Influence of Coal Ash on Dense Bituminous Macadam

Abstract

In the present study, dense graded bituminous mix specimens are prepared using natural aggregate as coarse aggregates, bottom ash as fine aggregates and coal ash as filler. Proportion of aggregate for dense graded bituminous macadam (DBM) grading has been considered as per MORTH (2013) having nominal maximum aggregates size (NMAS) 26.5 mm. The bitumen used is VG20. Firstly, bottom ash and fly ash was used as fine replacement in DBM mix. In this, the total coal ash content is taken as 35% by weight of the total mix, from which the percentage of fly ash as mineral filler is fixed, i.e. 5% of weight of the mix. The bottom ash content is varied according to the DBM gradation specified in MORTH (2013). Detailed study with Marshall test results were used to determine the Marshall characteristics, optimum binder content and also optimum use of coal ash. The maximum stability value of 11.826 kN was achieved when 14% of coal ash by weight of the mix was mixed for preparing DBM samples. It is finally observed that results are not only satisfactory, but also much improved engineering properties with coal ash as fine aggregate and filler. Utilization of non-conventional aggregate like coal ash may help to find a new way of bituminous pavement construction.