What is a push-off test?
• A push-off test is a procedure to measure the friction, bearing, adhesion, and bonding conditions at the slab-subbase interface. This test consists of casting a slab with an approximate thickness of the projected pavement on top of the same subbase type. A range of slab sizes have been used in the past, but we have generally used a 3 x 5′ slab. A horizontal force is applied on one side of the slab with a hydraulic jack and a load cell is used to measure the applied load. Dial gages are installed at the opposite side to measure the slab movement. The friction force per unit area is determined from the applied force divided by the area of the test slab. The testing history of friction force and slab movement during the push off procedure is recorded and the friction force at free sliding is evaluated.
