Influence of Rubber Powder Movement on Properties of Asphalt Rubber from the Mesoscopic View

The research on asphalt performance mainly focused on the macro performance and micro mechanism.Mesoscopic analysis was introduced to study the effect of rubber powder movement on asphalt rubber properties.After the preparation parameters and the preparation process of asphalt rubber were determined,the modification mechanism and rheological properties were analyzed which revealed the compatible stability mechanism.Then,the analysis model of asphalt rubber was established to focus on simulating the effect of rubber powder and the spatial movement on its mechanical properties.The experimental results show that rubber powder can make the asphalt rubber bear more uniform stress distribution and enhance the ability to resist deformation.Meanwhile,the rotational motion and final distribution of rubber powder have an obvious impact on the mechanical properties of asphalt rubber.In the selected feature points,the average stress of rubber powder at 0°space angle is only 34.1%of that at90°space angle.When the rubber powders are all in parallel in the ideal state,it enhances the mechanical properties the most.This study supplements the“mesoscopic”scale between macro and micro research.The relationship between micro mechanism and macro properties of asphalt rubber will be established from the mesoscopic perspective.It is also an effort to realize the effective correlation from micro,mesoscopic to macro in asphalt.

DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. 'the second plateau', appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

Biosorption of copper ions from dilute aqueous solutions on base treated rubber (Hevea brasiliensis) leaves powder: kinetics, isotherm, and biosorption mechanisms

The effciency of sodium hydroxide treated rubber (Hevea brasiliensis) leaves powder (NHBL) for removing copper ions from aqueous solutions has been investigated. The e?ects of physicochemical parameters on biosorption capacities such as stirring speed, pH, biosorbent dose, initial concentrations of copper, and ionic strength were studied. The biosorption capacities of NHBL increased with increase in pH, stirring speed and copper concentration but decreased with increase in biosorbent dose and ionic strength. The isotherm study indicated that NHBL fitted well with Langmuir model compared to Freundlich and Dubinin-Radushkevich models. The maximum biosorption capacity determined from Langmuir isotherm was 14.97 mg/g at 27°C. The kinetic study revealed that pseudo- second order model fitted well the kinetic data, while Boyd kinetic model indicated that film diffusion was the main rate determining step in biosorption process. Based on surface area analysis, NHBL has low surface area and categorized as macroporous. Fourier transform infrared (FT-IR) analyses revealed that hydroxyl, carboxyl, and amino are the main functional groups involved in the binding of copper ions. Complexation was one of the main mechanisms for the removal of copper ions as indicated by FT-IR spectra. Ion exchange was another possible mechanism since the ratio of adsorbed cations (Cu2+ and H+) to the released cations (Na+, Ca2+, and Mg2+) from NHBL was almost unity. Copper ions bound on NHBL were able to be desorbed at > 99% using 0.05 mol/L HCl, 0.01 mol/L HNO3, and 0.01 mol/L EDTA solutions.

Hybrid Modified Rubber Powder and Its Application in Cement Mortar

This research focused on using the waste rubber powder as a kind of regenerate resources to improve the mechanical properties of cement mortar.The two kinds of hybrid modified rubber powder TRP and ATRP were prepared by sol-gel method and then used in cement mortar.The structures and properties of them were studied.It is shown that the nano Si-O-Si network is generated in TRP and ATRP networks and the hydrophilic group is grafted on the surface of ATRP.The mechanical properties of rubber-treated mortar（RTM） were tested and the microstructures of them were also studied.Compared to the mortars with unmodified rubber powders（RP）,NaOH treated rubber powder（SRP） and coupling agent treated rubber powder（CRP）,the RTM with ATRP has the highest compressive strength and flexural strength.The stress-strain curves shown that the peak of stress of RTM with ATRP is increased and indicated the higher compression deformation and toughness.It is found that the interfacial adhesion between the ATRP and cement mortar is increased distinctly by SEM,which results in enhanced ductility and mechanical properties of RTM with ATRP.

Sequestration of toxic Pb(Ⅱ) ions by chemically treated rubber(Hevea brasiliensis) leaf powder

Rubber leaf powder （an agricultural waste） was treated with potassium permanganate followed by sodium carbonate and its performance in the removal of Pb（II） ions from aqueous solution was evaluated. The interactions between Pb（II） ions and functional groups on the adsorbent surface were confirmed by Fourier transform infrared （FT-IR） spectroscopy, scanning electron microscopy （SEM） coupled with X-ray energy dispersive spectroscopy （EDX）. The effects of several important parameters which can affect adsorption capacity such as pH, adsorbent dosage, initial lead concentration and contact time were studied. The optimum pH range for lead adsorption was 4-5. Even at very low adsorbent dosage of 0.02 g, almost 100% of Pb（II） ions （23 mg/L） could be removed. The adsorption capacity was also dependent on lead concentration and contact time, and relatively a short period of time （60-90 min） was required to reach equilibrium. The equilibrium data were analyzed with Langmuir, Freundlich and Dubinin-Radushkevich isotherms. Based on Langmuir model, the maximum adsorption capacity of lead was 95.3 mg/g. Three kinetic models including pseudo first-order, pseudo second-order and Boyd were used to analyze the lead adsorption process, and the results showed that the pseudo second-order fitted well with correlation coefficients greater than 0.99.

EXPERIMENTAL DEVICES OF PRODUCING SCRAP RUBBER POWDER WITH WAVE CRYOGENIC TECHNOLOGY

A system of producing scrap rubber powder with wave cryogenic technology isput forward. Main equipments such as wave refrigerator, vortex pulverizer and fluidized cooler arepresented. The key techniques about silica gel refreshing in desiccators and system drying arediscussed. The potential improvement of the system is pointed out. The manufacturing cost is lowerthan the cost of liquid nitrogen cryogenic method, and the quality is better than that of normaltemperature milling. Moreover, wave refrigerators have several advantages over turbine expendersapplied in the cryogenic milling system.

Blast performance of layered charges enveloped by aluminum powder/rubber composites in confined spaces

A layered charge composed of the JH-2 explosive enveloped by a thick-walled cylindrical casing(active aluminum/rubber and inert lithium fluoride/rubber composites) was designed and explosion experiments were conducted in a 1.3 m3tank and a 113 m3bunker.The blast parameters,including the quasistatic pressure(ΔpQS),special impulse(I),and peak overpressure(Δpmax),and images of the explosion process were recorded,and the influence of the Al content(30% and 50%) and Al particle size(1,10,and 50 μm) on the energy release of aluminum/rubber composites were investigated.The results revealed that the use of an active layer increased the peak overpressure generated by the primary blast wave,as well as the quasistatic pressure and special impulse related to fuel burning within tens of milliseconds after detonation.When the Al content was increased from 30% to 50%,the increases of ΔpQS and I were not obvious,and Δpmaxeven decreased,possibly because of decreased combustion efficiency and greater absorption of the blast wave energy for layers with 50% Al.Compared with the pure JH-2charge,the charge with 1 μm Al particles produced the highest Δpmax,indicating that better transient blast performance was generated by smaller Al particles.However,the charge with 10 μm Al particles showed the largest ΔpQSand I,suggesting that a stronger destructive effect occurred over a longer duration for charges that contained moderate 10 μm Al.

Studies on Mechanical and End-Use Properties of Natural Rubber Filled with Snail Shell Powder

A series of natural rubber-snail shell powder vulcanizates were compounded on a two-roll mill, and moulded on a compression moulding machine. The mechanical and end-use properties of the natural rubber vulcanizates were investigated at snail shell powder contents, 0 to 20 pphr. The snail shell powder was characterized for filler properties and sieved to 0.075, and 0.30 μm particle sizes. Carbon black was used as the reference filler. Results showed that the tensile strength, modulus, elongation at break, and resilience of the rubber vulcanizates were not enhanced on addition of snail shell powder. The hardness of the rubber vulcanizes were marginally increased at high snail shell powder content. However, the specific gravity of the rubber vulcanizates showed increases with increase in snail shell powder content. At a filler content above 5 pphr, snail shell powder exhibited good flame retardant property in the vulcanizates. The swelling indices of snail shell powder (0.075 μm) filled natural rubber were generally good, and better than those of snail shell powder (0.30 μm) filled natural rubber. Carbon black was found to show more property improvement for the natural rubber vulcanizates when compared to snail shell powder. Although the mechanical properties of snail shell powder filled natural rubber vulcanizates were not good, there were improvements in the end-use properties, an indication that snail shell powder could still find utilization in the rubber industry where specific end-use property of a rubber product is required.

Performance of the Cement Matrix Composite Material With Rubber Powder

The effect of the deferent rubber content substituted for fine aggregate on the mortar performance was studied.The effects of the rubber coated with the coating materials on the mortar compressive strength,bending strength and impact work were discussed.The optimum rubber powder content and the suitable coating material were found.Through the electrical probe test-BEI,SEI and calcium ion distribution,and the slight crack and the interface between the rubber and cement matrix are analyzed.The results show that the rubber powder coated with the surface treatment materials A,B and C has the capability of absorbing a large amount of energy under the compressive and flexural load and the slight cracks of R-C were controlled and restrained.

Interfacial Modification of Corn Stalk Cellulose Reinforced Used Rubber Powder Composites Treated with Coupling Agent

Corn stalk cellulose(CS)/used rubber powder(RP)composites were prepared by mixing,the silane coupling agent 3-Mercaptopropyl trimethoxysilane(KH590),r-Aminopropyltrieth oxysilane(KH550),isopropyl dioleic(dioctylphosphate)titanate(HY101)and bis-(γ-triethoxysilylpropyl)-tetrasulfide(Si69)were used to modify the interface of composites.The effects of the CS and coupling agents on the mechanical properties,thermal properties,interfacial morphology and structure of the composites were investigated,respectively.The results showed that the addition of CS could effectively improve the mechanical properties of the composites.Compared with the untreated composites,the interfacial bonding between CS and RP was significantly improved by the coupling modification treatment,and the tensile strength and elongation at break of composites with Si69 increased by 3.13 MPa and 10%,respectively,the Si69 showed the best coupling modification effect,followed by KH590,then KH550 and HY101 when the CS content was 25 pph(part per hundred)and coupling agent 1.5 pph,and the thermal decomposition temperature increased by 30℃.

Evaluating Simultaneous Impact of Slag and Tire Rubber Powder on Mechanical Characteristics and Durability of Concrete

In this experimental study,the impact of Portland cement replacement by ground granulated blast furnace slag(GGBFS)and micronized rubber powder(MRP)on the compressive,flexural,tensile strengths,and rapid chloride migration test(RCMT)of concrete were assessed.In this study,samples with different binder content and water to binder ratios,including the MRP with the substitution levels of 0%,2.5%and 5%,and the GGBFS with the substitution ratios of 0%,20%and 40%by weight of Portland cement were made.According to the results,in the samples containing slag and rubber powder in the early ages,on average,a 12.2%decrease in the mechanical characteristics of concrete was observed,nonetheless with raising the age of the samples,the impact of slag on reducing the porosity of concrete lowered the negative impact of rubber powder.Regarding durability characteristics,the RCMT results of the samples were enhanced by using rubber powder because of its insulation impact.Moreover,adding slag into the MRP-included mixtures results in a 23%reduction in the migration rate of the chloride ion averagely.At last,four mathematical statements were derived for the mechanical and durability of concrete containing the MRP and GGBFS utilizing the genetic programming method.

Study on Modification of Waste Rubber Powder in Cement-Based Composites Mixed with Waste Rubber Powder

In view of the disadvantage that the mechanical properties of cement-based composites can be significantly reduced by incorporating waste rubber powder in situ, the surface modification methods of the original rubber powder by coupling agent KH560, sodium hydroxide, polyvinyl alcohol (PVA), methyl hydroxyethyl cellulose ether (MHEC) and tetraethyl orthosilicate (TEOS) as precursors were adopted respectively. The modification of waste rubber powder was studied by Change rate of mortar strength of cement-based composite mortar mixed with waste rubber powder. The results show that the hybrid modification method using tetraethyl orthosilicate as precursor has better ef-fect. When 5 phr ethyl orthosilicate is added, the compressive strength and flexural strength of cement-based composite mortar can be increased by 31.7% and 28%. Scanning electron microscopy (SEM) results show that the surface of waste rubber powder with good modification effect has many pro-trusions and flake-like porous structures which are beneficial to its bonding with cement-based materials.

钢渣基盾粉/橡胶复合材料的性能及机理

基于利用超细立磨与钢渣制备钢渣基盾粉(简称盾粉)的研究成果,以橡胶工业配方制备盾粉/橡胶复合材料。测试矿物成分、化学成分、粒度分布、结构组成、微观结构和热稳定性,从微观层面阐述盾粉用于橡胶工业配方的相关机理。结果表明:当盾粉替代炭黑比例为5%~10%(质量分数,下同)时,盾粉与橡胶基体的相容性较好,盾粉/橡胶复合材料拉伸强度为16.16~17.06 MPa,高于15 MPa,拉伸伸长率为619.8%~668.21%,高于350%,磨耗量为130~196 mm^(3),小于200 mm^(3),均满足国标要求;当盾粉替代炭黑比例为5%时,盾粉/橡胶复合材料的硫化时间缩短、硫化速率指数提高。盾粉/橡胶复合材料燃烧时,一方面盾粉中SiO2与硫自由基、Fe、Zn、Al发生反应形成Si-Mg阻燃体系、Si-Al阻燃体系与Si-Fe消烟体系;另一方面盾粉与橡胶体系产生关联作用组成致密的炭层,阻止部分热量的传递与火焰的蔓延。

胶粉纤维改性水泥稳定碎石抗裂性能研究

针对水泥稳定碎石基层易开裂问题,在混合料中掺入适量胶粉及聚乙烯醇(PVA)纤维,开展强度、抗压回弹模量、干缩性能和扫描电镜试验(SEM);分别掺入橡胶粉、改性胶粉、PVA纤维、不同水泥剂量的胶粉纤维,对比其对混合料抗裂性能的影响。发现掺入材料对水泥稳定碎石混合料性能具有明显影响。掺入胶粉、改性胶粉后会降低混合料强度和抗压回弹模量,提升抗干缩性能;掺入纤维能增强混合料强度、模量和抗干缩性能;加入不同水泥剂量的胶粉纤维对混合料强度、抗压回弹模量提升效果明显,但降低了抗干缩性能;宏观力学指标试验和SEM试验结果显示出改性胶粉纤维与水泥基具有良好的黏结性,可以提升水泥稳定碎石混合料的抗裂能力。

废弃橡胶粉对水泥稳定碎石抗疲劳性能的影响

为了消除水泥稳定碎石基层因疲劳损伤产生的裂缝,采用三分点加载方法系统研究了不同废弃橡胶粉掺量下水泥稳定碎石的疲劳性能,运用三点弯曲梁法表征了掺加废弃橡胶粉的水泥稳定碎石抗疲劳机理.结果表明:掺加10、20 kg/m^(3)废弃橡胶粉的水泥稳定碎石疲劳寿命优于基准组水泥稳定碎石;当废弃橡胶粉掺量为10、20 kg/m^(3)时水泥稳定碎石的起裂韧度是基准组的1.49、2.58倍,失稳韧度是基准组的1.30、2.21倍,断裂能也较大,抗疲劳性能显著;当废弃橡胶粉掺量为30 kg/m^(3)时,水泥稳定碎石的抗疲劳性能并没有提高,这可能与废弃橡胶粉掺量过大导致弯拉强度降低有关.

胶粉/SEBS-g-MA共混比对复合材料粘弹行为的影响

研究了胶粉/SEBS-g-MA共混比对胶粉/SEBS-g-MA复合材料力学性能和粘弹行为的影响。结果表明:当共混比为60/40时,复合材料的力学性能最佳;随着胶粉用量的增加,应力松弛程度增大,随着热处理温度的升高,应力松弛可逆恢复程度先减小后增大;Mullins效应随着温度的升高逐渐减弱。

丁苯胶粉固井水泥浆的研究

本文对市售丁苯胶粉(SB)理化性能分析,并对其用于固井水泥浆进行探讨。红外光谱分析表明其是以高岭土为隔离剂的羧基丁苯胶粉,其水溶液粒度分布呈现纳米级颗粒并表明其具有良好可再分析特性;在水泥浆中单独使用丁苯胶粉存在破乳现象,若添加以十二烷基二甲胺羟丙基磺基甜菜碱LHSB与壬基酚聚醚TX-15组合物(质量比4∶1)为稳定剂时,可消除破乳现象,90℃和140℃稠化曲线均正常;水泥浆中引入丁苯胶粉,水泥浆略有增稠,失水和SPN值均变小,说明胶粉起到辅助降失水和提高水泥浆抗窜性能;胶粉影响水泥石24 h早期强度,但对于6 d后水泥石起到降模量和增加泊松比的作用,水泥石弹韧性得到了改善。

大掺量橡胶粉对沥青玛蹄脂碎石混合料低温性能的影响

为提高废旧轮胎的回收利用率,将轮胎粉碎加工成橡胶粉,采用等体积法替换石灰石集料,优化橡胶粉级配设计,制备聚酯纤维掺量0.4%和不同橡胶粉替代率(0、1.5%、2.0%、2.5%、3.0%、3.5%、4.0%)的沥青玛蹄脂碎石混合料(stone mastic asphalt, SMA)。基于马歇尔稳定度试验和半圆弯曲(semi-circular bending, SCB)试验,采用SCB试件的极限拉应力、断裂能、断裂韧性和断裂劲度综合分析了不同低温环境下橡胶粉对SMA-13沥青混合料抗裂性能的影响。结果表明:SMA-13沥青混合料的最佳沥青用量与橡胶粉掺量成正比,橡胶粉掺量的增加会提高混合料的弹性性能。与石灰岩沥青混合料相比,橡胶粉沥青混合料抗裂能力更加稳定和优异。当橡胶粉替换率为3%时,SMA-13沥青混合料抵抗变形能力最强,可显著提升其低温性能,为沥青路面材料组成设计提供了理论依据。

基于响应面法的半柔性路面材料低温性能研究

为提高半柔性路面材料(SFPM)低温抗裂性能,采用橡胶粉与硅烷偶联剂对水泥砂浆进行改性,制备复合半柔性路面材料(R&S-SFPM)。基于响应面分析法以劈裂抗拉强度、抗弯拉强度、最大弯拉应变、弯曲蠕变速率以及平均线收缩系数作为评价指标分析胶粉目数、掺量及硅烷偶联剂用量对SFPM低温性能的影响,并确定了可获得最优低温性能表现的R&S-SFPM掺配比例。结果表明:橡胶粉可提高SFPM的应力松弛能力,使其具有更好的柔韧性;硅烷偶联剂可提高SFPM力学强度。此外,橡胶粉及硅烷偶联剂掺量、胶粉目数均对SFPM低温性能改善效果有较大影响。当胶粉目数为60目、掺量为14%,硅烷偶联剂用量为0.72%时,R&S-SFPM综合低温效果最佳;与普通半柔性路面材料(O-SFPM)相比,R&S-SFPM的劈裂抗拉强度、抗弯拉强度、最大弯拉应变以及弯曲蠕变速率分别提高23.7%、7.6%、29.9%和15.2%。

微藻生物油对橡胶/SBS改性沥青性能的影响

为了改善橡胶粉与基质沥青的相容性,采用微藻生物油(MB)对橡胶粉进行改性,并与质量分数为5%的苯乙烯-丁二烯-苯乙烯(SBS)复合制备了改性沥青;通过红外光谱和扫描电子显微镜,分析了橡胶粉改性前后的变化;采用黏度、荧光、相分离测试,分析了改性前后橡胶在沥青中的分散性;通过动态剪切流变和多重应力蠕变恢复试验,分析了改性沥青的力学性能和耐老化性能。结果表明,MB的掺入提高混合体系中轻组分占比,促进胶粉(CR)在沥青中的溶胀发育,提高了改性沥青的贮藏稳定性、黏弹性和抗车辙性。