What water-cementitious material ratio should be used for a particular job when strength requirements are to govern?

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What water-cementitious material ratio should be used for a particular job when strength requirements are to govern?

Q. What water-cementitious material ratio should be used for a particular job when strength requirements are to govern?

 

A. When past performance records are available, the w/cm that has proven to meet the requirements with an appropriate degree of safety should be used. If such records do not exist and time and materials are available before the start of the work, the relationship between strength and w/cm can be established by direct tests using these materials. Guidelines for proportioning of concrete and evaluating strength results are given in ACI 211. With this relationship established over the range in strength that will be required, mixtures of whatever consistency that will be needed can be proportioned to use the aggregates most economically. If air-entrained concrete is required on part or all of the work, it should be included in the tests. Also, if more than one type of cement is likely to be required, for example a high-early-strength cement used for special purposes, it should be included in the tests.

 

References: SP-1(02); ACI 211.1-91

Topics in Concrete: Concrete Fundamentals; Mixture Proportioning; Specifications

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