142 | Page A DETAILED STUDY OF C.B.R. METHOD FOR FLEXIBLE PAVEMENT DESIGN Er. Jitendra Khatti [1] , Er. Amit Kumar Jangid [2] , Dr. K. S. Grover [3] 1 Scholar Ph.D., Geotechnical Engineering, Civil Engineering Dept., UTD, RTU, Kota (India) 2 Scholar MTech., Geotechnical Engineering, Civil Engineering Dept., UTD., RTU, Kota (India) 3 Professor, Civil Engineering Dept., UTD, RTU, Kota (India) ABSTRACT According to IRC recommendation, the California bearing ratio (CBR) value of subgrade is used for design of flexible pavements. The design of pavement may affect by the material which is used as pavement material. Black Cotton soil is expansive soil which expand when it contacts with water and this is the major reason of failure of black cotton soil strata. The engineering properties of black cotton soil may be used by fibre, ash, lime and sludge etc. CBR value depends on the liquid limit (Wl), Plastic limit (Wp), plasticity index (Ip), maximum dry density, optimum moisture content, shrinkage, swelling pressure, degree of expansiveness and permeability of soil or mix specimen. These tests are performed in laboratory of University Teaching Department, Rajasthan Technical University, Kota. This research paper deals with design of flexible pavement by using black cotton soil with different percentage of Kota stone slurry. In this research, the Kota stone slurry is mixed from 5% to 30% in black cotton soil. The engineering parameters are also determined by performed tests. For studying the behaviour of black cotton soil with different percentage of Kota stone slurry, the Atterberg’s limits (Liquid Limit, Plastic Limit, Plasticity Index), Sieve analysis, standard proctor test, California Bearing Ratio are performed. Keywords – California Bearing Ratio, Kota Stone Slurry, Effect on Plasticity Index, Degree of Expansiveness, Maximum Dry Density I. INTRODUCTION California bearing ratio is an empirical test and over the world, it is used for designing the flexible pavement. This method was developed by California Highway Department in 1928. The tests results are used in pavement design, in the duration of second world war. The CBR test is frequently used in the assessment of granular materials in base, subbase and subgrade layers of road and airfield pavements. CBR has become so globally popular that it is incorporated in many international standards ASTM 2000. For the pavement design, the Black cotton soil is used as a base material and for improving the engineering properties of black cotton soil, the Kota stone slurry is mixed from 0% to 30% by weight of black cotton soil. The black cotton soil is characterized by high shrinkage and swelling properties. Due to high swelling and shrinkage characteristics, the black cotton soil has been a big issue to highway