TECHNICAL NOTE Effect of Added Waste Rubber on the Properties and Failure Mode of Kaolinite Clay Milad Tajdini 1 • Ali Nabizadeh 2 • Hasan Taherkhani 3 • Hosein Zartaj 1 Received: 19 March 2016 / Revised: 9 July 2016 / Accepted: 11 July 2016 Ó Iran University of Science and Technology 2016 Abstract In this study, the shear strength parameters of the Kaolinite clay, as the control material, and the Kaolinite clay reinforced by different percentages of two different types of crumb rubber content have been evaluated. The consolidated drained and unconsolidated undrained triaxial and California bearing ratio tests have been conducted on the control and crumb rubber reinforced soils. Addition of crumb rubber would improve shear strength parameters such as cohesion, friction and dilation angles, stiffness and the ductility of the reinforced soil. 5, 10 and 15 % (by the weight of dry soil) of crumb rubber content were used in this study which were undergone confining stress levels of 100, 200 and 300 kPa and an optimum crumb rubber content is found, which results in the maximum bearing capacity of the soil. Also, due to the non-linearity of the failure mode of reinforced soil and inadequacy of Mohr– Columb envelope for describing the behaviour, a failure mode is proposed for the clay soils reinforced by crumb rubber. This failure criterion is useful for failure envelope of clay-rubber matrix. Keywords Clay soil Á Reinforced clay Á Waste crumb rubber Á Triaxial test Á CBR test 1 Introduction Kaolin is a term drawn from the high mountain range of Kaoling, meaning high peak, in China, which is comprised of white coloured porcelain soil. Kaolin mineralogical name is Kaolinite and its chemical formula is Al 4 (Si 4- O 10 )(OH) 8 with a stiffness of about 1–2, and melting point of 1785 °C. Its colour is white tending to yellow and, in some cases, a trace of green or blue colour may be seen, tastes like soil and, in moist condition, intensely smell of soil can be heard. This mineral is mostly plastic and is soluble in water, cold and light acids, warm and dense coloridric and sulphuric acids and insoluble hydroxide bases. Halosite, Toopi, Dikite and Nakrite are some types of this clay in nature. Due to its suitability for filling and coating, ability for softening surfaces, resistance against wear, low electrical and heat conductivity and catalyst property, Kaolin is widely used in production of con- struction materials and ceramics, and non-flammable materials and many other industries. On the other hand, rapid growth of industrialisation of societies has dramati- cally raised the waste tyres generation [1, 2]. Waste tyres are classified as non-degradable materials, and their non- controlled stockpiling has become a major threat for environment and public health. The main problem of this type of wastes is the generation of hazardous leaching in the landfill and the gases and heat produced from their incineration. & Hasan Taherkhani Taherkhani.Hasan@znu.ac.ir Milad Tajdini M.tajdini@tabrizu.ac.ir Ali Nabizadeh Nabizadeh.ali@gmail.com Hosein Zartaj H.zartaj@tabrizu.ac.ir 1 Department of Civil Engineering, Tabriz University, Tabriz, Iran 2 Geotechnical Engineering, Iran University of Science and Technology, Tehran, Iran 3 Faculty of Civil Engineering, University of Zanjan , Zanjan, Iran 123 Int. J. Civ. Eng. DOI 10.1007/s40999-016-0057-7