The benefits derived from rehabilitating portland cement concrete (pcc) pavements using asphalt concrete (ac) overlays may be minimized because of reflective cracking in the ac overlay. Reflective cracks can cause early deterioration of the asphalt pavement in the form of raveling and spalling adjacent to the joints. One method that has been successful in reducing reflective cracking is known as "carcking and seating." This method involves cracking the existing pcc pavement into smaller interlocking pieces that have aggregate-to-aggregate contact. This cracked pcc pavement is then seated with a heavy pneumatic-tired roller that prevents rocking or movement of the existing pavement. This procedure reduces the potential for reflective cracking by reducing the amount of movement at the joints due to temperature changes. Cracking the existing pcc pavement into smaller pieces reduces the strength of the rigid pavement, but little information has been published on how much loss is expected. This paper addresses the reduction in pavement strength due to the "cracking and seating" method by evaluating the effective modulus. Effective modulus values for the cracked pcc pavement were determined using measured deflection basins obtained by the falling-weight deflectometer (fwd) and comparing these deflection basins to those predicted by the elastic layer theory. The effective modulus values were obtained for theexisting pcc pavement before and after the pavement had been cracked and seated. The effective modulus values of the pavement layers were also determined after placing each intermediate course of ac overlay. This paper appears in transportation research record no. 1215, Pavement management and rehabilitation.
Abstract