Experimental studies to characterize gradation segregation of asphalt mixes

Abstract

Gradation segregation can be described as the non-homogeneity of the asphalt mix which includes coarse aggregates and fine aggregates which may tend to segregate during the process of crushing, stockpiling, mixing in hot mix plant, transportation and paving practices. There are various methods to determine the gradation segregation such as visual judgment, sand-paving test, digital image processing method, nuclear density meter measurement, ground penetrating radar, infrared thermal imaging etc., these detection methods are used to determine the segregation only on the paved asphalt mix but these methods cannot be used to evaluate the extent of segregation occurred before paving the asphalt mix. Since many researchers have carried out work on gradation segregation, still enormous work has to be carried out to determine the gradation segregation before paving the asphalt mix. Hence, in the present study, a test equipment is designed and fabricated to determine the gradation segregation that can be used in the laboratory. Using the test equipment and an index Δ∑Pi the extent of gradation segregation has been determined for various asphalt mixes such as Bituminous Concrete (BC) grading 1 and 2, Dense Bituminous Macadam (DBM) grading-1, Cold mix for Bituminous Concrete grading - 2 and Open Graded Friction Course (OGFC) mixes as per MORTH and ASTM are investigated. The results indicated that the extent of gradation segregation is severe for DBM grading-1, moderate segregation for BC grading-1 and no or slight segregation for BC grading-2, OGFC, and BC grading-2 cold. As the maximum nominal aggregates sizes increase segregation levels also increases and as the coarse aggregate sizes increases in the gradation of the mix the amount of segregation also increased and get segregated under gravity forces.