Civil Engineering Reference
In-Depth Information
damage, which occurs after hardening. The two terms, unfortunately, are
often used interchangeably.
Impact/mechanical damage and damage due to structural loading
These types of damage may be hard to distinguish on the basis of the
examination of laboratory samples alone and site observations in conjunction
with a structural assessment are required to unambiguously diagnose these
types of damage.
2.3 Characteristics of some common cementitious repair
materials
2.3.1 Hand-applied high-performance proprietary repair mortar
mixes
Modern proprietary high-performance repair mortars can be used to
produce very robust and durable repairs that benefit from low shrinkage
characteristics and very low permeabilities. They commonly have complex
compositions and can contain a very wide range of constituents in addition
to Portland cement and aggregates of various types. Among the range of
constituents that can be detected petrographically are:
• High-alumina cement/calcium aluminate cement
• Shrinkage-compensating cements
•
Microsilica (densified, undispersed clots)
•
PFA (pulverised fly ash) and PFA cenospheres
•
GGBS (ground, granulated blast furnace slag)
Figure 2.10
Photomicrograph of a thin section showing a proprietary repair mortar
containing PFA cenospheres and particles of unhydrated Portland cement. The PFA
throughout the field of view. The unhydrated cement grain occurs just to the left
of the field of view. There are also moderate quantities of portlandite crystals that
appear pale to white.
