GRADATION EFFECT ARISING FROM SELECTED AGGREGATE COMBINATION TECHNIQUES ON THE MIX DESIGN PROPERTIES OF HOT MIX ASPHALT (HMA)
Abstract
This project is centered on studying the gradation effects arising from selected aggregate combination techniques on the mix design properties of Hot Mix Asphalt (HMA). Straight line graphical (SLG), formula (using linear programing via micro soft excel solver) (FG) and trial and error methods (TEG) were adopted as the aggregate combination techniques in this study. The mix design properties considered are the voids in mineral aggregates (VMA), voids filled with bitumen (VFB), percentage air voids (Pav) and Marshall quotient (MQ). The Marshall mix design procedure was adopted in this study in preparation of HMA. From the results, OABs’ obtained were (53 % gravel and 47 % fine sand), (54.5 % granite and 45.5 % sand) and (58% gravel and 42% river sand) for SLG, FG and TEG respectively. The Optimum bitumen contents (OBCs) were obtained as 5.34 %, 5.17 % and 5.23 % for SLG, FG and TEG in that order. The mix design properties of the optimum HMA from SLG are; VMA = 15.27 %, VFB=74.65 %, Pav = 3.87 % and MQ = 2.63. This proved to be the best result compared to the other methods of aggregate combination. The SLG of aggregate combination was therefore recommended for producing HMA most especially in the combination of two aggregates. The FG is the easiest and shortest method of combining aggregates and should be encouraged in cases of three or more aggregates.
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