Risk of concrete carbonation with mineral industrial by-products

The research assesses the effect of selected type II additives on concrete carbonation. Siliceous fly ash, FASi, is used as a cement component or cement replacement in concrete; ground granulated blast furnace slag, GGBS, is used as a cement component; fluidised bed fly ash, FFACa, is used as a cement replacement; calcareous fly ash, FACa, is used as a fine aggregate replacement; and, silica fume, SF, is used as a cement or fine aggregate replacement. The results show that waste mineral additives increase the depth and rate of carbonation, while extending water curing time increases the resistance to carbonation of concrete containing additives, significantly in GGBS cement and concretes with w/c ratio above 0.35. The results show that in the case of concrete with mineral additives, such as ash and slag, the course of the initial water curing of concrete is a very important factor influencing resistance to carbonation. The application of waste mineral additives to concrete should include the lowest possible w/c ratio and the lengthiest possible water curing, immediately after the commencement of construction activity.