High-Throughput Screening of Geopolymerization Kinetics for Rapid Mixture Design Optimization

Geopolymer binders derived from industrial mineral wastes (IMWs) offer a sustainable alternative to Portland cement concrete. However, the variability in IMW feedstock composition necessitates careful optimization of activator formulations and processing conditions, a challenge that remains time- and resource-intensive. To address this, we developed a high-throughput (HT) FTIR-based screening methodology to rapidly evaluate the geopolymerization kinetics of carbonated ground granulated blast furnace slag (GGBS). Carbonated GGBS IMW was alkali-activated using sodium hydroxide and sodium silicate solutions under systematically varied liquid-to-solid (L/S) ratios (33–60 wt %), activator (Na2Si3O7/NaOH) volume ratios, and reaction temperatures (ambient, 40 °C, and 70 °C). The geopolymerization process, leading to the formation of sodium or calcium aluminosilicate hydrate (N–A–S–H/C–A–S–H) gel, was monitored by ATR-FTIR spectroscopy, which tracked characteristic vibrational bands associated with (Si–Al)–OH linkages, enabling the extraction of reaction rate parameters. The results demonstrated that increasing temperature accelerates geopolymerization kinetics, with alkali-activation rates following the trend 70 °C > 40 °C > ambient for most formulations, particularly at moderate silicate contents and L/S ≥ 50 wt %, while excessive silicate led to diffusion-limited behavior at elevated temperatures. Regression analysis using polynomial surface fitting revealed nonlinear interactions between silicate ratio and liquid fraction, with predictive fits reaching R2 = 0.94 under ambient conditions. Importantly, high-throughput FTIR-derived alkali-activation rates strongly correlated with compressive strength values (1–28 days), with optimized formulations achieving up to 67.6 MPa at 28 days. Overall, this study demonstrates a quantitative high-throughput framework for a rapid evaluation of geopolymerization kinetics and relating those to the long-term compressive strength of carbonated slag-based geopolymer systems.