Comparative Performance of Cement Kiln Dust and Ground Granulated Blast-Furnace Slag as Partial Cement Replacements: A Case Study on Mechanical and Durability Properties of Concrete

The use of industrial waste materials as partial cement replacement has become a popular topic for research to effectively reduce cement consumption, lower CO2 emissions and improve the sustainability of concrete production. In addition to environmental benefits, these materials have been shown to modify the mechanical and durability performance of concrete positively when used at appropriate amounts. In this study, an investigation was carried out to evaluate the effects of cement kiln dust (CKD) and ground granulated blast-furnace slag (GGBFS) as partial cement replacement at ratios ranging from 0% to 50% on the physical, mechanical, and durability behavior of the modified pervious concrete compared to the control one. The analysis proves that CKD reaches its optimum performance at relatively low replacement rates (from 5 to 10%), which results in increased early compressive strength up to 14.28 MPa (+19.3%) and tensile strength to 2.90 MPa (+55.9%). This is due to a greater particle packing and rapid hydration of cementitious materials. Oppositely, despite the decrease in compressive and flexural strength of concrete at 50% replacement ratio of cement by CKD (6.24 MPa and 1.45 MPa), GGBFS significantly increases the long-term durability. At a replacement ratio equal to 50%, GGBFS leads to permeability of 18.01 mm/s (−57.0%), water absorption of 2.53% (−56.0%), and freeze–thaw weight loss of 5.58%. Overall, low ratios (≤20%) of CKD and GGBFS are preferable for non-structural applications, as they provide performable permeability with enough mechanical and durability capacity.