How to Control Slab Cracks

One of the most common defects we are required to assess as engineers would be slab cracking, in particular ground slabs. 

While seemingly simple, ground slab cracking can result in on-going frustration both aesthetically and operationally. Cracking is not only un-sightly but can result in serious disruption to warehousing operations and water penetration can eventually result in pavement failure in external environments.

There are a number of issues that can contribute to concrete cracking including:

  • Size, shape and aspect ratio of concrete panel and spacing of joints;
  • Reinforcement size and depth of cover;
  • Concrete shrinkage specification;
  • Age of concrete at time of saw cutting (saw cutting should be completed within 24hrs to initiate early age cracking at the saw cut);
  • Insufficient depth of saw cut (inadequate to initiate crack);
  • Continuation of reinforcement across the sawn joint (reinforcement should stop each side of the proposed joint);
  • Inadequate curing;
  • Weather conditions at time of pour (i.e. hot and/or windy weather can cause premature drying);
  • Subgrade preparation/compaction resulting in differential settlement;
  • Over-loading of pavement; and
  • Water entry at joints (in-adequate sealant).

While concrete can be unpredictable and is always subject to shrinkage the challenge is to undertake measures that control the likely crack locations and limit the cracking widths to acceptable limits. Attention to detail at the design and construction stages will largely avoid unsightly and un-wanted cracking.

MPN can work with the client and design team to optimise design solutions. MPN’s team can evaluate whole-of-life costs and monitor construction to ensure design intent is implemented on site.

Author: Steven Byrne – Director