Description
Effect of warm mix additive on the performance of Crumb rubber modified asphalt: A case study
Ambika Behl, Satish Chandra, Siksha Swaroopa Kar
ABSTRACT. Rising energy costs and increased awareness of emission problems in the production of Hot Mix Asphalt (HMA) have drawn attention of field engineers to the potential benefits of Warm Mix Asphalt (WMA) in India. A number of new WMA processes and products are now available that have the capability of reducing the temperatures at which asphalt mixes are produced and paved without compromising the performance of the pavement. These new products can reduce production temperatures by as much as 40-50°C or more. Lower plant mixing temperatures would reduce the fuel consumption by as much as 30 percent or more and thus reduce the operational costs. Lower plant mixing temperatures would also reduce carbon emission.
Crumb rubber modified bitumen (CRMB) is composed of bituminous binder and waste tire rubber and is used in India on heavy duty and heavy traffic roads. Production of CRMB based hot mix asphalt (HMA) requires increased mixing time and higher mixing temperatures as compared to the conventional HMA, which is at odds with sustainable road construction practice. Higher mixing time and temperature leads to more energy consumption and more carbon emissions. The present study investigates the efficacy of a commercially available warm mix additive to bring down the mixing and compaction temperature of Crumb Rubber Modified Bituminous mix (CRMB) as compared to the conventional CRMB mix. Effect of warm mix additive on the performance properties of CRMB was studied in laboratory in first phase of the study. After the laboratory evaluation it was found that CRMB Warm mix can be successfully produced at temperature as low as 110℃ and can be compacted at 80-90℃ as compared to conventional CRMB hot mix (155℃). In the second phase, performance of a field section laid with CRMB-WMA was studied for 2 years and compared with control HMA-CRMB.
CRMB warm mixes performed equivalent to “Hot Bituminous Mixes” and the results indicated that the process is highly energy efficient and environment friendly.
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