Environmental Engineering Reference
In-Depth Information
of concrete (shotcrete) should be done with care as lift-off of the cover can be initiated
unwittingly.
18.3.4
Grout mixers, agitator pumps and other equipment
Houlsby (1977, 1978 and in WRC, 1981) strongly advocates the use of high speed, high
shear, “colloidal” mixers. This opinion is supported by US Corps of Engineers (1984),
Deere (1982), Gourlay and Carson (1982) and Bruce (1982). Figure 18.19 taken from
WRC (1981) shows the principle of some suitable mixers. The most commonly used mix-
ers are the “colcrete” or “cemix” type, which operate at 2000 rpm and 1500 rpm respec-
tively. The very high speed facilitates mixing by separating cement particles from each
other and wetting the surface of each particle. It is claimed (WRC, 1981) that mixing with
Figure 18.19.
Principles of operation of grout mixers (Houlsby, 1977, 1978 and WRC, 1981).
