Relationships Between SiO₂, Al₂O₃, Fe₂O₃, CaO, K₂O, and Expansion in the Determination of the Alkali Reactivity of Basaltic Rocks
The purpose of this work is to attempt to establish the relationship between the chemical elements leached out of basaltic rocks and the expansion measured on mortar bars by the ASTM C9 P214 method. Seventeen basalt samples from different locations in Argentina were selected. Solubilized SiO₂ was determined by the chemical test method (ASTM C-289). An aliquot of the solution was analyzed by ICP, indicating the presence of AI₂O₃, Fe₂O₃, CaO, K₂O, MgO, TiO₂, and MnO. The results obtained were statistically treated by the Principal Components method in order to determine whether there is a relationship between each of the analyzed elements and the expansion and, if any, their degree of participation. It was concluded that expansion is closely related to the dissolved silica contributed by the deleterious mineralogical components of basaltic rocks, especially volcanic glass and its alteration products, and poorly crystallized silica. The iron and calcium content does not have any influence on the reactivity. High values of solubilized silica would indicate that the basaltic rock has undergone an intense devitrification and/or silicification.