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.

Analysis of Highway Asphalt Modified with Recycled Rubber and Waste Plastics

In this study,it is shown how recycled rubber and waste plastics can modify the softening point and penetration of asphalt traditionally used for highways.It is shown that the modified asphalt can meet the performance index requirements when the components are present with a certain proportion or relative ratio(1:3.5).The dispersion process of the masterbatch in base asphalt can effectively be implemented,with good results and a smaller mixing time.The proposed approach may be regarded as a good strategy to achieve energy savings and protection of the environment.

Recycled materials in railroad substructure: an energy perspective

Given that the current ballasted tracks in Australia may not be able to support faster and significantly heavier freight trains as planned for the future,the imminent need for innovative and sustainable ballasted tracks for transport infrastructure is crucial.Over the past two decades,a number of studies have been conducted by the researchers of Transport Research Centre(TRC)at the University of Technology Sydney(UTS)to investigate the ability of recycled rubber mats,as well as waste tyre cells and granulated rubber to improve the stability of track substructure including ballast and subballast layers.This paper reviews four applications of these novel methods,including using recycled rubber products such as CWRC mixtures(i.e.,mixtures of coal wash(CW)and rubber crumbs(RC))and SEAL mixtures(i.e.,mixtures of steel furnace slag,CW and RC)to replace subballast/capping materials,tyre cells reinforcements for subballast/capping layer and under ballast mats;and investigates the energy dissipation capacity for each application based on smallscale cyclic triaxial tests and large-scale track model tests.It has been found that the inclusion of these rubber products increases the energy dissipation effect of the track,hence reducing the ballast degradation efficiently and increasing the track stability.Moreover,a rheological model is also proposed to investigate the effect of different rubber inclusions on their efficiency to reduce the transient motion of rail track under dynamic loading.The outcomes elucidated in this paper will lead to a better understanding of the performance of ballast tracks upgraded with resilient rubber products,while promoting environmentally sustainable and more affordable ballasted tracks for greater passenger comfort and increased safety.

Dynamical mechanical properties of wood-high density polyethylene composites filled with recycled rubber

Application of out-of-service rubber from a variety of sources is of both environment-protecting and resource-saving importance.To that end,recycled tire rubber was utilized as a filler to fabricate wood-high density polyethylene(HDPE)composite with enhanced toughening performance using the injection procedure in this work.Dosages of rubber powders were 0,5,10,and 15wt%based on the overall weight of poplar wood flour and HDPE(HDPE:wood flour=70꞉30).The injection-fabricated composites were subjected to a four-cycle repetitive compressing loadings(0-3 kN)and dynamical mechanical analysis(DMA,room temperature to 150℃,in the dual cantilever mode).It was found that the rubber-filled materials exhibit advantageous energy absorption performance compared to wood-HDPE composites under repetitive compressions.The rubber-filled wood-HDPE composites are thermomechanically labile in an environment with raised temperature.The HDPE matrix substance occupies the predominant role in thermally yielding of the overall composite,typically in the temperature range of 50-75℃ resulting in a loss modulus peak.Up to 130-150℃,all the composites fully loses their moduli with loss factor(Tan δ)reaching its peak values of 0.30-0.38.To conclude,rubber-filled wood-HDPE is a qualified material applicable in proper temperature range.

Dynamical mechanical behaviors of rubber-filled wood fiber composites with urea formaldehyde resin

Wood composites glued with thermosetting synthetic resins tend to show inadequate damping performance caused by the cured resinous matrix.Waste rubber maintains prominent elasticity and is feasible to be an optional modifier.To that end,composite panels of granulated tire rub-ber(GTR)powders and thermal-mechanically pulped wood fibers were fabricated in this study.Urea formaldehyde(UF)resin was applied as the bonding agent(10%based on wood/rubber total weight).Dynamical mechanical analysis(DMA)was conducted to disclose the thermo-mechanical behaviors of the rubber-filled wood fiber composites.Influence of two technical pa-rameters,i.e.,GTR powder size(0.55-1.09 mm)and addition content(10%,20%and 30%based on wood/rubber total weight),was specifically discussed.The results showed that storage modu-lus(E’)of the rubber-filled composite decreased while loss factor(tan𝛿)increased monotonously along with elevated temperature.A steady“plateau”region among 110-170°C was found where both E’and tan𝛿keep constant.Accordingly,tan𝛿showed two peak values at 103-108 and 231-233°C due to glass transition of lignin and thermal degradation of hemicellulose,respectively.Addition of rubber fillers resulted in lower bending and internal bonding strengths as well as stor-age modulus values.When the temperature was above 183°C,all the rubber-filled composites showed higher tan𝛿values than the control.The findings above fully demonstrate the improved damping performance of the UF-bonded wood fiber composites on account of rubber component.Further work is still needed to optimize the rubber/fiber interfacial bonding strength.