Sampling of reinforcement is always conducted by the site supervisor who should also get the copy of mill certificate and letter of origin of the sampled batch of steel bars available at time of submission for tests. The frequency and number of samples to be taken may vary at different contract stages and with different batches, sizes, types of steel bars and should be in accordance with the Specification. The samples are to be tested in the laboratory normally for ;
a) yield stress
b) elongation
c) tensile strength
d) bending and re-bending properties
e) unit mass
The results will represent the acceptance or failure of the sampled batch of steel bars. For sample of fabric reinforcement, it shall also be tested for weld shear strength.
The steel bar samples must be sawn cut to maintain the same feature and should be obtained from different pieces of steel bars to ensure a representative result. Someone might sample the whole lot of test specimens from only one or two numbers of steel bars to avoid material wastage and this malpractice is really risky. Once the test results fail to comply with the requirements, the representative batch of steel bars will be rejected, resulting that the finished work will become abortive and extra work will be required to replace these reinforcement in a concrete pour.
While the new batch of steel bars is delivered to site, it has to stockpile separately or being fenced off from the previous batches await testing before use. There is a general practice on site how to distinguish the running storage of steel bars to avoid the prompt use of newly delivered steel bars and leave behind the previous steel bars rusting at bottom of the heap, it is called the “ BYGO ” theory that is as follows: –
B for blue to identify steel bars delivered to the site between January and March
Y for yellow stands for the period between April and June
G for green stands for the period between July and September
O for orange stands for the period between October and December.
R – Red stands for rejection and the batch under tests is fenced off, the various stockpiles of steel bars could then be easily monitored.