Title: Achieving Durability In Design - Cracks & Crack Control

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Publication: CIA

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Date: 2/14/2011

Abstract:
There are three stages in the design life where cracking can occur, the plastic stage due to changes in concrete while it is hardening, early age due to changes while concrete cures in the hardened state and long term load induced cracks. Designers generally follow Australian Code requirements for maximum allowable strain in the reinforcement and assumes that will take care of early age strains, and in most concrete it does. However, where fine crack widths are required, or where concrete with a high heat output is used, code requirements alone may be insufficient to control crack widths adequately. Designers also often leave the plastic crack control entirely to the contractor. Unfortunately that may not be the best approach as specifications for mix design have a high impact on the requirements for plastic crack control. This paper considers requirements for all three stages from a design perspective to highlight where additional guidance might be given in Australian codes.