Valorization of cement kiln dust in activation and production of hybrid geopolymer composites with durable characteristics

The main target of the present paper is valorize the high alkalis in cement kiln dust for production of sustainable hybrid alkali activated composites, where these high alkalis content prohabit its recycle in building materials. The used precursors are electric arc slag (EAFS) and granulated blast furnace slag (GGBFS) as well as cement kiln dust (CKD) was studied. Activation was carried upon usage of 25% CKD, as it bears high alkali content that can initiate and propagate the polymerization process. The formed geopolymer composites were immersed in 5% MgSO4 solution to determine the stability upon sulfate attack. FTIR, XRD, SEM, compressive strength, and water absorption analysis were utilized to examine the obtained geopolymer under sulfate attack. Results clarified the potentiality of cement kiln dust in production of alkali activated composites with durable properties in sulfate solution and possess an optimization of strength values by EAFS up to 50%, followed by lowering in strength with EAFS increase, although possessing stability up to 12 months. Data elucidated a good stability and resistance of mix containing slag substitution by 50% EAFS and 25% GGBFS and resulted in further enhancement in both mechanical and microstructural characteristics by increasing matrix compaction and cohesion than the non-immersed samples (28 days).Formation of nucleation sites of CSH for geopolymer accumulation and precipitation by alkaline dissolution of aluminosilicate precursor.