Calcium sulfate: an alternative for environmentally friendly construction

Abstract

One of the challenges of the construction industry today is to develop and promote the use of environmentally friendly materials. The production and use of Portland cement clinker as a construction material is part of the problem because of its high generation of CO2 in its manufacture. Therefore, alternative materials that mitigate in some extent this situation become an important task in the development of new materials. The use of calcium sulfate in any form as a construction material has been limited due to its high solubility in water and low development of mechanical strength. However, its use as an alternative cementitious material provides a notable decrease on greenhouse gases produced when it is compared to the manufacture of other hydraulic cementitious materials, since the temperatures required in its manufacturing are relatively low. Therefore, in this study the feasibility of reuse of waste gypsum from the ceramics industry by milling and calcination was evaluated. This calcium sulfate was used as main component in the manufacture of ternary cementitious mixtures. Cementitious test mixtures were manufactured with CaSO4 synthesized from waste gypsum, ground granulated blast furnace slag and silica fume. Small additions of K2SO4, Ca(OH)2 and Portland cement clinker as chemical activators were used. The addition of blast furnace slag and silica fume to the calcium sulfate systems improved its properties and prevented the dissolution in wet environments. The compressive strength achieved by some systems was near 20 MPa at 56 days of curing, showing that this material may be a feasible option for the manufacture of masonry or elements with low structural strength requirements with a proper behavior in wet environments.