Properties and Performance of a Pulverized Fly Ash Grout

A laboratory investigation was conducted in order to develop a new grout based on fly ash produced in Greece. Ptolemaida fly ash was selected because of its hydraulic properties and was pulverized (Blaine specific surface over 8,300 cm2/gr, D15=1.3 *mm, D50=6 *mm, and D85=20 *mm) in order to improve its groutability and its hydraulic activity. Pulverized fly ash (PFA) suspensions with selected additives have properties comparable to those of ordinary and microfine cement suspensions. Clean sands were injected using two specially constructed devices. Hydraulic conductivity, unconfined compression, and UU and CU-PP triaxial compression tests were conducted on grouted sand specimens. Coarse sands can be grouted effectively with PFA suspensions. Conventional groutability ratios were found to overestimate the groutability of these suspensions. Grouting with PFA suspensions reduces sand hydraulic conductivity by up to seven orders of magnitude and yields unconfined compression strength values up to 3,000 kPa. The Mohr-Coulomb failure criterion represents the behavior of grouted sand with cohesion values ranging from 280 to 450 kPa and angle of internal friction slightly higher than that of the sands.