Physicomechanical Characteristics Research Articles

Unveiling physico-mechanical and acoustical characteristics of fly ash geopolymers through the synergistic impact of density and porosity

This paper investigates the physico-mechanical and acoustic properties of fly ash geopolymers via casting and pressing methods. The existing research lacks comprehensive insight into the relationship between variations in geopolymer density and their impacts on both physico-mechanical properties and sound insulation and absorption capabilities. Geopolymers, as sustainable construction materials, are pivotal in mitigating noise and providing structural strength. To surpass these limitations and achieve either higher or lower densities in geopolymers, alternative approaches are necessary. Casting (non-foamed and foamed with 1.0, 2.0 and 3.0 foam-to-geopolymer paste ratio) and pressing methods were employed to produce a range of geopolymer densities between 1400 kg/m3 – 2200 kg/m3. The pressing method produced a highly dense geopolymer with an excellent compressive strength of 116 MPa. While the lightest geopolymer produced by adding a foaming agent had a compressive strength of 13 MPa. Good sound transmission loss (66.1 dB) was achieved by highly dense pressed geopolymers. Highly porous geopolymers achieved an excellent sound absorption coefficient of 0.79. The density variation and preparation methods greatly affected the pore size and distribution which subsequently affected the acoustical properties of the geopolymers. Manipulating the density and porosity of the geopolymers is essential for creating spaces with optimal acoustics to meet building codes and noise control regulations.

A laboratory study on the durability of limestone wastes in harsh environments for their suitability as aggregate in concrete

One of the critical environmental issues in the Chegeni area (Lorestan Province, western Iran) is the production of a large volume of limestone wastes during the quarrying operations. Releasing limestone wastes in the areas neighboring the quarries has caused visual damage to the environment, and adverse effects on the quality of the soil, running water, and groundwater used for agricultural and drinking water purposes. One solution to this issue can be recycling limestone wastes to produce building materials. In the present study, a comprehensive laboratory program is planned for the durability evaluation of the limestone wastes under harsh environments for their suitability as aggregate in concrete. For this purpose, five aging tests, including freeze-thawing (F-T), salt crystallization (SC), acid attack (AA), wetting-drying (WD), and heating-cooling (HC), were conducted on the limestone sample up to 60 cycles. After every 10 cycles, the physico-mechanical characteristics of the sample, including porosity (n), Brazilian tensile strength (BTS), point load index (PLI), and P-wave velocity (Vp) were determined. Moreover, the pores structure modification of the sample subjected to aging tests was examined through scanning electron microscopy (SEM). Data analyses revealed that the sample is highly vulnerable to the AA and SC processes but is durable against FT, WD, and HC actions. These results were in good agreement with the SEM data such that the sample exposed to AA and SC underwent more changes in their pore structure compared to FT, WD, and HC. Among the physico-mechanical characteristics, the Vp and PLI had the highest and the lowest accuracy, respectively, in the durability evaluation of the sample exposed to aging tests. Based on the data analysis, limestone wastes can be used as aggregate in concrete in environments with the possibility of FT, WD, and HC. However, this type of concrete is not suitable for conditions with occurrences of the AA and SC. Finally, in addition to reducing the environmentally harmful impacts of the study area, using limestone wastes as aggregate in the construction of concrete can also be a practical solution for sustainable development from an economic viewpoint. The results of the present study can be used for assessing limestone wastes produced in other areas of Iran and the world.

Experimental investigations on physico-mechanical properties of kaolinite clay soil stabilized at optimum silica fume content using clamshell ash and lime

This investigation examines the effect of clamshell ash (CSA) and lime additives on the physico-mechanical characteristics of kaolinite clay soil stabilized at the optimum silica fume content. Laboratory tests were performed to assess plasticity, shrink-swell characteristics, compaction characteristics, unconfined compressive strength (UCS), shear strength characteristics, mineralogical and morphological microstructure characteristics of stabilized soil specimens. The kaolinite clay soil was stabilized at its optimum silica fume content (6%) to produce the highest strength and was altered with three non-identical proportions of clamshell ash and lime (3%-9%). Cylindrical soil specimens, 76 mm in height and 38 mm in diameter, were moulded and treated for curing periods of 1, 7, 14, and 30 days to examine the strength of the altered soil. The findings revealed that, adding clamshell ash and lime significantly alters the plasticity, shrink-swell, maximum dry unit weights, and optimum moisture contents of the silica fume-stabilized soil. In terms of strength, the beneficial effects of CSA and lime additives were found to be more significant with more extended curing periods. Incremental increases in curing periods resulted in further enhancements in UCS, cohesion, and internal friction angle, indicating continued strength development over time. Microstructural analysis using field emission scanning electron microscopy and X-ray diffraction provided insights into the interparticle bonding mechanisms and microstructural changes induced by the addition of CSA and lime. The emergence of cementitious phases and pozzolanic responses between soil particles and stabilizers contributed to the densification and strengthening of the stabilized soil matrix. The findings of this study provide valuable insights into the potential of clamshell ash and lime additives to enhance the engineering properties of kaolinite clay soil stabilized with silica fume. These results have implications for sustainable soil stabilization practices, offering a promising approach to improve the performance of soils for various engineering applications, including construction and geotechnical projects.

Evaluation of bioactivity, biocompatibility, and antibacterial properties of tricalcium silicate bone cement modified with wollastonite/ fluorapatite glass and glass-ceramic

This work's main objective is to assess the effects of wollastonite/fluorapatite glass (G) and glass-ceramic (GC) on tricalcium silicate's (TCS) bioactivity and physico-mechanical properties. To achieve this goal, 10 and 20 wt percent of G or GC were used in place of TCS. The constructed specimens were kept submerged in SBF solution for 4 weeks at a temperature of approximately 37 ± 0.5 °C to create the hydroxyapatite layer (HA) on the cement paste surface and evaluate their biological behavior. Additionally measured were bulk density, apparent porosity, and compressive strength. The principal components had been studied using X-ray diffraction and Fourier transform infrared spectroscopy. An energy dispersive spectroscopy (EDS)-equipped scanning electron microscope (SEM) was used to examine the materials' morphology. The antibacterial and cytotoxic properties were also evaluated. The findings demonstrated that during soaking in SBF, bulk density and porosity ranged from 1.38 to 1.5 g/cm3 and from 44.99 to 39.12 %, respectively, and the results for compression strength varied from 65 to 88 MPa. The outcomes demonstrated that all of the prepared samples' surfaces had the hydroxyapatite layer (HA) formed on them following their immersion in the biological fluid (SBF). Additionally, it was discovered that raising the percentage of GC (TCS/20GC) in synthetic samples improves TCS cement's physico-mechanical and bioactivity characteristics. Furthermore, these substances had minimal cytotoxic effects on the typical fibroplast cell line of humans (BJ1), indicating their potential utility in dental applications. Ultimately, the antimicrobial test demonstrated good inhibitory behavior against the pathogens Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa.

Physicomechanical, Wettability, Corrosion, Thermal, and Microstructural Morphology Characteristics of Carbonized and Uncarbonized Bagasse Ash Waste-Reinforced Al-0.45Mg-0.35Fe-0.25Si-Based Composites: Fabrications and Characterizations.

An effort was being made to incorporate waste bagasse ash (WBA) both in carbonized and uncarbonized form into the formulation of Al6063 matrix-based metal matrix composites (MMC's) by partially substituting ceramic particles for them. In the process of developing composites, comparative research on carbonized WBA and uncarbonized bagasse powder was carried out in the role of reinforcement. Microstructure investigations revealed that carbonized WBA particles were properly distributed throughout the aluminum-base metal matrix alloy. They also had the appropriate level of wettability. The reinforcement of carbonized WBA particles in AA6063-based matrix material had a maximum tensile strength of 110 MPa and a maximal hardness of 39 BHN when 3.75 wt % of the particles were used. The deterioration in tensile strength (6.25 wt % of WBA) and the appearance of porosity and blowholes can be enumerated by tensile fractography-based scanning electron microscopy (SEM) analysis. The reinforcement of carbonized WBA particles in AA6063-based matrix material was found to have a maximal percent elongation of 14.42% and the highest fracture toughness of 15 Joules when 1.25 wt % of the particles were employed. For AA6063/3.75 wt % carbonized WBA-based MMC's, the minimum percent porosity was determined to be 5.83, and the minimum thermal expansion was found to be 45 mm3. As the percentage of reinforcement in bagasse-reinforced composites increases, the density of the material, the amount of corrosion loss, and the cost all decrease gradually. The AA6063 matrix, with a composition of 3.75 wt % carbonized WBA-based MMC's, had satisfactory specific strength and corrosion loss. The AA6063 alloy composite's microstructure analysis revealed that carbonized WBA enhanced the material's mechanical characteristics, contributing to its excellent mechanical capabilities. The results of the corrosion test showed that carbonized WBA-reinforced composites exhibited reduced weight loss due to corrosion, whereas uncarbonized bagasse powder was an inappropriate reinforcement. The SEM analysis of AA6063 alloy/3.75 wt % carbonized WBA ash reinforcement-based MMC's exposed to a 3.5 wt % NaCl solution has exhibited the development of corrosion pits as a result of localized attack by the corrosive environment. The thermal expansion test showed that the composite with uncarbonized bagasse powder as reinforcement have a high shrinkage rate in comparison with the composite with 3.75 wt %. The composite's mechanical characteristics and thermal stability were enhanced by the presence of hard phases like SiO2, Al2O3, Fe2O3, CaO, and MgO, as revealed by X-ray diffraction analysis. This made it suitable for use in a variety of applications.

Impact of NaOH Treatment on the Chemical, Structural, Physico-mechanical, and Thermal Characteristics of Jute Species

Impact of NaOH Treatment on the Chemical, Structural, Physico-mechanical, and Thermal Characteristics of Jute Species

The Effect of Chitosan Incorporation on Physico-Mechanical and Biological Characteristics of a Calcium Silicate Filling Material.

A tricalcium silicate-based cement, Biodentine™, has displayed antibiofilm activity when mixed with chitosan powder. This study aimed to assess the effect of chitosan incorporation on the physico-mechanical and biological properties of Biodentine™. In this study, medium molecular weight chitosan powder was incorporated into Biodentine™ in varying proportions (2.5 wt%, 5 wt%, 10 wt%, and 20 wt%). The setting time was determined using a Vicat apparatus, solubility was assessed by calculating weight variation after water immersion, radiopacity was evaluated and expressed in millimeters of aluminum, the compressive strength was evaluated using an Instron testing machine, and the microhardness was measured with a Vickers microhardness tester. In addition, surface topography of specimens was analyzed using scanning electron microscopy, and the effect of chitosan on the viability of human embryonic kidney (HEK 293) cells was measured by a colorimetric MTT assay. Incorporation of 2.5 wt% and 5 wt% chitosan powder delivered an advantage by speeding up the setting time of Biodentine material. However, the incorporation of chitosan compromised all other material properties and the crystalline structure in a dose-dependent manner. The chitosan-modified material also showed significant decreases in the proliferation of the HEK 293 cells, signifying decreased biocompatibility. Chitosan incorporation into calcium silicate materials adversely affects the physical and biological properties of the material. Despite the increased antimicrobial activity of the modified material, the diminution in these properties is likely to reduce its clinical value.

Acoustical Efficiency and Physico-Mechanical Characteristics Study for New Composite Material: Ethylene Vinyl Acetate and Wood Sawdust

Developing neoteric composite materials (CM) that improve the acoustic efficiency and mechanical properties become the target of many scientists in the last decade. This paper presents research on developing new CMs using Ethylene Vinyl Acetate (EVA) and sawdust (SD) of different weight concentrations which can be help to improve the acoustic and mechanical properties of the EVA polymer materials. Prototypes of EVA composite in form of flat plates with different weight concentrations of sawdust namely; 0, 2.5, 5, 10, 20 and 30% were produced. One of the interesting applications of this new CMs is to use it as a floor covering in buildings and manufactures. The acoustic efficiency parameters namely, impact noise reduction and sound absorption are experimentally studied. The obtained results articulate that covering floors with the designed composite material of EVA/SD as filler can decrease ISR up to 14 dB. Also, it gives peak sound absorption coefficient about 0.6 for 30 % of SD at mid-frequency band. The greatest proportion of SD aggregate EVA does not entail a higher acoustic performance. The tensile strength of the composite increases to 15.5% when the SD content is 5% and the tensile strength drops with increase the SD content up to 30%. Therefore, SD may be utilized as filler and consolidation in the EVA matrix, which will save expenses and assist the environment.

Synthesis and performance study of novel antibacterial and anticorrosive polyurethane IPN

Polyaniline has been extensively used for the corrosion protection of polymeric materials. However, there have been few studies on its combined antimicrobial activity when used in combination with silver molybdate. In this study, we synthesized silver molybdate (Ag2MoO4) crystals using a homogeneous precipitation method. Polyaniline-dodecylbenzenesulfonic acid/castor oil(PANI-DBSA/CO) mixtures were prepared in an encapsulated state by in situ polymerisation. Subsequently, PANI/Ag2MoO4-PU interpenetrating polymer network(IPN) composite coatings(P/A-PU) were produced by dispersing Ag2MoO4 and PANI-DBSA/CO in polyurethane using ultrasonic dispersion. The composite coatings were characterized using Fourier transform infrared spectroscopy(FTIR), X-ray diffraction analysis(XRD), and transmission electron microscopy(TEM). The study confirmed that composite coatings with uniformly dispersed nanoparticles of PANI and Ag2MoO4 encapsulated by CO and epoxy resin E-44 grease exhibit improved physico-mechanical characteristics. The research also evaluated the effect of nanoparticles on the corrosion behaviour of the coatings using electrochemical impedance spectroscopy and kinetic potential polarisation experiments. The study investigated the antimicrobial properties of P/A-PU composite coatings on Escherichia coli(E.coli) and Staphylococcus aureus(S.aureus) by conducting bacterial growth curves, protein leakage, and fluorescence staining experiments. The aim was to establish a causal connection between the coated surfaces and the observed antimicrobial properties. The study demonstrated that incorporating IPN of polyaniline polyurethane into the coating composites improved their anticorrosive properties. Furthermore, the addition of silver molybdate at a mass ratio of 0.3 % resulted in a remarkable 99 % antimicrobial activity against E.coli and S.aureus.

Effects of high temperatures on physico-mechanical characteristics of autoclaved aerated concrete

The study aims to determine the compressive strength, as well as linear and volumetric deformations of autoclaved aerated concrete with an average density of 600 kg/m3 after holding at temperatures in the range of 100–800 °C. The compressive strength of test samples was determined using an IP-100 hydraulic press in accordance with the state standard GOST 10180 “Concretes. Methods for determining the strength of control samples” State Standard. It was experimentally established that after holding aerated concrete samples at a temperature of 100 ºС, its compressive strength increased by 6.2 %, which is associated with the loss of an excess moisture during heating. A further increase in the temperature to 600 ºС insignificantly affects its strength characteristics. At an increase in the test temperature to 800 ºС, the residual compressive strength of samples averaged 62.6 % of the control sample strength. Linear dimensions of samples begin to vary at a temperature of 300 ºC and do not exceed 1.56 % of initial values up to a temperature of 600 ºC. A further increase in the temperature to 800 ºС reduces the linear dimensions of aerated concrete samples by 15.15 %. Volumetric deformations of autoclaved aerated concrete samples in the temperature range of 300–600 ºС are less than 5 %, while, for the temperature of 700–800 °С, they range from 25 % to 38.9 %. The studied aerated concrete can withstand high temperatures up to 600 °C without significant variations in its physical and mechanical characteristics.

A novel cement mortar comprising natural zeolite/dodecyl alcohol shape stable composite phase change material for energy effective buildings

Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.

Fabrication and Analysis of Physico-Mechanical Characteristics of Chemically Treated Bhendi Fiber Reinforced Thermoplastic Composites: Effect of UV Radiation

Unidirectional polypropylene (PP) composites reinforced with bhendi fibers (BFs) were produced after BFs were subjected to UV light at different intensities. Mechanical parameters such as tensile strength, tensile modulus, and impact strength of irradiated BF/PP composites significantly improved compared to non-irradiated counterparts. To enhance their properties, different amounts of 2-hydroxyethyl methacrylate (HEMA) in methanol were applied to the surfaces of irradiated BFs, and UV light was subsequently used to cure them. Tensile strength, tensile modulus, and impact strength values rose by 32%, 20%, and 37%, respectively, after the optimized grafting and mechanical properties. Alkali solutions were applied to BFs for 30 minutes at varying temperatures and concentrations to alter their surfaces. Then, using the same UV light, BFs were photocured after being grafted with an optimal HEMA solution. Of all the composite samples treated with 10% HEMA, the alkali + 10% HEMA-treated composites exhibited superior mechanical performance. SEM studies exhibited that the optimized alkali with 10% HEMA treated composite had better dispersion than the 10% HEMA treated composite. Water absorption was significantly lower in the treated than in the untreated sample. According to weather studies, the treated specimens may have less loss tensile characteristics than the untreated specimens.

Effect of the degree of corrosion damage in reinforcing bars on composite action with concrete

Introduction. The article examines the possibility of using steel reinforcement with instances of corrosion and determines the maximum degree of corrosion damage in reinforcing bars (rebars). Although long-term studies show that corroded reinforcement can be used in the manufacture of reinforced concrete structures, some studies and regulatory documents provide different conditions for the use of such rebars, as well as establishing different corrosion thresholds (thickness of the rust layer on the rebar surface).Aim. To determine the maximum thickness of the rust layer on the surface of corrugated rebars, at which the physicomechanical characteristics of reinforcement are preserved and the capability for composite action with concrete is not hampered; to determine the degree of corrosion damage in rebars at which its use in reinforced concrete is permissible in order to revise the existing regulatory documents on the protection of structures against corrosion.Materials and methods. The experimental studies were conducted on rebar specimens of two classes (A500 and A800) exhibiting different degrees of corrosion damage (rust layer thickness of 0, 150, 250, and 300 μm). In order to determine the composite action with concrete, B15 and B20 concrete was used. The physicomechanical characteristics of rebars with different rust layer thicknesses were determined on rebar specimens having a diameter of 12 mm and length of 400 mm according to the procedure specified in State Standard 12004-81. The reinforcing steel resistance to corrosion cracking was determined on rebar specimens having a diameter of 12 mm and a length of 400 mm as per the procedure given in State Standard 31383-2008. The passivating effect of concrete on steel reinforcement was determined on concrete specimens — 70 × 70 × 140 mm prisms, with rebars having a diameter of 12 mm and a length of 120 mm in the center — according to the procedure given in State Standard 31383-2008. The bond between rebars and concrete was determined on concrete specimens-cubes (150 mm on edge), with rebars having a diameter of 12 mm and a length of 500 mm in the center — using the procedure specified in State Standard 31938-2012.Results. The study yielded experimental data on the physicomechanical characteristics of rebars exhibiting different degrees of corrosion damage; on the resistance of reinforcing steel to corrosion cracking; data on the passivating effect of concrete of two classes on steel rebars exhibiting different degrees of corrosion damage; data on the bond between rebars corroded to various degrees and concrete of two classes.Conclusions. As part of the work, an experimental research program was developed and implemented, which involved the production and testing of rebar specimens of two classes exhibiting four degrees of corrosion damage with the use of concrete of two classes and. The experimental study results were used to determine the effect of corrosion damage of varying degree in rebars on the characteristics of reinforced concrete. The presence of a rust layer on the rebar surface of up to 150 mm in thickness was found not to degrade its physicomechanical characteristics, not to decrease its resistance to corrosion cracking, and not to reduce its composite action with concrete. Any further increase in the thickness of the rust layer on rebar surface reduces these characteristics, except for the bond to concrete. No dependence of rebar-concrete bond stress on the rust layer thickness was observed.

Spark Plazma Sinterlenmiş Cu-SiC Kompozitlerinin Fiziko-Mekanik ve Elektriksel Özelliklerinin Değerlendirilmesi

In this study, SiC reinforced Cu matrix composites were produced by spark plasma sintering to provide rapid consolidation and to prevent weak interfacial bonding and grain growth, undesired phases at the interphase region. In addition, the influence of the reinforcement ratio (vol.% 10, 20, 30) and particle sizes (1, 11, 24 µm) on the physico-mechanical (density, hardness) and electrical characteristics of copper composite materials was aimed. The bulk density values were determined by Archimedes’ method, SEM, EDS, and XRD analysis were used to identify microstructural factors and phase analysis. It was found that the selection of the appropriate sintering regime is very important for composite samples to reach nearly fully dense Cu-SiC composites with proper interfacial bonding between Cu and SiC grains without the formation of any undesired phases, results in very high relative density (min. 99.48%), low total porosity (0,15-0,52), good hardness (HV 122-186) and electrical conductivity. When fine SiC grains (~1 micron) are used and the amount of SiC increases, the hardness value of the composites was effectively improved without much loss in electrical conductivity. In this respect, this study provides an effective solution for the production of Cu-SiC composites with excellent combined performance.

Mineralogical, geochemical, and physico-mechanical features of Bidzar (North Cameroon) termite mound materials and its suitability in producing fired bricks with marble powder additive

Les matériaux de termitières de Bidzar (Nord Cameroun) ont été caractérisés pour une potentielle utilisation comme matériau de construction. Pour atténuer le problème environnemental causé par l’exploitation du marbre de Bidzar, ce dernier a été utilisée comme additif (0, 5, 10, 15 et 20%) avant cuisson à 900, 1000, 1100 et 1200°C. Les matériaux de termitières sont composés de quartz, illite- smectite, vermiculite, chlorite, muscovite, calcite, hématite, et anatase avec pour principaux oxydes SiO2 , Al2O3 , et Fe2O3 . Ce sont des argiles sableuses et des argiles très sableuses dont la granulométrie est indiquée pour les produits creux, les tuiles et les briques. Certaines briques montrent des gonflements après cuisson jusqu’à 1100°C pendant que les autres présentent des retraits à la cuisson. Les autres caractéristiques des briques cuites sont : densité apparente (1,60–1,96 g/cm3 ), porosité (19,39–34,41%), absorption d’eau (10,41–21,44%), résistance à la flexion (1,25–5,64 MPa) et résistance à la compression (2,89–18,76 MPa). L’ajout de marbre couplé à la présence de matière organique (4,04–5,35%) augmente l’absorption d’eau tout en réduisant le retrait linéaire et la résistance mécanique à cause de la transformation de CaCO3 durant la cuisson qui entraîne la création d’une porosité secondaire. Ces caractéristiques physico- mécaniques répondent néanmoins aux standards des matériaux de construction.
 
 Termite mound materials (TMM) from Bidzar (North Cameroon) were characterized for their potential use as raw materials for the fired brick industry. To alleviate the environmental problem caused by the exploitation of the Bidzar marble, marble powder (0, 5, 10, 15, and 20 wt%) has been used as an additive in the formulation of bricks before firing at 900, 1000, 1100, and 1200°C. The TMM are made up of quartz, illite-smectite vermiculite, chlorite, muscovite, calcite, hematite, and anatase, with SiO2 , Al2O3 , and Fe2O3 being the main oxides. These materials are sandy clays or strongly sandy clays, which can be used for the manufacture of hollow products, roofing tiles, and masonry bricks. Some studied materials exhibit expansion up to 1100°C, while others show shrinkage at all studied temperatures. The varied characteristics of fired bricks are bulk density (1.60–1.96 g/cm3 ), apparent porosity (19.39– 34.41%), water absorption (10.41– 21.44%), flexural strength (1.25–5.64 MPa), and compressive strength (2.89–18.76 MPa). The addition of marble powder coupled with the presence of organic matter (4.04– 5.35%) increases the water absorption while decreasing the linear shrinkage, flexural strength, and compressive strength of bricks due to the transformation of CaCO3 during firing, which leads to the creation of secondary porosity. Nevertheless, these physico-mechanical characteristics meet the standards of construction materials.

Computational assessment regarding structural rehabilitation of a reinforced concrete decanter tank

The article describes the analysis of an industrial structure (reinforced concrete decanter tank for the drinking water’s storage in the Iasi – Romania area) in order to justify the proposals for structural rehabilitation to ensure structural stability. In this regard, a computational model was created in Graitec Advanced Design, using the physico-mechanical characteristics of the materials (concrete, reinforcement) from the initial design. Subsequently, using the data obtained from the technical assessment report and the non-destructive tests carried out on the structural elements, it was found a depreciation of the concrete grade (C25/30 → C16/20), at the current stage. At this stage (the structure’s service state) a modelling of the degraded structure was achieved by comparing the results obtained by Graitec Advanced Design and Axis VM, in order to realise an extended structural analysis between initial and current state. A solution for the rehabilitation of degraded elements using polymeric composite materials reinforced with carbon fibers was proposed, which was validated by the Sika CarboDur Composite systems (software program for the design of consolidation solutions).

Effects of external influencing factors on the microstructure and physico-mechanical characteristics of glass-reinforced polymer composite material based on polyimide binder

The article presents the results of experimental studies of the effects of external influencing factors (natural exposure in climatic zones, such as a temperate climate and a climate with an industrial atmosphere, during accelerated climatic tests in a thermal humidity chamber, during thermal aging, exposure in technical environments) on the microstructure and physical and mechanical characteristics of a glass-reinforced polymer composite material grade VPS-72 based on polyimide binder grade VS-51. The state of the surface of fiberglass samples after exposure was studied for one year.

The Influence of TiO2 Nanoparticles on the Physico–Mechanical and Structural Characteristics of Cementitious Materials

The urgent need for sustainable construction that corresponds to the three pillars of sustainable development is obvious and continuously requires innovative solutions. Cementitious composites with TiO2 nanoparticles (NT) addition show potential due to their improved durability, physico–mechanical characteristics, and self-cleaning capacity. This study aimed to evaluate the influence of NT on cementitious composites by comparing those with 2%–5% nanoparticles with a similar control sample without nanoparticles, as well as an analysis of cost growth. The experimental results showed an increase in bulk density of the material (4.7%–7.4%), reduction in large pore sizes by min. 12.5%, together with an increase in cumulative volume and cumulative specific surface area of small pore sizes, indicating densification of the material, also supported by SEM, EDS, and XRD analyses indicating acceleration of cement hydration processes with formation of specific products. The changes at microstructural level support the experimental results obtained at macrostructural level, i.e., modest but existent increases in flexural strength (0.6%–7.9%) and compressive strength (0.2%–2.6%) or more significant improvements in abrasion resistance (8.2%–58%) and reduction in water absorption coefficient (37.5%–81.3%). Following the cost–benefit analysis, it was concluded that, for the example case considered of a pedestrian pavement with a surface area of 100 m2, using 100 mm thick slabs, if these slabs were to be made with two layers, the lower layer made of cementitious composite as a reference and the upper layer with a thickness of 10 mm made of cementitious composite with 3% NT or 4% NT, the increase in cost would be acceptable, representing less than 15% compared to the cost for the exclusive use of cementitious composite without NT.

Preparation and Characterization of Novel Sulfoaluminate-Cement-Based Nonautoclaved Aerated Concrete.

The production of autoclaved aerated concrete via the autoclaving process incurs substantial energy consumption, posing a challenge to sustainable economic development. Herein, a novel nonautoclaved aerated concrete (NAAC) was prepared using sulfoaluminate cement as the primary raw material and aluminum powder as the aerating agent. The physicomechanical characteristics and pore structures of the sulfoaluminate-cement-based (SAC) NAAC (SAC-NAAC) were examined through X-ray diffraction, thermogravimetry, and scanning electron microscopy. The findings revealed that the optimal mechanical attributes of the SAC-NAAC were achieved at a water-cement ratio of 0.55, with a specific content ratio of polycarboxylate superplasticizer-borax-calcium stearate-sodium hydroxide at 0.24%:0.32%:0.36%:2.90%, along with 0.40% aluminum powder. The SAC-NAAC samples, with a bulk density range of 600-750 g/m3, exhibited a compressive strength of 3.55-4.16 MPa, porosity of 45.9-63.5%, and water absorption rate of 60.2-74.4%. The weight loss in the SAC-NAAC with different aluminum powder contents ranged between 15.23% and 16.83%. The prismatic ettringite (AFt) crystals served as the main source of strength for the SAC-NAAC, and AH3 was attached to the AFt surfaces in a microcrystalline gel phase, thereby further enhancing the strength of the SAC-NAAC. Thus, the lightweight, high-strength SAC-NAAC has great potential as a nonautoclaved aerated concrete.

Numerical and Experimental Investigation of Nano zinc Oxide's Effect on the Mechanical Properties of Chloroprene and Natural Rubber (CR/NR) Composites

Nanocomposites, especially natural rubber (NR), have been extensively studied for their unique features and superior performance in tire applications. The present research investigated the impact of zinc oxide nanoparticles (ZnO) on the performance of typical rotary machine seals made of chloroprene rubber / natural rubber (CR/NR) composites. An ordinary standard rubber two-roll mill and hydraulic press were used to prepare high-temperature vulcanized CR/NR samples filled with ZnO nanoparticles. Tensile strength, tear resistance, abrasion resistance, resilience, and hardness were measured to determine the effects of nanoparticles on these physical and mechanical properties. Based on the various hyperelastic modeling schemes, enhancement in multiple characteristics of the control sample, such as overhaul properties, was observed. Furthermore, results show that increasing nanoparticle content in the vulcanisates increased the physicomechanical characteristics, such as hardness, resilience, tensile strength, and elastic Modulus at 200% strain. Moreover, hyperelastic analytical modeling shows that the differences with experimental results are less than 5%.