Priming of concrete substrates is not usually required under typical circumstances. However, due to variations in concrete quality, surface conditions, surface preparation and ambient conditions, reference test areas are recommended to determine whether priming is required to prevent the possibility of blisters, debonding, pinholes and other aesthetic variations. Note: Given the fluidity and relatively thin-layer installation of Sikafloor®-24 NA PurCem® a primer for porous substrates or a scratch coat where the surface profile demands such, are highly recommended.
Smooth Application
For smooth non-broadcasted applications, a primer or scratch coat is required.
Primer
Mix and apply a primer coat of Sikafloor®-31NA PurCem at a consumption of approximately 168-224 ft2/unit (15.6-20.8 m2/unit) per coat to achieve a complete 15-20 mils w.f.t. coverage of the substrate, using a short or medium nap roller. Work the priming resin well into the surface, making sure the floor is fully wetted and then pull back lightly with the roller to the required thickness. Prime retaining (anchor) grooves but do not fill. Allow a cure period of at least 3 hours at 68°F (20°C) before application of the smooth screed mortar.
Scratch Coat (optional)
Where the surface profile requires such and where a flat floor is intended, mix and apply a scratch coat of Sikafloor®-24 NA PurCem® using steel trowels to spread the materials at a consumption of approximately approximately 215 ft2/unit (20 m2/unit) per unit, achieving a minimum 40 mils (1 mm) thickness. This application must be applied to seal the concrete surface, fill in surface irregularities; including pock marks, non-moving control joints and cracks. (Note: Should the scratch coat at 40 mils (1 mm) not fill and level the irregularities, additional coats can be applied, observing the necessary inter-coat curing times). Allow a cure period of at least 3 hours at 68°F ( 20°C) before application of the screed.
Smooth Screed:
Mix and pour the Sikafloor®-24 NA PurCem® onto the floor. Spread to the desired thickness, from 80 - 160 mils (2 - 4 mm), at approximate consumptions of 107 ft2 (10 m2) per unit at 80 mils (2 mm) to 53.5 ft2 (5 m2) per unit at 160 mils (4 mm), using a notched trowel or pin or cam gauge rake. Note: Take care to spread freshly mixed materials across the transition of previously applied mixes before the previously applied material begins to set. Immediately spike roll the surface to release trapped air in the matrix. Roller spikes must be at least three times longer than the applied product thickness. Allow a minimum 24 hours cure period at 68°F (20°C) before foot traffic.
Broadcast Application 125 mils (3 mm) Primer
Priming or scratch coat of concrete substrates is not usually required under typical circumstances. However, due to variations in concrete quality, surface conditions, surface preparation and ambient conditions, reference test areas are recommended to determine whether priming is required to prevent the possibility of outgassing blisters, debonding, pinholes and other aesthetic variations. For a primer, use either Sikafloor®-31NA PurCem FS or Sikafloor®-24 NA PurCem® Scratch Coat.
Screed: Mix and pour the Sikafloor®-24 NA PurCem® materials on the floor. Spread mixed material to approximately 107 ft2 (10 m2) per unit at 80 mils (2 mm) to 53.5 ft2 (5 m2) per unit at 160 mils (4 mm) using a screed gauge rake or trowel. Take care to spread newly mixed materials across the transition of previously applied mixes before the surface begins to set. Immediately spike roll the surface to release trapped air in the matrix. Broadcast selected aggregate to rejection. Aggregate must fall vertically to avoid surface defects / do not broadcast up to the transition line of new mixes, always broadcast 2 - 3 feet beyond the wet edge. Allow broadcast surface to cure sufficiently to be able to resist foot traffic without damaging the surface. Remove excess aggregate by sweeping or vacuuming until surface is free of all loose particles and dust.
A topcoat of Sikafloor®-31NA PurCem or other topcoats depending on applications can be applied to lock in the aggregate. Allow a minimum 12 hour cure period at 68°F (20°C) before light traffic after the Sikafloor®-31NA PurCem is applied.
