Effect of Curing Conditions on the Porosity Charcteristic of Metakaolin-Fly Ash Geopolymers
AIR FORCE RESEARCH LAB TYNDALL AFB FL MATERIALS AND MANUFACTURING DIRECTORATE/AIRBASE TECHNOLOGIES DIV
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The porosity characteristics of metakaolin MK- and fly ash FA-based geopolymers cured under ambient, thermal, and moist conditions were investigated using nitrogen adsorption porosimetry. In general, surface areas were higher for materials prepared from FA 29.0-59.2 m2g than for MK 5.3-12.8 m2g. Total pore volumes ranged from 0.034-0.104 ccg for MK-based materials and from 0.077-0.089 ccg for FA-based materials. For MK-based geopolymers, curing under ambient conditions resulted in a single, broad pore size distribution PSD between 250-500 A. PSDs for MK-based geopolymers cured using thermal or moist methods were bimodal with broad peaks between approximately 60-250 A and 250-500 A. For FA-based geopolymers, a single, broad PSD was observed and ranged from 20-100 A for ambient temperature cured materials and 40-200 A for materials cured under thermal or moist conditions. The observed pore size distributions were accompanied by a shift to higher wavenumber in the position of the main geopolymer band in the A TR-FTIR spectra of geopolymer materials after thermal or moist curing, indicating a higher concentration of Si-0-Si bonds formed in the materials cured at elevated temperatures. These results suggest that the observed PSDs result from Si-0-Al and Si-0-Si bond formation during curing and are affected by the curing conditions.
- Polymer Chemistry
- Manufacturing and Industrial Engineering and Control of Production Systems
- Fluid Mechanics
- Combustion and Ignition