Why does our concrete still crack and leak?

This article discusses the reasons for cracking and leaking in reinforced concrete, with particular reference to basement structures.Concrete cracks in different ways at various stages of its life-cycle, depending on the restraint on its contraction movement: stresses from temperature drop can be enough to trigger cracking. Controlling cracking by reinforcement is possible when the reinforcement is stronger than the cracking force, so that as the contraction increases a new crack forms at the next weakest cross-section. Models are given for calculating minimum reinforcement content for immature and mature concrete and the complete analysis consolidated into a flow chart for fully restrained structures. It is suggested that a maximum concrete strength should be written into specifications. British Standards 8007, 8102 and 8110 contribute relevant material to construction of basements but ignore contraction in mature concrete. The case study considers the floor slab of a basement car park, where extensive cracking and leaking have occurred. The author believes that controlled cracks initially formed in the immature concrete but as the concrete strength increased the cracks widened uncontrollably rather than letting new cracks form. Some theories on treating cracks are discussed. The author proposes that concrete thickness chosen should be the minimum needed for the structural capacity, with sufficient reinforcement to control cracking. (A)

Language

  • English

Media Info

  • Pagination: 40-43
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01043784
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Mar 9 2007 8:24AM