Overview
The research project concerning the testing method of the Compressive Strength on the Stack has been finished in 2006. But there is no accepted reference material for calibrating the apparatus for testing of mechanical and physical properties of aggregates. This could lead to a lack of precision or even misinterpretations due to petrographic or geometrical inhomogeneity’s of the laboratory samples, of the test portions or of the test specimens for determining the bias of the procedure.
It is therefore necessary to have recourse to reference material with well-defined characteristics for making precise and reliable determinations of the repeatability and reproductibilty of any testing method for determing the physical and the mechanical properties of aggregates.
The aim of this project is to provide determination of the repeatability and the reproducibility of the compressive strength on the stack. Furthermore it is planned to provide research, determination and descriptions of the characteristics of reference materials.
The methodology of this project will be used according to SN 670 901 6a (EN 932-6): Tests for general properties of aggregates. Part 6: Definition of repeatability and reproducibility.
Funding
Results
The research concerning the compressive strength of aggregates on the stack was published in 2006. The repeatability and the reproducibility were intended to complete the standard SN 670 830.
Following conclusions are made in the project:
- Due to the insufficient number of data neither repeatability nor the reproducibility can be calculated.
- The results suspect an association between temporal pressure build up and pressure resistance of the aggregate.
- Strictly observed results needs the standard specifications or the specified test conditions.
- The valid data have pointed out that the dispersion within a laboratory probability is low.
- Further conclusions are not possible because of the small number of data.
The final conclusion is as follows:
The laboratories have not or could not comply consistently with the test specifications and for the most part, the results of the three laboratories involved in this research had to be rejected. For this reasons neither the repeatability nor the reproducibility of the testing method could be calculated. A reference material has been characterized for this testing method. More research is necessary.