A proposal of pozzolanic pre-qualification of geological materials: X ray diffractometry as an alternative method

Abstract

This paper presents an alternative method for the evaluation of the pozzolanic potential of geological materials. This method is based on X ray powder diffraction analysis of mortars obtained from a mixture of two parts of lime (calcium hydroxide) and one part of ground material and water. The mixture is put to dry in an oven at 30º C during 7 days when maximum consumption of lime due to pozzolanic reaction occurs. The mortar is ground and then submitted to X ray powder diffraction analysis, which reveals new compounds formed as products of pozzolanic reaction. The most important compounds are associated with hydrated calcium silicate (C-S-H) and its derivatives with aluminum, iron, sodium and potassium. The presence of these new compounds indicates that the geological material may present a favorable pozzolanic reaction and be, therefore, a natural pozzolan.