Overview
When the mandate of research FA n° 22/92 "realisation of tests in way of European normalisation on a sampling of Swiss aggregates used in the production of road surfacing" was realised, the size 10/14 was the only one tested with the Los Angeles test according to the future EN and with eleven steel balls. But today, that size doesn't belong to the "Basic set plus 1", set which was chosen by Switzerland.
According to the test norm EN 1097-2 "Methods for the determination of resistance to fragmentation", the aim of the project is to execute a serial of Los Angeles tests on size 4/8, 8/11 and 11/16 of aggregates. The values which will be obtained are not known because the number of steel balls used for the test is different for any size and never the same than in the Swiss norm.
The spectrum of known values shall allow the Swiss members of the ad hoc commissions of the European committee for standardisation to negotiate the limiting values which will be exhibited in the future standards, and avoid that too strict or too widespread values be imposed.
The methodology is as follows:
- Sampling of aggregates from 10 quarries / gravel pits, having provided the materials used in the FA research mandate 22/92 "tests were performed in the process of European standardisation on a sample of Swiss aggregates used for making road surfaces ". The choice of the 10 sites of the 20 who participated in the above mandate will be defined so as to be representative and Swiss production and Los Angeles range of values obtained in accordance with EN 10/14 22/92 FA fraction of the mandate.
- Sieving fractions taken in pure cuts 4/8, 8/11 and 11/16
- Performance of the test according to EN 1097-2 Los Angeles on 30 fractions (3 cuts, 10 sites)
- The repeatability r and reproducibility R will not be tested as they are appended to the standard EN 1097-2.
Funding
Results
Consequently, and taking into account the standard test EN 1097-2 "Method for the measurement of the resistance to fragmentation", a set of Los Angeles trials on fractions 4/8, 8/11 and 11/16 was carried out in the course of this research-work (the values which were obtained using these fractions were, at first sight, not known, as the number of balls depends on the fraction being tested and differs from the Swiss standard in use).
The range of the values obtained on these new fractions, according to the standard EN 1097-2, must allow the Swiss members of the commission of the European Committee for Standardization to negotiate the limiting values which will appear in the future standards and prevent that too restrictive or too broad limits are imposed.
This research concluded with recommendations aimed to adapt the requirement already in use.