Crack Width Design

Concrete cracks under service loads because conventional steel reinforcement requires a development length of approximately 800 mm before it engages — meaning cracks must open wide enough for the rebar to begin working. The characteristic displacement at yield for an N20 bar is approximately 3 mm, far beyond acceptable crack widths. Standard designs produce service crack widths of 0.37–0.46 mm, leading to water ingress, corrosion, durability problems, and costly remediation. Achieving the 0.10 mm crack width required for watertightness (AS 3735) with conventional reinforcement alone would require 3–4× more steel — an impractical and expensive approach.

SteelX twisted steel reinforcement (TSR) behaves like rebar at micro scale but with a development length of only 8 mm — compared to 800 mm for conventional N20 bar. SteelX untwists under load rather than relying on friction bond, engaging immediately as cracks initiate. Added to the concrete mix at 15–40 kg/m³ alongside conventional reinforcement, SteelX reduces stress on the conventional bars, increases crack spacing density, and limits mean crack widths by 75–90%. E5 Internal Cure is added to reduce the risk of plastic shrinkage cracking by controlling early-age moisture loss and ensuring complete hydration. Together, SteelX controls structural cracking while E5 prevents plastic shrinkage cracking — addressing both crack mechanisms.

• Basement walls, podium slabs, and below-ground structures requiring crack control
• Water-retaining structures designed to AS 3735
• Exposed architectural concrete with aesthetic crack width requirements
• Structures in aggressive exposure environments (marine, industrial)
• Any concrete element where crack width control is critical to performance or durability

• Crack width design and analysis to AS 3600 / AS 3735
• SteelX dosage optimisation for target crack widths
• Structural engineering support and certification
• Post-pour crack monitoring and reporting