Although the performance relationship for the CTB material [6] has been used at AAS for
some time, a thorough laboratory investigation based on local materials had never taken place. As
it showed that the design is very sensitive for the performance relationship of the CTB, a
laboratory program [8] was executed to confirm its validity for the standard mix used by AAS
based on 60% recycled concrete and 40% milled asphalt rubble. Slabs of 600x600x150 mm were
made and used to saw beams of 600x100x100 mm and core 150 mm diameter specimen. The
beams were used for the Four Point Bending (4PB) test set-up, whereas the cores were cut in half
to be used for the Semi Circular Bending (SCB) test. As the determination of the mechanical
characteristics based on the preparation of beams is very labor-intensive and expensive, the SCB
procedure was chosen to confirm its usefulness in comparison with the 4PB. It takes less effort to
obtain SCB sample from existing pavements and there is less damage to be repaired. Figure 1
shows the results of both tests in comparison with the fatigue model used up to now [6] based on
a flexural tensile strength of 2.25 and 2.50 MPa. The laboratory test results show close
correlation with the performance relationship for a flexural tensile strength of 3.00 MPa, as
shown is Figure 1.