Study on properties of recycled tire rubber modified asphalt mixtures using dry process
Introduction
With the rapid development of the automobile industry and higher standard of living of people in China, the quantity of autos increased sharply, China is facing the environmental problem related to the disposal of large-scale waste tires. In accordance with the statistic data, 80 million scrap tires were produced in 2002, and with 12% of growth rate every year, the total number of abandoned tires will be expected to reach 120 million in 2005 and 200 million in 2010 [1]. How to deal with the huge number of waste tires has become an urgent problem of environment in China.
The disposal of waste tires in the world primarily has three ways to deal with such as landfill, burning and recycling. Recycled tire rubber applied to pavement may be the best way to reduce waste tires in large quantities and, at the same time, improve some engineering properties of asphalt mixtures.
The history of adding recycled tire rubber to asphalt paving material can be traced back to the 1940s when the U.S. Rubber Reclaiming Company began marketing a devulcanized recycled rubber product, called Ramflex™, as a dry particle additive to asphalt paving mixture. In the mid-1960s, Charles McDonald developed a modified asphalt binder with the addition of crumb rubber called Overflex™ [2]. Crumb rubber can be incorporate by a wet process or dry process. Wet process refers to modification of asphalt cement binder with 5–25wt% of fine tire rubber crumb modifier (CRM) at an elevated temperature. The dry process includes mixing the rubber particles with aggregates prior to addition to asphalt. The main differences between the two processes consist in rubber particle size, rubber amount, rubber function, and incorporation facility [3].
Although the dry process presents some advantages in relation to the wet process, mainly concerning the costs involved and to the higher amount of rubber to be used, the research all over the world have concentrated mainly on the wet process. This choice may be explained by the irregular performance of some experiment sections built with the dry process, unlike the wet process, which has presented more satisfactory results [4].
This paper presents an experiment research on recycled tire rubber modified asphalt mixtures using dry process. Special designed dense gap-aggregate gradations were employed to give enough space to accommodate rubber. Two laboratory tests were performed to evaluate the performance of resistance to permanent deformation at high temperature and cracking at low temperature of rubber modified asphalt mixtures. Tested results were compared and analyzed statistically. The single factor variance analysis (ANOVA) has been performed to determine the significance at a certain confidence limit.
Section snippets
Aggregate, binder, crumb rubber and gradation
Crushed stones of diabase and limestone were used for coarse aggregate and fine aggregate, respectively. Hydrated lime as mineral filler was obtained from a commercial source. SBS modified asphalt binder was obtained from a commercial petroleum company. A Cycled Rubber Industry Ltd., Shanghai, China, supplied recycled tires rubber. The rubber was granulated under room temperature, and freed of wire and fabric. The range of rubber particle size was 1–3 mm, its appearance was shown in Fig. 1.
Test results and ANOVA analysis
Properties of aggregate and crumb rubber are shown in Table 2 and SBS modified asphalt binder are shown in Table 3. Fig. 5 illustrates four aggregate gradation curves employed in tests. Test results of the Marshall mix design with rubber modified asphalt mixtures and control mixture are summarized in Table 4, which contain bulk specific gravity, air voids, voids in mineral aggregates (VMA), voids filled with asphalt (VFA), stability, flow and OAC.
DS of the samples in rutting test and failure
Marshall mix design
In Table 4, it is found that bulk specific gravity, stability, flow and OAC of asphalt mixtures are affected by the addition of tire rubber. Because the specific gravity of rubber is far less than that of aggregate, the bulk specific gravity of rubber modified asphalt mixtures decrease with the increase in rubber contents. Due to lower compressive strength and higher elasticity of rubber, the stability and flow decrease with the increase in rubber contents. The values of stability and flow are
Conclusions and recommendations
Based on the results of evaluation and analysis, conclusions and recommendations of this study are described as the following:
- 1.
From the results of Marshall mix design, special gap-aggregate gradation and SBS modified asphalt binder are recommended for recycled tire rubber modified asphalt mixtures using dry process.
- 2.
All of stability and flow values are satisfied with the Marshall criteria.
- 3.
Based on the analytical results of rutting test and indirect tensile test, the addition of tire rubber in
Acknowledgement
The author gratefully acknowledges the guidance for the paper provided by Professor Lv Weimin from Tongji University of Shanghai.
References (7)
- Jiang Zhi-Yun. The status and development of waste tireresources recycling in china. Chinaire Resource Recycling;2005....
- Sacramento county DERA and Bollard & Brennan, Inc., report on the status of rubberized asphalt traffic noise reduction...
- et al.
Investigation and evaluation of ground tire rubber in hot mix asphalt
(1989)
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