Investigating the suppression of road dust by wheat straw Ash

Abstract

Dust is a common problem on gravel or unpaved roads in Uganda and the world at large. It is a serious threat to gravel road users both from a health and safety point of view. Dust is lost as fine material which would act as a binder hence their loss leads to degradation of the road manifested in form of potholes, corrugations and rutting. Dust can be reduced on the roads by hygroscopicity and agglomeration. This project focused on agglomeration of fine soil particles by use of wheat straw ash which is a pozzolanic material obtained by burning of wheat straw. Gravel material was sampled from Namboole-Jokas-Mukono road at chainage 5+700 LHS from the top surface to a depth of 150mm (bottom of the gravel wearing course). The project was aimed at investigating the effectiveness of the wheat straw ash in suppressing road dust. Wheat straw ash was used at dosages of 2%, 4%, 6% and 8%. The tests carried out included Atterberg’s limits, Proctor, Direct shear, Unconfined Compressive Strength and California Bearing Ratio. The results show that the optimum quantity of wheat straw ash for adequate strength and engineering properties is 6%. At this optimum, CBR increased from 4.1% to 34.8% (88% increase) and UCS increased from 191.8KPa to 383.6KPa (50% increase). The plasticity index decreased from 25.4% to 19.4% (39% decrease). The grading coefficient reduced from 35.8 to 24.7 (31% decrease) while the shrinkage product also reduced from 544.4 to 154.8 (72% decrease). Before recommending the use of the wheat straw ash, a field trial should be carried out to validate the laboratory results to guarantee its effectiveness for technical application.