Influence of Aragonite-Derived Bio-Calcium on Hydration Products and Microstructure of Cement Paste

Abstract

Aragonite-derived bio-calcium originates from food industry waste and has potential for partial replacement of ordinary Portland cement (OPC) in cementitious systems. The objective was to study the effect of partial replacement of OPC with cuttlebone powder (CBP) on hydration products and microstructure. The six mixture groups used CBP contents of 0%, 10%, 20%, 30%, 40%, and 50% to partially replace OPC by weight at a constant water-to-binder ratio of 0.5. The specimens were cured under submerged water conditions for 28 days. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric/derivative thermogravimetric (TG/DTG), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analyses were conducted to evaluate hydration-related characteristics and microstructure evolution. The results showed that calcium hydroxide (CH)-associated weight loss decreased from 7.41% in the control specimen to 3.98% in CBP40, whereas carbonate-associated weight loss increased from 2.80% to 15.06% in CBP50. Carbonate decomposition midpoint increased from 688.25 °C to 767.41 °C after CBP incorporation. XRD and FTIR showed broader diffraction profiles and carbonate-related absorption bands. SEM revealed granular morphology in CBP10–CBP30, whereas CBP40 and CBP50 exhibited heterogeneous and agglomerated morphology. EDS showed that the Ca atomic percentage increased from approximately 66% to 82%, whereas the Si atomic percentage decreased from approximately 31% to 16%. CBP modified hydration products and microstructure, particularly at replacement levels of 20–30%. Higher replacement levels promoted stronger carbonate-associated characteristics and more heterogeneous morphology. Further investigation is required to clarify the mechanism before CBP can be fully evaluated as a partial replacement for OPC.