Handbook for Bridge Inspections - TSP2

7.3.2 Measuring the Depth of Carbonation
Purpose
To measure the depth of carbonisation in concrete in order to
assess the risk of corrosion of tile reinforcement or to discover the
cause of the damage.
Carbonisation wi ll 1ead to corrosion of the reinforcement once the
carbonisation has reached the actual re inforcement elements.
Carbonisation in concrete progresses most quickl y in a dry climate
(inland areas) and/or in areas subject to road traffic or ind ustri al
pollution.
Figure 7.3-3: Carbonised COllcrete
Carboni sation is nol usually a problem in good qua lity concrete
and when the cover is described as being 30 mm or morc and has
been so applied.
Procedures
Reference is made to the NOf\vegian Public Roads Administration
Handbook No. 0 15: "On Site Testing", Method No. 15.554.
scope
General
Measuring the depth o f carboni sat ion can be necessary in the fo l­
lowing cases:
* Bridges built during or immedi ately after the Second World War
* Older girder bridges ut ili sing unstressed reinforcement and clo
sely spaced reinforcement guides on the underside of the beams;
these may also have been cast in concrete without stone ele
ments.
* Sections with little cover (I 0-30 mm)
* Sections showing clearly corroded reinforcement
* Sections containing porous or bad quality cement
* When cutting out pieces of concrete or making chl oride profil es
Acceptance Inspection
Measuring the depth of carbonisation is not necessary in this case.