Impact of partial cement dust replacement in unsaturated polyester: assessing material performance and waste valorization for sustainable management

This study is a continuation of the earlier studies (The effective treatment of dye‑containing simulated wastewater by using the cement kiln dust as an industrial waste adsorbent) and (The effective remediation of heavy metal-laden wastewater by employing cement dust derived from industrial activities as a sorbent) as an attempt to provide a comprehensive image of the possible useful uses of cement dust. In this research, a polymer composite consisting of an unsaturated polyester (UP) thermoset matrix and micro-sized cement kiln dust (CKD) as filler with an addition percentage range of 0-10% was synthesized to achieve maximum utilization of this harmful waste that influences the environment and public health. Studying the structure revealed the presence of characteristic UP and CKD peaks in all the XRD and IR spectra, confirming the physical interaction between the filler and the matrix. The inclusion of CKD up to 10% decreased the degradation temperature of the UP resin. The water absorption data for the UP-CKD composites revealed a maximum water uptake of 0.55% with nonlinear behavior compared to UP doped with other inorganic fillers. An increase in the CKD content to 10% increased the limiting oxygen index (LOI) of UP above the oxygen percentage in the air (21%), promoting the fire resistance properties of the system. Prime mechanical properties in terms of ultimate tensile strength, Young's modulus, bending (flexural) strength, and flexural modulus decreased from 27.54 to 7.57 MPa, and from 1118.4 to 260.45 MPa, and from 25 to 11.49 MPa, and from 4.68 to 2.15 MPa, respectively, while both elongation (%) at break and hardness revealed fluctuating behavior with increasing CKD content. Poor dispersion and agglomeration, and hence low adhesion and poor bonding between the CKD filler and the UP, were the main reasons for this observed declining behavior, as exhibited from SEM illustrations. The as-prepared UP-CKD can be used in various applications where there is no need for distinctive mechanical performance, such as tables and benches manufacturing.