Frequently Asked Questions

Why would a contractor choose Renderoc 65 over a standard repair mortar for bridge pier concrete repair?

The depth of concrete removed during repair preparation is the primary driver. Standard bridge pier concrete repair after carbonation or chloride-induced spalling may require removal of contaminated concrete to a depth of 20 to 40 mm below the original surface — within the capacity of standard repair mortars such as Renderoc HB in standard thicknesses. However, where chloride-induced corrosion has penetrated more deeply, where the concrete is severely cracked, or where poor initial concrete quality means the cover concrete must be removed to a greater depth, the repair defect may be 50 to 65 mm deep. Filling a 65 mm deep void with a 20 mm maximum thickness mortar requires at least four application passes, each requiring cure time before the next coat. Renderoc 65 fills the same void in a single coat, reducing both the total application time and the number of days required on site for the repair operation.

Can Renderoc 65 be applied to soffits and overhead surfaces at the full 65 mm thickness without sagging?

Yes. Renderoc 65 is specifically formulated to be applied at up to 65 mm on vertical and overhead surfaces without sagging or slipping during the plastic period. The coarse aggregate grading, high polymer content, and thixotropic consistency of the mixed mortar provide resistance to gravitational slippage on vertical surfaces and soffits. However, achieving the full thickness on an overhead surface requires skill from an experienced repair mortar applicator — the mortar must be applied in a firm, supported manner, pressing the mortar firmly against the substrate and building up the profile in controlled layers within the single coat, rather than applying all 65 mm in a single thrown-on layer. The bond coat (Nitobond SBR or Nitobond EP) must be in the correct tacky condition when the repair mortar is applied — a dry or over-cured bond coat will significantly reduce adhesion and increase the risk of sagging.

What curing is required after application of Renderoc 65 and how long before it can be painted or coated?

After application, Renderoc 65 must be cured immediately to prevent moisture loss and plastic shrinkage cracking. On vertical and overhead surfaces in India, where ambient temperature and low relative humidity cause rapid evaporation, curing for a minimum of 3 days is required. Acceptable curing methods include applying a curing compound (such as Concure WB) as soon as the surface has achieved initial set, covering with damp hessian kept moist for the curing period, or wrapping with polyethylene sheeting. Subsequent coatings and surface treatments (protective coatings, anti-carbonation paints, or waterproofing systems) should be applied once the mortar has achieved adequate compressive strength and has reduced in moisture content — typically 7 to 14 days after application depending on the coating system specified. Renderoc 65 repaired areas should not receive flexible waterproofing coatings within less than 7 days.