STUDY ON STABILITY TESTS FOR DESIGNING SOIL-BITUMEN MIXES

Abstract

Various stability methods for the design of soil-bitumen mixes are known, but only the Modified Hubb-ard's Field teat or Extrusion Method has been standardised by the American Society for testing Materials. Present investigation aims at comparing the Extrusion test results of the Soil-bitumen mixes with the other common stability methods viz. California Bearing patio, Iowa Bearing Valuer North Dakota Cone and Unconfined Compressive Strength tests, in order to arrive at some design criteria for mix-design by these tests. In this investigation three soils were selected and cutback grade MC3 was used in three differ-ent proportions. It has been found that for the purpose of deciding the approximate value of optimum bitumen content at which stability value is maximum, any of the fore-said stability methods may be employed. California Bearing Ratio, Iowa Bearing Value,. North Dakota Cone test and un-confined compressive strength test values vary linearly C I I with Extrusion test value for each soil. General correlation of stability values by these tests for different soils has not been possible with the Extrusion test value. Hence design criteria by-the various tests corresponding to the generally accepted criteria of the Extrusion test could not be established. ii]