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The pH value of the hardened portland cement and concrete ranges from over 12.5 to values as high as 13.5, due to the presence of alkalis in cement. Partial replacement of portland cement with supplementary cementing materials such as coal fly ash, blast furnace slag, silica fume, and natural pozzolan can decrease the pH value depending on the characteristics and dosage of the material used. The dissolution and leaching of hydration products of cement can affect the pH value of groundwater. Increased pH of groundwater can be expected around the surface of concrete but is not expected to penetrate far into the groundwater matrix, because the transport rate from the concrete is low. The width of the affected zone is mainly controlled by the rate of flow of the groundwater around the surface of the concrete. Keywords: Portland cement; supplementary cementing materials; hydration; hydration products; concrete; dissolution; leaching; pH value; groundwater |
