Influence of particle size on free-CaO extraction and phase-level behavior in cement using ethylene glycol

Free-CaO represents a reactive component that is not fully incorporated into the clinker matrix, and it can also form or equilibrate with Ca-bearing clinker phases. Conventional wet-chemical methods often lack the selectivity required to distinguish free-CaO from other calcium-bearing phases (Ca(OH) 2 , C 3 S, β-C 2 S, C 3 A, C 4 AF). In this study, ethylene glycol is evaluated as an extractant for calcium phases in Portland cement clinker (PCC). Wet extraction experiments confirmed high CaO recovery regardless of concentration, whereas Ca(OH) 2 showed lower and content-dependent recovery. When applied to PCC with different particle sizes, ethylene glycol treatment revealed particle-size–dependent dissolution trends: coarse and fine particles showed preferential extraction of Ca–Si phases, whereas fine particles exhibited noticeable changes primarily in calcium-aluminate domains, indicating that C 3 A may be particularly susceptible to interaction with ethylene glycol. This investigation supports the use of ethylene glycol as an optimal extraction solvent for assessing reactive calcium in cementitious materials and the effects of mineral phases must still be carefully through combined analysis of wet-chemical and XRD patterns.