Waste automobile tires are used as additives or replacements instead of traditional materials in civil engineering works. In geotechnical engineering, tires are shredded to certain sizes and mixed with soil, especially used as backfill material behind retaining walls or fill material for roadway embankments. Compared to soil, rubber has high damping capacity and low shear modulus. Therefore, it requires the determination of the dynamic characteristics of rubber/soil mixtures. In this paper, the cyclic behavior of recycled tire rubber and clean sand was studied, considering the effects of the amount and particle size of the rubber and confining stresses. A total of 40 stress‐controlled tests were performed on an integrated resonant column and dynamic torsional shear system. The effects of the relative size and proportion of the rubber on the dynamic characteristics of the mixtures are discussed. The dynamic properties, such as the maximum shear modulus, strain‐dependent shear modulus, and damping ratio, are examined. For practical purposes, simple empirical relationships were formulated to estimate the maximum shear modulus and the damping ratio. The change in the shear modulus and damping ratio with respect to shear strain with 5% of rubber within the mixture was found to be close to the behavior of clean sand.

In this study, optimum bitumen content (OBC), an important parameter on Marshall Design is described with a mathematical model by using statistical design method. The effects of independent variables such as number of blows, temperature, additive rate and bitumen content are analysed. The simultaneous optimisation of the dependent variables such as practical specific gravity, voids, voids of filled with asphalt cement, Marshall stability, flow and Marshall coefficient is determined with the central composite design. The optimum conditions are detected with 70 blows, temperature of 160°C, additive amount of 10% and OBC of 4.484%. The desirability function is applied to determine local optimisation points. Following the model application, practical specific gravity is estimated to be 2.418 g/cm³ with voids of 4%, voids of filled asphalt of 71.74%, Marshall stability of 1138.4 kgf under optimum conditions. While it is necessary to pour 126 samples to achieve a result with these variables in Marshall Design under normal conditions, the results are achieved just by pouring 30 samples thanks to the models established.

While seismic waves propagate through soil deposits, a part of their energy dissipates which results in a decrease in the amplitude of the applied shear stresses. To better understand the mechanisms leading to the dissipation of applied energy in fine-grained soils, undisturbed specimens having different geotechnical characteristics obtained from a site investigation after 1999 Kocaeli earthquake, were tested in a series of cyclic triaxial tests. Analysis of cyclic test data suggests that portions of fine-grained soil deposits, i.e., silts and clays could have developed high excess pore pressures and significant shear strains during cyclic loadings which contribute to stability problems. The effects of various factors such as confining stress, dynamic stress amplitude, and pore-water pressure accumulation on the cyclic softening of fine-grained soils were investigated and evaluated using the energy criterion.

Using waste rubber in asphalt mixes has become a common practice in road construction. This paper presents the results of a study on the rheological characteristics of rubber‐modified asphalt (RMA) concrete under static and dynamic loading conditions. A number of static and dynamic creep tests were conducted on RMA mix specimens with different rubber sizes and contents, and a series of resonant column tests were conducted to evaluate the shear modulus and damping values. To simulate the stress‐strain response of traffic‐induced loading, the measurements were taken for different confining pressures and strain levels. The results of the study indicated that rubber modification increases stiffness and damping ratio, making it a very attractive material for use in road construction. However the grain size of the rubber is very important. Although RMA may cost up to 100% more than regular asphalt, the advantages it brings, such as an increased service life of the road and proper waste utilization contributing to a more sustainable infrastructure, may justify the added cost.