Papers by Keyword: Cohesion

Abstract: This study examines the influence of low proportions (<2.5%by mass) of 40/63 mm gravel on the shear strength of hardfill used in the Mallegue-Amont Dam (Tunisia). To address the coarse nature of the material, a custom medium-scale direct shear apparatus was developed, despite its non-standard dimensions. Nine mixtures with varying sand-to-gravel ratios were prepared to evaluate the effect of fine content. Experimental testing was supported by statistical analysis and validated through numerical simulations using FLAC3D. Results indicate that the 40/63 mm fraction has a negligible effect on shear strength parameters. Instead, the mechanical response is predominantly controlled by cementation and particles smaller than 40 mm. Numerical modeling confirmed the reliability of the experimental findings and reinforced the validity of the adapted testing approach. The study demonstrates that representative shear strength parameters can be obtained using non-standard equipment, provided mixture preparation and mold dimensions are carefully controlled. These insights contribute to cost-effective hardfill design and improved durability of dam and infrastructure projects.

Abstract: Nowadays, the application of protective coatings based on polymer materials is a widespread method of protecting products and parts of water transport from the effects of various environments and is used to increase their service life after repair and restoration work. Application as a base for polymer composite materials based on epoxy resins is considered relevant. To improve the adhesive and mechanical characteristics of polymer composites, their physical and chemical modification was carried out. In particular, it is promising from a practical point of view to introduce into the epoxy resin a microdispersed filler of synthesized aluminum-copper charge (SACC) with a negligible content. It was established that in order to obtain protective coatings or products for increasing the resource of water transport with increased indicators of adhesive and cohesive characteristics, it is necessary to form a composite with the following number of ingredients: epoxy oligomer – 100% by mass; hardener PEPA – 10% by mass; microdisperse filler synthesized aluminum-copper charge – 2 % by mass. The mechanism of activation of interphase interaction during crosslinking of materials due to the formation of chemical bonds between side groups and segments of the epoxy oligomer and active centers on the surface of particles, such as Al+, Cu+, CuAl2 and Al4C3 is substantiated. It is shown that the adhesive-cohesive properties of materials depend mainly on the volume of the boundary surface layers that are formed around the filler particles during the polymerization of composites. The density of such layers differs from the density of the initial ingredients - polymer and filler and is determined by the following criteria: the level of wetting of the dispersed particles with a low-viscosity Newtonian oligomer, their dispersion and specific surface area, the presence of active centers on the surface. A model of the formation of epoxy composites in the presence of a dispersed filler is proposed. The model assumes the gradual formation of boundary surface layers around filler particles. In particular, it is shown the possibility of forming a network structure of a polymer with supramolecular globular inclusions in a polymer system without a filler, as well as successive stages of structure formation of composites in the presence of a filler.

Abstract: A The marble processing industry in the Peshawar region generates a significant amount of waste during the cutting and processing stages, with approximately 20 to 25% of the total processed stone ending up as waste. This waste is often disposed of in open land, causing severe environmental problems. To address these issues, this study investigates the use of waste marble dust for soil stabilization as an economical and sustainable solution, particularly in regions where granular material for backfilling is scarce. Granular soil (sand) samples were mixed with varying percentages of waste marble dust (3.5%, 7%, 14%, 21%, and 28% by dry weight of soil). A series of geotechnical tests, including specific gravity, sieve analysis, modified Proctor compaction tests, and large direct shear tests, were conducted on both natural and marble dust-stabilized soils. The modified Proctor tests identified an optimum moisture content and maximum dry density at a 14% marble dust mixture. Subsequent large direct shear tests on this optimum mixture revealed enhanced shear strength parameters, including improved cohesion and angle of internal friction. The results demonstrated that incorporating marble dust into granular soil significantly improved its geotechnical properties. At the optimum 14% marble dust content, the soil exhibited increased compactness and enhanced shear strength, making it a viable alternative to traditional backfill materials. This study not only offers a cost-effective approach to soil stabilization but also provides a sustainable solution for managing marble waste, contributing to environmental preservation especially for Peshawar city and the development of local construction projects.

Abstract: This article deals with the sealing of problematic cement-based building material and its adhesion and cohesion after exposure to water. Aqupanel cement board is chosen as a problematic material for the needs of this research. Furthermore, sealants are selected according to several criteria. These criteria include the manufacturer's recommendations on the suitability for use of cementitious substrates, affordability, and commercial availability for the average consumer. The selected sealants, the so-called primers, are then used for selected sealants. Test specimens are made of selected materials, which consist of two cement base plates, a primer, and an applied sealant. These test specimens with correctly matured sealant are further conditioned and tested according to the European standards ČSN EN ISO 8339 and ČSN EN ISO 10591. The results of these two tests are carefully recorded in the result tables and then evaluated and compared. These results show that for a tensile test without the use of water, it is necessary to apply a greater tensile force for the failure of the test specimen than for a tensile test after exposure to water. Furthermore, based on these results, we can say that polyurethane sealant is more resistant to tensile stress than acrylic sealant, for which the value of maximum elongation at failure of the test specimen is even several times higher.

Abstract: Geotechnical structures, design of embankment, earth and rock fill dam, tunnels, and slope stability require further attention in determining the shear strength of soil and other parameters that govern the result. The shear strength of soil commonly obtained by conducting laboratory testing such as Unconfined Compression Strength (UCS) Test and Unconsolidated Undrained (UU) Test. However, random errors and systematic errors can occur during experimental works and caused the findings imprecise. Besides, the laboratory test also consuming a lot of time and some of them are quite costly. Therefore, soft computational tools are developed to improve the accuracy of the results and time effectively when compared to conventional method. In this study, Artificial Neural Network (ANN) was employed to develop a predictive model to correlate the moisture content (MC), liquid limit (LL), plastic limit (PL), and liquidity index (LI) of cohesive soil with the undrained shear strength of soil. A total of 10 databases was developed by using MATLAB 7.0 - matrix laboratory with 318 of UCS tests and 451 of UU tests which are collected from the verified site investigation (SI) report, respectively. All the SI reports collected were conducted in Sarawak, Malaysia. The datasets were split into ratio of 3:1:1 which is 60:20:20 (training: validation: testing) with one hidden layer and eight hidden neurons. The input parameter of Liquidity index (LI) has shown the highest R-value (regression coefficient) which are 0.926 and 0.904 for UCS and UU model, respectively. In addition, the predictive models were tested and compare with the predicted and observed cohesion obtained from the collected experimental results. In summary, the ANN has the feasibility to be used as a predictive tool in estimating the shear strength of the soil.

Abstract: The polymeric adhesives for the installation of basalt elements on a metal base are designed primarily for environments with increased chemical and mechanical stress. They are composed of polymer resins (epoxy, polyurethane) as binders, as well as organic additives and mineral admixtures that mainly fulfill the function of filler. In all sectors of today's construction industry, maximum efficiency in the production of materials is required for sustainability purposes, which, however, must never be at the expense of the quality or the required performance. Due to these requirements, great emphasis is placed on the maximum use of secondary raw materials. Talc is used as the primary filler for polymer adhesives. Sawdust, tire rubber, and fly ash are used as secondary raw materials. The use of these in building supplies can positively affect some physical and mechanical properties of polymeric adhesives. Also, the use of secondary raw materials has the above-mentioned ecological benefit. Basic properties, such as bulk density and adhesion to both metallic and basalt elements, were monitored. The details of the cohesion of the adhesive with the bonded material, as well as the distribution of secondary raw materials in the polymer matrix, were assessed microscopically.

Abstract: Coatings deposited by detonation spraying equipment CCDS2000 using alumina powder are studied. CCDS2000 is characterized by a computer control system, robot compatible spraying unit (gun barrel), a portable chiller, two powder feeders, and other peculiar properties. This installation allows to deposit coatings on complex shape surfaces and thin-walled parts under optimal conditions. Studies of the coating properties included measurements of coating microstructure, porosity, microhardness, adhesion, cohesion, abrasive and erosive wear, and dielectric properties (specific resistivity and dielectric strength). The detonation sprayed coatings have an adhesion of 60-70 MPa, cohesion of 100 MPa, microhardness of 1500 HV₁₀₀, porosity of about 1% (measured on microsections of coatings using OLYMPUS Stream Image Analysis software). Impregnation of coatings with silicone oil showed that the real open porosity of coatings is up to 6%. Dielectric strength of the ceramic layer with the thickness of 200 μm exceeds 30 kV/mm. Specific resistivity depends on atmospheric humidity and when the relative humidity is less than 60%, the specific resistivity is greater than 10¹³ Ω·cm.

Abstract: Gypseous soil disturbed in many regions in the world. Existence of this soil with high gypsum content caused many damages to the buildings and structures that built on it due to dissolve and leaching of the gypsum slates by the flow of water through the soil mass. Therefore, it is necessary to study the properties of such soil. The dissolve of gypsum depends on many factors such as (gypsum content, temperature and other factors). Another important factor which is the acidity of the dissolution liquid must be considered. This study observes the influence of Acetic acid (CH3COOH) on the gypseous soil. Laboratory models includes (270 mm diameter) and (500 mm height) thick steel cylinder container and 17.1 kN/m3 density gypseous soil compacted in three layers, with gypsum content about 58% . The relation between the soaking time and the shear strength parameters was investigated. Also, plastic square container dimensions (250 mm x 250 mm x 300mm) used with same conditions to observed the deformation of the soil. The aim of this study is to simulate the infiltration of Acid in Gypseous soil. Test results show that increase cohesion of soil for diluted acid while decrease cohesion values for concentrated acid. Angle of friction for soil was increase for diluted and concentrated acid.

Abstract: Based on the test results of the coatings applied by gas-dynamic deposition, the paper evaluates the possibility of using the “pin” and “ring separation” methods to examine the cohesive strength of coatings on tensile test. There is a limitation of the “pin” method application for coatings with porosity due to a significant scatter in results (≤50%). Using the method of the “ring separation” with a high reliability of the results (scatter ≤5%) makes it possible to evaluate the effect of technological parameters of deposition, as well as changes in the phase composition of the coating on cohesion. For example, the cohesive strength of the aluminum coating decreases from ≈180 MPa to ≈50 MPa with rising deposition temperature from 180°C to 540°C; a sharp drop in cohesion of the applied metal layer from 78 MPa to 44 MPa is observed for the coating based on copper and zinc particles on formation of βʹ - and γ phases.

Abstract: The aim of the research was to verify whether it is possible to use specific types of treated hazardous waste as a filler in special epoxy based polymer mortars. In particular, it was a neutralizing sludge (NS-HW) with a relatively high content of heavy metals and other hazardous substances. This alkaline sludge is formed as a by-product of galvanic plating of steel elements in the baths, which are subsequently thickened and neutralized with calcium hydroxide. During the experimental verification, it was determined what resulting mechanical properties can be achieved by using 40% of the treated neutralizing sludge as a filler. In order to compare the achieved properties, a reference filler in form of a silica flour was used in the same binding matrix, and the polymer mortar containing waste foam glass of approximately the same fraction. It was discovered that, at the same percent filling, the polymer mortar with neutralizing sludge (NS-HW) had a similar tensile strength similar and cohesion with the concrete substrate as the reference material with the silica flour. Furthermore, it has been shown that this filler lowering the environmental footprint does not affect the chemical resistance of the polymer mortar to aggressive liquid solutions. As part of the microstructure observing, the uniformity of the filler distribution in the hardened polymer mortar, the incorporation of sludge particles into the epoxy matrix, and the quality of the polymer mortar bonding to the concrete was monitored using a high resolution digital microscope.