Analysis of Support Conditions Under Joined Concrete Slabs Along USH 18/151

The Wisconsin Department of Transportation has been constructing jointed concrete pavements incorporating open graded permeable base (OGPB) layers for a number of years. The OGPB layer has been constructed using non-stabilized, asphalt stabilized, and cement stabilized aggregates of varying gradations. Test sections have been established throughout the State of Wisconsin and have been monitored for performance for the last 5 years. To date, little if any performance variations after limited trafficking have been noted for jointed PCC sections constructed over OGPB layers as compared to those constructed over conventional dense graded aggregate base layers. Data was collected along USH 18/151 in lowa/Dane Counties from a total of 17 test sections constructed to monitor performance variations due to base layer design, transverse joint sealing practices, and transverse joint doweling. The field data collected for this research included slab dimensions, surface detections from central slab and slab comer positions, and slab temperature measurements at various slab depths. In addition to the collected field data, construction records were reviewed to determine base layer design and pavement surface thickness as measured by cores extracted after construction. The data was used in conjunction with back calculation procedures developed by the author to establish slab-by-slab interior and corner foundation support k-values. The ratio of corner k-value to interior k-value, termed the slab support ratio, was used to identify slabs which were not uniformly supported by foundation materials. This research concluded that for the test sections included, little or no evidence of poor support could be found. However, based on the limited data obtained, there were some indications of poor support due to base layer densification. As a result of this research investigation, the author recommends a more detailed study of certain test sections included in this study to better quantify the reasons for the indications of poor support. In addition, testing is recommended along other jointed concrete test sections within Wisconsin to examine the impact of heavier trafficking on the quality of support provided by base layers of varying design