Effect of mix parameters on performance and design of cold mix asphalt

Abstract

Cold mix technology is lagging behind in both research and application fields which is quite observable in a developing country like India. This is the primary motivation underlying selection of this cold mix technology as the present research area. Besides, it has environmental and economical advantages over hot mixes. Till now there is no universally accepted cold mix design procedure. In the absence of uniformity in the laboratory cold mix design procedures followed by different researchers/agencies/organisation, it is difficult to form reliable correlations and to have a comparative study between experimental results reported by them. Hence the objectives of this project work are aimed to select important mix parameters and determine their effects on performance of Cold Mix Asphalt (CMA). The mix parameters selected for the present work are (i) method of compaction, (ii) level of compaction, (iii) additives and (iv) aggregate gradation. It is observed that Bailey method for gradation selection is the only method for HMA/SMA mixture which analyses the aggregate gradations both considering the blend by volume as well as blend by weight. In this study Bailey’s concept has been considered for cold mix design. All the mix parameters have been selected to assess the effect on Marshall properties of CMA mixture. Initially a suitable experimental methodology has been prepared and then the effects of selected mix parameters on performance of compacted mix are studied. Finally a comparative study for above results has been done on basis of the Marshall Stability and air void content of the cold mix. Considering all the selected mix parameters it is observed that only in case of gyratory compaction the adequate air void range (3 to 5 %) in cold mixes can be achieved. Besides, though each and every parameter has contributed to increase the Marshall Stability of cold mixes, cement and developed gradations have shown more significant increase in stability of cold mixes.