1 General Provisions
1.0.1 This standard is established to unify the method for evaluation of concrete compressive strength and ensure the strength of concrete meeting the quality requirements of concrete project.
1.0.2 This standard is applicable to evaluation of concrete compressive strength.
1.0.3 The evaluation of concrete compressive strength shall not only conform to this standard but also the provisions of current relevant national standard.
2 Terms and Symbols
2.1 Terms
2.1.1 Concrete
It refers to the engineering material formed by the cement, aggregate and water at a certain mixture proportion after stirring, forming, curing and hardening.
2.1.2 Age of concrete
It refers to the elapsed time of concrete from the beginning of mixing, by day or hour.
2.1.3 Strength of concrete
It is the mechanical property of concrete characterizing its ability to resist external force. The strength of concrete in this standard refers to concrete cube compressive strength.
2.1.4 Evaluation of conformity
It refers to the judgment to determine whether the strength of concrete is qualified or not according to certain regulations.
2.1.5 Inspection batch
It is composed by qualified concrete and the total concrete used for evaluation of conformity.
2.1.6 Inspection period
It refers to the specified statistic time to determine the standard deviation of concrete strength of inspection batch.
2.1.7 Sample size
It refers to the group number of concrete specimens representing inspection batch and used to evaluate quality.
2.2 Symbols
——The average value of concrete cube compressive strength at the same inspection batch;
fcu,k——The standard value of concrete cube compressive strength;
fcu,min——The minimum value of concrete cube compressive strength at the same inspection batch;
——The standard deviation of concrete cube compressive strength at the same inspection batch by the evaluation methods with unknown standard deviation;
σ0——The standard deviation of concrete cube compressive strength at the same inspection batch by the evaluation methods with known standard deviation;
λ1, λ2, λ3 and λ4——The evaluation factor for quality;
fcu,i——The cube compressive strength representative value of the number i group of concrete specimens;
n——The sample size.
3 Basic Requirement
3.0.1 The concrete strength grade shall be divided according to the standard value of cube compressive strength. Concrete strength grade shall be represented by symbol C and the standard value of cube compressive strength (by N/mm2).
3.0.2 The standard value of cube compressive strength shall be one of the population distribution values of concrete compressive strength of cube specimens (made and cured by standard method; the side length is 150mm) measured at 28d age by the standard test method; the probability of strength being less than this value shall be 5%.
3.0.3 The strength of concrete shall be inspected and evaluate by batches. One inspection batch shall be composed by the concretes with same strength grade, testing age and almost the same production condition and mixture proportion.
3.0.4 The strength of concrete produced continuously in large quantity shall be evaluated by the statistic method specified in Section 5.1 of this standard. The strength of concrete produced in small amount shall be evaluated according to the non-statistic method specified in Section 5.2 of this standard.
Foreword I
1 General Provisions
2 Terms and Symbols
3 Basic Requirement
4 Sampling and Testing
5 Evaluation of Conformity for Compressive Strength
Explanation of Wording in This Standard
