CEMENT AND LIME PRETREATMENT OF ROUNDED OARSE AGGREGATES FOR ASPHALTIC CONCRETE WEARING COURSE MIXTURES

• Main Author: Siahaan, M.Rudy
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/2882
• Institution: Institut Teknologi Bandung

Rounded (Uncrushed) aggregate is rarely used in the production of asphalt concrete mixtures; the inability of such aggregate to interlock and the generally smooth surface of the particles results in an aggregate framework with poor resistance to traffic load. The normal procedure, when rounded aggregate only is available, is to crush it and thereby increase particle interlock and inter-particle surface friction. An alternative that merits investigation is improvement of the surface frictional characteristics of rounded aggregate particles by first coating them with lime or cement. The objectives of this research were to compare the laboratory performance characteristics of specimens of wearing course mix made with rounded and crushed coarse aggregate and to determine the effect on these characteristics of using rounded coarse aggregate precoated with lime and cement. <br /> A 1:1 slurry (by weight) of lime/ cement and water was found, by visual inspection, to provide optimum coating of the coarse aggregate particles. Fine aggregate particles were not coated. The properties of asphaltic concrete wearing course specimens made with the coarse aggregates investigated in this research meet the Bina Marga specification for medium traffic conditions. Over the range of bitumen contents investigated, the Marshall stability of specimens made with crushed coarse aggregate was consistently highest, that of specimens made with rounded coarse aggregate consistently lowest. Coating of rounded coarse aggregate with lime and cement resulted in some increase in stability. All of the mixes investigated showed good resistance to water damage, the mix made with lime-coated aggregate being particularly resistant to water damage. The mix made with lime-coated rounded coarse aggregate had the highest Indirect Tensile Strength value. Regarding the Wheel Tracking Test, the mix made with rounded coarse aggregate had the least resistance to permanent deformation.