The pH measurement for the evaluation of the adverse
influence of free calcium carbonate on the environment is
displayed in Fig. 6. Porous concretes containing an industrial
by-product known as Pozzolan recorded pH of 10.2 to
11.17 from the 7th day after the specimen was immersed,
which is lower than that of ordinary concrete. From the 5th
week following dipping, the pH began going down and at
the 90th day following immersion, the pH became less than
9, which is suitable for growth and inhabitation of organisms.
The earlier pH drop in the porous concrete than in the
ordinary concrete may be due to the larger specific surface
and the added Pozzolan in the porous concrete.