Influence of the thermally and hot water treatment of cement kiln dust on the Physico-chemical features of Portland cement

Blended cement could reduce the harmful effect of cement manufacture, which is composed mostly of Portland cement and one or two compounds called supplementary cementitious materials (SCM). This kind of paper studies the impact of the partial replacement (5%, 10%, 15%, 20%, and 25% wt.) of Portland cement by treated cement kiln dust (CKD) on the hydration characteristics of Portland cement. The treatment of CKD was carried out by two methods: i) thermal treatment by firing CKD at 700 °C and 800 °C for 2 h, and ii) immersing CKD in hot water at 30 °C, 70 °C, and 90 °C for 24 h with continuous stirring. Porosity, bulk density, and compressive strength measurements were performed to examine the mechanical properties. Hydration characteristics were investigated by combined water determination through a curing time up to 90 days and free lime measurement after 90 days of curing. Air voids fractal dimension and 2-D porosity were measured using SEM micrographs processing employing ImageJ software. FT-IR and SEM techniques provided additional data about hydration yields and their microstructure, respectively. The outcomes exhibit that the partial replacement of Portland cement by CKD (thermally treated at 800 °C/treated in hot water at 90 °C) enhances the hydration rate, and mechanical properties of blended cement compared with the blended cement include CKD (thermally treated at 700 °C/treated in hot water at 30 °C, and 70 °C) or compared with the blended cement contain CKD (without treatment).