Use of ceramic-waste powder as value-added pozzolanic material with improved thermal properties

Abstract

Limited investigations evaluated the synergistic effects between ceramic waste powder (CWP) and blast furnace slag (BFS) on the pozzolanic activity and thermal properties of cementitious materials. In this paper, tested binders were produced by substituting the cement by either 20% CWP, 40% BFS, or combinations of 20% CWP and 30% BFS; the physicochemical characterizations were performed at various hydration ages. Scanning electron microscopy (SEM) images showed that the calcium hydroxide crystals are particularly visible in the paste prepared with cement only, while these crystals are considerably reduced for the paste containing CWP and BFS additions. Such results were confirmed by the Frattini and strength activity index tests, reflecting the occurrence of synergistic reactions that enhanced the pozzolanic reactions and led to increased amounts of calcium silicate hydrates. Regardless of the firing temperature, mortars prepared with a ternary binder composed of cement, CWP, and BFS exhibited improved residual strength and thermal conductivity. Such data can be of particular interest to cement producers and concrete technologists seeking improved sustainability and recycling processes of CWP materials.