19 June 2001
Because the cost is high and the material is inflexible in thick layers,
epoxy concrete is used mainly for thin section repairs. Proprietary, prepackaged
systems should be used. Generally, the aggregate is a silica sand with little or
no material passing the No. 100 sieve (dust). The aggregate must be clean and
absolutely dry. Not all epoxy resins will bond to damp or wet concrete, so check
the manufacturer's specifications.
Epoxy mortars consist of 1 part epoxy resin to 4 to 7 parts sand by
weight. The resin is usually made up of two components that are batched by
volume and thoroughly mixed before combined with the aggregate. Epoxy
concrete contains 1 part epoxy resin to 6 to 10 parts aggregate by weight. Equal
parts of the fine and coarse aggregate are used. Epoxy concrete should be
placed in layers no more than 5 cm thick, so that excessive heat build up does
not occur. Generally, one should avoid using epoxy mortars because of their high
coefficient of thermal expansion that leads to early disbondment of the repair.
PLANNING THE REPAIRS. The first steps in planning a repair will be
Conduct an inspection to determine the course and scope of
Determine operational or functional constraints on the facility
because of the needed repair.
Establish a priority for the repair.
Based on these factors, planning will then proceed to determine if the
job should be done in-house or on contract, the repair technique to be used,
method of placing the concrete, special skills required, and unique equipment
requirements. If underwater repairs are involved, give special attention to
planning for the unique requirements, particularly involving safety.
Seismic Impact of Repairs. Any concrete repair that alters
significantly the mass of a structure may increase seismic vulnerability. A
structural analysis by a qualified structural engineer is required to ensure
earthquake safety is not compromised by the repair.
Special Skill Requirements. Most concrete repair techniques and
methods of placement require:
Normal skills associated with concrete construction
Setting reinforcing steel