One of the most important functions of supervision during the execution of a road contract is technical quality control, that is, control whether the materials and works supplied by the contractor meet the technical requirements in the contract specifications. There are two types of quality control, which are described below:
1.control of methods
Law control is usually carried out by the consultant’s field staff who are to be on site and supervise the contractor during the execution of works. In addition, field personnel will perform simple measurements, such as recording the thickness of the fill layers, the temperature of the asphalt material, and the deterioration of the cement concrete.
Method control is done according to the type of work. Where methodology is of great importance and continuous supervision is required to achieve quality, or where, in some cases, it is difficult to improve quality, there should always be a field engineer on site. Examples of this are heaping, asphalt laying and concreting etc. Where the method of work is of little importance or the quality is consistently achieved by the contractor, there may be no need for continuous monitoring.
Examples are soil excavation and compaction.
2.control of final results
End result control includes field tests such as control of the evenness of complete pavement layers and laboratory tests, for example Marshall tests on asphalt materials. Other tests are a combination of field and laboratory tests. An example of this is compaction control of earthworks where the density obtained is determined through a field test, and where the IS/AASHTO density with which the result should be compared is found through a laboratory test. Final result control is performed by laboratory technicians, and most of the work consists of laboratory tests.
The frequency of end-result control depends on the quality parameters to be checked. Parameters that can vary significantly are controlled continuously. Examples are the formation of asphalt material and the compaction of asphalt courses. With regard to regulating laboratory tests the specification usually stipulates the number of tests. Laboratory testing will normally be intensified when work is started and in cases where difficulties arise regarding compliance with quality requirements.