Design of Artificially Cracked Concrete Specimens for Virginia Department of Transportation Material Evaluation

About the report:

The penetration of chloride ions and moisture through cracks in reinforced concrete structures can accelerate the corrosion of steel reinforcement and shorten the service life of the structure. The purpose of this study was to develop a method for simulating cracks of varying widths in concrete as a means of assessing various methods that are used to reduce the detrimental effects of cracks in reinforced concrete bridge decks. Once a promising design using shims set in concrete to simulate cracking was achieved, the specimens with simulated cracks were used to evaluate two materials that are routinely used by the Virginia Department of Transportation (VDOT) to reduce damage in reinforced concrete with cracks. The two materials were crack sealant and corrosion-resistant reinforcement.

The study developed removable shim designs that provided for a more rapid acceptance and quality control corrosion test for crack sealant products. The designs also provided for an indication of the sealants’ ability to restrict chloride intrusion into a crack and the subsequent initiation of corrosion. In addition, a permanent shim constructed using Type 5 filter paper attached to Permacel double-sided tape provided a controlled way of testing the corrosion resistance of different types of corrosion-resistant reinforcement. Finally, it was determined that water-soluble shims formed a semisolid mass while being dissolved with water that sealed the crack openings and did not provide the crack needed to evaluate the behavior of sealant materials.

The study also found that Type 25, Type 4095, and MX-45 sands were not optimal for comparing the relative penetration performance of the crack sealants but that the MX-45 sand specified by Virginia Test Method (VTM) 101 should continue to be used. Although all six sealants evaluated met the requirements of VTM 101, the most promising sealants based on greater crack penetration and retention of the coating on more area of the crack face were a high molecular weight methacrylate and two low viscosity epoxies. Using these sealants at room temperature, workers have at least 5 minutes but less than 15 minutes on average to work sealants into cracks for greater than 95% penetration. Finally, the 4-oz waxed paper cups specified in VTM 101 were not available.

The study recommends that VDOT revise VTM 101 to specify a 5-oz waxed paper cup that is readily available. Further, the Virginia Transportation Research Council and VDOT’s Materials Division should continue to the develop the filter paper shim design for a more rapid acceptance and quality control corrosion test for corrosion-resistant reinforcement and the removable shim design for a more rapid acceptance and quality control corrosion test for crack sealant products.

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