Frequently Asked Questions

What is the correct repair system sequence for structural column concrete repair using SikaTop 122 Plus after chloride-induced reinforcement corrosion?

The correct sequence for chloride-induced column repair using SikaTop 122 Plus follows the EN 1504 principle of electrochemical re-alkalisation or removal of deteriorated material and then applying protective mortar. Step 1 — Concrete removal: break out all deteriorated, carbonated, and chloride-contaminated concrete to a minimum 15 to 25 mm behind the reinforcement bar using breaker, chipping hammer, or hydrodemolition; ensure all concrete with chloride content above 0.4 per cent by cement weight is removed. Step 2 — Reinforcement cleaning: clean exposed reinforcement bars to Sa 2.5 visual standard by grit blasting; if bar cross-section is reduced more than 20 per cent, consult the structural engineer for bar replacement or supplementary carbon fiber reinforcement (SikaWrap). Step 3 — Reinforcement protection: apply SikaFerro or Sika Monotop 910 N corrosion protection primer to all exposed reinforcement in two brush-applied coats. Step 4 — Concrete priming: prepare the concrete substrate by SSD dampening then apply Sikadur 32 Normal epoxy bonding agent scrubbed into the surface; apply SikaTop 122 Plus wet-on-wet while Sikadur 32 is still tacky. Step 5 — Mortar application: apply SikaTop 122 Plus by hand trowel in 10 to 40 mm layers, compacting into all voids and to the reinforcement bars. Step 6 — Curing: apply Sika Antisol S curing compound or wet hessian immediately after final trowelling.

How many coats of SikaTop 122 Plus are needed to repair a 100 mm deep column spall and what is the correct inter-coat waiting time?

For a 100 mm deep column spall repaired with SikaTop 122 Plus, three application layers are required. SikaTop 122 Plus should not be applied in a single layer exceeding 50 mm because: thick single-layer application increases heat of hydration in the repair mortar mass, increasing the risk of thermal shrinkage cracking; and very thick single coats have a greater tendency to sag on vertical surfaces even with the thixotropic formulation. The recommended procedure for a 100 mm deep repair is: First coat (scratch coat): 20 to 30 mm applied by trowel, cross-hatched with a scarifier or notched trowel to key the surface, and allowed to firm up (typically 4 to 8 hours at 25 to 30 degrees C) but not dry completely. Second coat (filling coat): 40 to 50 mm applied onto the damp first coat without additional Sikadur 32 priming (the polymer mortar bonds adequately to a freshly cured same-product base coat when applied within 24 hours), again cross-hatched and allowed to firm up. Third coat (finishing coat): 20 to 30 mm applied to restore the original profile, finished flush or slightly proud with a wooden float, then lightly sponge-floated for surface texture matching the adjacent concrete. Total waiting time between coats: minimum 4 hours (at 25 degrees), maximum 24 hours; if the previous coat has been allowed to cure more than 24 hours, lightly abrade and dampen the surface before applying the next coat.

What is the coverage rate and quantity of SikaTop 122 Plus required to repair a 2 m x 1 m x 30 mm average depth column spall?

For a 2 m x 1 m x 30 mm average depth column spall, the volume of repair mortar required is 2.0 x 1.0 x 0.03 m = 0.06 m3 = 60 litres. SikaTop 122 Plus mixed to standard consistency has a fresh yield of approximately 14 to 15 litres per 25 kg bag set (Component A + Component B combined as supplied). Therefore 60 litres of fresh mortar requires approximately 4 bag sets (4 x 25 kg = 100 kg Component A). Account for 10 to 15 per cent wastage and irregular repair geometry with a factor of 1.15 — so order 5 bag sets (125 kg Component A) plus the corresponding Component B liquid. If the repair is complex, irregular in depth (ranging from 10 to 80 mm), or involves multiple smaller spots on the same column, increase the order to 6 bag sets and return unused sealed bags. For project tendering, SikaTop 122 Plus coverage is approximately 16 to 18 kg per m2 per 10 mm thickness of repair mortar placed. Contact Space Arc Engineering for current SikaTop 122 Plus pricing and supply arrangements for your project volume.