#Pool plaster professional

The rust from the rebar then bleeds upward toward the surface and generally creates a black spot first. If the rebar remains exposed while the new plaster surface is applied, then water will penetrate through the surface after the pool is filled up with water, and begin to rust the rebar. Many times in the process of pouring the shotcrete the rebar may not get fully covered by the cement and remain exposed. This shotcrete is approximately 6 inches thick throughout the pool. This steel rod is used in combination with shotcrete, or gunnite, to create a solid foundation in the beginning stages of building a pool. Rebar is short for reinforcement bar that is used for structural integrity anytime concrete is used. These white spots have absolutely nothing to do with the balance of the water. The pool will have to be completely resurfaced. The time it takes for spotting to appear depends on how weak, soft, and porous these areas are to start with. When pool plaster is properly mixed and properly troweled, a hard, dense (non-porous), homogenous, and durable surface is created that can withstand the fluctuation of water balance for many years. This contrast in color between the random white spotting and the larger gray areas surrounding the spots makes this problem more unsightly. When specific areas of a plaster surface become porous and become carbonated, the spots become lighter (white) in color than the surrounding denser plaster surface.Īnother factor that makes white soft spots become readily visible is due to the overall smooth “graying” of plaster which is caused by the addition of calcium chloride to the plaster mix. This has also been documented by the American Concrete Institute and the Portland Cement Association. The addition of calcium chloride to the plaster mix also contributes to shrinkage and micro-cracking. When water is troweled back into the plaster surface, a watery cement mixture (known as laitance) is created and results in porosity, shrinkage, and micro-cracking.

R J Lee also determined that the spots and the surrounding areas had not been etched by aggressive water. These improper practices create a weak, porous, and softened surface in localized areas. The main contributory issues are adding calcium chloride to the plaster mix, applying excessive water onto the plaster surface while troweling, and overly late troweling. The lab determined that improper plastering practices are what cause the spotting problem. Lee Group, studied plaster samples (cores) from pools that had developed the spotting problem.

#Pool plaster professional

In 1999, a professional cement research lab, R. This problem was given the name of “spot etching” by pool plasterers who (incorrectly) believed aggressive pool water caused the spotting. The smooth, but unsightly white spots generally begin to show up within the first year after plastering. White spotting occasionally develops in new white and dark-colored plaster pools.