Carbonation tests on concrete

The depth of carbonation is determined on the external surface of extracted concrete cores or on their internal surface when these are split along planes normal to the surface exposed to the air, or on site by taking concrete samples by chiselling or analysing the extracted dust by drilling at various depths. The surface of the exposed concrete conglomerate is then sprayed using a nebulizer with a 1% phenolphthalein solution in ethyl alcohol. Determination of the depth of carbonation should usually be carried out immediately after sampling. The pink color of the sprayed sample indicates the absence of the carbonation phenomenon (alkaline pH ≈ 12); vice versa, the non-colouring of the same indicates that the pH has significantly dropped (pH ≈ 9) and therefore the rebars are exposed to oxidation following the loss of protection of the initially alkaline cement paste.
Reference standards: UNI 9944:1992, UNI 14630:2007.