This is because it is more economical to use the local aggregate as much as possible. Up to now in Barito Selatan, Central Kalimantan,Indonesia.
Aggregates for Hot Mix Asphalt (HMA) have to be imported from Barabai, South Kalimantan, about 200 km distance from Buntok city, from which the aggregate arc considered meeting the required specification.
In the south Barito , however the natural source of local aggregates is actually available; the coarse aggregates arc found in Karau river at Awang village, gravel and sandstone arc found in Barito river and limestone boulder arc available at Sibung village. Unfortunately, these local aggregate arc never tested before for their characteristic performance,
so that local contractors arc still importing their aggregates from Barabai. This investigation is performed to test the characteristic performance of local aggregate of south Barito, included abration test, affinity for asphalt, water absorption and specific gravity of aggregate.
It is found that the local aggregate has met the specification, except abration of the local limestone, which is over than 40%, so that the limestone is not to be used as coarse aggregate.
In this study, the aggregate mixture containing crushed gravel from Awang village, natural gravel and sand from Barito river, added by mineral filler of limestone, can be designed to meet the number V gradation type of SNI 1737 - 1989-F as recommendation.
To improve Asphaltic Concrete (AC type) in quality and cost, the local aggregates are mixed with aggregates from Barabai in six variation and tested with Marshall for heavy traffic requirement (75 blows). The variation mixture of aggregate arc: Variation I for 100% local aggregate mixture, Variation 2 for 100% aggregate mixture from Barabai, Variation 3 for mixture of 75% local sand and gravel + 25% aggregate from Barabai, Variation 4 for mixture of 50% local sand and gravel + 50% aggregate from Barabai, Variation 5 for mixture of 25% local sand and gravel + 75% aggregate from Barabai and Variation 6 for mixture of 0 % local sand and gravel + 100% aggregate from Barabai.
The Marshall Stability values obtained are 800 kg, 960 kg, 1010 kg, 1150 kg, 1500 kg and 2100 kg for Variation 1 to 6, respectively, and they are for optimum asphalt of 5.45 % , 5.15 % , 4.93 % , 5.10 %, 5.23% and 5.30 %, respectively. The production cost per m3 asphaltic mixture arc Rp 1,138,546.00., Rp 1,351,996.00., Rp 1,124,813.00, Rp 1,196,890.00., Rp 1,242,159.00. and Rp 1,337,162.00, for Variation 1 to 6, respectively.
Marshall immersion tests for Variation 4, 5 and 6 produce Retained Stability Index of 77.3%, 87.1%, 77.45%, respectively, which mean the retained strength are exeeding the minimum acceptance of 75 %.
The mixture of Variation 4 is selected to be used in Barito Selatan district because its optimum usage of local aggregate and 11.47% saving cost when compared with Variation 2 that involves only imported aggregate from Barabai. It is also found that the Variation 6 is the best in quality for heavy traffic, yet it is still cheaper than the Variation 2.
