Influence of Coarse Aggregate in Portland Cement Concrete on Spalling of Concrete Pavements (1244-11)

Spalling is a form of distress in concrete pavements. However, the current state of knowledge and the available prediction models on spelling indicate a lack of understanding of the spalling mechanism. This research attempts to fill the need to develop a framework to incorporate spalling in the design of concrete pavements based on a mechanistic approach. The report presents results from a comprehensive field survey on spalling in concrete pavements in Texas. Based on the results from this field survey, a mechanism for spalling is proposed. According to this mechanism, spalling is the culmination of damage initiated as delaminations early in the life of pavements. The development of delaminations is related to the concrete mix design and conditions at the time of paving including ambient conditions and the method of curing. The delaminations are extended into spalls as a result of fatigue damage induced by traffic and temperature fluctuations in the pavement. Early-age analysis of concrete pavements was performed using a finite element program developed to predict stresses in the pavement caused by shrinkage. Results from the analysis indicated that a high level of stress sufficient to create delaminations may be generated at a very early age. The coarse aggregate type in concrete was noted to have a significant effect on the level of spalling. Based on results from laboratory studies, a mechanism on how the aggregate type influences spalling is proposed. This proposed spalling mechanism is included in a framework to incorporate spalling in the design of concrete pavements.