Epoxy adhesive for precast concrete
Epoxy adhesive applied between precast concrete bridge segments as shown in figure 1, epoxy materials are used widely in maintenance and repairing of damaged concrete structure, the using of epoxy in joining bridge segments is more delicate, the behavior of epoxy adhesives are influenced by temperature, humidity, and salinity.
The selected epoxy adhesive should satisfy the following:
- good workability at different temperature.
- the epoxy adhesive should have a good consistency to allow application for thick coating
- curing independent of temperature and humidity.
- good bonding with the concrete without reduction of bonding by the passage of time and varying humidity.
- Negligible creep deformation.
- resistance to temperature variation.
- developing high strength early
The application of epoxy is a very important process and involves many steps, each step is important and it should be followed in sequence to produce a perfect joint between precast segments. it is preferred to use one team for the entire job
- the surface of precast segments should be roughened and cleaned properly to ensure perfect bonding of epoxy and concrete.
- adhesive component, resin, and hardener should be delivered to field on cleaned and closed container. the damaged container should never be used
- the mixing of the adhesive component should begin when the other segment about to be installed.
- the adhesive component shall be mixed properly used a mixer, mixing should be done at low speed to minimize the stirring of air in the mix
- the adhesive should be applied immediately after mixing and before elapsing of the pot time (15 min to 30 min).
- the adhesive should be applied in uniform layers and it is preferred to apply it in both segments.
- the adhesive should not be applied around prestressing cable so when the adhesive is pressed it will not disturb the cable.
- temporary post-tensioning should be done within 75min to 90min from applying the adhesive
The functions of epoxy adhesive:
- applying the epoxy joint between precast segments will help in sealing and protecting the prestressing cable from the environment.
- the concentration of stresses due to voids and irregularities will be reduced by applying epoxy adhesive, the epoxy adhesive will fill this voids and irregularities and help in distributing stress and eliminating stress concentration.
- it will help in transferring shear stress between the joints.