Frequently Asked Questions

What is the difference between using Sika Monotop 910 N and SikaFerro 903 as reinforcement corrosion protection primers and when should each be specified?

Sika Monotop 910 N and SikaFerro 903 are both two-functional reinforcement corrosion protection primers from Sika but differ in composition and system fit. Sika Monotop 910 N is a one-component product that adds water on site, making it easy to handle; it is the specified primer in the Sika Monotop system (Sika Monotop 910 N for bar priming and bonding bridge, then Sika Monotop 612 repair mortar) and designed specifically for use within this system. SikaFerro 903 is a two-component product (polymer liquid Component B + cementitious powder Component A mixed on site) that provides a higher polymer content in the dried coating and slightly higher corrosion protection performance. Both products are appropriate for standard structural concrete repair of carbonated or chloride-contaminated columns, beams, and slabs in buildings and infrastructure. When to specify Sika Monotop 910 N: specify when using the complete Sika Monotop system (Sika Monotop 910 N + Sika Monotop 612 repair mortar) for a consistent one-manufacturer repair system. When to specify SikaFerro 903: specify for use with SikaTop 122 Plus (two-component repair mortar) or when the project specification separately requires a corrosion protection primer with a documented polymer content and the bonding function is handled by Sikadur 32 epoxy bonding agent. Both products are acceptable under EN 1504 Principle 11 and meet equivalent corrosion protection performance standards — consult Space Arc Engineering technical team for specific project system selection.

How should Sika Monotop 910 N be applied as a bonding bridge on an existing concrete substrate and what is the critical timing for the subsequent repair mortar placement?

Sika Monotop 910 N applied as a bonding bridge on existing concrete has four critical requirements: surface preparation, consistency, coverage, and timing of overcoating. Surface preparation: the concrete substrate must be mechanically prepared to CSP 3 to 4 (grit blast or scabble) to remove laitance and open the concrete surface pore structure; blowing with compressed air then dampening the surface to SSD (saturated surface dry) condition — visibly wet surfaces must be left to dry to SSD before primer application. Consistency: mix Sika Monotop 910 N powder with clean water to a thick, lump-free slurry consistency suitable for vigorous brush application — not as thin as a paint but not as stiff as a mortar. Coverage: scrub the slurry firmly into the prepared concrete surface using a stiff bristle brush with circular scrubbing action, ensuring the slurry penetrates the surface pores and covers the entire repair area including vertical and horizontal faces. Coverage rate: approximately 0.5 to 0.8 kg per m2. Timing: this is the critical step. Apply Sika Monotop 612 or SikaTop 122 Plus repair mortar while the Sika Monotop 910 N slurry is still in the wet-on-wet (tacky) state — typically within 1 to 2 hours of slurry application at 25 to 30 degrees C in Indian conditions. If the slurry dries out completely (turns white and powdery) before the repair mortar is placed, it becomes a weak, dusty separation layer. Remove dry Sika Monotop 910 N slurry by brushing or compressed air, apply fresh slurry, and place the repair mortar immediately.

What quantity of Sika Monotop 910 N is needed per m2 of repair area in a typical structural column repair with 20 mm deep concrete removal and 12 mm diameter bars at 150 mm centres?

For a structural column repair with 20 mm average concrete removal depth and 12 mm diameter bars at 150 mm centres in both directions, the Sika Monotop 910 N is applied to two surfaces: the concrete substrate face and the exposed reinforcement bars. Concrete substrate coverage: approximately 0.6 to 0.8 kg of Sika Monotop 910 N per m2 of exposed concrete face (this is the face area of the repair, not the volume). Reinforcement bar coverage: for a 12 mm diameter bar grid at 150 mm x 150 mm centres, each m2 of repair area has approximately 13 bars in each direction (6.5 m of bar in X and 6.5 m in Y direction = 13 m total bar length per m2 of repair face). Surface area of bars per m2: 13 m x pi x 12 mm = 13 x 0.0377 = 0.49 m2 of bar surface per m2 of repair face. Sika Monotop 910 N coverage per coat on bars: approximately 0.8 to 1.0 kg per m2 of bar surface per coat x 2 coats = 1.6 to 2.0 kg per m2 of bar surface. Total Sika Monotop 910 N for bar priming: 0.49 m2 bar surface x 1.8 kg per m2 per coat x 2 coats = approximately 1.8 kg of Sika Monotop 910 N for bar priming per m2 of repair face. Total combined (concrete bonding + bar priming): approximately 2.4 to 2.6 kg of Sika Monotop 910 N per m2 of repair face area. For a project estimate, add 10 per cent for waste and round up to full bags.