Low-pressure crack injection is usually completed by installing low-pressure surface ports and ceiling the crack the injection ports. Several methods can be used to seal over the cracks before injection a common method is to use epoxy paste as it is very strong and easy to apply the basics are listed below with their characteristics.
901 epoxy paste, 901 epoxy is asked semi fast surface paste that is mixed 1:1 and is used to hold surface ports in place and seal over the cracks is usually dispensed onto a paper plate or cardboard for hand mixing and will usually Cure within two hours. The process can be sped up by warming up the paste first in hot water before mixing this can shorten the cure time of the epoxy to approximately 1 hour.
302 epoxy paste, 302 epoxy is a fast setting epoxy that is also mixed 1:1 and is used by most of our contractors as it is a much faster setting epoxy. Usually only small amounts are mixed at a time until the applicator is familiar with the setting time and if it is heated up like the 901 it will cure in less than one hour and will be ready for injection.
Hydraulic cement, hydraulic cement can also be used when the wall is wet when epoxy paste cannot be used, it is more difficult to apply the hydraulic cement but will work well with leaking walls it may take a bit of practice in applying the hydraulic cement to make a good seal. There is also times when epoxy paste may have been used on the first part of the crack that was dry and applicator had to switch to hydraulic cement and finish ceiling around the ports and crack if the surface is wet. Hydraulic cement works well when injecting polyurethane but can be a problem when injecting epoxy as leaks may develop and they may become harder to seal off.
One other method of using hydraulic cement was to install quarter inch copper tubing into the cracks and seal around using the hydraulic cement. The copper tubing extended from the wall a few inches and after injection directly into the copper tube the copper would be bent to seal off. Some of the drawbacks with hydraulic cement can be that it may not cure very fast and may not be very strong when injections build up a fair amount of pressure and risk pushing all of the hydraulic cement off the wall.
Thermosetting resin, also known as bondo (autobody filler )can be used to hold low-pressure or copper tubing ports on the wall that is to be injected, it has similar characteristics to epoxy but can cure very fast if you are not ready for it or if you mix too much product. Bondo is also very good at sealing over large cracks as it is relatively thick and can be spread with a standard putty knife, it is also handy if you run out of regular epoxy paste and need to get the job done. Some contractors prefer using bondo as it is relatively low-cost and sets up fast.
Bridging large cracks
Bridging large cracks can consume a lot of epoxy or sealing product to help avoid this, the best way is to use a fiber tape mash similar to what is used in drywall finishing. The fiber tape can be used across the wide gaps of cracks and your sealing paste or other will easily cover this it will also help the paste add strength across the gap