Quality Control Tools to Identify Source Variability of Class C Fly Ash and Its Impact on Freshly Mixed Cement-Fly Ash Paste

摘要

The objective of this research was to identify tools available for quality control (QC) of as delivered class C fly ash. Tools investigated included penetration type devices and test procedures including the Iowa Set Time Test, Gillmore Needle, and Vicat Needle. Class C fly ash samples were obtained from 11 sources available to Louisiana Department of Transportation and Development (LADOTD). Samples were obtained twice a week for ten weeks for a total of about 20 samples per source. Statistical modeling was used to determine if a relationship existed between the various initial and final set times and the maximum temperature of the fly ash paste and the fly ash chemistry and fineness. Set time devices yielded similar results for both initial and final set. The test methods pointed out significant differences in set times between buckets within a source, but further testing when incorporating portland cement showed these differences to be negligible in effect. A suitable correlation was found to exist between the calcium oxide and sulfur trioxide content and the maximum temperature of the fly ash temperature results.