Determination of the quality of the coarse crushed aggregates for SMA during mix design, type testing and factory production controll

Stone skeleton mixes have an excellent resistance to permanent deformation under heavy traffic loadings because the traffic loading is carried by the large mineral aggregate parts in the mix which are in mutual contact. This is only possible in case the air voids in the mineral aggregates in the mix are not completely filled with mortar. However, the characteristics of the constituent materials can vary through the year. In case e.g. more weaker parts are present in the coarse mineral aggregates during production than in type testing, it is possible that the mix will be overfilled. To tackle this problem an adjusted type testing and factory production control procedure is developed in the Netherlands. In this procedure the characteristics of the coarse mineral aggregate are established in an extra test using gyratory compaction. With this test the FRs-value (Filling Ratio Stone Skeleton) is determined. During production of the stone skeleton mix the FRs-value of the coarse mineral aggregate is compared with the FRs-value in the type testing procedure. In case there is a discrepancy between the two values, the amount of coarse aggregates in the mix is adjusted. In the paper the background of this new type testing and factory production control procedure will be presented. Also the extra tests, which will be part of this procedure, will be discussed.