investigating the effect of compaction level and aggregate grading of stone materials in base layer on bitumen penetration rate

One of the layers that is applied on the base layer in asphalt pavements and increases the cohesion between the two layers, is the prime coat layer. due to the fact that there are usually problems with the prime coat penetration into the base layer and penetration is not usually done well, there is a need to identify the factors affecting the penetration into the base layer. in this study, the penetration rate of prime coat coatings made of emulsified bitumen css-1h on the grain base level with different aggregate grading (aggregation close to the lower, middle and upper limits in two different types of aggregate grading) and different compaction levels were examined. optimum water content, density, california bearing ratio (cbr) and the permeability of the samples were also examined. according to the results, the compressive strength of stone materials samples increases with approaching the upper limit (fine grain) and increasing the compaction. also, increasing the grain size and decreasing compaction, increases the prime coat penetration rate, so that the 90% compacted sample with aggregate grading type 3 has the highest penetration rate. the effect of moisture is obvious on the prime coat penetration, so that prime coat penetration rate is greatly reduced in saturation mode, but moisture in the base layer can help the prime coat to penetrate into the base layer.