Sustainable disposal of cement kiln dust in the production of cementitious materials

• Published in: Journal of cleaner production 2019-09, Vol.232, p.1218-1229
• Main Authors: Abdel-Gawwad, Hamdy A., Heikal, Mohamed, Mohammed, Mona S., El-Aleem, S. Abd, Hassan, Hassan Soltan, García, S.R. Vásquez, Alomayri, Thamer
• Format: Article
• Language: English
• Subjects: Cement kiln dust; Strength activity index; Sustainable recycling; Thermal activation; White Portland cement; White pozzolan
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2019.06.016

In the present work, sustainable use of cement kiln dust (CKD) and feldspar (FS) in the production of pozzolanic materials with different reactivity and whiteness were investigated. The proposed method includes thermal treatment of CKD and FS at 1000 °C in the presence of sodium hydroxide to convert crystalline- FS/CKD -structure to amorphous one. Different FS/CKD mixtures were designed at weight ratios of 50/50, 66.66/33.33, and 80/20 (P-1, P-2, and P-4, respectively) to optimize the whiteness and amorphous content of the produced pozzolans. A preliminary study revealed that the amorphous content and the whiteness of the prepared pozzolan strongly depend on FS/CKD weight ratio. The optimum pozzolanic materials with high 89% whiteness and 100% amorphous content were obtained in the case of P-4. The individual replacement of white Portland cement by 30 wt % of the synthetic pozzolans resulted in the enhancement of 28-days compressive strength. The use of P-4 pozzolan not only increased the mechanical properties of white Portland cement, but also enhanced its whiteness. Non-thermally treated FS/CKD blend (as the counterpart of P-4 pozzolan) showed a lower pozzolanic activity as compared with thermally treated one. Regardless of the change in the strength activity index (SAI) and the rate of Ca(OH)2 consumption, all synthetic pozzolans demonstrated a higher pozzolanic activity. [Display omitted] •Experimental method was proposed to beneficial disposal of cement kiln dust.•Pozzolans were prepared by thermal activation of cement kiln dust and feldspar.•The whiteness and amorphicity of pozzolan strongly depends on cement kiln dust content.•The pozzolanic reactivity enhances with decreasing cement kiln dust content.•The prepared pozzolan can be used as a partial replacement to white Portland cement.