Development and Characterization of a CKD-Based Carbon-Bearing Admixture for In-Situ Concrete Applications

On one hand, the global cement industry is responsible for about 5% of the emission CO2, a major greenhouse gas. On the other hand, the manufacture of cement produces cement kiln dust (CKD) as a byproduct; every 1000 kg of cement produced yields about 150 kg to 200 kg of CKD. Mineralogically, the primary content of CKD is calcite (CaCO3) and lime (CaO) in addition to magnesium oxide (MgO) and minor components. Coincidentally, the major oxides available in CKD react with the CO2 to form stable carbonates, thus offering a potential of utilizing CKD as a carbon sink, thereby reducing the carbon footprint of cementitious construction materials and offering environmental and economic benefits. The proposed research aims to develop a 'CKD-based carbonate admixture' for concrete applications through the carbonation of CKD, and then study the physical, chemical and mineralogical characteristics of the developed admixture. A number of carbonation strategies and parameters will be tried with a view to selecting the most economical system for achieving full carbon sequestration potential of CKD. Further, the research intends to utilize the developed carbonate material to produce blended cement mortal mixtures and evaluate them for key engineering properties towards understanding the applicability of the developed material as a concrete admixture. Additionally, the characteristics of the developed carbonate material, both individually and in blended cement mortar mixtures, will be compared with that of limestone power, a common carbonate admixture. In the proposed research, the characterization of raw and carbonated materials will be conducted by through particle size analysis (LDS), differential thermal analysis (DTA)/thermogravimetric analysis (TGA), X-ray fluorescence (XRF) and quantitative X-ray diffraction (QXRD) analysis. In addition to mechanical characterization, the carbonated CKD mortar mixtures will also be subjected to DTA/TGA and QXRD analyses. The significance of this work lies in its attempt to develop a new strategy for carbon sequestration in building materials and beneficial utilization of major byproducts of cement manufacture