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TRIMIS

Incidence of round or partially round shape of aggregates on the skidd resistance of bituminous mixtures. Additional testing regarding the introduction of the standard EN 13043. (VSS2002/405)

PROJECTS
Funding
Switzerland
Switzerland Flag
Duration
-
Status
Complete with results
Geo-spatial type
Other
Project website
STRIA Roadmaps
Vehicle design and manufacturing (VDM)
Transport mode
Road icon
Transport sectors
Passenger transport,
Freight transport

Overview

Background & Policy context

The application of the future European standards, following the GATT agreements, will bring on new tests and with them new requirements. To be able to select materials (for roadways) that satisfy Switzerland’s needs without downgrading Swiss material that meet the requirements usually asked from them, it is necessary to evaluate the influence of the percentage of round or partially round aggregates used in S type mixtures and special mixes such as those of SMA, MR, DRA types.

The restrictive application of the European standard regarding the percentage of round or partially round aggregates in bituminous mixes would mean that the gravel pits that produce this type of material couldn’t continue to do so without major modifications to their equipment. A less rigorous application of the European standard can be contemplated. But at present it isn’t possible to evaluate the effect of the choice of a less severe class (of crushed materials) on the users security as regards grip.

So this research aims to evaluate the influence of the crushed materials rate, along the lines of the future European standards, on the macrorugosity and microrugosity parameters of the surfacing used as wearing course.

Objectives

The main aim of the project is to evaluate the influence of the percentage of crushed elements on the surface condition of a wearing course bituminous mix with an emphasis on the case of special surfacing mixes with a small contact surface (SMA, MR, DRA).

Methodology

The methodology includes the following activities:

  1. Qualification examination of aggregates. Study of the rounding of the grains according to SN and the EN reconstituted fractions 4/8 and 8/11 mm corresponding to the new European fractions.
  2. Laboratory Manufacture compaction table LPC plates dimensions 400 mm x 600 mm x 70 mm features representing 2 formulas; 1st a AB 11 grading curve continues, the 2nd MR 11 a discontinuous grading curve. This represents a matrix of 2 and 5 aggregate formulas, 10 different surface characteristics. Sand, the filler and bitumen will be the same source for the 10 studied formulas, thereby allowing a better demonstration of the effect of the quality of the various tested gravel.
  3. Evaluation of the surface characteristics of the samples produced according to the following:
  • Determination of the percentage of grains with rounded faces present on the surface
  • Sample Photos characteristics
  • Determination of macroroughness through the height sand HSV after making the film with this binder and without binder film
  • Determination of the slip resistance by means of SRT pendulum with the film of binder present and without binder film.

Funding

Parent Programmes
Institution Type
Public institution
Institution Name
Swiss Government: State Secretariat for Education and Research
Type of funding
Public (national/regional/local)

Results

The project focused on assessment of the impact of the rate of broken surfaces of aggregates from gravel pits on the state of asphalt surface, especially non-slip quality and macro-roughness, firstly a type AB traditional coating S / H and moreover a special coating type MR.

The relationship between the percentage of round faces appearing on the surface of the coated manufactured in the laboratory and the corresponding variation SRT values on the one hand, and that between the percentage of rounded sides on the surface and the percentage elements partially crushed or round should allow Switzerland to select a category of EN requirements not preterit gravel pits aggregates suppliers without compromising on user safety.

This research made it possible to evaluate the incidence of the aggregate rate with natural surfaces (not crushed and broken), of a Swiss gravel material selection, on the surface condition of asphalt mixture, in particular the anti-skid property (skid resistance) and macrorugosity. A selection of 5 gravel pits representative of the sources of provisioning currently exploited on the Swiss territory was endorsed by the commission of experts VSS 4.01 – Granulats minéraux.


In this study it was examined that a widely use of gravel materials in wearing courses, containing an average content of 7% totally rounded particles and 72% crushed or broken particles and totally crushed or broken particles, is to be envisaged.


The correlation between the percentage of round faces appearing on the surface of the asphalt mixture manufactured in laboratory and the variation of corresponding SRT values on the one hand, and the correlation between the percentage of round faces on the surface and percentage of partially crushed or rounded particles on the other hand, made it possible to recommend for Switzerland the adoption of a new category of standards EN 13043, which doesn’t penalize gravel pits providing aggregates, with no concessions on users safety.

Partners

Lead Organisation
EU Contribution
€0
Partner Organisations
EU Contribution
€0

Technologies

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