Improved Performance of JPCP Overlays.

摘要

The overall performance of Michigan concrete overlays has been good. However, some recent JPCP overlay projects have developed premature distress with signs of pumping. It is suspected that lack of drainage was the main cause for the distresses ranging from corner breaks to longitudinal slab cracking originating at the joint. A joint UM-MDOT forensic investigation was initiated in December 2009 to determine the causes for these distresses. The forensic investigation confirmed that pumping, which is the rapid movement of trapped water from a moving truck axle across a joint, is the major cause of distress, and a result of inadequate drainage. Inadequate drainage was associated with construction related issues ranging from blocking water to reach the drainage trench to omitting the drainage system. Improved drainage solutions were developed jointly. Finite element analysis (EverFE) predicts that concrete overlays are more sensitive to developing top-down longitudinal slab cracking from loss of joint support, due to the stiffer slab support condition that exists as compared to JPCP on aggregate bases. Pavement roughness as measured by IRI (International Roughness Index) complemented forensic investigation results that support the pumping mechanism. Two distinctly different performance stages were identified from IRI results. Initially the percentage of good IRI (IRI < 95) for a project length is constant and nearly 100%. This is the period where pumping erosion has little if any structural level effect, but is developing at the sub-structural level. This period is much shorter if drainage is ineffective. Implementing the findings from this study will enable MDOT to consistently extend the anticipated service life of concrete overlays.