Geomechanical behaviors of shale in many geotechnical engineering areas, such as shale gas extraction, tunnel excavation, slope engineering, are highly influenced by anisotropy and hydration. In this ...work, a number of ϕ25 mm × 50 mm shale specimens were prepared with three levels of moisture contents and seven bedding plane orientations (β, in degrees) relative to the axial direction. A series of compression tests for these specimens was then conducted under four different confining pressures to investigate their geomechanical behaviors considering the combined effect of anisotropy and hydration. The results demonstrate the following points. 1) During the water absorption process, the shale specimens swell and suffer damage, which are primarily observed along the bedding plane. 2) The curve of compressive strength (peak deviatoric stress) vs. β is “U-shaped,” with the lowest value at β = 30°. The apparent elastic modulus decreases with the increase in β and then remains nearly unchanged when β > 45°. As β increases, the strains at peak stress and average apparent Poisson's ratio increase first and then decrease when β > 30°. 3) The plastic deformation stage and residual stress stage, which negatively relate to the elastic-brittle properties of shale, become more obvious with increasing moisture content, and the specimen for which β is closer to 30° exhibits a more significant change of that. 4) With increasing moisture content, the compressive strength and axial strain at peak stress decrease, apparent elastic modulus decreases nonlinearly, and average apparent Poisson's ratio increases approximately linearly. 5) The effect of anisotropy on the compressive strength decreases with increasing confining pressure and this weakened effect by confining pressure becomes less with increasing moisture content. 6) With the increase in β, the effect of water absorption on the compressive strength first strengthens a little and then weakens when β > 30° or 45°, and this change with β becomes more significant under higher confining pressure. 7) The effect of confining pressure on the compressive strength strengthens a little when β < 30° and then weakens with the increase in β, and this change with β weakens with increasing moisture content. 8) The anisotropy of shale could be the major controlling factor for geomechanical behaviors, and water absorption along the bedding plane can enhance the effect of anisotropy. The results can not only guide the design and construction of geotechnical engineering structures related to shale, but can also be used as a reference for geological research on the deformation and failure of shale formations affected by water intrusion and geological stresses.
•Swelling and damage of hydrated shale mainly generate along the bedding plane.•Effect of anisotropy on strength decreases with increasing confining pressure.•Shale changes from brittleness to elastic-plastic with increasing moisture content.•Strength and axial strain at peak stress decrease with increasing moisture content.•Elastic modulus reduces and Poisson's ratio increases as increasing moisture content.
In order to explore the effect of the foaming agent type on the properties of foamed mixture lightweight soil mixed with bauxite tailings (FMLSB), low-density (437.5 kg/m3 and 670 kg/m3) and ...high-density (902.5 kg/m3 and 1170 kg/m3) FMLSB were prepared using protein-based and synthetic-based foaming agents (AF and SF, respectively). The foam stability, micro characteristics, compressive strength, fluidity, and volume of water absorption of the FMLSB were investigated. The results showed that the foam made from AF had better strength and stability compared to SF. The internal pore sizes of both AF- and SF-FMLSB at low density were large, but at high density the internal pore sizes and area porosity of AF-FMLSB were smaller than those of SF-FMLSB. In terms of compressive strength, the compressive strength of AF-FMLSB was improved by 17.5% to 43.2% compared to SF-FMLSB. At low density, the fluidity of AF- and SF-FMLSB is similar, while at high density the fluidity of AF-FMLSB is much higher than that of SF-FMLSB. In addition, the stable volume of water absorption of SF-FMLSB is smaller than that of AF-FMLSB at low density, and the corresponding water resistance is better, but the situation is reversed at high density.
•Realizes the value-added reuse of waste sandstone resources.•Micron quartz grains <150 µm can improve compressive strength and ASR property.•Provides a convenient method in testing ASR.•S-sand ...produced from sandstone by-product can be used as high-quality fine aggregate.
The construction industry is facing a shortage issue of river sand, therefore broadening new sources of fine aggregate is imminent. This paper demonstrates the feasibility of a recycled sand from sandstone waste in mortar manufacturing by comprehensive assessment of workability, mechanical properties, water absorption, alkali silica reaction (ASR). The recycled sandstone sand (S-sand) has a smoother microscopic morphology and better particle size distribution than river sand (R-sand). Fine particles smaller than 150 µm in R-sand usually contain a large amount of impurities (such as clay) and are considered harmful. However, the S-sand containing ∼15.7% µm quartz grains <150 µm significantly improves the mortar performance in terms of compressive strength and ASR property. At the same water to binder ratio, the mortar using the S-sand shows worse workability than that using R-sand but a slight increase of water to binder ratio or adding water reducer improves not only the workability but also mechanical properties. For the ASR test, the S-sand shows potential uncertain risk as per ASTM C 1260. Using calcined clay or fly ash to replace 25% cement can effectively inhibit expansion risk. The compressive strength is reduced due to ASR, however, as the ASR progresses, it is somehow restored. This study also finds the good linear relationship between length change of mortar bar and mass change, which can be used to predict the sand ASR property. The results showed that S-sand produced by waste sandstone by-products can be used as high-quality fine aggregate.
•Concrete reinforced with steel fibers recovered from waste tires is investigated.•The elastic modulus, linear shrinkage, and water absorption are determined.•The strengths and their energy ...absorptions and toughness indices are reported.•Reduction in linear shrinkage is noted.•The compressive and split tensile strengths and their energy absorptions improved.
The increasing pollution burden is a significant hurdle in achieving the United Nations’ goals for a sustainable society. Various methods are used to handle pollution, including recycling waste into new products and using waste to improve other materials’ properties. In this respect, the trend of using waste materials, especially waste fibers, in the construction industry to improve the strength and durability of concrete is also receiving attention. Currently, most countries use raw steel fibers from waste tires (RSFs) to enhance the properties of cement composites. Using RSFs in construction materials can help decrease pollution and produce low-cost sustainable materials. Therefore, it is essential to explore the suitability of RSFs for enhancing the properties of cement composites. This study aims to explore the suitability of RSFs for durable and sustainable cement composites. The study’s specific aim is to evaluate the efficiency of locally available RSFs of Bratislava, Slovakia, for improving local concrete durability and strength properties. For this purpose, the concrete C20/24 of Cemix Bratislava is used. 0.30% to 0.75% of RSFs are added in raw form by volume fraction of the concrete. A statistical analysis of 1057 RSFs is performed to determine the frequencies of their dimensions. The workability of the concrete is measured by using the slump test. The concrete’s hardened properties, including compressive strength (CS), split tensile strength (SS), flexure strength (FS), and modulus of elasticity (EM), are evaluated. In addition, water absorption (WA) and linear shrinkage (LS) are also determined. All tests are performed following the ASTM standards except the test for EM. The precrack and postcrack energy absorption and toughness index are also reported for each strength property. The maximum enhancement of 20% and 16% is noted in CS and SS for RSF-incorporated concrete. At the same time, the FS did not improve. The WA increased, and LS decreased for RSFRCs compared to PC. Therefore, it can be concluded that raw steel fibers from discarded tires have the potential to be used for producing sustainable and durable concrete.
The disposal of sludge generated by water treatment by chemical coagulation is considered an environmental problem that has attracted attention of researchers worldwide, whose objective is to promote ...strategies for their productive use. This study addresses results of studies conducted in the recent 7 years on the aluminous sludge use in the manufacture of ceramic products. The literature shows that the proportion of sludge and the firing temperature are two key factors that affect the final ceramic products technological properties: water absorption, mechanical resistance, porosity and bulk density. It is concluded that it is feasible to incorporate water treatment sludges in partial replacement of one of the constituent materials of clay bodies, with additions up to 10% sludge and firing temperatures above 1000 °C.
Background; Bakery products such as cakes are widely consumed all over the world; so, their enrichment with nutrients is an effective way to prompt the people health. This goal can be achieved using ...the powder of dried fruit and vegetable in cake formulation.
Scope and approach; In this paper, the effects of dried fruits and vegetable powder (apple, quince, orange, various berries, grape pomace, mango, peach, melon, carrot, pumpkin and mushroom) on the batter rheology, physicochemical properties, organoleptic aspects and microbial attributes of the cakes were reviewed. It was determined that these kinds of powder raised the fibers content and nutritional values of the cakes (antioxidants, vitamins and minerals). The high water absorption capacity of the fiber affects batter rheology, the texture, volume, density and microbial attributes of the cake.
Key finding and conclusion; In conclusion, powder of fruit and vegetable exhibited benefits of attracting the consumers by improving appearance, texture, nutritional values, sensorial properties and shelf life of the cake.
•Bakery products such as cakes are widely consumed all over the world.•Powder of dried fruits and vegetables are good source of nutrients.•Cake formulation with this is an effective to prompt the people health.•The powder affects color, texture, nutritional and sensorial aspects of the cake.
Sufficient amounts of fluorographene sheets with different sheet-size and fluorine/carbon ratio were synthesized for preparing of fluorographene/polyimide hybrids in order to explore the effect of ...fluorographene on the dielectric properties of hybrid materials. It is found that the fluorine/carbon ratio, width of band gap, and sheet-size of fluorographene play the important roles in determining the final dielectric properties of hybrids. The fluorographene with high fluorine/carbon ratio (F/C ≈ 1) presents broaden band gap, enhanced hydrophobicity, good dispersity and thermal stability, etc. Even at a very low filling, only 1 wt %, its polyimide hybrids exhibited drastically reduced dielectric constants as low as 2.1 without sacrificing thermal stability, improved mechanical properties obviously and decreased water absorption by about 120% to 1.0 wt %. This provides a novel route for improving the dielectric properties of materials and a new thought to carry out the application of fluorographene as an advanced material.
This investigation explores the water intake characteristics of hybrid composite samples composed of Wood Dust as organic filler (WD), Prosopis Juliflora as fiber (PJF), and epoxy as matrix. The ...specimens underwent immersion in both distilled and seawater environments for a duration of 240 hours. The composite samples, with compositions of 10WD + 30PJF + 60 PF, 20WD + 20PJF + 60 PF, and 30WD + 10PJF + 60 PF, were subjected to moisture content measurements at different intervals. Mechanical properties were tested following ASTM standards for both dry and wet conditions. Results indicate that seawater immersion leads to higher moisture absorption compared to distilled (condensed) water, with the fiber (PJF)-rich composite (30PJF +10WD + 60 PF) exhibiting the greatest water absorption. The water absorption pattern exhibited by the hybrid composite of WD/PJF/PF does not adhere to a Fickian behavior. Tensile, flexural, and impact properties were evaluated, with the (10WD + 30PJF + 60 PF) specimen showcasing superior performance in dry conditions, boasting a tensile character of 51 MPa, flexural (bending) strength of 60 MPa, and impact value of 1.4 KJ/m
2
. However, its strength diminishes upon exposure to distilled water and seawater. SEM analysis of fractured surfaces from seawater-exposed specimens provides additional insights. In conclusion, this study sheds light on the influence of immersion on moisture absorption and mechanical properties, emphasizing the prevalence of non-Fickian behavior and the varying performance of different compositions, with the (10WD + 30PJF + 60 PF) composition demonstrating remarkable strength under dry conditions.
•The effect of GGBFS and SF in RAC are presented using RSM.•RSM is an efficient method for predicting and optimizing the properties of RAC.•Some equations for prediction of properties of RAC are ...presented.•The equations provided an excellent correlation between variables and responses.
Concrete is the most consumed material in the construction industry, and using recycled concrete aggregates (RCA), silica fume (SF) and ground-granulated blast-furnace slag (GGBFS) in concrete could reduce its negative environmental impacts by preserving natural resources and reducing construction and demolition (C&D) waste generation and CO2 emissions. Optimizing the mix design based on both mechanical and durability properties of RAC has not been performed. In this study, the mechanical properties and durability of Recycled Aggregate Concrete (RAC) containing GGBFS and Silica Fume (SF) were evaluated via Response Surface Methodology (RSM). The GGBFS was used to reduce the environmental pollution caused by cement production and balancing the negative effect of RA on the mechanical properties of concrete. The results indicated that RA had a negative effect on durability properties of concrete at 7 and 28 ages, while it had no effect on the properties at 90 days. Finally, optimized mix designs were obtained based on two specific scenarios. In the first scenario, the mix design with the highest of both mechanical and durability properties was obtained. In the second one, a mix design with the highest amounts of GGBFS, SF and RA, was achieved, due to the environmental issues related to concrete production.
•Natural fibre inclusion in soil blocks positively affects mechanical properties.•Fibre reinforced soil blocks have improved resistance against wearing and erosion.•0.5% fibre content by weight is ...recommended to practitioners for use.•Correlations between properties do not follow those for binder stabilised blocks.•The importance of soil type vs. fibre type depends on the property of interest.
This study investigates the properties of soil blocks stabilised with fibres from agricultural waste. Laboratory experiments including density, water absorption, shrinkage, compressive strength, tensile strength, wearing and erosion were conducted on soil blocks made with two soil types and enhanced with three fibre types at 0.25–1wt.%. It was found that the physical, mechanical and durability properties of the blocks were generally improved and a recommendation of 0.5wt.% fibre content and high clayey soil are made. Many assumptions about relationships between properties established for binder stabilised blocks are found to be inappropriate for fibre reinforced blocks.
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