Pool plaster mottling is one of the most common complaints in new pool construction, and the industry's standard explanation, installer error or bad water chemistry, is usually wrong.
The real cause is calcium hydroxide migration during cement cure, and it has been a solved problem in commercial concrete construction since the 1950s. The pool industry just never picked it up.
This episode covers the full mechanism: how Portland cement produces calcium hydroxide as a hydration byproduct, why it migrates to the surface, what it does when it gets there, and how the LSI determines whether y...