Minimizing alkali leaching in the concrete prism expansion test at 38 °C

Unwrapped concrete prisms (70 × 70 × 260 mm in size; three prisms for each concrete mix) made with two different alkali-reactive aggregates and four different alkali contents were subjected to expansion tests at 38 °C and RH >95% (CPT-38 °C tests). Appositely designed storage containers with reduced net container volume/concrete volume ratio (Vnc/Vconcrete = 2.32; one prism per container) were used. Alkali leaching was found to be very low (8-10% Na2Oeq leached) and little affected by concrete alkali content. A good correlation between alkali leaching and Vnc/Vconcrete ratio was obtained using both the data of the present study and the results of two other studies available in the literature. This suggests the suitability of the Vnc/Vconcrete ratio as a key parameter for designing reliable CPT-38 °C tests.