CoatingsPro Magazine

JUL 2013

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Left For this 3,000 ft² (279 m²) job, the six-person crew arrived on site with a pre-abraded concrete substrate. However, the blasting left ZTI with an extreme amount of bugholes to fill. "The parging wasn't somet hing I was planning on," explained Keough. "It kind of threw the schedule off a little bit." But without fixing the honeycombing effect that was left after the abrasive-blasting, the crew would have had to apply at least double the polyurea to fill the large voids. "It's just one of those surprises on the job," he continued — one of those unexpected things that you just have to deal with. Nothing an experienced applicator can't handle. For the parge coat, Keough used Cement All to build up the face of the tank. "I spoke with Jeff Downing, a representative for VersaFlex, and he was the one who recommended the Cement All," explained Keough. Then he contacted the Cement All rep in Miami to find out where it could be purchased locally. After getting the cement-based product, the crew troweled it onto the entire interior of the tank from feather edge to a half-inch (1 cm) thickness. Then they gave the entire 30-foot by 20-foot by 7-foot (9 m x 6 m x 2 m) tank a sponge finish. This gave a texture for the final coat — the polyurea — to adhere to. Not only did the crew run into delays because of the honeycombing at this early stage in the job, but they also ran into a rain delay. Being in southern Florida means rain, and for two of the seven days that the crew was on the job, the rain came down. It started to drip through a pipe by the access hatch into the tank, which was almost entirely submerged underground. Luckily, the tank didn't experience any serious leakage, and the rain came only while the crew applied the Cement All. They never sprayed when environmental conditions weren't acceptable, so if it was raining, they weren't spraying. They still wanted to wait for the groundwater to dissipate before they moved forward, though. "Polyurea is supposed to be able to go over damp surfaces and ice, but adhesion at the end of the road is what we're looking for, and dry is better," said Keough. So although the Cement All only needed 12 hours to cure for non-breathable coatings, like the 64 CoatingsPro g July 2013 polyurea, the ZTI crew waited a full 24 to 28 hours to make sure that everything was completely dry before moving on. delAyed iMPACt Because of the extra time and effort that needed to be added during these two setbacks right off the bat, it took the crew an extra few days to complete the project. In cases like these, particularly when the contractor is dealing with a government entity with limited resources, all the crew could do was complete the work that needed to be done to end up with a successfully coated tank. The duo hopes that the completed project will help them achieve additional work in the future, and working through unexpected challenges such as the honeycombing helps show they have their client's best interest at heart. Regardless, the rest of the job went off without a hitch. When the crew came back in after the rain, they got right back into the flow of things by prepping the tank for the coatings. In the 25 years that the tank has been in use, the water has never reached the tank's ceiling nor has any spalling occurred. Therefore, the crew wasn't contracted to coat the top of the tank, just the sides and bottom. They cut a quarter-inch-wide (0.64 cm) keyway at the intersection of the ceiling and the vertical wall and ran steel tape right below that. The steel tape would be used during the last step when the polyurea was spray-applied. As Keough applied the coating, another crew member would walk behind him and pull the steel to create a clean, top edge. However, that wouldn't happen for a few days down the line. In the meantime, the crew finished prepping by hanging visqueen with 3M painters tape onto anything that they wanted to protect from over-spraying. This included the 2-foot by 2-foot (61 cm x 61 cm) access hatch that the crew used to enter the tank (via a ladder). They also covered the head of the three pipes that are used to send the water throughout the city, which were each about 18 inches (46 cm) in diameter. The pipes, though, had been removed so that the crew could beLow The crew troweled Cement All onto the entire surface before applying the primer, which was one step in meeting NSF International's standard on drinking water system components.

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