Frequently Asked Questions

What is the standard procedure for using Dr. Fixit 303 Latex as a bondcoat on a smooth RCC column face before plastering, and why does this step prevent the chronic plaster de-bonding problem seen on concrete in Indian buildings?

Plaster de-bonding on RCC (reinforced concrete) column, beam, and soffit faces is one of the most persistent and frustrating defects in Indian building construction. The problem is structural: standard cement-sand plaster applied directly to smooth concrete achieves a pull-off bond strength of only 0.2 to 0.5 MPa on smooth form-finished concrete surfaces — insufficient to resist the combination of plaster self-weight (relevant for soffit plaster), thermal cycling stresses (differential thermal movement between the dense concrete column and the less dense plaster on its face), and hydration shrinkage of the plaster itself. The solution — applying Dr. Fixit 303 Latex bondcoat before plastering — works by fundamentally changing the bond mechanism from mechanical keying (which depends on surface roughness that smooth concrete lacks) to polymer adhesion (which is independent of surface texture and provides consistently high bond values). The correct procedure for 303 Latex bondcoat application on an RCC column face is as follows. Step 1 — Surface preparation. The concrete column face must be clean, free of form-release agent, curing compound, laitance, oil, and loose concrete. Form-release agent is the single most common cause of bondcoat failure — if the agent is not fully removed, the bondcoat bonds to the agent film rather than to the concrete, and the entire plaster plus bondcoat falls off as a unit when the agent film breaks. Remove form-release agent by washing with a degreasing detergent solution and scrubbing with a stiff brush, then rinsing thoroughly with clean water. Allow the concrete to dry. If the concrete surface is very smooth (from steel formwork), light wire-brushing or low-pressure grit blasting will increase surface roughness and further improve bondcoat adhesion. Step 2 — Mix the 303 Latex bondcoat. Place a measured quantity of Dr. Fixit 303 Latex in a clean container (do not use a contaminated bucket). Add OPC 53 grade cement gradually at a ratio of 1 part 303 Latex to 2.5 parts OPC cement by weight (approximately 1 litre of 303 Latex to 2.5 kg of cement). Mix with a stick or paddle mixer to a smooth, lump-free slurry consistency. Add a small amount of water (not more than 10 percent of the 303 Latex volume) if the slurry is too thick to brush. Mix only the quantity that can be applied within 30 to 40 minutes in Indian summer conditions. Step 3 — Apply bondcoat. Using a stiff-bristled masonry brush, scrub the 303 Latex bondcoat slurry firmly onto the clean concrete column face. Apply in vigorous circular motions to work the bondcoat into the surface pores and texture. Coverage: approximately 0.5 to 0.8 kg of mixed bondcoat per square metre. The bondcoat layer should be thin (1 to 2 mm) — it is a bonding agent, not a gap filler. Step 4 — Wait for the bondcoat to become tacky. Allow the bondcoat to stiffen (become semi-dry and tacky to the touch) — typically 20 to 40 minutes at 30 degrees C in Indian conditions. Do not allow it to dry completely hard. The tacky state is critical: fresh cement plaster pressed into a tacky bondcoat interlocks with the polymer network and achieves maximum bond. Plaster applied to a bone-dry bondcoat has only mechanical contact (no polymer adhesion) and reverts to the low bond of direct concrete plastering. Step 5 — Apply plaster immediately. While the bondcoat is still tacky, apply the first coat of cement-sand plaster (scratch coat) by pressing it firmly onto the column face. Tamp and scratch the surface to provide key for the second (float) coat. The result of correctly applied 303 Latex bondcoat is a pull-off bond strength of 1.5 to 2.5 MPa — 3 to 5 times higher than direct concrete plastering — sufficient to permanently retain the plaster on smooth concrete columns, beams, and soffits throughout the service life of the building.