Materials † Silicone solutions in organic solvent.
Aluminium stearate solutions.
Water soluble silicone formulations (siliconates).
Methods † High pressure injection (0„70 † 0„90 MPa) solvent based.
Low pressure injection (0„15 † 0„30 MPa) water based.
Gravity feed, water based.
Insertion/injection, mortar based.
Pressure injection † 12 mm diameter holes are bored to about two-
thirds the depth of masonry, at approximately 150 mm horizontal
intervals at the appropriate depth above ground (normally 2†3
brick courses). These holes can incline slightly downwards. With high
(low) pressure injection, walls in excess of 120 mm (460 mm)
thickness should be drilled from both sides. The chemical solution is
injected by pressure pump until it exudes from the masonry. Cavity
walls are treated as each leaf being a solid wall.
Gravity feed † 25 mm diameter holes are bored as above. Dilute
chemical is transfused from containers which feed tubes inserted in
the holes. This process can take from a few hours to several days
to effect. An alternative application is insertion of frozen pellets
placed in the bore holes. On melting, the solution disperses into the
masonry to be replaced with further pellets until the wall is
saturated.
Chemical Damp-Proof Courses for Remedial Work (1)