SUITABILITY OF A MIX OF RECLAIMED ASPHALT CONCRETE, VIRGIN AGGREGATES AND A CATIONIC EMULSION AS A COLD MIX SURFACING MATERIAL FOR LOW VOLUME ROADS

Abstract

Increase in the number of high volume roads constructed to bitumen standards in the past five years in Kenya hasled to a strain in the supply of scarce natural resource aggregates. Some of the existing roads have undergonereconstruction which involved removal of top asphalt concrete surfacing layer to accommodate new layersunderneath. The disposal of the old asphalt concrete surfacing layer in the open spaces has led to environmentaldegradation. Lack of sufficient funds has led to low volume roads being left in a deplorable state. The mainobjective of the study was to evaluate the suitability of a mix of reclaimed asphalt concrete, virgin aggregates anda cationic emulsion as a surfacing material for the construction of low volume roads. The research involvedlaboratory investigations and a design process to evaluate the engineering properties of reclaimed asphaltconcrete, virgin aggregates and a cationic emulsion and there after designing an optimal mix. Cost comparisonbetween the production costs of an optimal mix against costs of producing conventional mixes was done to assessthe savings obtained when the optimal cold mix was used. A mix proportion that provided an average maximumMarshall Stability value of 4500N and flow value of 3mm was taken as an optimal mix. The results of the studyindicate that the stability values obtained for the optimal mix were greater than the minimum specified of 3300Nas per Road Note 19 for low volume roads. Production costs of reclaimed asphalt concrete cold mix were found tobe cheaper than the conventional mixes. The study concludes that reclaimed asphalt concrete cold mix is a suitablesurfacing material for low volume roads. It’s therefore recommended as an economical and environmentallyfriendly surfacing material.