Self-compacting geopolymer mixture: Dosing based on statistical mixture design and simultaneous optimization

The high flowability of self-compacting geopolymer mixtures (SCGMs), combined with the characteristics of high mechanical performance, durability, and low CO2 emission, has attracted considerable scientific interest. Because it is embryonic, SCGM technology demands efficient dosing methods and the consolidation of mixing rules. This study uses statistical mixture design combined with simultaneous optimization to formulate SCGMs. Thirteen established formulations using screening design methodology form the basis for the elaboration of regression models that relate the mini-slump spread, the V-funnel flow time, the apparent porosity, and the mechanical properties (axial compressive strength and bending strength) of the mixtures with the weight content of the components. The mixtures were prepared using metakaolin, a solution of NaOH, alternative laboratory-prepared sodium silicate (SiO2/Na2O = 3.81), quartz sand, and superplasticizer. The optimal self-compacting formulation, i.e., the one with the highest performance-to-cost ratio, presented NaOH molarity of 9.02 M, Na2O/Al2O3 ratio of 1.42, volumetric concentration of solids equal to 0.52, spreading diameter of 258 mm, flow time of 7 s, compressive strength of 25.16 MPa, and tensile strength of 8.56 MPa. The Scheffe linear polynomials were suitable for predicting the properties of SCGM. The statistical mixture design, combined with multi-objective optimization, was found to be an innovative and reliable alternative for dosing SCGM. (C) 2020 Elsevier Ltd. All rights reserved.