This process blends traditional placement methods with pressurized grouting techniques. There are several advantages with this process, including high bondability, low shrinkage, reduced cracking, and increased strength. Preplaced aggregate concrete ensures that separation between the aggregate and cementitious grout does not occur. This is especially important when placements occur underwater where traditional placement methods have a higher tendency to “wash” the cement right out of the aggregate.
PAC can also lead to cost savings because it reduces the need for heavy equipment. Often, work on water-based structures requires sizeable equipment to successfully complete a placement. However with PAC, the aggregate can be slurred into the forms and then grout can be pumped to the placement site from up to several hundred feet away. This virtually eliminates the need for heavy equipment or large floating marine plants.
The PAC process is described below:
- Formwork and structural steel are installed.
- Washed aggregate is slurred into place.
- Grout is pumped into the formwork, starting at the bottom and finishing at the top.
- Forms are pulled after cure time is complete, leaving a strong, aesthetically pleasing finish.