Durability of Saw-Cut Joints in Plain Cement Concrete Pavements

摘要

The objective of this project was to evaluate factors influencing the durability of the joints in portland cement concrete pavement in the state of Indiana. Specifically this work evaluated the absorption of water, the absorption of deicing solutions, the relationship between the degree of saturation and concrete deterioration, and the role of Soy Mehyl Esters as a potential concrete sealant. The aforementioned items were studied in conjunction with the observation of premature joint deterioration in concrete pavements. Previous work by the PI identified that deteriorating joints were observed to frequently have standing water and damaged joint sealant. To better understand the potential mechanisms responsible for joint deterioration, a series of mortars were tested that are consistent with the mortar fraction of concrete paving mixtures. The first portion of the work examined the role of deicing salt solutions on the wetting and drying behavior of concrete elements (this was a joint series of experiments with SPR 3093). It was observed that salts altered the equilibrium relative humidity of the solution, as such concrete containing deicing solutions dried less frequently than concrete containing only pore solution. Further, it was observed that the rate of water absorption was related to the square root of ratio of surface tension and viscosity. Salt solutions have a slower rate of absorption than plain water. It was also observed that concrete previously exposed to deicing salts also exhibited an altered rate of water absorption. The second portion of the work examined the concept of the degree of saturation and its relationship with freeze-thaw damage. Specifically mortars with different air contents were examined. Fagerlund developed a model that proposed a critical degree of saturation could be correlated with the onset of freeze-thaw damage. The work suggests that absorption testing should be used to determine the degree of saturation which can be used to estimate the time to reach a critical degree of saturation. Once this critical degree of saturation was reached freeze-thaw damage was inevitable. While entrained air was observed to slow the time to reach a critical degree of saturation, this critical degree of saturation could not be avoided. The final portion of the work examined the potential use of penetrating concrete sealers (like soy methyl esters) to reduce water absorption and the corresponding freeze-thaw damage. While absorption testing was able to show the benefits of sealers, differences were observed regarding the influence of sealer composition on freeze-thaw damage.