Reflection Cracking In Asphalt Overlays On Broken And Seated Concrete Pavements PDF Download

This report presents the details of a study conducted by Infrastructure Management and Engineering (INFRAME) to review condition of selected break and seat (B/S) and rubblization projects constructed by Ohio Department of Transportation (ODOT), and also to demonstrate the ability of various pavement breakers to produce desired breaking patterns and fractured particle sizes required by ODOT specifications. A program of field evaluations was undertaken on four test projects. The pavement on SR-4 was rehabilitated in 1993 by breaking the underlying jointed reinforced concrete pavement with a pile hammer prior to constructing an asphalt overlay. The pavement on SR-36 project was rehabilitated in 1992 by rubblizing the existing jointed concrete pavement with a Resonant Pavement Breaker (RPB) and constructing an asphalt overlay. The continuous concrete pavement on I-70 was rubblized in 2005 with a Multi Head Breaker (MHB), in preparation for an initial asphalt overlay. On the I-71 project, MHB was used to demolish the existing jointed reinforced concrete pavement and demonstrate the capabilities of MHB to produce various fracturing patterns. At each test site, a test pit was dug and a visual assessment of the condition of the fractured pavement overlay and subbase/subgrade was made. Measurements were made of the fracturing pattern at the surface of the concrete and gradation tests were performed to determine the particle size distribution at various depths within the fractured slab. Deflection tests were performed to determine the effect of the observed breaking patterns on the stiffness of the pavement layers. Examination of test pit material indicated that the pile hammer used in constructing the B/S sections on the SR-4 project did not provide the vertical through cracking and steel debonding required by the project specifications. Despite this, the overlay on the B/S section provided vastly superior reflection crack performance than the untreated control section. The MHB equipment used on I-70 appeared capable of providing the breaking patterns and particle sizes required by ODOT specifications. However, the MHB equipment used on I-71 by a different contractor did not produce the desired results; a significant amount of large, un-cracked pieces were observed particularly below the reinforcing steel, regardless of desired breaking pattern. On the other hand, the Resonant Pavement Breaker (RPB) equipment used on SR-36 produced fractured particle size distribution and steel debonding required by ODOT specifications. The principal recommendation of the study is to improve ODOT's specifications for fractured slab techniques. On all types of fracturing projects, the quality control requirements need to be modified to require that test pits be more frequently used to ensure that the specified particle size distributions are in fact being achieved throughout the depth of the slab. On rubblize projects, the present particle size distribution requirements need to be re-examined to ensure that the fracturing operation will avoid, not merely delay, reflection cracking in the subsequent overlay.