Valorizing Cement Kiln Dust and Glass Powder: A Binder Study on Sustainable Partial Cement Replacement

The production of cement ranks as a major source of global CO₂ emissions because of the high energy requirements needed to create clinker. The construction industry is actively seeking ways to reduce its carbon footprint. Utilizing industrial waste materials to partially replace cement can lower emissions. This research evaluates a ternary binder system which uses Cement Kiln Dust (CKD) and Glass Powder (GP) to replace a portion of Type IL (Portland Limestone) cement. The mixes were made with a fixed water-to-binder ratio of 0.44 and contained 15% GP by mass while the CKD content ranged from 0% to 10%. The fresh paste properties were tested using ASTM C1437 flow tests and ASTM C191 setting-time measurements. Hardened state performance was determined by ASTM C109 compressive strength tests on 50 mm cubes at 7 days for all mixes and 28 days for specific mixes. The microstructural development was studied using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). The addition of GP resulted in a 12.5% increase in flow and a 35-minute reduction in initial setting time when compared to the 100% cement control. The addition of CKD up to 5% maintained workability but resulted in an additional 185-minute reduction of initial set time; higher CKD amounts (≥ 7%) caused paste stiffening and excessive setting acceleration. The mix containing 5% CKD and 15% GP (IGC 4) showed the highest 28-day compressive strength of 31.89 MPa among all CKD-containing blends because it achieved an optimal combination of filler, pozzolanic, and alkali-activation effects. The FTIR spectrum of IGC 4 showed increased Si–O–Si and O–H band intensities, and XRD analysis demonstrated a wider amorphous hump together with reduced portlandite peaks which indicated better C–S–H formation and less residual lime. The research shows that combining approximately 5% CKD with 15% GP produces a low-carbon binder which preserves workability and speeds up setting and maintains mechanical strength thus providing a sustainable method to utilize landfill kiln dust and waste glass.