Characterisation of bituminous macadam for road construction in Bangladesh

Abstract

In this investigation an attempt is made to study the characteristics of bituminous macadam for road construction in Bangladesh. This study includes the selection of a suitable aggregate grading for bituminous macadam basecourse. Attempts are made to study and compare the properties of brick-aggregate bituminous macadam with those of natural aggregate bituminous macadam. Bituminous mixes using different types of aggregates and in accordance with different gradings are studied. Effect of types and amounts of filler on the behaviour of brick aggregate bituminous mixes are investigated. Behaviour of dense graded bituminous mixes with picked jhama brick aggregate are investigated for different compactive energies. Study on the effect of soaking period on the compressive strength different mix types is also included. Standard Marshall mix design procedure is followed in the design and testing of these mixes. The testing includes the determination of stability, flow, density, voids in the mixes and the optimum asphalt content. The study reveals that 'Picked Jhama' brick-aggregate bituminous mixes are as good as crushed stone-aggregate mixes for use in the basecourse of bituminous pavements, from the standpoint of stability, stiffness, deformation and voids characteristics. However, the bitumen requirements for one cubic metre of 'picked jhama' brick-aggregate bituminous mixes is 66.14 kg more than those of crushed stoneaggregate bituminous mixes. The investigation also indicates the possibility of using non-plastic sand as a filler material in the brick-sand bituminous mixes. It is also found that soaking of bituminous macadam mixes for more than 72 hours largely reduces the compressive strength. Bituminous macadam base course mixes with picked jhama brick aggregates give satisfactory results when they are constructed using dense grading, good compaction, optimum filler and subjected to lower soaking period.