Influence of Foundation Support Conditions on the Intelligent Compaction Measurements for Hot-Mix Asphalt

This paper presents findings from a field study conducted on a 5.2 km long roadway section on Route 4 in Kandiyohi County, Minnesota. The study involved mapping the existing granular subbase layer and the overlaid hot-mix asphalt (HMA) non-wearing and wearing course layers with a Sakai double drum intelligent compaction roller integrated with a compaction control value (CCV) measurement system. Comparison of CCV maps for the subbase and HMA layers showed that “soft” and “hard” areas identified on the subbase layer were reflected on the HMA layers. Analysis of the CCV measurements yielded a statistically significant relationship showing that variability observed in HMA layer measurements are strongly influenced by the variability in the subbase layer. During construction, a small section of the HMA non-wearing course layer showed premature cracking under construction traffic. The “failed” area produced low CCV values in both subbase and HMA layers. A review of construction records indicated that the subgrade layers in the “failed” area also experienced significant rutting under test rolling. Results demonstrate the importance of foundation support conditions on the performance of the HMA surface layer and the CCV measurements in the HMA layer are a reflection of the stiffness of the foundation layer.