Use of an ellipsoidal subregion of interest in the space of mixture components to the optimization of a fluoroanhydrite-based self-leveling floor composition

The present research studies the formulation and optimization of a self-leveling composition for floor toppings. This formulation is, in particular, based on a fluoroanhydrite which is a by-product of a Tunisian plant for fluorhydric acid preparation; it also contains aggregates, a neutralizing agent, a hydration accelerator and, especially, a plasticizer prepared by sulfonation of the lignin extracted from the black liquor of a Tunisian esparto grass soda pulping process. The optimization of four responses (plasticity, compressive strength, initial and final setting times) has been carried out in two steps. First, we obtain a coarse composition with a relatively acceptable rheological properties. Second, we carry out a mixture design in the surroundings of the retained composition aimed at obtaining a product with the required characteristics formulated by the users of this kind of materials. To this end, the evolution of the plasticity and the setting times of the fresh mortar and the compressive strength of the hardened mortar in a four-component system with constraints were analyzed using a mathematically independent variable approach. Finally, and in order to reach a near-optimal composition, we use the desirability functions to optimize the four responses simultaneously. This allows us to determine the coordinates of a composition which is characterized by high plasticity, acceptable compressive strength and relatively rapid setting times.