Use of Crushed Gravel in Concrete Paving

This project summary report summarizes the research performed in Texas Department of Transportation (TxDOT) Project 0-4826. TxDOT has used siliceous river gravel (SRG) aggregates for many years in the construction of continuously reinforced concrete (CRC) pavement; however, in many instances these pavements have been subject to delamination and spalling distress, and have been very expensive to maintain and repair. Previous TxDOT-funded field studies have confirmed that spalling is a consequence of early-age delaminations. The goals of this three-year project were to develop a test protocol to measure the bond strength between coarse aggregate and mortar, to determine measures or practices that can be applied to improve delamination resistance and spalling performance of the gravel concrete in CRC paving, and to provide guidelines and recommendations to minimize early-age delamination in SRG-CRC paving. Researchers found that some gravels performed very well, while others with the appropriate adjustment in construction methods could provide satisfactory performance. The aggregate-paste interfacial bond for a given cement paste was found to be a function of the combined effects of key aggregate properties (physical, chemical, and geometric). The application of utility theory to evaluate the overall contribution of aggregate properties to the bonding performance of concrete, combined with climatic conditions at the time of construction, enabled the research team to propose construction guidelines, including selecting the best method of construction, modifying the mixing sequence, and optimizing key available construction and weather combinations to minimize the potential for delamination and spalling distress.