pH represents the acidity or alkalinity of a fluid—therefore there is no pH without water. So what’s the pH of a dry concrete surface? It can’t be measured. But what’s the pH of fresh concrete? About 12.5 or 13—very alkaline. As the concrete carbonates from the CO 2 in the atmosphere, the pH goes down—into the range of 8 to 10. But the pH of a puddle of water on an open concrete surface will never get to 7 (neutral). When the pH of a concrete surface is measured, it is cleaned lightly with sandpaper to open the surface without removing the carbonated layer. But what does this pH actually represent?
Learn more about measuring pH and moisture of floors from Peter Craig and Scott Tarr in WE55 ICRI Slab Moisture Testing Technician Educational Review