EURONORM IN UKRAINE. CRUSHED STONE
We continue to compare domestic and European norms and today we are talking about not less important material – crushed stone (rubble).
All over the world, crushed stone, as a coarse aggregate for mixtures, is divided into appropriate fractions by grain size. Sieves with round or square meshes are used for specific fractions selection, the range of each fraction size may vary in different countries.
In Ukraine, the technical requirements for crushed stone are set out in two main standards:
1. DSTU B V.2.7-75-98 “Dense natural crushed stone and gravel for construction materials, products, structures and works. Technical specification”, the standard is valid from 01.01.1999;
2. DSTU B EN 13043: 2013 “Aggregates for bituminous mixtures and surface treatment for road pavements, airfield pavements and parking areas” (EN 13043: 2002, IDT), the standard is valid from 01.10.2014.
The main properties of crushed stone are:
- grain shape;
- freeze resistance.
As in Europe also in Ukraine there are clear requirements to the grading.
According to the national standard, the grading of crushed stone is evaluated by total residues on sieves with mesh sizes d, 0.5 (d + D), D and 1.25 D.
According to the Euronorm - by passing through sieves with mesh sizes 2 D, 1.4 D , D and d/2.
Tolerances to the grading of coarsw aggregates in Europe are higher than in Ukraine. Thus, for compliance with EN standard, the residue on a sieve with a larger mesh size can be up to 15%, and the pass through a sieve with a smaller mesh size - up to 35%, while in DSTU in both cases it should be up to 10%.
In Ukraine, the shapes of grains are evaluated by the content of grains of lamellar (needle) and pin shape, such grains include grains which thickness or width is less than three times or more in length.
According to EN 13043, the shape of the grains is evaluated by the lamellar coefficient, screening of aggregate through the sieves with square and slit-like meshes, and the shape of the grains can be evaluated by the coefficient of shape, which is analogous to the content of lamellar grains.
In Ukraine, unlike Europe, the requirements to the strength of a coarse aggregate are established, which is determined by grinding strength at compression in the cylinder.
Additionlly, EN 13043 establishes the requirements for grinding resistance by Los Angeles coefficient, which are almost similar to the domestic method for determination of abrasion.
Also, the Euronorm establishes the requirements for the coarse aggregates resistance to polishing, to surface abrasion, wear and abrasion with studded tires, which are not available in our country.
The national standard characterizes freeze resistance of crushed stone as possible number of cycles of variable freezing and thawing. Freeze resistance can also be determined by the results of saturation tests in sodium sulfate solution and drying.
In Europe, freeze resistance is determined similarly, but the number of cycles of variable freezing and thawing or aging in magnesium sulfate and drying is less in many times.
!!! But the main difference between Ukrainian and European requirements is the type of sieves meshes and the size fraction. Thus, according to the national standard, the size fraction is determined using the sieves with round meshes and the grain size from 5 mm to 80 mm, and in Europe the size fraction is determined using the sieves with square meshes and the grain size from 2 mm to 63 mm.
The main disadvantage both, of European and also of the Ukrainian standards is that they do not establish requirements for the use of crushed stone depending of the grade/category. And, if DSTU for a certain type of product (asphalt mixture, etc.) establishes requirements for the properties of coarse aggregates depending on its type and grade, the European requirements for the mixture gives only a reference to EN 13043. This indicates the need to develop the guidelines on requirements for crushed stone depending on the area of application of road construction materials on their basis. Prior to the development of such documents, the application of European standards cannot be as effective as possible.
At the same time, due to the narrower fractions and the sieves with square meshes required by EN, it is possible to choose an asphalt mixture with a denser skeleton, which can further affect the durability of the road pavement. The greater number and variety of size fractions provided by Euronorm makes it possible to obtain an asphalt mixture with the better predictable performance indicators, as well as more accurately calculate the need for crushed stone, thus saving material and technical resources.
So, the requirements for crushed stone established in the national DSTU are similar to those of EN. At the same time, certain basic requirements of Euronorm should be implemented in Ukraine to improve the riding qualities of asphalt pavements which will be arranged from mixtures with coarse aggregates. But for the quality implementation of European practices, there is a need in preliminary analysis and development of a number of guidelines that will take into account different requirements for materials depending on their application area.