Impact of replacement materials and geometry on pH due to leaching in fresh concrete

When freshly cast concrete is exposed to water this can result in an increase in the pH of the water, which in turn can have an adverse effect on the local flora and fauna. The use of replacement materials and the specimen geometry have been identified as potentially reducing this impact. This paper reports the results of a study investigating the effect on leaching of fresh concrete containing fly ash replacement up to 30% and slag replacement up to 65% in cubic and cylindrical specimens. The results show that the use of replacement materials can be beneficial in reducing the impact of leaching from freshly cast concrete, with the slag being the most effective. This is primarily attributed to the reduction in the alkali oxides and the differing hydration mechanisms. The geometry was also identified as affecting the rate of leaching, with cylindrical specimens leading to higher rates of leaching.