Improvement in the resistance against moisture presence in plasters and self-levelling screeds based of natural anhydrite waste

Abstract

The anhydrite is a natural compound that co-exists alongside with the gypsum rock in some geological formations. Formulating new products for plasters and self-levelling screeds is the most common way to treat and recover the anhydrite waste in Europe. In this case, we´ll re-use natural anhydrite waste originated in a gypsum quarry located in the province of Alicante (Spain), having in mind this could be extrapolated to any other gypsum quarries. The compound is chemically composed of anhydrous calcium sulfate that could be activated through catalysts, hydrating and turning itself into dehydrate calcium sulphate (gypsum). The aforementioned material presents great aptitudes for self-levelling screeds due to its good reology and little shrinkage. Generally, they are used in building industry once the building envelope is finished and water tight as its water solubility restricts its use in damp environments. The current paper presents improvements in the resistance against water presence by dosing damp-proof product as siloxan derivatives and zinc stearate. There have been obtained important improvements in the reduction of superficial absorption and capilarity absortion. Also the effect of these aditives on the mechanical properties of the self-levelling compound have been studied in this paper.