Neoformation products associated with alkalisilica reaction, developed in concrete prisms and mortar bars, show variable morphologies and compositions. Those variabilities depend on many factors like the type of solution used, the test time, the rock type that has participated in the reaction and the microestructural characteristics of silica present in these aggregates, the availability of space for nucleation and growth of the neoformation products and their interaction with the cement paste, etc. In this work neoformation products developed in mortar bars (IRAM 1674) and concrete prisms (IRAM 1700) made with crushed stones from the province of Córdoba are studied to advance about what factors influence in those variabilities and how they do it. Posttest samples were studied by stereomicroscopy, polarized light microscopy in thin sections and scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS).