Grout Installation Methods and Equipment
What to know
Candidates must understand placement by gravity (pour), pressure injection, and pumping; the role of mixers, colloidal mixers, agitators, packers, and injection ports; and how to avoid voids, segregation, and air entrapment. Know the difference between low-pressure and high-pressure injection, when each is appropriate, and how injection pressure relates to crack width and substrate strength.
Traps in questions
- Using high pressure on a weak or thin substrate, causing lift-off or new cracking.
- Mixing too long or too fast, entraining air and shortening pot life.
- Failing to vent or to inject from low to high in a void, trapping air.
- Letting grout sit in lines or hoppers without agitation, causing set-up and blockage.
Worked example / rule of thumb
For a fine crack, use a low-viscosity grout and start with low pressure-often around 20–40 psi at the port-and increase only if flow stops. Rule of thumb: inject at the lowest pressure that maintains flow; stop when grout appears at the adjacent vent or refusal occurs.
Key concepts to name
Colloidal mixer, paddle mixer, agitator, packer, port spacing, injection pressure, gravity feed, tremie, venting, refusal, and pot life.