Technical Reference

Treatment Procedures.

Step-by-step waterproofing, structural repair and rehabilitation methods, grouped by the chemistry they use, each mapped to the Armstrong products that carry it out. Select a treatment to view the full procedure and product recommendations.

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Treatment · Epoxy systems

Epoxy Mortar Repairs

Three-part epoxy mortar for spalls, member cracks and patch repairs

Applications

Column and beam cracksSpalled ceilings with rods visibleSlab soffitsTerrace patch repairsDamp or overhead repairsBridge deck patchesUnderwater piers and spillways

Procedure

Remove all loose, hollow and flaking concrete back to sound material. On cracked columns and beams, cut a U-groove about 6 mm wide and 12 mm deep along the crack and blow out the dust.
Expose the rusted length of each bar, clean the steel and coat it with ALSTRONG ZP 777. It is surface dry in 1 hour.
Mix ROOFBOND EP Part 1 to Part 2 at 2:1 and brush one thin, continuous coat onto the prepared concrete and into the grooves. On very porous concrete apply a second coat straight after.
Mix ROOFCRETE EP: pour the hardener into the base, mix for 3 minutes with a slow-speed drill, then add the silica filler slowly. For deep sections, add site-graded aggregate.
Place ROOFCRETE EP on the ROOFBOND EP while it is still tacky, within 30 to 50 minutes. Pack spalls tightly around and behind the bars, fill crack grooves flush with the adjacent surface, and lay terrace patches level with the surrounding slab. Finish with a steel trowel.
Where a crack runs through a column or beam, follow the groove filling with epoxy injection through 12 mm holes at about 300 mm centres.
Below water, use ROOFCRETE EUW instead. Mix it on the surface, press it firmly onto the substrate by hand or trowel and allow 48 to 72 hours underwater to cure.
Clean tools with acetone. The mortar cures without water. Finish and paint, and fix the leak that started the damage.

Important Suggestions

Pot life of both epoxies is 90 to 120 minutes at 27°C. ROOFBOND EP bonds to damp or dry concrete, but no water may stand on the surface. Load-bearing members are assessed by an engineer first. For large plastering areas, the cement-based route with ROOFCRETE AR 576 polymer mortar is the usual choice; epoxy mortar is used where strength, speed or chemical resistance matters.

Why This Treatment?

An epoxy system bonds to damp concrete, does not need wet curing overhead, gains strength fast and resists chemicals. ROOFCRETE EP reaches 93 N/mm² compressive strength at 7 days with a 4 N/mm² bond to concrete, so a filled crack or patch ends up stronger than the concrete around it.