Microstructure, chemical compositions, and soft computing models to evaluate the influence of silicon dioxide and calcium oxide on the compressive strength of cement mortar modified with cement kiln dust

Cement kilns are used for the pyroprocessing stage of the manufacture of Portland and other types of hydraulic cement. Calcium carbonate reacts with silica-bearing minerals to form a mixture of calcium silicates. Over a billion tons of cement are made per year, and cement kilns are the heart of this production process: their capacity usually defines the capacity of the cement plant. As the main energy-consuming and greenhouse-gas–emitting stage of cement manufacture, improving kiln dust efficiency has been the central concern of cement manufacturing technology. Emissions from cement kilns are a significant source of greenhouse gas emissions, accounting for around 2.5% of non-natural carbon emissions worldwide. This study evaluated the effect of the primary two components of CKD, such as SiO2 and CaO, on the long-term compressive strength of cement-based mortar up to 360 days of curing. For that purpose, 167 data of cement-based mortar samples modified with CKD were collected from literature and analyzed. Water to binder ratio (w) ranged from 0.34 to 0.76, CKD content ranged from 0 to 50% (dry weight of cement), different CaO and SiO2 of CKD and cement ranged from 17.64 to 25.45%, and 51.45 to 65.57%, respectively. Several soft computing models were used to predict the compressive strength of the cement-mortar modified with CKD. It was revealed from the modeling results that are increasing both SiO2 and CaO contents (%) resulted in increasing the compressive strength of the mortar. Based on the sensitivity analysis, the curing time is the most influential parameter in the compressive strength prediction of cement-based mortar modified with CKD.