSGC samples. The ideal substitution ratio varied between 20% and 30% based on weight.

Fabrication and mechanical properties of multi-principal cation (Mg,Ti,Cr,Zr,Al,Si) mullite ceramic

Milti-principal cation oxide ceramics with excellent mechanical properties for potential applications in coating materials. A Multi-principal cation mullite (MPCM) ceramic is synthesized with MgO, TiO2, Cr2O3, ZrCl2O·8H2O and Al2O3, SiO2 via solid state reaction at 1600 °C. It is determined that 96.9 % of the sample composition is mullite. MPCM ceramic exhibits higher compressive strength (981 ± 19 MPa) and fracture toughness (3.37 ± 0.05 MPa∙m1/2), the compressive strength has raised by 453 MPa, and the added value of solution strengthening (452 MPa) is gained by using solid-solution strengthening theory. The improvement of compressive strength is mainly due to the solution strengthening effect of the four oxides(Mg, Ti, Zr, Cr), and the improvement of fracture toughness is caused by the grain hindrance during crack propagation. Moreover, its application at the high-temperature resistant coating is verified through experimentation. The interfacial binding force, as an important mechanical property index for ceramics, is researched. In this study, pure mullite powder and MPCM powder are coated onto the refractory TaWNbV alloy matrix by slurry coating method, and the interfacial toughness of the two coatings mingled with the matrix is calculated to be 72.9 and 62.6 J·m−2, respectively. The “shrinking cylinder” model is introduced to interpret the oxidative weight gain mechanism of the two coatings.

Augmenting bamboo strength and thermal stability for sustainable construction

In modern timber structures, the prevalent use of metal fasteners for structural connections introduces concerns related to their high thermal conductivity, which can induce excessive charring of adjacent wood and compromise joints fire resistance. To address this, the exploration of high-strength bio-materials presents a promising alternative. In this study, an eco-friendly methodology was employed to augment the densification of bamboo, resulting in the creation of composite-modified bamboo without the use of organic thermosetting resin. Comprehensive investigations were conducted to evaluate its mechanical properties and high-temperature performance. Microscopic alterations were unveiled through Fourier Transform Infrared spectroscopy (FT-IR) and scanning electron microscopy, complementing each other in revealing substantial changes. The results of chemical constituents and FT-IR analyses corroborated the observed alterations. A noteworthy observation is that the modification of composite materials significantly increased modulus of elasticity, bending, and tensile strengths of bamboo, with a slight improvement in compressive strength. Additionally, it concurrently enhanced ductility. The thermal stability of composite-modified bamboo exhibited an initial increase followed by a subsequent decline over duration. The increased density induced by hot pressing facilitated the formation of a denser charring layer, effectively serving as a protective shield against external heat and oxygen. Consequently, this limited the degradation of bamboo constituents under high-temperature conditions. The optimal alkaline treatment duration for 9 mm thick bamboo was determined as 7 h based on the methodology established in this investigation.

Development of sustainable engineered cementitious composite with enhanced compressive performance at elevated temperatures using high volume GGBFS

This study presents the development of an environmentally sustainable hybrid polyethylene (PE)-steel fibre reinforced engineered cementitious composites (ECC) to achieve enhanced compressive performance at elevated temperature. Utilizing a unique blend of industry by-products—ground granulated blast furnace slag (GGBFS), dolomite powder, and fly ash, with supplementary cementitious materials exceeding 50% replacement level, the developed ECC achieves remarkable improvement in compressive strength, both at ambient and elevated temperature conditions. A total of 340-cylinder specimens were tested to analyse the compressive properties after exposure to 20–800 °C, and the effect of different binders, fibre ratio on the residual compressive behaviour was investigated. Additionally, effects of the critical fire test parameters such as pre-drying and cooling treatment were also studied. The research findings indicate that incorporating high-volume GGBFS blends significantly improved the compressive performance of the ECC irrespective of the type of test parameters. Notably, a specific blend comprising of GGBFS, fly ash (GGBFS:fly ash = 1:0.2) and dolomite (15% by binder weight) demonstrated 138 MPa strength at room temperature and at least 75% and 45% strength retention at 600 °C and 800 °C, respectively. This was significantly higher than the values reported in literatures (∼48% at 600 °C and ∼12% at 800 °C) for similar type of ECC. The study also highlights the impact of sudden cooling in water and confirms the occurrence of both thermal shock and rehydration through microstructural analysis. Environmental impact analysis was also conducted to demonstrate the low carbon emission of the developed ECC.

Preparation and Characterization of Date Palm Bio-Oil Modified Phenolic Foam.

In this work, the potential of biomass-derived date palm bio-oil as a partial substitute for phenol in the phenolic resin was evaluated. Date palm bio-oils derived from date palm were used for the partial substitution of phenol in the preparation of phenolic foam (PF) insulation materials. Date palm waste material was processed using pyrolysis at 525 °C to produce bio-oil rich in phenolic compounds. The bio-oil was used to partially replace phenol in the synthesis of phenolic resin, which was subsequently used to prepare foams. The resulting changes in the physical, mechanical, and thermal properties of the foams were studied. The substituted foams exhibited 93%, 181%, and 40% improvement in compressive strength with 10%, 15%, and 20% bio-oil substitution, respectively. Due to the incorporation of biomass waste material, the partial reduction in phenol uses, and the favorable properties, the date palm bio-oil substituted phenolic foams are considered more environmentally benign alternatives to traditional phenolic foams.

Mechanical properties and microstructure of brick aggregate concrete with raw fly ash as a partial replacement of cement

In response to environmental concerns, researchers explore fly ash as a cement replacement material, and crushed bricks as a cost-effective and load-reducing aggregate, particularly where stone chips are scarce. Therefore, this study investigates the mechanical properties and microstructure of brick aggregate concrete (BAC) with raw fly ash (FA) as a partial replacement of cement. The research involved casting raw FA based BAC (FBAC) cylinders (100 mm diameter and 200 mm height) and prism (100 × 100 × 500 mm) with varying levels of FA (0–25%) using a constant mix proportion by volume of 1:1.5:3 (cement : fine aggregate : coarse aggregate) with a water to binder (w/b) ratio of 0.50 and three curing ages (7, 28, and 90 days). Tests for mechanical properties, including compressive strength, split tensile strength, flexural strength, modulus of elasticity, and Poisson's ratio were conducted to assess the behavior of FBAC, and microstructure were then investigated at 28 days. The results indicated that increasing the FA content up to 15% led to gradual improvement in compressive strength and tensile strength values. At 28 days, the highest values of compressive strength and split tensile strength were observed at 10% FA, with 7.9% and 14.2% increase, respectively, compared to the control concrete. However, the flexural strength of FBAC decreased gradually with cement replacement. On the other hand, modulus of elasticity and Poisson's ratio increased gradually up to 20% and 25% cement replacement, respectively. Up to 15% FA enhanced a more uniform and compact microstructure than that of control concrete. Several equations have been developed to express relationship between compressive strength and other mechanical properties of FBAC. Hence, up to 15% raw FA as a partial replacement of cement improved the mechanical properties and microstructure of BAC.

Impact of Alkaline Concentration on the Mechanical Properties of Geopolymer Concrete Made up of Fly Ash and Sugarcane Bagasse Ash

Geopolymer concrete (GPC) is a novel and environmentally friendly type of concrete that eliminates the use of cement, resulting in a significant reduction in carbon emissions and a more sustainable construction material. Alkaline activators are used in GPC to achieve rapid strength development. The most popular alkaline activators are sodium/potassium silicate and sodium/potassium hydroxide, which are known contributors to carbon emissions, hence limiting the advantages of GPC; therefore, reducing the amount of these alkaline activators that contribute to carbon emissions is necessary for developing a more sustainable geopolymer concrete. In this study, the influence of the variation in sodium hydroxide molarities on the performance of fly ash/sugarcane bagasse ash-based-geopolymer concrete was investigated. The different molarities used were 10 M, 12 M, 14 M, and 16 M sodium hydroxide solutions. In addition, the effect of sugarcane bagasse ash content (0%, 5%, 10%, 15%, and 20%) on the fresh and hardened geopolymer concrete properties were examined. The slump test, compression test, split tensile test, and flexure test were conducted on the cast samples. The results of this study showed that raising the concentration of NaOH from 10 M to 16 M while maintaining a sodium silicate to sodium hydroxide ratio of 2.5 resulted in a 3.75–10.2% improvement in compressive strength after 28 days. It is worth noting that, even at a concentration of 10 M, the concrete still achieved high strength.

Effect of Calcium Aluminate and Carbide Slag on Mechanical Property and Hydration Mechanism of Supersulfated Cement

Supersulfated cement (SSC), a low-carbon, energy-efficient, eco-friendly cementitious material, is mainly made from industrial byproducts. However, SSC’s slow early strength development leads to inadequate initial hardening and reduced durability, which restricts its practical application. This study investigated the potential enhancement of SSC by incorporating calcium aluminate (CA) and carbide slag (CS) alongside anhydrite as activators to address its slow early strength development. The effects of varying CA and CS proportions on the mechanical property and hydration mechanism of CA-CS-SSC were examined. Results indicate that employing 1% CA and 4% CS as alkaline activators effectively activates slag hydration in the 1CA-4CS-SSC, achieving a compressive strength of 9.7 MPa at 1 day. Despite the limited improvement in early compressive strength of other mixtures with higher CA and lower CS proportions in the CA-CS-SSC system, all mixtures exhibited enhanced compressive strength during long-term hydration. After 90 days, ettringite formation in the CA-CS-SSC system decelerated, whereas anhydrite remained. Concurrently, the formation of C-S-H continued to increase, promoting late compressive strength. The mechanism for enhancing the early compressive strength of the CA-CS-SSC system is attributed to the swift hydration of CA with anhydrite, dissolution of fine slag particles, and reaction with anhydrite under conditions with suitable alkali content to augment the ettringite production. This process also generates a C-S-H and OH-hydrotalcite to fill the void in the skeleton structure formed by ettringite, resulting in a dense microstructure that improves early compressive strength.

The effect of flame treatment on the compressive strength of composite sandwich panels made of pure epoxy resin H‐shaped structures and hollow glass bead/epoxy resin composite material

AbstractAt present, syntactic foam composites (HGB/EP) made of epoxy resin (EP) and hollow glass beads (HGBs) have received extensive attention in the research field of lightweight materials because of their high compression strength‐to‐density ratio. However, the deep‐sea environment has put forward higher requirements for the compressive properties of materials. The traditional sandwich structure with HGB/EP as the core has gradually failed to meet the requirements for the mechanical properties of equipment deeper in the ocean. This paper proposes a sandwich structure comprising a pure EP H‐shaped structural component as the rigid skeleton and an HGB/EP syntactic foam composite as the lightweight filling component. The pure EP H‐shaped structural component was subjected to flame treatment using a butane flame jet at different distances. The compression resistance of the resulting sandwich structure was tested, and the results showed varying degrees of improvement in compressive strength after flame treatment. The effects of flame treatment on the surface adhesion performance of the pure EP were characterized using compression‐shear tests, optical microscopy, contact angle tests, infrared spectroscopy, and flame temperature tests. The results demonstrated that flame treatment at a distance of 0 cm significantly increased the oxygen‐containing functional groups on the surface of the pure EP, improved the wettability of the pure EP surface, increased the adhesive strength between the pure EP H‐shaped structural component and HGB/EP, and enhanced the compressive strength of the sandwich structure. The shear strength of the shear test specimens improved by 33.0%, while the compressive strength of the sandwich structure specimens increased by 17.5%.Highlights The sandwich structure composed of pure epoxy resin H‐shaped structure and foam composite material was prepared. The distance of flame treatment affects the surface chemical groups of epoxy resin. Flame treatment significantly improved the surface wettability of epoxy resin.