Papers by Keyword: Physico-Mechanical Properties

Abstract: Serious efforts are currently undertaken to produce sustainable composite building materials by exploiting industrial by-products. This study examines the use of industrial by-products, specifically limestone filler and silica fume, as alternatives to cement and fine aggregates (washed or non-washed sand), for the production of a novel sustainable cementitious masonry block. The research involved the design of various mixtures with different proportions of the aforementioned raw materials and the evaluation of their mechanical, durability and thermal performance. The findings reveal that, depending on the type of sand used (washed or non-washed), high volumes of limestone filler can be incorporated into the mixtures, without compromising the overall performance of the end-product. This approach not only promotes the use of waste by-product materials in the design and production of composite building materials, but also contributes to more eco-friendly and sustainable construction practices.

Abstract: The main perspective of this paper is enhancing the physico-mechanical and protective characteristics of concrete. This was achieved by incorporation Layered double hydroxide (LDH) in mix design of concrete with different doses. The concrete specimens were prepared with LDH percentages (0.5, 1.0, 1.5, and 2) % by the cement weight. After the characterization of LDH, the prepared concrete specimens were investigated as follows: the workability and density of the fresh concrete, effect of the addition of LDH on the compressive strength of hardened concrete were determined. The protective performance of concrete was evaluated by determining water absorption, contact angle, and chloride permeability. The obtained results detected that the physico-mechanical and protective performance of concrete are enhanced gradually by the addition of LDH up to 1.5% as follows; concrete slump decreased from 110 mm for control sample (concrete without LDH addition) to 47mm for M3 sample (concrete with 1.5% LDH) by 57% decrease percent. Density of concrete with 1.5% LDH increased by 5% as compared with control sample. Compressive strength increased by 25% for concrete with 1.5% LDH as compared with controls one. On the same time experimental results demonstrated that both water absorption and chloride permeability were decreased by 20% & 43% respectively, meanwhile contact angle increased by 24% for the same comparative samples. After this percent (1.5%), LDH is agglomerate and therefore unable to disperse uniformly so the optimum calculated percent of LDH for enhancing concrete performance is 1.5%.

Abstract: The article presents the results of studies of the positive effect of compounds of the type A(NO₃)₂, as modifiers of the aluminosilicate adhesive of the composition Na2O∙Al2O∙6SiO2∙20H2O, on increasing the strength of adhesive joints of wood of various species. The grade strength increases 1.39 times compared to the strength of the adhesive that does not contain these compounds. According to the degree of influence on the shear strength along the fibers, the additives can be ranked in the series Ba (NO₃)₂ > Ca (NO₃)₂ > Mg (NO₃)₂ > 95%Ca (NO₃)₂+5%NH₄NO₃. It is noted that for gluing samples from a pine substrate, it is advisable to add magnesium and barium nitrates to the aluminosilicate glue in an amount of 1% (by weight); beech wood - calcium and barium nitrates in the amount of 1 and 0.5% (by weight); oak wood - calcium nitrates in an amount of 1% (by mass), a mixture of nitrates in an amount of 0.5% (by mass) and barium nitrate in an amount of 0.5 and 1.5% (by mass). According to the influence on the strength of adhesive joints, the substrates can be ranked in the order beech > oak > pine. Further studies will present the results of the effect of alkaline earth metal nitrates on the deformation properties of adhesive joints and on rheokinetic and colloid-chemical properties.

Abstract: The revolution towards using lignocellulosic agro-residues as polymer composite reinforcements compels a fresh look at the entire operations from inception to final composite products. Chemical treatment is a frequently reported method that enhances interfacial and fiber-matrix adhesion properties. However, our study utilised seawater treatment for fiber surface modification as an eco-friendly and cost-effective approach compared to the toxic chemical reagents. Banana trunk layers were immersed in seawater for 7, 14, 21, and 28 days at ambient conditions before fiber extraction. Our results revealed that the treatment duration affected the extracted fibers’ physico-mechanical properties compared to untreated fibers. Scanning electron microscopy showed significant alterations in fiber surfaces. At optimum treatment duration, we found that treated fiber density increased to 1.31 g/cm³, cross-sectional area decreased by 45.6 % and tensile strength increased to 389 Mpa. This research was undertaken to demonstrate the potential of utilizing the abundant non-potable seawater for banana fiber extraction process as a way of lessening use of toxic chemicals and freshwater scarcity in the desert and arid regions.

Abstract: The article presents the results of studies of the effect of lithium, sodium, potassium and ammonium nitrates on the physical and mechanical properties of aluminosilicate adhesives intended for gluing wood and structures based on them. Nitrates were introduced into the aluminosilicate adhesive of composition Na₂O·Al₂O₃·6SiO₂·20H₂O in amounts of 0.5, 1 and 1.5 wt. %. Changes in the shear strength along the fibers of substrates made of pine, beech, and oak wood were studied after 7 and 28 days of hardening of aluminosilicate adhesives in vivo. It is shown that for gluing pine wood it is most expedient to use adhesives containing lithium nitrate, potassium nitrate and ammonium nitrate is within 1.5 wt. %, the shearing strength along the fibers after 28 days of hardening is 1.7-1.8 times higher than the strength of the adhesive without additives. For gluing beech wood, it is most advisable to use adhesives containing potassium and ammonium nitrate in an amount of 1.5 wt. %, the shearing strength along the fibers after 28 days of hardening is 1.5 times lower than the strength of the adhesive without additives. For gluing oak wood, it is most advisable to use adhesives containing lithium nitrate, potassium nitrate and ammonium nitrate in amounts of 0.5 and 1.5 wt. %, the shear strength along the fibers increases by 1.3-1.5 times for 7 and 28 days of hardening compared to the strength of the adhesive without additives. According to the degree of influence on strength, modifying additives can be ranked in the series LiNO₃×3H₂O>KNO₃>NH₄NO₃>NaNO₃.

Abstract: The purpose of the work was to study physico-mechanical properties of glued connections of wood rods, toothed lamellae after splicing and corner spike clamping of window frames which were obtained in the production conditions. The alkaline aluminosilicate binder-based adhesive (glue) of the composition 0.8Na₂O·Al₂O₃·4.5SiO₂·20H₂O modified using organo-mineral additives was used in testing. After solidification of the adhesive, the samples were cut to determine the strength of frame corner joints in bending, glued timber connections for splitting along the grains, toothed glued connections in bending and water resistance of the glued connections of timber elements. The results of these tests showed high values of strength characteristics in case of the proposed modified alkaline aluminosilicate binder-based adhesive (glue), which were by 1.5 times higher than those in case of the WoodMax (D2) taken as a reference glue, and in water resistance complied with Class D2/D3 as per PN-EN 204.

Abstract: Over the last years, the increasing need of cost saving and environmental protection has led to finding alternative methods and materials in construction. One of these methods is the alkali-activation, which can transform alumino-silicate binders, like siliceous fly ashes, blast furnace slags, into useful materials. On the other hand, little focus has been given to study the potential uses of high calcium fly ashes (HCFAs), which are also produced in Europe and constitute the half of total fly ash output.In this paper, a calcareous fly ash (F) from Agios Demetrios power plant in Greece was studied in combination with different alumino-silicate materials such as pozzolan, diatomite and brick dust in order to improve their physico-mechanical characteristics. Pastes were mixed with an alkaline activator, which consists of a sodium silicate solution and sodium hydroxide solution 10M. The weight ratio of NaOH:Na₂SiO₃ was 1:1. At the fresh state, setting time of the mixture was measured after mixing. Prismatic specimens were matured at different temperature conditions (25°C for 2 days and 65°C for 2 days). The samples were tested under flexural and compressive strength at the ages of 2, 7 and 28 days. Volume deformation and open porosity were also determined.

Abstract: In this paper, the physico-mechanical properties of alkali-activated mortars (CF/S) containing calcareous fly ash (CF) from the combustion of lignite and ladle furnace slag (S) from the steelmaking process as binders as well as sand and glass cullet as inert material have been studied. The constituents were mixed with the alkaline activator (NaOH:Na2SiO3 was 1:1). The binders and aggregates were used in a ratio 1:3 while a part of sand was replaced by glass aggregates (60%). The specimens (dimensions 40x40x160 mm) of alkali-activated mixtures CF/S: 100/0, 80/20 and 50/50 were cured at 25 °C for 2 days and then were placed in humid environment (95±5 % RH, 25 °C). Then the mechanical strength and porosity at 7-d, 28-d and 90-d age were measured. All of the CF/S specimens exhibited compressive strength around 15 MPa at 28 days. After the 28-d age the specimens of CF/S mortars were exposed to wetting/drying and freeze/thaw cycles to have an estimation of durability of alkali-activated CF/S mortars and compared to the Portland I42.5 cement mortars (PC) of high strength 43 MPa. Mass loss of specimens was measured by weighing them. The results showed that alkali-activated CF/S mortars appear to have similar or slight lower behavior to wetting/drying and freeze/thaw cycles compared to net cement mortars.

Abstract: A new method of layered silicate (montmorillonite) intercalation by polyvinylpyrrolidone in the solution under ultrasonic treatment is described in this work. The structure and thermophysical properties of the developed nanomodifier and the components rational ratio have been investigated. The effect of intercalated montmorillonite on physico-mechanical, thermophysical and insulating properties of polycaproamide PA-6 has been determined.

Abstract: This research focused on physical and mechanical properties of biocomposite made from bamboo and citric acid as natural binder. Bamboo particles was mixed with citric acid at 0 – 40 wt% resin content based on air-dried particles and each mixture was hot pressed at 180 °C for 10 min. The result showed that addition of citric acid could improve significantly the physical and mechanical properties of particleboard. The thickness swelling was 50 % for bamboo binderless particleboard (0 wt%), whereas it decreased to 7 % under a resin content of 10 wt%. The optimum resin content in this study was 30 wt%, while the modulus of rupture dan the modulus of elasticity were 14 MPa and 4.5 GPa, respectively. The ester linkages were detected by Fourier transform infrared spectroscopy, indicating that carboxyl groups from citric acid reacted with hydroxyl groups from bamboo to produce better properties of particleboard, especially its dimensional stability. Based on these results, it was concluded that citric acid could be as a potential natural binder for bamboo particleboard.