CIGMAT Report: Update From This Unique, Industry-Specific Ongoing Research Program

By C. Vipulanadan, PhD, P.E., professor of Civil Engineering, director of CIGMAT and the Texas Hurricane Center for THC-IT | September 2010 Vol. 65 No. 9
1) Macro-cells 2) Macro-holes in the Macro-cell walls 3) Macro-cell walls. Fig. 1: Microstructure of a polyurethane grout.

Test plans
(i) Full Scale Test
The coatings can be applied to a dry or wet concrete surface. A dry coating condition simulates the new concrete surface while the wet condition simulated the rehabilitation. The testing program developed for evaluating coating materials are briefly discussed [Vipulanandan, 1996, 2005].

(a) Hydrostatic Pressure Test: Hydrostatic back pressure on concrete structures due to the water table was simulated by using 900 mm (36 inch) inner pipes and 1,600 mm (64 inch) outer pipes with two specially designed concrete end plates and pressurizing the annular space with water (Fig. 6). Steel frames were used to support the entire assembly. Coating the inner pipe surface represented the most difficult conditions encountered in coating structures such as lift stations. The total area available for coating was 14 square meters (150 square feet).

Wet test: The 900 mm (36 inch) concrete pipe was installed in the test chamber and pressurized at 105 kPa (15 psi) for at least two weeks before applying the coating.
Dry test: Coating was applied to new 900 mm (36 inch) diameter concrete pipe. The coated pipe was then placed in the pressure chamber for hydrostatic pressure testing.

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Fig. 6: Hydrostatic test configuration

(b) Measurements
Visual Inspection: The coated surfaces were visually inspected regularly and information on blistering, spalling, discoloring and cracking were noted and photographed. ASTM D 714 is used to characterize the blister size and frequency and is designated as dense, medium dense, medium or few, accordingly.

Bonding Test (CIGAMT CT-2 or modified ASTM D 4541): In situ bonding tests on the coating materials were performed at the end of the hydrostatic test. A 51 mm (2 inch) diameter core drill was used to core into the concrete surface and isolate the test area. A metal piece was glued to the coating with an epoxy. After curing for 24 hours, the bonding test was performed using a hydraulic loading system to determine the bonding strength and the type of failure.

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