A Comparative Study on The Effect of Compaction on Strength and Physical Properties of Stone Matrix Asphalt Compacted by Marshall Compaction and SUPERPAVE Gyratory Compaction Methods.

Abstract

The last decade has witnessed a dramatic increase in vehicular traffic on roads in a developing country like India. This has raised additional traffic, augmented axle loads and increased tire pressure on pavements designed for earlier era. In this regard, besides considering increasing the pavement thickness due to the traffic loads, steps must also be taken to extend the pavement life by using different compaction methods such as gyratory laboratory compaction method to have durable mix and better simulate field conditions. Studies have been done to compare both laboratory compaction methods to verify different findings according to different conditions and climate. In this study Marshall Specimens were prepared for Stone Matrix Asphalt Mix (SMA) according to MORT&H – 2009 specifications with 80/100 neat bitumen by both Marshall Compaction and SUPERPAVE gyratory compaction methods and studied for changes in volumetric properties, and OBC obtained. The results obtained in this study shows that there is no substantial change in the OBC obtained from both the compaction methods. It was also seen that there was slight reduction in the percentage voids of the total mix when compacted by SUPERPAVE gyratory compactor when compared to the Marshall Compaction method due to better compaction and rearrangement of particles. There was also a slight increase in VMA during gyratory compaction as compared to the Marshall Compaction method. The percentage voids in the total mix was found to decrease with the increase in the binder percentage. But the voids filled by mineral aggregates and voids filled by bitumen was found to increase with the increase in binder content in both the cases. Tensile Strength Ratio (TSR) for Marshall Specimens prepared at OBC of 6.6% by both Marshall compaction and Gyratory compaction was compared and was found that TSR for gyratory compacted specimens was more than Marshall compacted specimens by 1.20% . The percentage drain down for the mix prepared at OBC was found to be just 0.15% which was within the limits with the maximum permissible limit of 0.3% according to MORT&H – 2009 specifications. It was also found that standard 50 gyrations in gyratory compactor for SMA Mix had to be increased to 75 gyrations for better compaction equivalent to 50 blows on either side in Marshall Compaction and to attain similar volumetric properties as that of Marshall compacted specimens.