Experimental evaluation of mechanically stabilized earth walls with recycled crumb rubbers

Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth （MSE） walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents （5 wt%, 10 wt%, 15 wt% and 20 wt%） of recycled crumb rubber （RCR） to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry （PIV） technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.

Dispersion characteristics of clayey soils containing waste rubber particles

The rubber-containing waste materials have been widely used to improve the engineering properties of soils in recent years.Among others,granular rubbers are utilized in various ways to increase the bearing capacity and shear strength and to reduce the settlement and liquefaction potential of soils.The granular rubbers have many advantages such as temperature resistance,flexibility,tear-resistance,non-slip,and thermal and electrical insulation.This study presents the distribution characteristics of five different types of clayey soils with different engineering properties containing waste rubber particles(WRPs).On the other hand,determining and controlling the dispersion characteristics of clayey soils is two significant engineering problems.The study aims to solve these two remarkable and problematic issues in an eco-friendly and safe way.The role of WRP treatment in the investigation of soil dispersion behavior,which can cause dangerous problems such as piping,erosion,and dispersion,reflects the original and different perspectives of this study.Within this scope,geotechnical parameters of the clayey soils were determined.Subsequently,pinhole test,crumb test,double hydrometer test,and scanning electron microscopy(SEM)analysis were performed on the Na-activated bentonite,refined ball clay,Ukrainian kaolin,Avanos kaolin,and Afyon clay samples with different percentages of WRPs(0%,5%,10%,and 15%).Consequently,Avanos and Ukrainian kaolin clays gave the most limited response to the dispersion behavior with the addition of WRP.Also,WRP treatment on the ball clay and bentonite samples showed limited efficiency.Afyon clay,which was defined as dispersive by the three tests that determined its dispersion potential,showed 3 level changes in the pinhole tests and 2 level changes in the crumb tests,and gave the most effective results in terms of WRP efficiency.

Performance improvement of a crumb rubber modified bitumen using recycled glass powder

In this study, the efficiency of bitumen and asphalt mixtures modified with crumb rubber(CR) and recycled glass powder(RGP) is evaluated. From an environmental point of view, the application of RGP in asphalt mixtures is considered beneficial since it prevents accumulation of waste glass in the natural environment. Rheological and mechanical properties of modified bitumen samples were investigated by laboratory methods such as bitumen conventional tests and dynamic shear rheometer(DSR), and also by asphalt mixture performance tests including Marshall stability, indirect tensile strength(ITS),compressive strength, and indirect tensile stiffness modulus. The results showed that the application of RGP in place of CR has no negative impact on the efficiency of bitumen and asphalt mixtures and even improves their engineering properties except for the toughness index(TI). Moreover, a modification with 5% CR and 5% RGP in asphalt mixtures results in the best overall performance.

掺废橡胶微粒的再生混凝土物理力学性能

为了探索综合利用废弃混凝土和废弃轮胎2种废弃材料的可行性,研究了掺加废橡胶微粒的再生混凝土的物理力学性能.试验结果表明,橡胶微粒的掺入改善了新拌再生混凝土的工作性,显著减小了橡胶集料再生混凝土的密度,但其强度随之降低,与橡胶集料混凝土相近.经聚合物改性,水泥水化产物和橡胶微粒之间形成一层聚合物膜'桥',改善了水泥石结构形态,提高了橡胶集料再生混凝土的延性.

橡胶颗粒改性对橡胶集料混凝土强度的影响

废旧轮胎橡胶颗粒直接掺入混凝土会大幅度降低混凝土强度。从橡胶颗粒表面改性的角度出发,研究不同改性方法对混凝土强度的影响,探讨改各自的改性机理。结果显示:无水乙醇、氢氧化钠和酸性高锰酸钾三种改性方法均能不同程度地改善橡胶集料混凝土的抗压强度和抗折强度,但改性机理存在差异;其中酸性高锰酸钾改性对橡胶集料混凝土抗压强度的改善效果最好,无水乙醇改性对抗折强度的改善效果最好,氢氧化钠改性具有工艺简单、经济实用的优点。

橡胶钢纤维再生骨料混凝土断裂性能试验研究

以橡胶钢纤维再生骨料混凝土(crumb rubber and steel fiber reinforced recycled aggregate concrete,RSRAC)为研究对象,探讨橡胶掺量对其断裂性能的影响.设计了6组试件,包括5组不同配合比的RSRAC(橡胶体积分数分别为0、4%、8%、12%和16%)和1组不含橡胶的钢纤维原生骨料混凝土试件,每组含3个尺寸为100 mm×100 mm×515 mm带切口的小梁试件.基于三点弯曲断裂试验,得到了RSRAC的荷载-挠度曲线和荷载-裂缝张开位移曲线,通过计算RSRAC的断裂能和断裂韧度,分析了RSRAC断裂能和断裂韧度随橡胶掺量的变化规律.结果表明,RSRAC断裂能和断裂韧度随橡胶颗粒掺量的增加呈先增后减趋势,细骨料体积取代率为8%时,橡胶掺量可使RSRAC材料获得较好的断裂性能.

废橡胶粉在混凝土中的资源化利用

将废橡胶粉掺入混凝土是解决废橡胶资源利用和环境污染的好办法,具有广阔的发展前景。阐述了废橡胶粉在普通混凝土、再生混凝土中的应用现状,建议今后应拓宽废橡胶粉在其他建筑材料中的应用,为废橡胶粉的深入研究和利用提供了方向。

橡胶再生混凝土和易性试验研究

取再生粗骨料取代率为20%,用粒径0.55～2.36 mm橡胶颗粒等体积置换砂配制橡胶再生混凝土,通过混凝土坍落度试验研究了橡胶粒掺量、橡胶粒改性方式和粉煤灰掺量对混凝土拌合物和易性的影响规律。结果表明：掺橡胶粒的混凝土拌合物的流动性大于未掺橡胶粒的混凝土,且随着橡胶粒掺量的增加,混凝土拌合物的流动性逐渐增强;NaOH与KH-550复合改性混凝土拌合物的流动性最大,其他改性与未改性混凝土拌合物的流动性几乎相当;粉煤灰能够提高混凝土拌合物的流动性,由于超叠效应,复掺粉煤灰和橡胶粒的混凝土拌合物的流动性大幅度提高;橡胶再生混凝土拌合物具有良好的黏聚性和保水性。

双掺橡胶粒、粉煤灰的再生混凝土基本性能研究

在再生混凝土中双掺橡胶粒和粉煤灰,通过试验研究了橡胶粒、粉煤灰掺量和橡胶粒径对再生混凝土工作性和抗压强度的影响规律,并初步探讨了其作用机理。结果表明:随着橡胶粒或粉煤灰掺量的增加,再生混凝土的坍落度逐渐增强,28d立方体抗压强度不断减小,且粉煤灰对强度的降低幅度大于橡胶粒;由于两者的超叠效应,双掺橡胶粒、粉煤灰的再生混凝土坍落度比单掺或不掺时有较大的提升,而立方体抗压强度则出现较大幅度的下降;在橡胶粒、粉煤灰掺量相同的情况下,随着橡胶粒径的减小,再生混凝土的坍落度和28 d立方体抗压强度均随之降低;双掺橡胶粒、粉煤灰后,再生混凝土仍具有良好的黏聚性和保水性。

橡胶钢纤维再生骨料混凝土抗压性能研究

通过对立方体和圆柱体试件的抗压试验,重点分析了橡胶掺量(0、4%、8%、12%和16%)对RSRAC新型材料的破坏形态、应力-应变曲线、抗压强度、弹性模量(刚度)和耗能能力(延性)的影响。试验结果显示,随着橡胶掺量的增大,RSRAC的强度和刚度呈现逐渐下降的趋势,但影响程度不大;RSRAC材料的延性随着橡胶掺量的增加则呈现先增后减的趋势,并在橡胶掺量为8%时获得延性的最大值。

沥青路面研究与应用绿色技术进展

温拌沥青混合料、胶粉改性沥青混合料以及沥青混合料再生技术是沥青路面工程领域绿色技术的主要代表。系统介绍与分析这些绿色技术的特点、研究与应用现状,以利其大规模推广和应用。

Strength reduction factors for structural rubbercrete

Many researches have been carried out to study the fresh and hardened properties of concrete containing crumb rubber as replacement to fine aggregate by volume, yet there is no specific guideline has been developed on the mix design of the rubbercrete. The experimental program, which has been developed and reported in this paper, is designed and executed to provide such mix design guidelines. A total of 45 concrete mixes with three different water to cement ratio （0.41, 0.57 and 0.68） were cast and tested for fresh and mechanical properties of rubbercrete such as slump, air content, unit weight, compressive strength, flexural strength, splitting tensile strength and modulus of elasticity. Influence of mix design parameters such as percentage of crumb rubber replacement, cement content, water content, fine aggregate content, and coarse aggregate content were investigated. Three levels of slump value （for conventional concrete mixes） has been selected; low, medium and high slump. In each slump level, water content was kept constant. Equations for the reduction factors （RFs） for compressive strength, flexural strength, splitting tensile strength and modulus of elasticity have been developed. These RFs can be used to design rubbercrete mixes based on the conventional mix （0% crumb rubber content）

高温损伤对高强橡胶钢纤维再生混凝土抗压和抗弯性能的影响

以一种新型环保高性能混凝土——橡胶钢纤维再生骨料混凝土（RSRAC）为研究对象,探讨高温损伤和橡胶掺量对其抗压和抗弯性能的影响。试验设计了6组不同配合比的RSRAC[橡胶掺量（体积分数）分别为0%、4%、8%、12%和16%],考虑了4种不同温度（25℃、200℃、400℃和600℃）作用,制备了72个尺寸为150mm（直径）×300mm（长）的圆柱体和72个尺寸为150mm（高）×150mm（宽）×550mm（长）的小梁试件。通过实施轴压和三点弯曲试验,分析了高温损伤和橡胶掺量对RSRAC轴压和弯曲的破坏形态、抗压和抗弯强度、弹性模量、韧性等影响规律。研究结果表明：随着温度逐渐升高,RSRAC的抗压强度和抗弯强度出现大幅下降,抗压和抗弯强度与温度几乎呈线性关系;适量橡胶的掺入对提高RSRAC高温作用后的抗压和抗弯性能有一定的帮助;计及各级温度作用的影响,4%~8%是RSRAC抗压强度和弹性模量的最优橡胶掺量,8%~12%是RSRAC抗弯强度的最优橡胶掺量。