CIGMAT Report: Center Studies Concrete Coatings And Repair Methods For Corroded Steel Piles

By C. Vipulanadan, PhD, P.E., professor and director of Center for Innovative Grouting Materials and Technology (CIGMAT) and Texas Hurricane Center for Innovative Technology (THC-IT), Department of Civil and Environmental Engineering, University of Houston | October 2012, Vol. 67 No. 10

Commercially available silanes denoted as Silane-1 and Silane-2 were applied with the latex based coating denoted as Coating-1, to the concrete substrate. Silane-1 was a micro-emulsifiable concentrate based on silanes and alkoxysilanes. The typical dilution used was nine parts of water to one part Silane (volume based), although varying dilutions can be used to achieve different degrees of water repellency. Silane-2 was clear, penetrating and breathable water repellent designed for the protection of exterior above-grade concrete. It penetrates the surface and bonds chemically to the substrate, resulting in permanent attachment of the water repellent molecule. Coating-1 was water based latex coating with rapid drying, good adhesion and high flexibility. Coating-1 was applied using rollers. Application temperature was 65°F. The coated surface was left to dry for four days before testing. Some of the properties of pure silane and coating are summarized in Table 2.

Table 2: Properties of Pure Silane and Coating

Sample preparation and testing program

The experiments were performed at the University of Houston-CIGMAT laboratory. The test program comprised of coating the concrete specimens, immersion in various solutions followed by drying at room condition.

Concrete specimens were cured for at least 28 days before cleaning and drying prior to the application of silanes and the coating. The concrete surface was cleaned using a water blaster. The specimens were dried at room condition for one day before spraying the silane sealer. The silanes were applied by spraying onto the surface using 15 psi (103 kPa) low pressure positive displacement airless spray equipment. After applying the silane sealer, the specimens were cured for five days before applying the Coating-1 (latex-based). The coating was applied using a roller. The coating was white in color and the application temperature was about 20°C. The specimens were weighed during the coating cycle accurately to 0.01 gms. Addition of Coating-1 to the specimens changed the weight of the specimen by about 3%. The coated specimens were cured at room condition for 21 days before immersing in water and 15 % NaCl solution.

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