Durability of concrete repairs - Concrete Repair - page 240

standards have a general expectation that repairs should last for at least 25
years. Performances of the 230 case histories in relation to these requirements
are shown in Figure 14.9 and it is evident that there is a shortfall in the
expected performance.
The most successful repair lasted for 52 years and 10 per cent of the 230
repairs lasted in excess of 25 years.

14.5.2 Performance in relation to type of repair

Performances of the most common repairs, whether applied solo or in
combination, to all types of damage, are shown in Figure 14.10.

Patches
The two materials mainly used for patching were cementitious and polymer
modified mortars; others included fibre-reinforced mortars. Performances
were as follows:

• Cementitious patches, 45 per cent successful

• Polymer modified, 50 per cent successful

• Other materials, 25 per cent successful.

Although polymer modified materials are generally considered to be more
effective than cementitious mortars, there was little difference in the performances
in practice. This may be a reflection of assessments based on laboratory work
compared with behaviour when subject to the rigours of natural weathering in
the field or it may be due to earlier materials being less effective.

Coatings
Several types of coating were reported: barrier, hydrophobic and others
(aesthetic, anti-carbonation, unspecified). Performances were as follows:

80

70

60

50

40

30

20

10

0

Patch Coating C Inj Spray CP Strength *

Figure 14.10 Performance in relation to type of repair.
* Restoration of strength excluding replacement of corroded reinforcement