Civil Engineering Reference
In-Depth Information
pore-liners (water-repellents)
Common generic types
Main performance characteristics
Silanes
Siloxanes
Silicones
Numerous variations in
chemical type, content
of active material, and
solvent system are
available
May be 100% active
Silanes/siloxanes react in
situ with the concrete;
silicones generally
undergo drying only. In
both cases, the pores/
capillaries are lined with
a hydrophobic layer
Protect against water/chloride ingress in the absence of
hydrostatic pressure (questionable on ponded surfaces)
Some systems are approved for use on UK highway
structures
Negligible effect on ingress of moisture vapour, carbon
dioxide or oxygen
No benefit for resistance to chemicals, abrasion or
impact
Negligible effect on concrete appearance
Durability generally expected to be good, more so for
silanes/siloxanes, but claims vary
Relatively easy to apply/re-apply with minimal surface
preparation
Substantially dry concrete required
Low temperatures acceptable but hot/windy conditions
unfavourable (use of a 'paste' form preferred)
Common generic types
Main performance characteristics
Generally solvented,
although some water-
based dispersions can be
suitable
Thermoplastic
(acrylics, pu's)
Physically drying only
Thermosetting
(epoxy, pu's)
Chemically reactive and
physically drying
May be one- or two-
pack systems
Wide variations in solids
content, solvent/polymer
type are possible
Enhanced resistance to ingress of liquids, gases,
vapours, chemical attack and abrasion
Effectiveness depends on severity of service
conditions, specific requirements and porosity of
concrete/number of applications (2-3 is usual)
Some slight darkening of the concrete is usual and the
formation of a surface glaze may occur
Generally have reasonably good long-term
effectiveness as there is no dependence on surface
adhesion
Relatively easy to apply/re-apply with minimal surface
preparation
Can also be used effectively as a primer/sealer prior to
coating on porous/friable surfaces
