Mechanical properties and damage evolution characteristics of waste tire steel fiber-modified cemented paste backfill

During the process of constructional backfill mining,the cemented paste backfill(CPB)typically exhibits a high degree of brittleness and limited resistance to failure.In this study,the mechanical and damage evolution characteristics of waste tire steel fiber(WTSF)-modified CPB were studied through uniaxial compression tests,acoustic emission(AE)tests,and scanning electron microscopy(SEM).The results showed that the uniaxial compressive strength(UCS)decreased when the WTSF content was 0.5%,1%,and 1.5%.When the WTSF content reached 1%,the UCS of the modified CPB exhibited a minimal decrease(0.37 MPa)compared to that without WTSF.When the WTSF content was 0.5%,1%,and 1.5%,peak strain of the WTSF-modified CPB increased by 18%,31.33%,and 81.33%,while the elastic modulus decreased by 21.31%,26.21%,and 45.42%,respectively.The addition of WTSF enhances the activity of AE events in the modified CPB,resulting in a slower progression of the entire failure process.After the failure,the modified CPB retained a certain level of load-bearing capacity.Generally,the failure of the CPB was dominated by tensile cracks.After the addition of WTSF,a gradual increase in the proportion of tensile cracks was observed upon loading the modified CPB sample to the pore compaction stage.The three-dimensional localization of AE events showed that the WTSF-modified CPB underwent progressive damage during the loading,and the samples still showed good integrity after failure.Additionally,the response relationship between energy evolution and damage development of WTSF-modified CPB during uniaxial compression was analyzed,and the damage constitutive model of CPB samples with different WTSF contents was constructed.This study provides a theoretical basis for the enhancement of CPB modified by adding WTSF,serving as a valuable reference for the design of CPB constructional backfill.

Investigation of Working Bodies of the Device for Separation of Fibers Suitable for Spinning from Cotton Waste

It is known that fiber wastes (lint, down and seeds) produced at ginneries contain fibers that are suitable for spinning and can be used in industry, and their separation significantly increases the level of fiber production (1.9% - 2.5%). Based on these analyzes, the study aimed to create a new device that separates long fibers from lint and down. As a result, the amount of fiber output in the enterprise will increase and the enterprise will have significant economic benefits. In addition, the introduction of the device will prevent the addition of long fibers (longer than 16 mm) that can be used in the textile industry to the waste. This article focuses on the creation of a fiber separation device suitable for the treatment and spinning of fibrous waste produced in ginneries. The study theoretically examined the main working bodies of the fiber separation device from waste. Theoretical research is devoted to the study of the strength of the main working body of the fiber separation device−the separating saw drum and its shaft. In the study, the sawdust drum is a more stressed steel coating, and it was found that the strength reserve of this drum is [δТ] = 2.03 (where δТ = 0.8 - 2.5) was found to be. As a result of calculating the resistance of the saw drum shaft to stiffness and vibration, it was determined that the shafts are resistant to vibration under periodic loading and that the oscillation frequency along its axis through the critical rotation frequency is vcr=10.3 Gts.

Determination of Technological Parameters of Fiber Separation Device from Cotton Waste

This article examines the technological parameters of the device for the separation of fibers suitable for spinning by processing fibrous waste from the technological processes of ginneries. Technological processes in the cotton ginning industry include a complex of physical and mechanical advantages, the successful study of which is possible only with the use of modern achievements in science and technology. Therefore, it is advisable to conduct scientific research based on mathematical modeling. To justify the effective operation of the selected design of the cotton fiber separation device, it is necessary to select its optimal technological parameters. Improving the efficiency of the process of separation of spinning fibers from the composition of fibrous waste depends directly on technological parameters. The application of mathematical methods in the planning and conduct of research allows for determining the individual effects of the interaction of several factors that characterize the combined parameters of the optimization parameters, in contrast to traditional computational methods of research. As a result, it will be possible to obtain a mathematical model of the object understudy in a relatively small number of tests, which will simultaneously serve to obtain optimal solutions.

NaOH/Urea Swelling Treatment and Hydrothermal Degradation of Waste Cotton Fiber

In this study,waste cotton fabric was used as cellulose raw material and pretreated in aqueous NaOH/urea solution system to investigate the effect of NaOH/urea pretreatment solution on the hydrolysis of cotton fiber.The cotton fiber was pretreated with different conditions of aqueous NaOH/urea solution,and the pretreated cotton fiber was hydrolyzed under the same conditions as the original cotton fiber.The results of characterization analysis showed that water retention value of pretreated cotton fiber was higher than that of unpretreated sample.Moreover,the cotton fiber presented both a convoluted structure and a coarser surface,XRD results suggested that the crystallinity degree of cellulose decreased dramatically,more cellulose II appeared,and the hydrogen bond is broken.Among the different pretreatment conditions,the pretreatment effect was the best when the reaction temperature was 0°C,the solid-liquid ratio was 2:50,and the NaOH/urea ratio was 7:12.The hydrolysis experiments of pretreated and unpretreated cotton fibers showed that when the hydrothermal temperature was 230°C,the heat preservation was 2 h,and the hydrochloric acid concentration was 5 wt.%,the glucose yield reached 29.99%.H+could catalyze the hydrolysis of cotton fiber more effectively due to damage to crystal structure and hydrogen bonds.

Effect of Waste Paper Fiber on Properties of Cementbased Mortar and Relative Mechanism

The aim of this work was to investigate the effect of waste paper fiber on the properties of cement-based mortar and the relative mechanism. The cement-based mortars with various contents and mixing way of waste paper fibers were prepared and the slump flow, setting time and strength developments of all mortars were tested. Besides, Ca（OH）_2 content in hardened pastes at different ages and the microstructures of all mortar at 90 d were observed by scanning electron microscopy. The experimental results showed that in the process of mixing, more superplastizier was consumed to maintain the workability because of the absorption of water and superplastizer on waste paper fiber. With more waste paper fiber being added, longer setting time is available for the pastes with it because of the carbohydrate dissolving and its retarding to the cement hydration. Waste paper fiber is adverse to the early and later strength of cement-based mortar, but it increases the mortar strengths at 7 and 28 d. The strength, Ca（OH）_2 content and microstructure are related to the content and mixing way of waste paper fiber. Waste paper fiber helps produce the Ca（OH）_2 at 7 and 28 d, but this case is reverse at ages of 1 and 3 d. Overall, waste paper fiber leads to the appearance of more pores in the hardened paste. However, it increases the toughness of cement-based mortar.

Preparation and Characterization of Carbon Microspheres From Waste Cotton Textiles By Hydrothermal Carbonization

Carbon microspheres were prepared from waste cotton fibers by hydrothermal carbonization(HTC)with the addition of copper sulphate in this work.The important influence factors,temperature,concentration of copper sulphate,resident time were explored here.The smooth and regular carbon microspheres could be formed at 330°C with 0.15 wt%copper sulphate after 6 h from waste cotton fibers.The crystal structures of cotton fibers were destructed in a short resident time with 0.15 wt%copper sulphate from SEM images and XRD patterns of solid products.This strategy provides a new,mild and efficient method to prepare carbon microspheres from waste cotton fibers by HTC.FTIR spectra verified that the abundant functional groups existed on the surface of synthesized carbon microspheres.From XPS and element analysis results,the copper sulphate participated in the forming process of carbon microspheres indeed.The presence of copper sulphate in the carbon microspheres provided a possibility for the application in antibacterial field.Besides,the catalytic mechanism of copper sulphate on the hydrolysis and carbonization of waste cotton fibers were also discussed.In conclusion,the copper sulphate is an efficient agent for preparing carbon microspheres by HTC from waste cotton fibers.

Biodegradable Behavior of Waste Wool and Their Recycled Polyester Preforms in Aqueous and Soil Conditions

Present study deals with the biodegradable behavior of individual components and their preforms of nonwoven biocomposites developed from waste wool fibers including coring wool(CW),dorper wool(DW)and recycled polyester fibers(RPET).A respirometric technique was employed to estimate the production of CO_(2) during the biodegradation experiments under soil and aqueous media conditions.Functional groups of test samples before and after biodegradation were analyzed using Fourier transform infrared spectroscopy(FTIR).Leaching chemicals such as formaldehyde(hydrolyzed)and Chromium VI(Cr VI)was also measured.The CO_(2) emission in wool fibers CW and DW indicated 90%and 60%biodegradation in soil burial and aqueous media conditions respectively,for 100 days incubation.RPET fibers,20%and 10%biodegradation in soil burial and aqueous media conditions was measured respectively while the preforms of waste wool and RPET reflected 30%and 25%biodegradation in soil burial and aqueous media conditions,respectively.The degradation of end functional groups such as carbonyl(keto and ester),aldehyde and hydroxyl were also confirmed by FTIR.The DW and CW wool fibers showed higher Cr(VI)concentration as compared to the RPET.The released formaldehyde results showed higher concentration for RPET preforms as compared to waste wool preforms.These results suggest that waste wool preforms are extremely environment friendly as compared to RPET preforms.Thus,waste wool preforms it can be potentially utilized for preparing biocomposite materials and associated biobased products.

Synthesis and characterization of azo dyestuff based on bis(2-hydroxyethyl) terephthalate derived from depolymerized waste poly(ethylene terephthalate) fibers

This work aimed at effectively utilizing the chemically depolymerized waste poly（ethylene terephthalate）（PET） fibers into useful products for the textile industry.PET fibers were glycolytically degraded by excess ethylene glycol as depolymerizing agent and zinc acetate dihydrate as catalyst.The glycolysis product,bis（2-hydroxyethyl） terephthalate（BHET）,was purified through repeated crystallization to get an average yield above 80%.Then,BHET was nitrated,reduced,and azotized to get diazonium salt.Finally,the produced diazonium salt was coupled with 1-（4-sulfophenyl）-3-methyl-5-pyrazolone to get azo dyestuff.The structures of BHET and azo dyestuff were identified by FT1 R and ^1H NMR spectra and elemental analysis.Nylon filaments dyed by the synthesized azo dyestuff with the dye bath pH from 4.14 to 5.88 showed bright yellow color.The performances of the dyestuff were described with dye uptake,color fastness,K/S,L^＊,a^＊,b^＊.and △E^＊ values.