Property change of road aggregate with blasting effects

Abstract

Road aggregate is the largest component contributing to road construction. In Sri Lanka, naturally occurring sources that suits construction work are not available. Therefore, this requirement is most commonly fulfilled by excavating rocks and crushing them to suitable sizes. Demand for road aggregate has increased due to the current development of highway sector in Sri Lanka, and it is difficult to satisfy the requirement. In some areas of the country, especially in the Northern region, it is hard to fulfill these requirements due to several reasons such as archeological sites and environmental-sensitive forest areas. Therefore, quality control and fulfillment of the requirement with the available limited sources is a challenge. Considering the use of crushed rock for road construction, it is important to select materials in an acceptable quality. Especially when crushed rock is used for the road bases and surfacing, these properties play a vital role in ensuring durability. To ensure the quality, various tests have been introduced by relevant authorities. When selecting a source to produce crushed rock as road construction material, production from the selected source have to satisfy certain requirements. The los angeles abration value (LAAV) and aggregate impact value (AIV) is the two important tests which ensure the strength requirement of road aggregate. With the blasting operation, a considerable variation of rock fragmentation is noted. This is mainly due to the explosive quantity used for blasting operation. Types and features of explosives and blasting design also play an important role of rock mass fragmentation. In Sri Lanka, blasting design patterns and the explosives used do not vary considerably. But usage of explosives changes in continuous operation even the place is unchanged. These changes may be due to environmental conditions such as rainy seasons or due to some significant change of nature and properties of rock mass. The objective of this study was to identify the changes of AIV and LAAV with the use of explosive percentage used for the blasting operation and improve the strength of road aggregate by controlling the explosive usage for aggregate production. There was not found a relationship between explosive usage for blasting and the aggregate strength properties. But the significant relationship was found between the LAAV and AIV of the aggregate.