Frequently Asked Questions

How is Fosroc LP90 applied and what surface preparation is needed before treatment?

Fosroc LP90 is applied to a clean, dry concrete surface by roller or low-pressure airless spray. The concrete surface must be free of contamination that would prevent the penetrating treatment from entering the concrete pores: oil, grease, wax, curing compound, paint, or old coating residue must be removed by mechanical means (grinding, scarifying) or chemical cleaning before LP90 is applied. Laitance (the weak cement paste layer on the concrete surface produced by bleed water rising to the surface during curing) should be removed by light mechanical grinding or shot blasting before LP90 treatment — LP90 penetrating the laitance rather than the underlying sound concrete provides little benefit. The concrete must be dry — LP90 is solvent-based and the solvent carrier must evaporate from the concrete after application for the active ingredient to react with the calcium hydroxide in the cement paste. Two coats of LP90 may be needed on very porous or dusty concrete surfaces — the first coat is absorbed rapidly by the thirsty surface, and the second coat applied after the first has been absorbed provides the required treatment concentration in the surface zone.

Can Fosroc LP90 be used as a permanent floor treatment on an industrial warehouse floor or is it a temporary solution?

Fosroc LP90 provides a permanent improvement in the surface hardness and dust resistance of concrete that has been treated — it is not a temporary or maintenance treatment. The chemical reaction between the LP90 active ingredient and the calcium hydroxide in the cement paste produces a stable silicate gel that fills the pore structure of the concrete and cannot be removed by normal cleaning or traffic. The treated surface does not revert to a dusting condition after LP90 treatment. However, LP90 is a dust-proofing and light surface sealing treatment — it is not a heavy-duty floor coating that provides chemical resistance, impact resistance, or a decorative finish. For industrial warehouse floors that require only dust proofing and improved cleanability, LP90 is a cost-effective and permanent solution. For floors requiring higher chemical resistance, decorative finish, or the ability to mark bays and aisles with paint lines, a subsequent application of an epoxy or polyurethane floor coating system over the LP90-treated concrete provides the additional performance required.

Why do concrete floors develop surface dusting and can LP90 treat all types of dusting concrete?

Surface dusting in concrete floors arises from several causes, all of which result in a weak, high water-cement ratio surface zone. The most common cause in Indian construction is trowelling bleed water back into the concrete surface — when concrete is placed and finished, bleed water rises to the surface during the first 1 to 3 hours. If the concrete surface is power-trowelled or hand-finished before this bleed water has evaporated, the water is worked into the surface layer, greatly increasing the water-cement ratio in the top 5 to 10 mm of the floor and producing a weak, low-strength surface that dusts under traffic. Other causes include insufficient cement content, excessive water-cement ratio in the mix design, inadequate or absent curing, and placing concrete in hot and windy conditions that cause rapid surface drying before hydration is complete. LP90 is effective at treating dusting concrete from all these causes — the penetrating silicate reaction can improve the surface hardness regardless of the cause of the initial weakness. However, where the dusting is extremely severe (the surface can be scraped or brushed off by hand in a thick layer), mechanical removal of the weak surface layer by grinding or shot blasting before LP90 treatment provides a more durable and effective result than LP90 treatment of the defective surface layer alone.