Incorporation of AlCl{sub}3 and As{sub}2O{sub}3 in Composite Cement Systems

摘要

As part of an investigation into the consequences of adding inorganic metal salts to composite cements, based on blastfurnace slag (BFS) and pulverised fuel ash (PFA), the effect on the hydration behaviour of adding AlCl{sub}3 or As{sub}2O{sub}3 to the mix water of a number of cementitious systems was investigated using isothermal conduction calorimetry (ICC) and x-ray diffraction (XRD). Four cement systems were investigated; ordinary Portland cement (OPC), 3:1 BFS: OPC, 9:1 BFS:OPC and 3:1 PFA:OPC. AlCl{sub}3·7H{sub}2O and As{sub}2O{sub}3 were added to the mix water at 0.1% and 1% concentrations. Results from ICC indicated that the addition of As{sub}2O{sub}3 had very little effect on the setting and early hydration of any of the cements. AlCl{sub}3, however, inhibited the setting of the composite cements at the 1 % addition level but accelerated the OPC at 0.1 %. The expected hydration products were observed, with the additional observation of Friedel's salt in the presence of aluminium chloride additions and vaterite in both the aluminium and arsenic-containing systems after 180 days hydration.