Frequently Asked Questions

What is the correct procedure for using Sikadur 31 CF Normal to anchor 12 mm diameter starter bars into an existing concrete foundation for a building extension column?

Anchoring 12 mm starter bars into an existing concrete foundation with Sikadur 31 CF Normal is a critical structural operation — the anchor capacity depends heavily on correct hole preparation, adhesive filling, and bar installation. Step 1 — Hole drilling: drill holes in the existing concrete using a rotary percussive (SDS or core drill) bit at the diameter and depth specified by the structural engineer — typically 16 to 18 mm diameter for a 12 mm bar (4 to 6 mm annular clearance for adhesive) and minimum 10 to 15 x bar diameter depth (120 to 180 mm). Drill perpendicular to the concrete face; angled holes produce eccentric loading on the adhesive anchor and reduced shear capacity. Step 2 — Hole cleaning: thoroughly clean each hole using a nylon brush (brush 4 times rotating 360 degrees) followed by compressed air blowing (4 times), then repeat the brush and air cleaning sequence. Dusty holes are the most common cause of anchor failure in practice — uncleaned concrete dust coats the hole wall and provides a weak interlayer between the adhesive and concrete. Step 3 — Mixing: mix Sikadur 31 CF Normal to a uniform grey colour with no unmixed colour streaks — unmixed resin or hardener in the mix reduces strength. Step 4 — Adhesive filling: fill the clean hole to approximately 60 per cent of its depth with Sikadur 31 CF Normal (not 100 per cent — the bar displacement on insertion will push the adhesive up and overfilling will cause blow-out). Step 5 — Bar insertion: insert the clean, rust-free, degreased bar immediately and rotate slightly to ensure full contact. Hold vertical for 3 to 5 minutes. Do not disturb for minimum 24 hours.

What is the pot life of Sikadur 31 CF Normal during summer in Delhi (40 degrees C ambient) and how should work be planned to avoid wasting product?

At 40 degrees C ambient temperature (typical Delhi April to June summer), the pot life of Sikadur 31 CF Normal is significantly shorter than the standard 40 minutes at 23 degrees C — the exothermic epoxy curing reaction accelerates strongly with temperature. At 35 degrees C, the pot life is approximately 20 to 25 minutes; at 40 degrees C, approximately 15 to 20 minutes; at 45 degrees C (peak summer in some parts of Delhi NCR), approximately 10 to 15 minutes. The reduced pot life at Indian summer temperatures means: Mix only small quantities at a time — instead of mixing a full 1.5 kg cartridge or pouch, mix only the quantity that can be applied within 10 to 12 minutes, leaving a 3 to 5 minute safety margin. Work in shaded conditions — setting up under temporary shade canopies reduces ambient temperature at the work face and extends pot life. Pre-chill if possible — if the application site permits, store Sikadur 31 CF Normal Component A and Component B in a shaded, cool location (20 to 25 degrees C) immediately before mixing; cool starting temperature extends the pot life by 5 to 10 minutes. Work in the coolest part of the day — mornings (6:00 to 10:00) are significantly cooler than afternoon during Indian summer. Discard any mixed batch that has begun to heat up or stiffen noticeably in the mixing container — applying stiffened epoxy produces significantly reduced bond strength.

Is Sikadur 31 CF Normal suitable for bedding a 200 mm x 200 mm steel bearing plate on a bridge bearing pedestal and what preparation and thickness are required?

Sikadur 31 CF Normal is used for bearing plate bedding as an alternative to cementitious dry-pack mortar or SikaGrout 214-11 where the bearing plate to concrete clearance is 3 to 15 mm — within the gap-filling range of the paste adhesive. For bridge bearing pedestal bedding: first prepare the concrete pedestal surface to Sa 2.5 by grit blasting or hand grinding, remove all dust, oil, and laitance, and dry completely (the surface must be dry for epoxy bonding — Sikadur 31 CF Normal does not achieve design strength on damp or wet concrete). Apply a thin coat of Sikadur 31 CF Normal to the prepared concrete surface as a primer coat and to the underside of the steel bearing plate (clean degreased steel). Then apply a 3 to 15 mm thickness of Sikadur 31 CF Normal to the concrete surface as the bedding layer and lower the steel plate immediately onto the fresh adhesive. Lightly press and level the plate to achieve consistent contact across the bearing area — check level with a precision spirit level. Do not apply load to the bearing for minimum 24 hours at ambient temperature above 25 degrees C (3 to 5 days if ambient is 10 to 15 degrees C). After curing, the Sikadur 31 CF Normal bedding layer provides compressive strength above 60 MPa — significantly stronger than the underlying concrete — and will not creep under long-term sustained bearing loads, unlike lead or rubber bedding materials. For bearing plate clearances above 15 mm, use SikaGrout 214-11 non-shrink cementitious grout as the bedding material.