Assessing Strength Variability of Concrete Structural Elements

The average in-situ strength of a member, expressed as the strength of an equivalent compression test result, will be lass than of a standard cast specimen of the same concrete, which has been properly compacted and moist-cured for 28 days. The extend of the difference will depend on construction techniques, but general patterns can be defined according to member type. Variations in concrete supply will be due to differences in materials, batching, transport and handling techniques. These will reflect the degree of control over production and will normally be indicated by control and compliance test specimens in which other factors are all standardized. The present paper analyses the effectiveness of the rebound test and ultrasonic pulse velocity in evaluating the strength variability of concrete structural elements, expressed by: confidence interval, , colours “contour” plots showing areas of equal strength and ANOVA technique. The paper also shows criterion for concrete variability analysis. However, test results, is still small, and these criteria should not be used at random.