(732c) High-Throughput Testing Approaches for Geopolymer: Discovering the Ideal Recipe

Geopolymer concrete, derived from industrial mineral waste like coal ash and slag, offers a sustainable alternative to traditional Portland cement. However, the variability in feedstock composition poses a significant challenge in geopolymer production, requiring adjustments to process parameters such as alkali concentration and solid-to-liquid ratio for each feedstock. This study introduces a high-throughput strategy for optimizing the alkali activation process in forming geopolymer concrete from carbonated industrial mineral waste. Figure 1 outlines a three-step process: automated dispensing of carbonated residues and liquid alkali activator, reaction activation, and gel characterization. To achieve statistically relevant sample sizes, microtiter plates with 36 and 48 wells of approximately 1 cm diameter were designed and fabricated. A 3D-printed solid dispenser was used to accurately dispense fixed amounts (50 mg to 100 mg) of carbonated residue, while a robotic liquid dispenser (Dragonfly Discovery) added specific liquid solution volumes (0.01 ml to 0.1 ml) to the wells. The mixture was thoroughly mixed and compacted under high pressure at various temperatures. This study screened a range of reaction conditions including various alkali activators (NaOH, Na₂SiO₃, KOH, K₂SiO₃), solid-to-liquid weight ratios, pressure (500-3000 psi), and temperature (25°C to 70°C). The reaction between the liquid and powder components resulted in gel formation, which was characterized using FTIR spectrometer to analyze aluminosilicate network polymerization. The alkali activation process can be observed by shifting the main peak from 990 cm^-1 to 920 cm^-1. This change is expected due to the decrease of tetrahedral Si sites, replaced by the tetrahedral Al during the formation of N-A-S-H gel. This provides the information about alkali activation rates. For a specific condition of L/S 150 ul/ 0.1 g, the change in peak intensities is shown in figure 2. This variation is captured for all the process conditions to determine the alkali activation rates.

Currently, we are trying to correlate the spectroscopy signatures and alkali activation rates to reactivity quantified by calorimetry, thermogravimetry, and, eventually mechanical performance. Once validated, this HT screening approach will be used to supply data for ML, which is expected to drastically accelerate mixture development for on-traditional concrete.