ABSTRACT
Designed mixes place on the supplier of the concrete the responsibility for selecting the materials and proportions necessary to achieve the required strength and properties specified by the engineer. Designed mixes for special structural concretes cater for the use of other materials and the need to achieve special properties or finishes. According to BS8110, the limiting shearing stress on a concrete without special shearing reinforcement is not solely based on a simple relationship to the crushing strength of the mix. In CP110, the maximum design stress in the compression reinforcement was restricted to about four-fifths of the limiting value in tension, but this restriction has been removed in BS8110. BS5328 draws attention to the fact that strength testing is an essential factor in judging whether the concrete complies with its specification. Reinforcement complying with the requirements of BS4449, BS4461 and BS4483 has a specified characteristic strength corresponding to the minimum yield-point stress for the particular type of steel specified.
