Abstract
The increase in the number of discarded tires every year is becoming a major issue all over the world. Tires stockpiles and landfills have become a critical issue as they are considered a fertile environment for the breeding of rats and insects, a real fire hazard that may take up to months to extinguish and occupy a valuable, large area of land. One of the safest effective ways of recycling tires is that to use them as backfilling material, among different usages, in civil engineering projects due to their low unit weight and specific gravity. However, to use any material in the construction industry, several material properties must be evaluated, including the shear strength and stiffness parameters. Many factors control the measured parameters. One main factor that is known to have a significant effect is the particle size. This paper focuses on evaluating the effect of the particle size on the shear strength and stiffness parameters of six tire-derived aggregate (TDA) samples having particle sizes range between (9.5–101.6 mm) using a large-scale direct shear machine. The tests were conducted under three normal stresses: 50.1, 98.8 and 196.4 kPa using a constant shearing rate of 0.5 mm/min. The results of this study showed an increasing angle of internal friction as the maximum particle size increases. Moreover, the secant shear modulus also exhibited an increase by increasing the maximum particle size. Furthermore, equations to estimate the stress-strain curves of Type A-TDA for different confidence levels were developed, and their predictions were compared with experimental results to assess their suitability.
Highlights
The number of scrap tires generated every year all over the world is rapidly increasing.The reason behind this increase is that the number of vehicles is growing at an unprecedented rate, and the current technology is not targeting new means for recycling tires
The results showed that the angle of internal friction increased from 35.54◦ up to 42.24◦ for the samples with uniform particle sizes
El Naggar et al [8] reported the secant shear modulus of three samples; dust, medium and coarse tire-derived aggregate (TDA), to be around 400 kPa under 50 kPa normal stress and around 750 kPa under 100 kPa, which is expected to be less than the reported shear modulus in this study due to the difference in the particle sizes which was much smaller in El Naggar et al [8]
Summary
The number of scrap tires generated every year all over the world is rapidly increasing. The authors in this research investigated the shear strength parameters of coarse-grained soils for three samples with three different maximum particle sizes; 4.75 mm, 7.9 mm and 15.9 mm. The samples had an increasing maximum particle size (Dmax), which qualifies the samples for the study o4f the effect of the particle size effect on the shear strength parameters of TDA. Different samples from the same TDA type (i.e., tires obtained from the same source) showed that the specific gravity, void ratio and maximum and minimum dry densities and void ratios were similar. This was because the amount of steel in the same type of TDA was similar. 19.05 mm 38.1 mm 50.8 mm 76.2 mm 101.6 mm Density (kN/m3) and Void Ratio before Shearing
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