| Abstract: | Specifications for aggregates that are used in sub-base construction are based on knowledge that has been gained about the performance of similar aggregates when used for road construction and about the tests that best define the properties that are relevant to their performance. To assess the suitability of an aggregate for use in road construction, representative samples of the aggregate have to be subjected to these tests and the test results compared with values given in the specification. However, it is impossible to take a truly representative bulk sample of a large batch of material and to prepare that sample for test in a way that entirely excludes errors. These errors arise in taking the bulk sample from the batch (the sampling error) and in reducing the bulk sample to a mass suitable for carrying out the test (the sample reduction error). In addition, a test made on the same material will be subject to errors because of deficiencies in the test techniques of the operators and of the test equipment (the repeatability and reproducibility of the test). This means that in those cases where a material just passes or just fails to meet a specification limit doubts can exist between customer and supplier as to whether acceptance or rejection is really justified; it is therefore important to know the magnitude of the errors likely to arise from these causes. This paper describes work carried out to find the errors that arise in the determination of the particle-size distribution of sub-base aggregates. |
