THE INFLUENCE OF STEEL SLAG AND NANOCLAY ADDITIVES ON THE MECHANICAL AND DURABILITY PERFORMANCE OF UNSATURATED POLYESTER GYPSUM BASED COMPOSITES

Abstract

The current investigation examines the development and characterization of gypsum-based hybrids incorporating industrial steel slag, organo-modified nanoclay (Nanofil-15), and an unsaturated polyester (UP) resin. The formulations were designed to compare a conventional water-resistant system with UP-bound system. The fabricated samples were evaluated in terms of specific impact strength (Si), flexural performance, water absorption, and direct flame resistance. Microstructural analysis by scanning electron microscopy (SEM) was correlated with porosity (Vv) to clarify the relationship between packing efficiency and interfacial voids. The UP-bound gypsum (UPG) composite exhibited a substantial increase in impact resistance compared to the water-bound system primarily due to coordination interaction between the UP-carbonyl groups and the surface Ca²⁺ and Al³⁺ cations, which strengthen the interface
between the amorphous slag and crystalline gypsum phases. Incorporation nanoclay and stearic acid-modified slag (LS) further improved mechanical performance by promoting crack-deflection and interfacial micro-lubrication. The UP resin drastically reduced water absorption (< 1.0 %) by forming a hydrophobic shield around the mineral. Furthermore, slag additions which is rich in Fe₂O₃ and Al₂O₃ reduced the mass loss rate (MLR) by acting as an inorganic heat sink. These findings highlight the synergistic potential of polymer-mediated coordination to convert waste material into a durable, high-strength construction material.