The hydration characteristics when C2S is present in MSWI fly ash slag

Abstract

This paper reports on an investigation of the hydration characteristics when C2S is present in municipal solid waste incinerator (MSWI) slag. The results can be summarized as follows: thermogravimetric analysis (TGA) observations show lower amounts of CSH and Ca(OH)2 in samples where C2S is incorporated into MSWI slag, possibly due to the partial replacement (20–40%) of the mineral constituents by less active slag. In general, the incorporation of C2S into slag, decreases the initial hydration reaction, whereas it increases the pozzolanic reactions at a later stage, by consuming Ca(OH)2. The X-ray diffraction results are in good agreement with the TGA results. Moreover, the hydration degree of the C2S–slag pastes, as determined by nuclear magnetic resonance techniques, also indicates that the C2S–slag pastes show lower hydration degree values, at all ages (1–90 days) of hydration. This may be due to the inactive behavior of an acidic film on the grains of slag, which in term retards the hydration that occurs as the Ca(OH)2 breaks down the silica framework.