The results of the tests conducted by the GDDKiA laboratories are shocking – more than 90 percent of the cracks on the A2 route resulted from the obvious construction malpractice – the improper technological junctions of the particular layers of the road surface or the improper saw cutting of the layers of the motorway.
Why did the cracks appear so suddenly, in that many places at the same time? The cracks were initiated under the influence of very low temperatures in the weakest construction places, so mostly where the technological joint was not sealed or the saw cut was too deep. The so-called notch effect appeared, so, simply saying, the construction of the road was weakened. The accumulation of the stress led to the uncontrolled extension of the road and, as a result, the cracks appeared. The scale of the problem is a result of the consequent negligence of the contractors – the lack of sealing the technological joints, cutting the underlying layer of the surface, allowing the heavy goods vehicles traffic on the unfinished road.
The cracks could be avoided in a simple way. It would have been enough to clean the edges of the surface after finishing the phase of works, cut the edge of the surface evenly and to a proper depth, seal the technological joints, maintain the construction site clean and not allow heavy goods vehicles traffic on the uncompleted construction. Those simple methods, known already since the seventies of the last century, are enough to build a good road in a technology which ensures there will be no ruts – which are the incubus of the roads build of so-called soft asphalt.
The elimination of the ruts was the objective of the work of the Polish Road and Bridge Research Institute on the asphalt concrete of a high stiffness modulus, used for the first time 25 years ago in France. Adjustment of the French method, by RBRI, to the Polish conditions by the use of softer asphalt than that intended for the French conditions, was commissioned by the General Directorate for National Roads and Motorways. Such composition provided an even surface of the road without any ruts.
The composition was used in Poland for the first time in 2002 on the experimental section of S5 road. The experiment succeeded and due to that, already since 2003, design firms have begun to widely introduce the layers of the High Stiffness Modulus (HMAC). Since that time the High Modulus technology was no longer considered experimental and became a norm used not only on Polish, but also Czech, Slovak, French and Spanish roads.
In the Slovak climate, identical with the Polish weather conditions, the High Modulus technology was successfully used for example on the R1 motorway from Nitra to Bańska Bystrzyca, opened for traffic in the autumn last year. As the Slovak road administration ensures, the 40-kilometres road section, did not show any cracks in the laboratory tests.
Also in Spain the High Modulus is used widely and successfully. Furthermore, the High Modulus technology is recommended by the Spanish Research Institute (CEDEX) due to the possibility of obtaining the savings – both in construction and maintenance