Possibilities of using alizarin and neutral red indicators to determine the neutralized layer of concrete in the field

The article concerns with the prospects of using phenolphthalein test solution in practice surveying concrete and reinforced building structures planta. problem study is limits application on pH level determined (the indicator works only at 8≤rn≤10). There a need expanding application. In order to determine different zones we have modernize method by adding other indicators phenolphthalein. standard does not allow high degree accuracy determining most sensitive carbonation boundary concrete. We proposed sample additional acid-base alizarin neutral red. presented results experiments measuring surface neutralized layer alcoholic solutions red age size samples. As result, one (neutral red) allows expand compared obtained traditional modified methods. According it, more accurate one.