3.4—Bonding materials
Bonding materials can be used to bond new repair materials
to an existing prepared concrete substrate. Bonding materials
are of three types: epoxy based, latex based, and cement based.
a) Epoxy—Epoxy systems are covered in ASTM C 881.
Care should be taken when using these materials in hot
weather. High temperatures may cause premature curing and
creation of a bond breaker. Most epoxy-resin bonding
materials create a moisture barrier between the existing
substrate and the repair material. Under certain conditions, a
moisture barrier could result in failure of the repair when
moisture is trapped in the concrete directly behind the
moisture barrier and freezing occurs in this zone.
b) Latex—Latex systems are covered in ASTM C 1059.
Latex bonding agents are classified as Type I-Redispersible
and Type II-Nonredispersible. Type I bonding agents can be
applied to the bonding surface several days before placing
the repair materials; however, the bond strength is less than
that provided by Type II bonding agents. Type I bonding
agents should not be used in areas subject to water, high
humidity, or structural applications. Type II systems act as
bond breakers once they have skimmed over or cured.
Type II systems are best suited for bonding when mixed with
cement and water to produce a slurry. These are most
commonly used with PMC mixtures.
c) Cement—Cement-based systems have been successfully
used for many years. Cement bonding systems use neat
portland cement or a blend of portland cement and fine
aggregate filler proportioned one to one by mass. Water is
added to provide a uniformly creamy consistency.
Cementitious slurries are commonly used with PCC.
3.5—Coatings on reinforcement
Some epoxy, zinc-rich, and latex-cement coatings have
been proven in laboratory environments, but their performance
capability, due to holidays in the coating when field applied,
have been seriously challenged. In addition, once they are
applied, corrosion activity can no longer be determined by
standard testing procedures.
A thorough literature search discussing the pros and cons
of these materials and consultation with the manufacturer
should be conducted before using these materials.