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

Abstract

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. e 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 at different concentrations) as leaching media, and correlation of the leaching test results with a simple mass balance equation for sodium and potassium ions. e 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 with alkali-aggregate reaction in long-service concrete structures, like concrete dams.

The Influence of Slag Content on the Structure and Properties of the Interfacial Transition Zone of Ceramisite Lightweight Aggregate Concrete

“…Figure 11 reflects this process. This was attributed to the pozzolanic reactivity in the cementitious mix [39], where the Ca(OH) 2 at the interface underwent the reaction described in Equation ( 2). This reaction allowed the Ca(OH) 2 in the cement paste to participate in the reaction and promoted the transformation of Ca(OH) 2 into C-S-H (tobermorite).…”