Expanded Clay Production Waste as Supplementary Cementitious Material

Global warming stands as one of the most significant challenges facing our planet, primarily due to the substantial emissions of greenhouse gases into the atmosphere. Among the major contributors to these emissions is the cement industry, which ranks as one of the largest sources of CO 2 pollutants. To address this issue, a potential solution involves partially substituting cement with alternative materials, particularly waste generated by other industries. The aim of this study was to investigate the opportunity of using an industrial waste which originates from the cleaning of flue gas in the production of expanded clay as a supplementary cementitious material. The influence of expanded clay kiln dust on the properties of Portland cement was estimated by XRD, thermal, calorimetry and compressive strength analysis. The expanded clay kiln dust was used as received and it was additionally thermally activated at 600 °C. It was determined that the original dust can be distinguished by average pozzolanic activity; meanwhile, the pozzolanic activity of additionally activated waste increased by one third. Portland cement was replaced with both types of waste in various proportions. It was found that the additive of the investigated waste accelerates the primary hydration of Portland cement, generates the pozzolanic reaction, and incites the formation of calcium silicate hydrates and hydrates containing aluminum compounds. The addition of up to 25 wt.% of activated expanded clay kiln dust leads to a higher compressive strength of samples of Portland cement.