Comparative Evaluation of Concrete Sealers and Multiple Layer Polymer Concrete Overlays

About the report:

The report presents comparisons of initial evaluations of several concrete sealers and multiple layer polymer concrete overlays. The sealers evaluated included a solvent-dlspersed epoxy, a water-dlspersed epoxy, a silane, and a high molecular weight methacrylate. The multiple layer polymer overlays evaluated were constructed with two polyester resins and silica sand, two flexible epoxies and basalt aggregate, and three EP5-LV epoxies and silica sand. The report presents information on the permeability to chloride ion, the bond strength between the overlay and the base concrete, the skid number, and the cost of the sealers and overlays. The data collected to date indicate that penetrating sealers can usually be applied with a lane-closure time of less than 24 hours and can provide some protection against the infiltration of chloride ions at a low initial cost. Unfortunately, the sealers usually reduce the skid number, and their use will have to be restricted to bridge decks that have a high skid number, such as those with grooves made by tinlng or saw cutting. Of course, the sealers can be used to reduce the permeability to chloride ions of concrete components other than the deck. A high molecular weight methacrylate healer sealer covered with silica sand provided acceptable skid resistance and filled the cracks in a deck to a depth of about 0.5 in, depending on the width of the cracks. A multiple layer polymer overlay designated by the VDOT as class-I waterproofing provides more protection against the infiltration of chloride ions than do the sealers, but the time required for installation is usually more than 24 hours, and the initial cost is usually more than twice as much. These overlays will usually increase the skid number of decks with low skid numbers. Unfortunately, the skid number of the overlay decreases with age, and depending on the traffic, may decrease to an unacceptable level in two to four years. The class-I waterproofing exhibited a high bond strength and low permeability to chloride ions after four years in service. Bridge engineers agreed to stop the use of class-I waterproofing in 1986 because of the low skid numbers. Multiple layer polymer overlays constructed with polyester resin are similar to .class-I waterproofing. Their initial cost is somewhat greater, because they are usually constructed in three or four layers rather than the two used for the class-I waterproofing and because the binder application rate is greater, than that used for class-I waterproofing. The polyester overlays have an advantage over class-I waterproofing in that they can be installed in stages and thus allow lane closures to be restricted to off-peak traffic periods. Also, multiple layer polymer overlays constructed with polyester resin should maintain an acceptable skid number for 10 years. Initial evaluations of multiple layer polymer overlays constructed with two flexible epoxies and basalt aggregate also look encouraging. One hundred cycles of temperature change had little effect on the sealers, class-I waterproofing, and the flexible multiple layer epoxy overlays. The polyester overlays, particularly those constructed with brittle resins, showed an increase in permeability and a decrease in bond strength after being subjected to 100 or more cycles of temperature change. A 300-cycle test may provide more definitive results. The performance of the sealers and multiple layer polymer overlays will have to be evaluated for at least five years to allow for an accurate assessment of life-cycle costs.

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