Overview
In early January 1998, numerous Swiss standards were revised by the "Association Schweizerische Stassenfachleute" VSS. Among them, the Swiss standard SN 640 is 452c "hot mix foundation layers, request execution" [1]. The revision of this standard, the test of sensitivity to water has been added, where the strength is to be reviewed by hot mix foundation layers after immersion in water. An important point of this test is to determine the saturation or partial saturation level. The information contained in this standard are largely based on the requirements of ASTM D 4867-92, "Standard Test Method for Effect of Moisture on Asphalt Concrete Paving Mixtures", which are drafted in such imprecise that by modern standards in terms of quality assurance and reproducible practice is not guaranteed close to implementation. The aim of this project is the development of a methodology for determining and calculating the degree of saturation of Marshall´s bodies with different void content based on the ASTM and finishing work of a Swiss test specification for the implementation of the saturation (partial saturation).
The objective of the project is to develop a test method to evaluate the saturation level of Marshall specimen with various void contents. The basis for this test method is the relevant ASTM standards.
Following steps will be done during the project:
1. All specimens that were prepared for the same tests should be saturated with the same pressure.
2. The aided by the standard saturation level by 55 to 80% can be achieved with 300mbar pressure.
3. Saturation levels all specimens should comply with the defined in ASTM saturation limits between (55 and 80Vol-%).
4. The time between conditioning and testing must be the same for all specimens.
5. In cases where the test specimens have a difference of the void content of more than 1%, the degree of saturation on the basis of the volume of the test specimen has to be calculated.
Funding
Results
In summary this report concluded the following which are recommended for the next revision to the Standards:
1. All specimens prepared for a particular test should be saturated using the same pressure
2. The minimum saturation level required for HMF by the standard could be achieved using 300mbar pressure.
3. The time of testing after conditioning is very important for consistency of results and should be the same for all specimen.
4. In cases where the evaluation of structural damage is desired, especially when the difference in void content between various specimen is more that 1% the degree of saturation could also be based on volume of the specimen rather the volume of the voids.
5. A minimum saturation level as specified by ASTM (not in EN) is essential for the proper evaluation of the effect of water on the specimen. At the same time an upper allowable saturation level is necessary to exclude specimen that are damaged due to excessive water absorption and swelling.