General Knowledge
Rajeev Agarwal
BitChem Asphalt Technologies Ltd.
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In current practice,conventional bitumen emulsions grades (MS and SS-2) conforming to IS: 8887are used to prepare bitumen emulsion based mixes for road construction and maintenance as per IRC SP: 100: 2014. This is not found to be always consistent in quality due to the variable aggregate quality and improper gradation available in sites in different regions in India,different weather conditions at different sites even within  single State, requirement of pre-wetting of aggregates prior to mixing with bitumen emulsion as per IRC SP:100:2014 is mandatory, inability to measure the presence of existing moisture in aggregates in sites, non-standard mixing equipment available with contractors in different regions, inability to use mechanized HMP plant for dense/ semi-dense cold mixes and the inability to cover larger distances to sites with varied lead time and desired workability of the produced mix.
To overcome these challenges of emulsion based mixes technique, BitChem and CSIR-CRRI started laboratory experiments and field-based trials in different climatic conditions to develop the Tailor made Cold Mix technology. The first development was the use of a diagnostic procedure to determine the best aggregate-binder compatibility in the laboratory using a Bio-incubator by simulating site conditions as per the expected aggregate quality (including marginal materials) and site conditions during execution of work, the second step was to develop a portfolio of tailor made cold mix binders and select the best suitable to avoid pre-wetting of aggregates and provide the necessary lead time and workability to the mix, which shall be found appropriate to the above diagnosis, and lastly to develop& install  a proven cost-effective and simple conversion kit in existing Hot-mix plants to eliminate the need of heating the aggregates as well as to prepare dense/semi-dense mixes like seal coat or SDBC by using tailor made binders without jamming the plants.