Mechanical and physical enhancement of gypsum composites through a synergic work of polypropylene fiber and recycled isostatic graphite filler

Abstract

This paper deals with the enhancement of gypsum composites through the synergic work of polypropylene fibers (PPF) and isostatic graphite filler (IGF) additions. IGF is a waste by-product that has shown a good performance in plain gypsum, and in this research it is demonstrated that it can also be revalorized as gypsum matrix activator in reinforced gypsum-based composites. Hence, several series of gypsum composites with a 0–0.6% volume of PPF and with 0–5–10–15–20–25% of graphite addition by weight substitution of gypsum were developed and the mechanical and physical properties tested. The microstructure of the composite and the contact surface with fiber are also analyzed by Scanning Electron Microscopy (SEM). The progressive increase of graphite addition modifies the composite properties, increasing mechanical resistances (compressive strength, flexural strength, Young’s modulus, toughness), density and thermal conductivity and on the other hand, reducing their porosity and their water absorption. The mechanical performance obtained with PPF and IGF is similar to the increase of the fiber length or the volume fraction of the fiber added in gypsum-based composites, which can favor the manufacture of reinforced gypsum composites. This improvement is achieved through the activation of the gypsum matrix, through the nucleation of the hydrated calcium sulfate in contact with IGF, and the increase of fiber/matrix bond when IGF is added. Gypsum composites with IGF and PPF addition can be used in boards and renders in the construction industry, obtaining more durable and sustainable materials.