Influence on Mechanical Performance of Cementitious Mortar Incorporating Anhydrous Calcium Sulphate

The present paper contributes to the investigation on mechanical performance of cement mortar incorporating anhydrous calcium sulphate, in partial replacement of CEM IV/B 32.5 R cement and fine aggregates. The anhydrous calcium sulphate is a by-product derived from the industrial production process of hydrofluoric acid, and it is obtained by a reaction between sulfuric acid and acid grade fluorspar. It can be entirely recycled and used in many applications. It forms hydrates and absorbs water molecules. Due to the increased awareness on the environmental impact of the construction industry, it is necessary to increase the use of industrial by-products, reducing the use of raw materials, and respecting the environment. For this reason, an extensive experimental campaign was conducted on special cement mortars incorporating calcium sulphate to assess their suitability in the construction sector. Eleven mortar mixes with anhydrous calcium sulphate and a reference cement mortar without anhydrous calcium sulphate were made. The mixes had varying replacement ratios of cement (from 10% to 60%) and fine aggregates (from 10% to 30%). Fifteen prismatic specimens (40 x 40 x 160 mm) were cast, cured, and tested at 28 days for each mix. Carried-out tests included the consistency of fresh mortar, flexural and compressive strength of hardened mortar. The results obtained on all mixes showed suitable flow values, flexural and compressive strengths to masonry mortar. The primary goal of this study is to find the best cement mortar with the greatest content of anhydrous calcium sulphate.