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Concrete Cube and Cylinder Test Results Acceptance Criteria

Acceptance concrete test results

Acceptance of concrete test results

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Acceptance of Concrete Test Results

As per ACI-5.6 (2008) it is recommended to perform the test on concrete in fresh, hardened or old state by well qualified field-testing technicians. The respective technicians are supposed to collect and prepare the test specimens according to the specifications provided. Here, we will discuss some of the factors based on which the acceptance of concrete cube test, cylinder test and core test results is taken into consideration.

1. Acceptance Based on Frequency of Testing the specimens

The frequency at which the specimens are tested have an important role in justifying the acceptance of test results. Generally, the strength test is taken as average strength of minimum two cylinders of 150 x 300mm or three 100 x 200mm. These samples are made out of same concrete. The test is conducted after 28 days or the testing date as specified by the standard codes. This testing age will give the value of compressive strength of concrete fc’. The frequency of selecting the test samples for conducting the strength test of each class concrete, must not be less than the following:

2. Acceptance Based on Standard Cured Specimens

If the strength of a newly prepared concrete is determined by means of a standard-cured specimen, then the following two factors are considered to accept the test results.

3. Acceptance Based on Field Cured Specimens

The samples prepared for field testing (test cylinders) have to be prepared with the same sample material and time as that of the laboratory testing. The two test results won’t be considered as a acceptance criterion, but will provide us an idea about the curing procedures conducted in the field. When the strength that is designated for determining fc’ for the field cured cylinder is less than 85% that mentioned for laboratory cured cylinder, then focus must be given to protect and cure the concrete to improve its strength in the field. If the strength of field cured concrete strength exceeds the laboratory tested sample by an amount of 3.5MPa, we need not consider the limitation of 85%.

Low Strength Test Results

Certain criteria are to be followed when the test results obtained does not come under the above mentioned acceptance conditions. If the tested cylinders are deficient in strength or curing, then steps are to be taken in order to avoid under construction. When a particular concrete is found as low strength, then three cores have to be taken from the structure to perform the under strength test. The core samples have to be tested after 48 hours but not greater than 7 days. This must be properly guided by the liscensed design professional in charge. The strength of concrete is taken as acceptable, Deviating these test criteria will require to extract new cores and test additional cores. Mainly, the cores that is taken for testing will be aged than the testing age recommended for fc’. If the core test fails and does not give a satisfactory result, then it is asked to go for structural strength evaluation or the load test.        
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