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Residual Capability of Alkali Binding by Hydrated PozzolanicCements in Long-Service Concrete Structures

pubblicazioni - Articolo

Residual Capability of Alkali Binding by Hydrated PozzolanicCements in Long-Service Concrete Structures

La ricerca ha verificato l’esistenza di una capacità residua di assorbimento di alcali da parte di cementi pozzolanici già idratati, dimostrando la loro potenziale capacità di prevenire il rischio di reazione alcali-aggregato nelle strutture in calcestruzzo come le dighe.

An experimental procedure was developed and applied to cement pastes made with two different pozzolanic cements (CEM IV/B (P) and CEM IV/B (V)) in order to ascertain the existence of a residual capability of alkali binding by long-term hydrated pozzolanic cements and, at the same time, to evaluate the alkali retention capability and the concentration of OH- ions in the pore solution of such cementitious matrices. The developed procedure consisted of accelerated curing of cement paste specimens (150 days at 60°C and 100% RH), subsequent leaching tests at 60°C for 30 days by using deionized water or basic solutions (NaOH or KOH) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions.

The developed procedure was found to be appropriate for evaluating both the pore liquid alkalinity and the alkali retention capability by long-term hydrated pozzolanic cement pastes. A residual capability of alkali binding was also identified for both tested pozzolanic cements, thus indicating their potential ability to prevent (CEM IV/B (V)) or minimize (CEM IV/B (P)) the risk of deleterious expansion associated to alkali-aggregate reaction in long-service concrete structures, like concrete dams.

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