Civil Engineering Reference
In-Depth Information
The more common methods of surface preparation and coating application
are outlined in the following sections, where it is assumed that the surface
is basically sound. Hence, the following processes are not discussed: patch
repair/re-casting to rectify reinforcement corrosion, spalling or mechanical
damage; the treatment of joints and cracks; and the stemming of water
ingress/seepage.
Where a coating does form part of a complete repair package - for
example, following deterioration due to reinforcement corrosion -
many methods of in-situ assessment are used routinely. However, these
techniques contribute to surveys aimed at deriving a repair strategy and
specification rather than solely to quality control procedures. They include
the determination of concrete strength, depth of cover, corrosion activity
and permeability and are discussed in detail in several publications:
Concrete Society TR54 (Concrete Society, 2000), the topic 'Testing of
Concrete in Structures' (Bungey et al., 2006) and CIRIA Technical Note
143 (CIRIA, 1992).
Health, safety and environmental issues are not discussed here, but it
must be noted that certain assessments and actions are covered by statutory
regulations. Guidance can be obtained from published sources (see, for
example, BS EN1504-10 (BSI, 2003) and references therein) and from
product suppliers (Health & Safety Data Sheets with a regulated content
must be made available).
17.5.1 Surface preparation
Cleaning
Many techniques are used for preparatory cleaning and the most appropriate
will depend upon individual circumstances. The following methods are given
in approximate order of increasing severity:
• Wet scrubbing with emulsifying detergents and, where necessary, biocides
• Low-pressure water cleaning
• Steam cleaning
• Acid etching
• Hand/power wire brushing
• Grinding
• Wet or dry abrasive blasting (with vacuum recovery)
• Shotblasting
• Scarifying/planing (cutting teeth on rotating discs)
• Needle gunning
• Scabbling
• (Ultra) high-pressure water jetting (100-300 MPa)
• Flame blasting
•
Milling (cutting teeth on a rotating drum).
