# Mechanical Behavior of Sand Mixed with Rubber Aggregates
###### Abstract  
The main objective of this study is to compare the mechanical behavior of two sands (Hostun or Dune sands) mixed with crushed rubber obtained from used tires. However, it is essential to ensure that his geotechnical application do not result in long-term negative impacts on the environment. The chemical properties of these two sands are given by energy dispersive analysis X-ray fluorescence spectrometry. The mineral composition of these two sands is performed by X-ray diffractometry. The morphological characteristics of the sand grains are given by the analysis of the images of the two sands given by the scanning electron microscope. This study is based on 120 direct shear tests performed on sand-rubber aggregate mixtures. The results show that the rubber content of the aggregates has a significant effect on the shear strength of sand-rubber mixtures in both cases of sand. In fact, the shear strength of the sand-rubber mixture increases with increasing crushed rubber up to 20% for different normal stresses. The analysis of the test results also shows the effect of the angular shape of the sand grains on the interparticle friction. The contribution of the structure effect in the mobilized friction is analyzed by comparing the shear test results of Hostun and dune sand mixtures. shear strength behavior; sand-rubber mixtures; grain sand shape; friction angle; dilatancy +
Footnote †: journal: Applied  
0000-0002-0002-0002-0000][PERSON]  
0000-0002  
Other previous studies carried out in several laboratories have shown that increasing the rubber content in sand decreases the shear strength of the mixture [7; 8; 9; 10; 11; 12; 13; 14; 15]. Several studies [7; 8; 9; 10] showed that the shear strength and the friction angle increase with the rubber content of tires (thinner size) up to 20%, but beyond this value the last two decreases. [PERSON] et al. [11] showed that the shear strength increased up to an optimum of 30% by volume of granulated rubber. [PERSON] et al. [12] showed that the shear strength increased up to an optimum of 25% by volume and weight of rubber aggregates, respectively, and then it decreases beyond 25%. [PERSON] et al. [13] showed that the shear strength increased up until mixtures with 20% by volume of granulated rubber (Diameter less than 9 mm), then no increase was observed. Although the shear strength decreases above 20%, it still remains higher than that of pure sand. The friction angle first increases with increasing rubber content and then decreases, while the cohesion of sand always increases with increasing rubber content. [PERSON] and [PERSON] [14] showed that the shear strength and the friction angle of sand-rubber aggregates mixtures with an average relative density of the order of 55% and 95% increase with the increase in the rubber content up to 30%, then decrease beyond this value. Recently, studies by [PERSON] et al. [15] showed that the strength increases up to a crushed rubber content of 20% and then it decreases. According to the work of [PERSON] and [PERSON] [16], the shear strength and the friction angle increases with the rubber content. For other experimental condition, [PERSON] et al. [17] show that the friction angle increases with the rubber content up to 5% and then it decreases. [PERSON] et al. [18] show that the shear strength of the sand-rubber mixture depends on the rubber content and the ratio between the diameter of rubber aggregates and that of sand grains. They concluded that the latter with \(D_{r}\)/\(D_{s}\geq 1\) is higher than that of mixtures where \(D_{r}\)/\(D_{s}<1\) which allows us to say that the size of the rubber particles does not play a significant role. Concerning, the angle of internal friction of the mixtures, it increases with the addition of 20% of the rubber and decreases beyond. The results of the research work mentioned are summarized in Table 2.  
It is also important to note that, among other rubber properties, such as the elasticity modulus has a significant impact on the mechanical behavior of sand-rubber mixtures [17].