In designing reservoirs, the indirect tensile strength of the concrete mix is specified to be less than a specific value (e.g. 2.8 N/mm²) for potable water. Why should engineers put an upper limit of indirect tensile strength?
Answer: The crack width formation is dependent on the early tensile strength of concrete. The principle of critical steel ratio also applies in this situation. The amount of reinforcement required to control early thermal and shrinkage movement is determined by the capability of reinforcement
to induce cracks on concrete structures. If an upper limit is set on the early tensile strength of immature concrete, then a range of tiny cracks would be formed by failing in concrete tension. However, if the strength of reinforcement is lower than immature concrete, then the subsequent yielding of reinforcement will produce isolated and wide cracks which are undesirable for water- retaining structures. Therefore, in order to control the formation of such wide crack widths, the concrete mix is specified to have an indirect tensile strength at 7 days not exceeding a certain value (e.g. 2.8N/mm² for potable water). Reference is made to R. D. Anchor, A.W. Hill and B. P. Hughes (1979).
Answer: The crack width formation is dependent on the early tensile strength of concrete. The principle of critical steel ratio also applies in this situation. The amount of reinforcement required to control early thermal and shrinkage movement is determined by the capability of reinforcement
to induce cracks on concrete structures. If an upper limit is set on the early tensile strength of immature concrete, then a range of tiny cracks would be formed by failing in concrete tension. However, if the strength of reinforcement is lower than immature concrete, then the subsequent yielding of reinforcement will produce isolated and wide cracks which are undesirable for water- retaining structures. Therefore, in order to control the formation of such wide crack widths, the concrete mix is specified to have an indirect tensile strength at 7 days not exceeding a certain value (e.g. 2.8N/mm² for potable water). Reference is made to R. D. Anchor, A.W. Hill and B. P. Hughes (1979).
