Increase In Compressive Strength Research Articles

Effect of carbon dioxide mineralization curing on mechanical properties and microstructure of Portland cement–steel slag–granulated blast furnace slag ternary paste

To investigate the synergistic effects of steel slag (SS) and granulated blast furnace slag (GBFS) on cementitious systems during carbon dioxide (CO2) mineralization curing. Ternary paste specimens containing SS, GBFS, and Portland cement (PC) were prepared to analyze the influence of drying pre-treatment time and SS–GBFS mixing ratios on mechanical properties, CO2 fixation rate, and microstructure evolution. Results emphasize the significance of appropriate drying pre-treatment in enhancing mineralization degree and compressive strength. At 60 °C drying pre-treatment temperature, extending drying pre-treatment time up to 12 h enhances both compressive strength and CO2 fixation rate. However, beyond 12 h, a decline is observed in both parameters. Moreover, under the optimal drying pre-treatment time, the compressive strength of ternary paste specimens post-mineralization increases with higher SS content, with SS exerting a more pronounced positive effect on CO2 fixation rate and compressive strength compared to GBFS. After 4 h of mineralization curing, specimens with 50% SS and 10% GBFS demonstrate a 13.16% increase in compressive strength and a 9.16% increase in CO2 fixation rate compared to specimens with 10% SS and 50% GBFS. Microscopic test results reveal that the primary crystalline product in ternary paste specimens after mineralization is calcite, with traces of aragonite. The SS–GBFS mixing ratio has minimal effect on the type of reaction products but has a predominant influence on the total content and crystallinity of calcarea carbonica.

Synthesis and characterization of TiNbZrMo medium-entropy bio-composites: Microstructure, mechanical properties, and in vitro degradation.

This study reports the synthesis and characterization of hydroxyapatite (HA)-based bio-composites reinforced with varying amounts (by weight, 1-15 wt.%) of bio-medium entropy alloy (BioMEA) for load-bearing implant applications. BioMEA powders consisting of Ti, Nb, Zr, and Mo were mechanically alloyed for 100 h and subsequently added to HA using powder metallurgy techniques. To show the effect of BioMEA, the microstructure, density, and mechanical tests have been conducted and the synthesized BioMEA was characterized by scanning electron microscope (SEM), x-ray diffractometer (XRD), and Fourier-transform infrared spectroscopy (FTIR) analysis. In addition, in vitro degradation behavior and bioactivity analyses of bio-composites have been conducted. XRD analysis revealed the formation of BioMEA after 20 h of mechanical alloying. The highest density value of 2.47 g/cm3 was found in 15 wt.% BioMEA-reinforced bio-composite. The addition of BioMEA reinforcement led to a significant increase in hardness and tensile strength values, with the highest values observed at 15 wt.% reinforcement. Compression tests demonstrated a significant increase in compressive strength and deformation capability of the bio-composites with the highest values observed at 15 wt.% BioMEA addition. The highest toughness of 7.68 kJ/m2 was measured in 10 wt.% MEA-reinforced bio-composites. The produced bio-composite materials have an elastic modulus between 3.5-5.5 GPa, which may provide a solution to the stress shielding problems caused by the high elastic modulus of metallic implant materials. The most severe degradation occurred in 15 wt.% MEA-reinforced bio-composites, and the effect of degradation caused a decrease in Ca and an increase in Ti-Ni-Zr-Mo in all bio-composites. These findings suggest that HA/BioMEA bio-composites have the potential to be developed as advanced biomaterials with moderate mechanical and biological properties for load-bearing implant applications.

Suitability of using areca nut fiber as reinforcing material in compressed stabilized earth blocks (CSEB) for low-cost housing

An economical and cost-effective replacement for conventional building materials is Compressed Stabilized Earth Block (CSEB). However, they are vulnerable to erosion and cracking, particularly in humid settings. The use of natural fibers as reinforcement is found effective in overcoming this problem. Areca nut fiber which is a complete waste material in countries like Bangladesh and India is also a sturdy, adaptable, and water-resistant natural fiber that makes it the perfect choice as fiber reinforcement material for CSEBs. In this article, the strength performance analysis of areca nut fiber as a reinforcement material for CSEBs is investigated, where 0%, 0.85%, 2%, 5%, and 8% of areca nut fiber is mixed with soil that is stabilized with 10% cement. CSEB specimens of 4″ × 4″ × 4″ size have been made and tested for compressive strength, tensile strength, bulk density, and water absorption. It is observed that there is an 83.76% increase in compressive strength and an 8.89% increase in splitting tensile strength for 0.85% of areca nut fiber content specimen cured for 90 days. The water absorption was found a minimum of 9.07% for 0.85% areca nut fiber content and the minimum density of the block was observed at 1810 kg/m3 for the optimum percentage of 0.85% mix. The study indicates that using 0.85% of areca nut fiber content in stabilized CSEB shows a significant improvement in the strength characteristics of compressed stabilized earth blocks.Graphical

Mechanically suitable and osteoinductive 3D-printed composite scaffolds with hydroxyapatite nanoparticles having diverse morphologies for bone tissue engineering.

The challenge of integrating hydroxyapatite nanoparticles (nHAp) with polymers is hindered by the conflict between the hydrophilic and hygroscopic properties of nHAp and the hydrophobic properties of polymers. This conflict particularly affects the materials when calcium phosphates, including nHAp, are used as a filler in composites in thermal processing applications such as 3D printing with fused filament fabrication (FFF). To overcome this, we propose a one-step surface modification of nHAp with calcium stearate monolayer. Moreover, to build the scaffold with suitable mechanical strength, we tested the addition of nHAp with diverse morphology-spherical, plate- and rod-like nanoparticles. Our analysis showed that the composite of polycaprolactone (PCL) reinforced with nHAp with rod and plate morphologies modified with calcium stearate monolayer exhibited a significant increase in compressive strength. However, composites with spherical nHAp added to PCL showed a significant reduction in compressive modulus and compressive strength, but both parameters were within the applicability range of hard tissue scaffolds. None of the tested composite scaffolds showed cytotoxicity in L929 murine fibroblasts or MG-63 human osteoblast-like cells, supporting the proliferation of the latter. Additionally, PCL/nHAp scaffolds reinforced with spherical nHAp caused osteoactivation of bone marrow human mesenchymal stem cells, as indicated by alkaline phosphatase activity and COL1, RUNX2, and BGLAP expression. These results suggest that the calcium stearate monolayer on the surface of the nHAp particles allows the production of polymer/nHAp composites suitable for hard tissue engineering and personalized implant production in 3D printing using the FFF technique.

Study on the influence of rock bridge angle on the size effect of rock uniaxial compression.

As a basic parameter of rock, the rock bridge angle plays an important role in maintaining the stability of rock masses. To study the size effect of rock bridge angle on the uniaxial compressive strength of rocks, this paper adopts the principle of regression analysis and combines numerical simulation to carry out relevant research. The research results indicate that: (1) the uniaxial compressive strength decreases with the increase of the rock bridge angle, showing a power function relationship; (2) The uniaxial compressive strength decreases with the increase of rock size and tends to stabilize when the rock size is greater than 350 mm, showing a significant size effect. (3) The fluctuation coefficient of compressive strength increases with the increase of rock bridge angle and decreases with the increase of rock size; When the rock size is 350 mm, the fluctuation coefficient is less than 5%; (4) The characteristic compressive strength and characteristic size both increase with the increase of the rock bridge angle.

Novel activation method of waste concrete powder for sustainable clinker-free binder

This study investigates the environmental and mechanical implications of incorporating silica fume into lime-activated thermo-mechanically treated waste concrete powder (TMWCP) to develop a sustainable clinker-free binder. The novel activation method involves thermo-mechanical treatment of WCP, followed by lime and calcium formate chemical activation. The results demonstrated that incorporating silica fume enhanced the pozzolanic reactivity, which led to the formation of C–S–H, pore refinement, and a dramatic increase in compressive strength. For instance, the incorporation of 20 % and 25 % silica fume exhibited compressive strength of 46 MPa and 43 MPa after 28 days of curing. The developed clinker-free binder with the addition of 20 % silica fume demonstrated a reduction in mineral resource consumption of 99.3 % and CO2 emissions of 13 % and 69.3 % compared to the sample without silica fume and ordinary Portland cement, respectively. This study offers a promising avenue for the widespread utilization of WCP as an environmentally friendly clinker-free binder.

Production and Characterization of Recycled Polypropylene Composite Reinforced with Cotton Fabric Waste

Composite materials have played an important role throughout human history, from housing early civilizations to enabling future innovations. This study explores the development of composite materials from recycled polypropylene and cotton fabric waste targeted for different applications. The composites were manufactured by the melt-mixing method. The effects of cotton fabric waste content on various composite characteristics were investigated using tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength, compressive strength, and water absorption. The study showed that with an increase in cotton fabric waste content, properties such as tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength, and compressive strength increase up to the optimum level, while a decrease in these properties is observed after the optimal level. The maximum tensile strength of 57.84 MPa, tensile modulus of 1.31 GPa, flexural strength of 55.32 MPa, flexural modulus of 2.7 GPa, impact strength of 33.06 kJ/m2, and compressive strength of 53.68 MPa were obtained. The water absorption rate increased with an increase in the cotton fabric waste weight proportion. From the result of this study, it can be concluded that the optimal mechanical and water absorption properties were achieved at 30% cotton fabric waste content. Therefore, creating composites from recovered polypropylene and cotton fabric waste can have both environmental and financial benefits.

Influence of Steam Curing Temperature on the Characteristic of Self-Compacting Concrete Incorporating Palm Shell Ash

Self-Compacting Concrete (SCC) is proven as durable concrete and applied to constructions. In this paper, a study was conducted to analyze the influence of variations of steam curing temperature (SCT) and water/binder (w/b) ratio on the characteristics of SCC incorporating 10% Palm Shell Ash (PSA) as a partial substitution for cement mass. The SCT was arranged from 25 C to 80 C. The variation of w/b in the compositions of SCC was 0.325, 0.350, and 0.375. The results showed that using PSA, the variation of SCT and the w/b ratio influenced the workability of the fresh concrete. The PSA, SCT, and the w/b ratio affected the concrete compressive strength and mass density. The increased SCT caused a lighter density and greater compressive strength. However, the decreased compressive strength occurred due to an excessive SCT of 70 C and above. The SCT of 60 C, 10% PSA, and w/b ratio of 0.350 in the mixture produced the greatest compressive strength of 36.27 MPa at 28 days of age, while without SCT, the greatest compressive strength of 36.78 MPa was achieved at the age of 28 days containing 10% PSA and w/b ratio of 0.325. It indicated that the w/b ratio was more influential than the SCT on the increase of the SCC compressive strength.

Effects of core geometry, silica nanoparticles, and polyurethane foam on the mechanical properties of a novel circular-shaped core sandwich panels under compression test: Experimental study

For the first time in this paper, a composite sandwich panel with a novel circular-shaped core reinforced with silica nanoparticles (SNPs) is designed and fabricated using the vacuum-assisted resin transfer molding (VARTM) method. Carbon fibers and epoxy resin are utilized to construct the composite sandwich panels, followed by polyurethane foam injection. After fabrication, the sandwich panels undergo uniform compression testing to examine their mechanical behavior and properties. In this study, the effects of various parameters, such as core length, core height, weight percentage (wt.%) of SNPs, and polyurethane foam, on the compressive strength of the structure are evaluated. To validate the results, a finite element simulation of the sandwich panel compression test is performed using ABAQUS software, and the results obtained are compared with experimental data, showing good agreement. The results of this research demonstrate that adding SNPs within a specific range results in a considerable enhancement of the structural strength. Adding SNPs up to 3% leads to approximately a 19% increase in the compressive strength of the structure. However, adding 4 wt.% SNPs results in a decrease of about 12% in the strength of the sandwich panel. Additionally, the core’s geometry significantly influences the control of compressive strength and rigidity of the sandwich panel. In other words, by increasing the core length, the compressive strength increases by 38%, while increasing the core height decreases compressive strength by about 30%. Also, it is found that adding polyurethane foam to the sandwich panel, despite a slight increase in weight, leads to a significant increase in compressive strength by about 32% and postpones its ultimate failure. Eventually, the hybrid specimen exhibits a strength approximately 57% greater than that of the pure foamless sandwich panel.

Multi-scale analysis of carbon mineralization in lime-treated soils considering soil mineralogy

Mineral carbonation is emerging as a reliable CO2 capture technology that can mitigate climate change. In lime-treated clayey soils, mineral carbonation occurs through the carbonation of free lime and cementitious products derived from pozzolanic reactions. The kinetics of the reactions in lime-treated clayey soils are variable and depend primarily on soil mineralogy. The present study demonstrates the role of soil mineralogy in CO2 capture and the subsequent changes caused by carbon mineralization in terms of the unconfined compressive strength (UCS) of lime-treated soils during their service life. Three clayey soils (kaolin, bentonite, and silty clay) with different mineralogical characteristics were treated with 4% lime content, and the samples were cured in a controlled environment for 7 d, 90 d, 180 d, and 365 d. After the specified curing periods, the samples were exposed to CO2 in a carbonation cell for 7 d. The non-carbonated samples purged with N2 gas were used as a benchmark to compare the mechanical, chemical-mineralogical, and microstructure changes caused by carbonation reactions. Experimental investigations indicated that exposure to CO2 resulted in an average increase of 10% in the UCS of lime-treated bentonite, whereas the strength of lime-treated kaolin and silty clay was reduced by an average of 35%. The chemical and microstructural analyses revealed that the precipitated carbonates effectively filled the macropores of the treated bentonite, compared to the inadequate cementation caused by pozzolanic reactions, resulting in strength enhancement. In contrast, strength loss in lime-treated kaolin and silty clay was attributed to the carbonation of cementitious phases and partly to the tensile stress induced by carbonate precipitation. In terms of carbon mineralization prospects, lime-treated kaolin exhibited maximum carbonation due to the higher availability of unreacted lime. The results suggest that, in addition to the increase in compressive strength, adequate calcium-bearing phases and macropores determine the efficiency of carbon mineralization in lime-treated clayey soils.

Dolomite-Based Concrete: A comprehensive review on mechanical properties

Concrete, an extensively used material contributes to greenhouse gas emissions due to use of Portland cement (PC). The production of PC worldwide is approximately 4 billion tons annually accounting for 8% of global CO2 emissions. To address this environmental challenge and mitigate carbon footprint, various industrial waste such as Fly Ash, Ground Granulated Blast Furnace Slag, Metakaolin, Eggshell Powder, and Sugarcane Bagasse Ash have been employed to partially replace PC, alleviating disposal issues. A waste/byproduct of the dolomite business, dolomite powder is produced yearly in amounts of 1.75–2 million tons (MT), or 25% of the industry's total production (7–8 MT). The current paper intends to summarize the related research on the usage of dolomite powder as a PC replacement in relations to compressive, flexural and split tensile strength. A bibliographic analysis is done using VOSviewer providing relationships between the keywords and countries doing research on dolomite powder. Concrete incorporating dolomite exhibits enhanced mechanical properties, boasting a 5–10% increase in compressive strength, 6–12% higher tensile strength, and a 5–10% boost in flexural strength at a 10% dolomite replacement rate. This is because dolomite has a smaller particle size which fills the miso and macro pores improving the microstructure of concrete and decreasing the porosity Thus, the dolomite as a PC replacement increases overall performance and has proven to be a sustainable option for construction practices.

Silver and silicon doped βTCP scaffolds with gentamicin or ceftazidime loaded P(3HB) coatings as multifunctional biomaterials for bone regeneration

The risk of bacterial infections is a significant challenge faced frequently in the use of implants or scaffolds for bone regeneration. Therefore, this study focusses on the development and characterisation of novel β tricalcium phosphate (βTCP) scaffolds co-doped with silver and silicon, along with composites coated with antibiotic-loaded poly(3-hydroxybutyrate) (P(3HB)) layers. The successful incorporation of silver and silicon dopants while maintaining the formation of βTCP phase was confirmed using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) analysis. The developed materials demonstrated comparable total and open porosity (∼64–70 vol%), suggesting high interconnectivity between pores conducive to nutrient transport and tissue repair. The increase in compressive strength was achieved for both doped (4.73 ± 0.79 MPa) and P(3HB) coated (5.79 ± 0.92 MPa) scaffolds due to the fine bioceramic microstructure and polymeric coating. Silver and silicon-modified βTCP demonstrated enhanced growth inhibition of Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains in vitro compared to the pure βTCP. P(3HB) coatings, enriched with gentamicin or ceftazidime, exhibited burst and sustained release of the antibiotics from the scaffolds up to 120 h further intensifying the bacteria-killing capability, with evident inhibition zones observed in vitro. Moreover, the composites exhibited apatite-forming ability, suggesting their bioactive potential. In vivo evaluation using Caenorhabditis elegans demonstrated the lack of toxicity of the tested materials. The simultaneous incorporation of the dopants and antibiotic-loaded P(3HB) coatings not only offer a dual antibacterial approach but may also facilitate bone regeneration. However, further in vitro and in vivo investigations are needed to assess their potential in clinical application.

Performance of foam concrete developed from construction and demolition waste

Unconscious industrialization, urbanization and consumption of natural resources pose a serious threat to the environment. The threat can be reduced by upcycling construction and demolition waste (CDW) in the production of foam concrete, which is a special type of concrete used especially for thermal insulation purposes. This study aims to use of CDW as a source of fine aggregate (0-4 mm) in the production of foam concrete mixtures. A series of mixtures with target density values between 500 and 900 kg/m3 were designed with various recycled aggregate and foam contents to investigate the physical, mechanical and thermal properties of the mixtures. Findings of the study reveal that mixtures with an elevated foam content possess a greater number of larger pores, which, as observed through microscopy, form interconnected structures that are porous. On the other hand, adding more fine recycled material (FRM) makes the matrix denser, which reduces the overall porosity and increases the packing density. In contrast to increased content of FRM, correlation coefficient of (-0.77) reveal a more powerful inverse relationship between risen level of foam content (-0.67) and the reduction ratio of fresh-to-dry density and the increase in compressive strength from 7 to 28 days. It is also known that mixes with more foam have better thermal insulation because they trap more air, while mixes with more FRM show an increase in thermal conductivity. The sensitivity analysis showed that changes in thermal conductivity are almost three times as sensitive for FRM content, which means they have a bigger effect than changes in foam content. Employing the Taguchi method, (R_0.714) emerges as the most efficient tested combination indicative of superior overall performance. Notably, the Taguchi method predicts the untested combination (0.100-F/C ratio + 0.714-R/C ratio) as potentially more efficient, suggesting avenues for further exploration and optimization. This study furnishes valuable insights into sustainable construction practices by reutilizing CDW in foam concrete production, thereby contributing to both environmental conservation and enhanced structural outcomes.

Effect of activator concentration on setting time, workability and compressive strength of sustainable concrete with alkali-activated slag binder

The global need to reduce carbon dioxide (CO2) emissions prompted studies on sustainable alternatives to conventional concrete made with ordinary Portland cement (OPC) binders. Alkali-activated ground granulated blast furnace slag (GGBS) is a promising sustainable to OPC in terms of the impact on the environment and reduction of CO2 emissions. Concretes and mortars made with alkali-activated binders demonstrate promising fresh and mechanical properties. This article presents the findings of an experimental study investigating the fresh and mechanical properties of mortar using alkali-activated GGBS binder. The activators used were sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution with 6 M, 8 M, 10 M, and 12 M molarities. The study assessed their initial setting time, workability, and 28-day compressive strength. The study evaluated the effect of partial replacement of GGBS with 5 % silica fume. The compressive strength was determined after 28 days of curing in three different environments: 1) ambient air temperature, 2) water submersion, and 3) water immersion for 7 days followed by 21 air curing in ambient temperature. The results showed an increase in compressive strength with higher NaOH concentration but a corresponding decrease in initial setting time and flowability. Depending on the curing method, efflorescence, and blue-green pigmentation were seen during the physical assessment of the samples. The highest 28-day compressive strength was 67.5 MPa when the NaOH activator molarity was 10 mol/L which represents an optimum concentration for strength development. Replacing 5 % of the GGBS binder with silica fume resulted in a decrease in the 28-day compressive strength and workability without affecting the initial setting time.

Feasibility of compacted attapulgite/diatomite amended clayey soils as gas barrier materials

Compacted clay liners are extensively used as barriers to control the upward diffusion of vapors of volatile or semi-volatile organic contaminants released from unsaturated contaminated soils at industry-contaminated sites. This study aimed to investigate the gas diffusion barrier performance of compacted clayey soils amended with three agents including attapulgite and diatomite individually, and attapulgite/diatomite mixture. The properties including water retention, volumetric shrinkage, gas diffusion, and unconfined compressive strength were evaluated through a series of laboratory tests of amended compacted clayey soils. The results demonstrate that the decrease in volume proportions of inter-aggregate pores leads to an increase in unconfined compressive strength (qu). Both hydrophilic groups and microstructures of attapulgite and diatomite result in an increase in water retention percent (Wt) of compacted clayey soil specimens after amendment regardless of the type of agent or initial water content (w0). Furthermore, the ratio of the gas diffusion coefficient (De) to the gas diffusion coefficient in the air (Da) was significantly reduced owing to a decrease in volume proportions of inter-aggregate pores, hydrophilic group, and microstructures of attapulgite and diatomite. Scanning electron microscope analyses revealed that rod-shaped attapulgite filled the inter-aggregate pores formed by clay particles, whereas the disc-shaped diatomite particles, characterized by micropores, failed to obstruct the inter-aggregate pores due to their larger particle size. Mercury intrusion porosimetry (MIP) analyses showed a reduction in pore volume in the inter-aggregate pores, leading to a reduction in the total pore volume for both the attapulgite and attapulgite/diatomite mixture amended clays, which is in accordance with the scanning electron microscope (SEM) results. The findings are pertinent to the practical application of compacted clay liners as gas barriers against the upward migration of volatile or semi-volatile organic contaminants at contaminated sites.

Reduced graphene oxide (rGO) reinforced CoCrFeNiMn high entropy alloy: microstructure, mechanical properties, and corrosion behavior

The CoCrFeMnNi high entropy alloy (Cantor), and its variant incorporating 0.2 wt% reduced graphene oxide (rGO), denoted as Cantor + rGO, were successfully synthesized using mechanical alloying followed by spark plasma sintering. Comprehensive characterization utilizing FESEM, XRD, and TEM provided detailed insights into the microstructural features of the materials. The addition of rGO reduced crystallite size from 209 nm to 169 nm, promoted a uniform distribution of carbide phases of smaller size, and enhanced microhardness from 421.8 HV to 510 HV for Cantor and Cantor + rGO, respectively. The incorporation of rGO into the Cantor structure led to an increase in compressive yield strength (CYS) from 1100 MPa for Cantor to 1250 MPa for Cantor + rGO sample. A significant decrease in corrosion current density of samples from 6.1 ± 1.5 μA/cm2 for Cantor to 1.4 ± 0.9 μA/cm2 for Cantor + rGO was observed due to the addition of rGO reinforcement. Moreover, the pitting corrosion resistance was increased in rGO-reinforced Cantor, as revealed by cyclic polarization test. This research underscores the potential for utilizing rGO as a reinforcing agent to optimize the mechanical and corrosion resistance characteristics of HEAs, offering promising avenues for advanced materials in diverse applications.

A novel bio-based water reducer for concrete application: Facile process and techno-economic analysis of xylonate bioproduction from lignocellulosic residues

The xylonate was bioproduced directly from lignocellulosic residues, and the application properties of crude xylonate powder were investigated with a promising potential as a bio-based concrete water reducer. The overall integrated process was evaluated on the view of mass balance and techno-economic analysis using Aspen Plus modeling. 56 g/L of calcium xylonate (XA-Ca) can be obtained within 8 h from acidic corncob hydrolysate (ACH) at a 100 % yield with the whole-cell catalysis of Gluconobacter oxydans. At the addition of 0.2 wt% in the dry concrete content, XA-Ca powder and sodium xylonate powder prepared from pure xylose and ACH could reduce water used in concrete by 15 %, 14 %, 13 %, and 13 %, respectively. XA-Ca from ACH led to a 33% increase in concrete compressive strength and a 24% increase in concrete flexural strength at day 7 compared to the blank group. The techno-economic analysis showed the minimum XA-Ca powder price to be $ 0.806/kg which can be economically feasible. This study provides a practical and economical process prototype for the industrial concrete water reducer application of novel bio-based xylonate produced from lignocellulosic residues.

Synthesis, growth mechanism, and performance of in-situ catalytic growth Al4SiC4 whiskers in Al2O3–SiC–C refractories

Ceramic whiskers exhibit excellent performance due to their special structure, making them widely used in the field of refractories. In this work, a novel Al4SiC4 whisker was designed to improve the mechanical properties and thermal shock resistance of Al2O3–SiC–C (ASC) refractories. By introducing nickel nitrate as a catalyst, the Al4SiC4 whiskers with a special "stalactite" structure could be directly grown in situ at the operating temperature of ASC (1450 °C). Combining the experimental results and first-principles calculations, the AlNi2Si alloy formed during the heat treatment process acted as catalyst sites, AlO, SiO and CO were easily absorbed on the Ni55 surface. Subsequently, the Al–O, Si–O and C–O bonds were broken and reacted with each other to grow Al4SiC4 whiskers according to the vapor-liquid-solid mechanism. As expected, the incorporation of Al4SiC4 whiskers resulted in a 57.4 % increase in cold compressive strength (CCS) and a 47.2 % increase in residual strength ratio (RSR) of the ASC refractories due to the strengthening mechanism of whisker bridging. This study presents a novel research strategy for enhancing the properties of refractories.

Compressive Strength of Concrete Containing Merapi Cold Lava Sand

Reports from the literature state that Merapi sand is a good material as a filler in concrete to replace some of the fine aggregate because it has a high content of silica (SiO<sub>2</sub>) and the sharp edges of the silica form angular particles. The potential function of Merapi sand as a filler and its use as a waste material prompted this study to be carried out. The objective of this study is to determine the potential of Merapi Sand in terms of concrete compressive strength as an effective replacement for local sand in the Cikarang area. In this study, Merapi cold lava was crushed to the size of fine aggregate by passing a 2.26 mm sieve. The percentages of Merapi sand used as a partial substitute for local sand are 10%, 20%, and 30%. The results of this study show that Merapi sand concrete (MSC) 30% at age of 7 days and 28 days provides the highest increase in compressive strength of 17.4% and 15.8% respectively compared to normal concrete (NC). The addition of a percentage of Merapi sand as a partial replacement for local sand tends to increase the compressive strength of the concrete. Based on this study, Merapi sand has the potential to be used as a partial replacement for local sand in increasing the compressive strength of concrete and reducing cold lava waste.

Experimental verification of innovative spatial reinforcement of ultra-high performance concrete with mesh tubes

The article presents the concept of innovative spatial concrete reinforcement, consisting of a new, patented reinforcement system with mesh tubes. The concept of spatial reinforcement is a proposal for homogenization of composite concrete structures, which in a unique and very effective way allows the use of reinforcing material in the form of an ordered structure of glass fibres. A comparative analysis was carried of the test results of concrete composite samples reinforced with mesh tubes made of high-strength glass fibre, with the results on concrete samples without reinforcement and on fibre concrete samples containing an equivalent amount of glass fibres of two different lengths, made of the same type of glass fibre as the mesh tubes. Base concrete with ultra-high performance properties was used for the tests. Experimental tests concerned the strength and deformation properties of the composites, i.e. compressive strength, direct tensile strength and splitting tensile strength, and secant modulus of elasticity in compression. Beam models were also tested in a four-point bending test, which made it possible to determine the load-carrying capacity, flexural strength and analyse the cracking and failure mechanism. Comparative analysis of the experimental results showed the high effectiveness of the proposed spatial reinforcement of concrete with glass fibre mesh tubes. The use of spatial reinforcement resulted in an increase in compressive strength, direct tensile and splitting tensile strength by 5 %, 29 %, 27 % respectively, compared to fibre concrete. However, the load-carrying capacity of the spatially reinforced beam was 85 % higher compared to the fibre concrete beam.