The Novelty of Partially Replacing Cement with Gypsum: Optimum Mix Design and Structural Applications
Abstract
Cement is widely noted to be the most expensive binding material. The construction industry would value a suitable and effective alternative binder product that would considerably minimize the use of cement and ultimately reduce construction costs. This study investigates the possibility of using gypsum as an alternative binding material. Thus, an optimum concrete mix was obtained by partially replacing cement with gypsum, and the addition of sand to the initial gypsum mix was also explored. Derived from experimenting with 18 mixes, an optimum mix was obtained which consisted of gypsum, 2% superplasticizer, 5% cement, sand-to-gypsum ratio of 2:1, and w/binder ratio of 0.28, which resulted in a 28-day flexural strength of 9.04 MPa and compressive strength of 32.43 MPa. Thus, an increase of 83% and 51% was achieved in the flexural and compressive strength compared to the initial cement mix. This optimum mix was used in the construction of beams and their behavior was compared with normal concrete beams for shear and flexure. The incorporation of gypsum in specific beam configurations has resulted in an increase in load capacity and deflection of 16.7 % and 29.6%, respectively. More importantly, the presence of gypsum did deter the early initiation of cracks.