Microscopic and Physico-Mechanical Properties of Hydrated Anhydrite Using Sulphate Activators PDF

Keywords

anhydrite, sulphate activators, sediments

Abstract

Anhydrite deposits either as weathering products or original sediments are found, over huge gypsum bodies in the Ras Malaab area near the Gulf of Suez, Egypt. Anhydrite can be converted to a useful building material by partially transforming the anhydrite into gypsum using chemical activators. The used activators are: ZnSO4, K2SO4 and MnSO4. The Physico-mechanical properties of hardened natural anhydrite such as dry and wet compressive strength, bulk density, water absorption and apparent porosity are discussed. The results show that the addition of 3% MnSO4 gives the highest values of dry (~175 kg/cm2) and wet compressive strength values (~100 kg/cm2). These increase of activators percentage leads to the decrease of both water absorption and apparent porosity values. X-ray diffraction analysis (XRD) is used to detect the percentage of transformed gypsum. A polarizing microscope was used to describe the micro-structure, cleavage planes, crystal structure and the new phases which were confirmed by scanning electron microscope (SEM). Many factors were found to control the gypsification process such as type and percentage of activators, time of curing, difference in potentiality and electronegativity, in addition to the position of the elements of activators in the periodic table.