Response Surface Methodology Optimization of Greener Cement Production: Exploring the Effects of Tunisian Phosphogypsum and Raw Meal Fineness on Energy Efficiency and High-Performance Cement Manufacturing

Cement manufacturing is an energy-intensive process and one of the main sources of human-made CO₂ emissions, requiring cleaner and more efficient production methods. This study provides an integrated evaluation of how industrial raw meal fineness and the addition of treated Tunisian phosphogypsum (PG) affect clinker burnability, the temperature for clinker formation, cement quality, and overall energy use. A Central Composite Design was used to statistically optimize three key variablesPG content (0-5 wt %), raw meal fineness (<i>R</i> _{100 μm} = 9.4-20%), and burning temperature (<i>T</i> = 1250-1450 °C)to create reliable quadratic predictive models. These models showed excellent accuracy, with correlation coefficients (<i>R</i> ²) > 0.97, and all models had good precision (adequate precision >16), indicating strong signal-to-noise ratios and solid statistical validity. The best conditions (PG = 2%, <i>R</i> _{100 μm} = 11.88%, <i>T</i> = 1250 °C) allowed a 200 °C reduction compared to conventional industrial processing (1450 °C, 0% PG, <i>R</i> _{100 μm} = 19.7%), leading to an 18.76% decrease in specific energy consumption. Under these conditions, the modified clinker had a low free CaO content (1.775%) and a favorable phase composition (C₃S = 52.056%; C₂S = 18.371%), staying within industry standards while controlling SO₃ levels (2.844%). The resulting cement showed notable mechanical improvements, with compressive strength increases of 44.62% at 7 days and 27.55% at 28 days compared to traditional cement. Overall, the multiparameter optimization approach enhances clinker reactivity, boosts cement performance, and reduces thermal energy needs, providing a practical and reproducible method for low-carbon clinker production.