Erection grouting

Figures 13.30a and b shows the results of an 0.25 min and Imin gel time, respectively. Both these gel times are relatively short, but the difference in results is striking. Although dilution losses are almost negligible based on the measured relationship between the grout volume injected and the total volume stabilized, the displacement that occurred with slower gelation would make it extremely difficult to erect an effective cutoff curtain. Of importance also is the fact that at the somewhat longer gel time, all the material placed in the coarsest sand was completely washed away by groundwater flow.

At gel times of 4min and lOmin (Figs. 13.30c and d), effects were very severe. For both these injections virtually all the grout was washed out of the two coarser sands. The stabilized masses that remain have volumes of half or less of those obtained with the shorter gel times and represent a very inefficient use of material. Further, this would also be an extremely ineffective attempt at erecting a grout curtain. 

Precast concrete erection. Each employee engaged in the erection of precast concrete members (including, but not limited to the erection of wall panels, columns, beams, and floor and roof tees ) and related operations such as grouting of precast concrete members, who is 6 feet (1.8 m) or more above lower levels shall be protected from falling by guardrail systems, safety net systems, or personal fall arrest systems, unless another provision in paragraph (b) of this section provides for an alternative fall protection measure. 

In hollow core work, as in other precast concrete erection, others are not typically on the work deck until the precast concrete erection is complete. The deck is not complete until the leveling, aligning, and grouting of the joints is done. It is normal practice to keep others off the deck until at least the next day after the installation is complete to allow the grout to harden. 

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