mix it up
Rehabilitate Concrete Pavements with Slab Fracturing T
The benefits of using asphalt overlays for rehabilitation of Portland cement concrete (PCC) pavements are grounded in economics and longterm performance. The Federal Highway Administration (FHWA) reports that the United States has 108,603 lane miles of composite pavements (PCC overlaid with asphalt), which is nearly double the lane miles of PCC-surfaced pavements. This means that nearly two-thirds of the concrete pavements in the United States have been overlaid with asphalt. However, a persistent problem with asphalt overlays on PCC pavements is reflective cracking of joints and cracks through the asphalt overlays over time. Ultimately, reflective cracking leads to a shortened performance life of the
Distribution of Back-Calculated Moduli of Fractured Slabs
Slab Fracturing Techniques for PCC Rehabilitation 12 // march/april 2021
overlay. Rather than removing the concrete, which can be costly to the owner agency and increase delay time for the traveling public, slab-fracturing techniques can be used prior to placement of an asphalt overlay to significantly reduce stress concentrations at concrete joints and cracks. Slab-fracturing techniques include three methods: • crack and seat for PCC without steel reinforcement; • break and seat for PCC with steel reinforcement; and
• rubblization for any type of concrete pavement. Crack and seat is intended to reduce the effective slab length of PCC pavements by producing tight surface cracks. Break and seat is similar but typically requires greater fracturing effort. The rubblization process typically fractures slabs into fragments with a nominal size of 4 to 8 inches. Because the existing pavement remains in-place, there are no hauling or disposal costs, resulting in substantial cost savings for state agencies. Researchers at the National Center for Asphalt Technology (NCAT) in 2020 com-
