INFLUENCE OF COMBINED FLAKINESS AND ELONGATION INDICES OF COARSE AGGREGATES ON THE BITUMINOUS CONCRETE MIXTURE WITH NMAS OF 12.5MM

Pramukh N, K M Mallesh, Mohammed Ilyas Anjum

Abstract: In India, approximately 98% roads are flexible types, probably because of economy. There are two million miles of paved roadways in India. The hot mix asphalt (HMA) is used on approximately 98% of all paved surfaces. Increasing traffic volumes, tire pressure, and Loading in recent time has place more demand on engineering roads. Technically, a well-designed and constructed road will not only support regional and national development of a country, but also assist in sustaining the life span of the infrastructure. To achieve this, an adequate mix design is essential. Aggregates are one of the key materials used in the construction of the Flexible pavements which they constitute about 95 % in the bituminous mixtures. Aggregate are the largest amount of material that can be found in HMA. Aggregates make up between 80% to 90% of total volume or 94% to 95% of the mass of hot mix asphalt (HMA). Therefore, aggregate properties are very important in HMA because it will affect the performances of the HMA. The influence of combined flakiness and elongation indices on Marshall properties of coarse aggregate with NMAS 12.5mm was studied in this paper. Coarse aggregate were manually tested for combined flakiness and elongation indices and were separated under four different percentages(CFIEI 30-35%, 35-40%, 40-45% and 45-50%). Gradation was fixed as per MoRTH specifications(Upper, middle and lower limit).Optimum bitumen content(OBC) was determined for middle limit gradation with combined flakiness and elongation indices of 30-35%.workability(torque) values were determined at temperatures 900C, 1100C and 1300C for three gradation limits with different combined flakiness and elongation indices and graphs were plotted to validate effect of combined flakiness and elongation indices.

Keywords: NMAS, Gradation, Optimum bitumen content, Workability

DOI: https://doi.org/10.15623/ijret.2015.0416007