Hybrid Metamodeling of Aesthetic Properties of Eco-Friendly Cement-Based Materials Incorporating Pozzolans

Natural Pozzolans are an effective alternative admixture for eco-friendly cement (green cement). They replace a large amount of clinker and contribute to supplementary hydration reactions. However, their colors alter the cement's aesthetic properties. Indeed, natural Pozzolans present a wide range of colors due to their mineralogical diversity and varying geological conditions. Consequently, when they are added to clinker, the final aesthetic properties of the cement change according to their coloration. In this work, we have successfully introduced a mixture design strategy to study the combined effect of three local pigmented natural Pozzolans on the aesthetic properties of pozzolanic cement. The outputs are two objective functions, such as the lightness L* and the hue angle h*. The resulting model is a special cubic model derived from Scheffé's canonical polynomial that describes the global tendency of color cement in space explored by three Pozzolans. Then, the models are hybridized with other models, such as radial and spline functions. The hybrid metamodels of the lightness L* and the hue angle h* are exact interpolators that ensure the models fit data points with a null mean square error. Our findings provide a powerful tool for streamlining the formulation of eco-friendly cement with respect to coloration, without altering the other hydraulic and mechanical properties.