AGGREGATES SUSTAINABILITY THROUGH PREPARATION OF BITUMINOUS MIXES AT COMBINED GRADATION

Mohamed Ilyas Anjum

Abstract: Aggregates have to primarily bear load stresses and resist abrasive action of traffic movement under dry and wet conditions, when used in the surface course of the pavement. T he aggregate gradation plays a vital role in securing desirable properties of resulting bituminous mixes. Different types of mixes are used under different conditions. Generally, the mixes are designed adopting midpoint gradation from the respective gradation tables. Often, the desired mix properties are not completely satisfied and needs some reworking of gradation. Sometimes the required quantity of aggregates may not be available in nearby areas so as to design a required type of mix. To overcome this, the desired aggregates may have to be brought from far off places, leading to time and cost escalation. This further aggravates the already prevailing scarcity of aggregates. Alternatively, if aggregates are available and satisfies the graduation requirements of two different type of mixes, attempt may be made to design a mix combining the gradation of two types of mixes. Possibly, the resulting mix could still satisfy the specified requirements. If so, the available aggregates could be used economically, without compromising on the quality of mixes. This would result in aggregate sustainability. With this objective, two types of bituminous mixes namely SDBC and BC were prepared at midpoint gradation of the specified ranges, as per MoRTH gradation tables and subsequently by combining the above two gradations taking average of the two midpoint gradations. The Marshall mix properties were compared and found that the mix requirements are largely satisfied at the combined gradation as well

Keywords: Aggregate, sustainability, bituminous mixes, midpoint gradation, combined gradation

DOI: https://doi.org/10.15623/ijret.2013.0212037