Frequently Asked Questions

What is the correct timing and procedure for broadcasting Sika Chapdur onto a concrete slab in North Indian summer conditions at 40 degrees C?

Correct timing of Sika Chapdur broadcast is the single most critical factor in dry shake floor hardener application quality. The broadcast window is defined by the bleed water evaporation stage: broadcast must occur after bleed water has disappeared from the concrete surface (a visibly wet, shiny surface indicates bleed water is still present — broadcasting into wet bleed water dilutes the hardener and weakens the surface) but before the concrete surface has stiffened to the point where the hardener cannot be trowelled in. In North Indian summer at 40 degrees C ambient temperature, bleed water disappears within 30 to 60 minutes of concrete placement, and the surface can begin stiffening within 60 to 90 minutes — this gives a broadcast window of only 30 to 60 minutes in peak summer. The procedure: after bleed water has evaporated (test by pressing a finger lightly onto the surface — if no water film appears around the finger, broadcasting can begin), spread the first half of the Sika Chapdur dose evenly by hand broadcast or mechanical spreader across the floor area. Allow the broadcast hardener to absorb moisture from the concrete surface for 3 to 5 minutes (it will darken as it absorbs moisture), then power-trowel with disc trowel to blend the hardener into the surface. Broadcast the second half dose and repeat. Finish with steel pan trowel passes to achieve the required surface finish. In extreme summer heat, work floor pours during early morning (4:00 to 8:00) when ambient temperatures are lower and the broadcast window is longer.

What application rate of Sika Chapdur is recommended for a logistics warehouse floor with reach-truck traffic on 5 tonne-capacity machines?

For a logistics warehouse floor with reach-truck traffic (5 tonne capacity machines with steel or polyurethane wheels, turning movements at pallet racking legs), the recommended Sika Chapdur metallic grade application rate is 4.5 to 5.0 kg per m2 for the aisle and turning areas, with 3.5 to 4.0 kg per m2 for the less-trafficked storage bay areas. The higher rate in aisle areas provides additional hardener concentration in the wear zone, increasing the metallic aggregate density in the surface layer and further improving abrasion resistance where the highest wheel contact stresses occur. For context: application rates below 3 kg per m2 are suitable only for light pedestrian and light wheeled traffic (small hand pallet trucks); 3 to 4 kg per m2 for medium-duty counter-balance forklift traffic; 4 to 5 kg per m2 for reach-trucks, VNA (very narrow aisle) trucks, and heavy counter-balance trucks (above 3.5 tonne); above 5 kg per m2 (up to 8 kg per m2 in two separate broadcast passes) for extremely heavy wear applications such as steel coil storage with moving equipment or continuous steel-wheel trolley traffic. For your 5-tonne reach-truck warehouse, contact Space Arc Engineering for a project-specific recommendation that includes slab design (base concrete strength and thickness) and Sika Chapdur application rate for the specific traffic pattern.

Can Sika Chapdur be used on a concrete slab in a cold storage facility at minus 20 degrees C and does it perform differently at very low temperatures?

Sika Chapdur metallic floor hardener can be used on concrete floor slabs in cold storage facilities. The metallic aggregate and cement matrix in the Sika Chapdur-treated surface layer are not affected by low service temperatures — the metallic iron aggregate maintains its hardness at minus 20 degrees C and the concrete below also maintains its compressive and abrasion strength at subzero temperatures. However, two cold storage-specific considerations apply. First, the base concrete mix design for the cold storage floor slab should be specified for freeze-thaw resistance (minimum 350 kg OPC, w/c ratio below 0.45, with Sika AER air-entraining admixture at 4 to 5 per cent air content) to prevent freeze-thaw spalling of the slab body under temperature cycling as the cold room is initially cooled and loaded with goods. Sika Chapdur does not provide freeze-thaw protection to the base concrete — this must come from the mix design. Second, on a cold storage floor that will be exposed to forklift traffic carrying wet products or condensation water, the concrete surface and Sika Chapdur layer may be exposed to repeated wetting and freezing. At standard 3 to 5 kg per m2 application rate with proper trowelling, the Sika Chapdur surface is dense and of low permeability, providing good resistance to freeze-thaw surface scaling. For very aggressive cold storage environments (blast freezing tunnels at minus 35 to minus 40 degrees C), consult Sika technical through Space Arc Engineering for additional surface treatment options such as Sika epoxy sealer over the Chapdur-treated surface.