The Structural Engineer > Archive > Volume 84 (2006) > Issues > Issue 23/24 > Why does our concrete still crack and leak?
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Why does our concrete still crack and leak?

Current knowledge of the behaviour of reinforced concrete appears to be not good enough to enable us to design basements which do not crack and leak. The paper discusses the possible reasons for this, and makes proposals for better designs in future. This starts with the life cycle of concrete and the importance of restraint. Formulae for minimum reinforcement contents to control cracking in both immature and mature concrete are then derived. This is illustrated by a flow chart. The misleading advice in codes of practice and industry guides is discussed, and the true tensile strength of concrete is analysed. Although the outcome is a recommendation for higher reinforcement contents than are currently employed, it is based on a sound theoretical approach backed up by the evidence of basements which still crack and leak. Furthermore, if cracking is not controlled, all the crackcontrol reinforcement that is in the concrete has been wasted. A reversal of traditional design philosophy is proposed, with the concrete section first selected at minimum thickness and then adequate reinforcement provided. Stuart J. Alexander MA, CEng, FIStructE, FICE, MCMI WSP Group