Concrete is probably the only major construction component that is manufactured on site as opposed to in controlled factory conditions. Concrete placement has traditionally been regarded as an unskilled job. While it is the responsibility of the concrete supplier (in the case of using ready-mix concrete) to control the quality of the concrete product, the construction contractor play a significant role in assuring quality of concrete during its placement. Suggest FIVE (5) quality assurance activities that can be done by the contractor on site in order to produce high quality concrete works. (no reference)