Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration.
Abstract .It is becoming increasingly popular to utilize numerical simulation models to predict the long-term performance of concrete pavements and structures. The majority of these models have been developed using laboratory test data that considers concrete in an uncracked state. While uncracked concrete exists as the best case scenario, frequent cracking occurs in real structures that could have a profound impact on life cycle performance. Cracks from several sources may accumulate and interact thereby accelerating the deterioration of concrete. For example, the distributed cracking caused by freeze/thaw damage can substantially increases the rate of water absorption and reduces the load carrying capacity of concrete. To accurately simulate the performance of actual concrete facilities, the role of cracking and its cumulative effect on the changes of material properties should be accounted for in these models. The main goal of this investigation was to assess the influence of cumulative damage in concrete and to quantify its influence for use in life-cycle performance modeling. Samples were taken from five concrete pavement sections based on age, traffic, and overall performance to assess existing damage and to identify possible sources responsible for inducing the damage. These results were used as a baseline to assess the types of damage that merited laboratory investigation. After the field assessment, laboratory investigations were conducted to simulate the damage that may be expected in the field. After various levels of damage were introduced in laboratory specimens, durability tests (freezing and thawing and water absorption) and direct tensile test were performed to develop an understanding of how the pre-existing damage accelerated the deterioration process. Specifically, it was determined that cracks caused by freezing and thawing dramatically increase the rate and amount of water absorption while cracks caused by mechanical loading only increased the absorption in a local region. Further, freeze-thaw damage dramatically reduces the direct tensile strength and modulus of elasticity of concrete until the aggregates begin to pull out of the matrix. This results in a larger fracture process zone in the damaged concrete than in the undamaged concrete.17.