Frequently Asked Questions

What is the correct packer spacing and injection pressure for Sikadur 52 injection into a 0.2 mm structural flexural crack in an RC beam?

For Sikadur 52 injection into a 0.2 mm flexural crack in an RC beam, the correct parameters are as follows. Packer spacing: for a 0.2 mm crack width, the resin penetration per injection point (the maximum distance resin will travel from the injection packer before the pressure drops below the viscosity-flow threshold) at 2 to 4 bar injection pressure is approximately 200 to 300 mm in a clean, open crack with no tortuosity. Therefore space the injection packers at 150 to 200 mm centres along the crack length — slightly closer than the expected penetration distance to ensure complete filling. Packer installation: drill packer holes at 45 degrees to the beam face, angled to intersect the crack at the beam core (typically at mid-depth of the beam or through the depth if accessible from both sides). Drill 12 to 14 mm diameter holes of 50 to 75 mm depth. Install mechanical injection packers (expandable rubber-tipped nipples) in each hole. Injection pressure: inject Sikadur 52 at 2 to 4 bar through a pressure-limiting injection pump — do not exceed 4 to 5 bar as higher pressure can cause hydraulic wedging and crack widening. Injection sequence: start at the lowest or one end packer and inject slowly until resin appears at the adjacent packer (indicating full filling between the two packers), then move to the next packer. After injection, leave packers in place for 24 hours before removing and seal packer holes with Sikadur 31 CF Normal. The beam surface over the crack should be sealed with epoxy paste before injection to prevent resin leakage from the crack face.

What is the minimum crack width that can be successfully injected with Sikadur 52 and how does crack condition (dry, damp, or wet) affect suitability?

The minimum practical crack width for Sikadur 52 injection is approximately 0.1 mm — at this crack width, the low viscosity of 200 to 350 mPas allows penetration under 2 to 4 bar injection pressure, though filling efficiency decreases below 0.15 mm as crack tortuosity and surface roughness impede flow. Cracks below 0.1 mm width cannot be reliably filled with Sikadur 52 by standard low-pressure injection — consider surface sealing with Sikadur 31 CF Normal or awaiting further crack development. Crack condition and Sikadur 52 suitability: Dry crack (no moisture or water visible at any point in the crack): Sikadur 52 achieves full design bond strength and compressive strength after cure. This is the optimal condition. Slightly damp crack (moisture visible at some points but no free water or active seepage): Sikadur 52 can be injected but bond strength at damp areas may be reduced by 10 to 20 per cent compared to dry condition. Surface-dry but cool concrete absorbs moisture from air and the crack faces may be damp — pre-dry with warm dry air if accessible. Actively leaking crack (water flowing through the crack, even slowly): Sikadur 52 is NOT suitable. The water flow washes the uncured resin from the crack before it can gel, and the epoxy cure is severely inhibited by wet concrete surfaces. Specify Sika Injection 101 (hydrophilic PU foam) for active leaks first to stop the water flow, allow the crack to dry out over 1 to 4 weeks, then re-assess whether Sikadur 52 consolidation injection is appropriate for the dried crack.

After Sikadur 52 injection, how can the quality and completeness of the crack filling be verified and what happens if the injection is incomplete?

Verifying Sikadur 52 injection completeness is important for structural consolidation work and can be done using several methods. Visual resin emergence: during injection, monitoring the emergence of resin at adjacent packers and at the crack surface confirms that resin has passed between the injection point and the monitoring point — this is the most practical real-time quality check during injection. Post-injection core sampling: after the epoxy has fully cured (7 to 14 days), core samples (50 mm diameter) can be taken through the injected crack zone; the core is split or sliced through the crack plane and the crack cross-section inspected — complete injection shows a continuous, transparent-to-amber epoxy fill across the crack, while incomplete areas show voids or residual crack openings. Rebound hammer profiling: local high-rebound values at the injected crack compared to lower values at uninjected areas adjacent to the repair indicate improved concrete hardness at the injection zone. Ultrasonic pulse velocity (UPV): the velocity of ultrasonic pulses increases across an injected and consolidated crack compared to an open crack — UPV testing before and after injection documents the improvement. If cores reveal incomplete filling (voids in the epoxy or unfilled sections of the crack), additional injection packers should be drilled and grouted at mid-spacing between the original packers, and Sikadur 52 re-injected at 2 to 3 bar until continuous resin flow is confirmed at all monitoring points. Contact Space Arc Engineering for specification of a comprehensive quality assurance programme for Sikadur 52 injection on critical structural elements.