If time is not available for preliminary tests, how can the desired strengths be ensured?

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If time is not available for preliminary tests, how can the desired strengths be ensured?

Q. If time is not available for preliminary tests, how can the desired strengths be ensured?

 

A. Average w/cm strength curves exist, which have been established by many tests in many laboratories for a wide range of materials complying with the specifications of ASTM. ACI 211.1 gives the relationship of w/cm to strength for air-entrained and non-air-entrained concretes. The w/cm is selected based on the required average strength and not the design strength. The average strength exceeds the design strength by a sufficient margin to keep the proportion of low test results within specific allowable limits (ACI 214). It is highly recommended that time be budgeted for trial batching, because that is the only sure way of determining if the desired properties can be achieved with the selected proportions of materials.

 

References: SP-1(02); ACI 211.1-91; ACI 214R-11

Topics in Concrete: Mixture Proportioning; Quality Assurance; Testing

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