The road and its experts
Recall the background. When the state decided to create a backup for the ever-overloaded Leningradka, a concessionaire appeared, who undertook to build the road on time and serve it for 31 years (until 2042). And for this to charge a passing fee. In order, firstly, to “recapture” your money, and secondly, as in any business, to earn more. However, in this case, the concessionaire is required not only to turn the line through on a turn-key basis, but also to be responsible for its operation for a long time. And this means that it’s bad to build, hack, save on materials, it’s not profitable for him. Well, in addition, five independent organizations, very competent in the field of road construction, oversee the progress of work.
- British independent technical expert AECOM
- project management - Vinci Group
- State - Rostekhnadzor Service
- concessor - state-owned company Avtodor
- general contractor - Mostotrest
and the concessionaire itself is the Northwest Concession Company.
Everything's under control
We were brought to the object on a comfortable Ikarus, then we were transplanted to the well-groomed “grooves”. What to do, construction is construction.
The route "Moscow-St. Petersburg"
However, they assured that the road itself is completely dry and you can walk calmly without staining your shoes. It turned out to be true.
First, they showed the journalists the basis of the basics - how they check the degree of compaction of the lower sand layer. Most often, the density is measured with a special instrument with a needle at the end. This is the so-called express check method. Less accurate, but instant.
Checking the degree of compaction of the sand layer
Another way of checking is more complicated - with a device in the form of a cylinder, a specialist takes a sample of compacted sand and takes him to a laboratory for detailed analysis.
Checking the degree of compaction of the sand layer
Already laid layers of fresh asphalt pass a similar verification procedure. The photo shows how, using a special installation, a piece in the shape of a cylinder (core) is cut out in asphalt, and it is also sent to the laboratory for multi-level tests.
Sawing an asphalt sample for testing in a laboratory
It should be noted that each of the three layers of asphalt passes the test, and at the place of cutting they put a “patch” of necessarily the same composition as that of the sample taken.
What will builders do if the sample taken is still rejected? “There haven’t been such cases yet, but if this still happens, then the section is waiting for the layer to completely re-lay to the extent that it will not meet the standards. Asphalt is laid in pieces of several tens of meters. They will shift the whole piece,”commented Sergey Ilyinsky, Director of Public Relations and Marketing at SZKK LLC.
Only girls in the laboratory
It was not at all surprising that painstaking work requiring special attention was entrusted to women. Who else but they are able to consistently and thoroughly engage in this necessary business - to daily study and analyze the samples taken. So, we have a pavement cylinder cut from an already prepared section of the road. It is thoroughly washed and sawn into six parts intended for different types of tests.
comprehensive asphalt samples
During the research, the water saturation of asphalt concrete, its strength at various temperatures and the coefficient of water resistance are analyzed. One of the test methods: the sample is melted in a special furnace and see how its “ideal” structure differs from the existing one.
Another sawn cylindrical asphalt sample is left as is, without dividing it into parts. Perhaps the most important work is carried out with it: it is checked for shear stability and crack resistance. To do this, the core is placed between two powerful presses and slowly squeezed.
Checking the asphalt sample for shear and crack resistance
A sensor attached to the device indicates at what point the coating begins to break down. The purpose of the study is to understand how long a rut will form on the road surface.
The softening temperature of bitumen is determined on the device "Ring and ball".
The device "Ring and Ball"
For this, a sample of the material is melted, dehydrated, filtered through a metal mesh and mixed thoroughly until the air is completely removed. Then the resulting liquid is poured into the rings of the device. After this, the rings are cooled at a temperature of 25 ± 10 ° C for 20 minutes, and then the excess alloy is cut with a sharp knife. In the center of each cast ring, a steel ball is laid. The pendant with rings and balls is again introduced into the vessel with water and heated. The temperature at which the ball together with the squeezed bitumen sinks to the bottom, is the softening temperature.
The laboratory still has many different instruments that check the composition and density of the roadway and reinforced concrete structures for a whole range of parameters. But in this case, talking about all the technologies used is not so important. The essence is clear: the quality of the road is really monitored and very closely. Because this road is not ownerless, it has a specific owner who is interested in serving as long as possible.
What is checked:
- mineral (crushed stone, sand) and binders (bitumen, polymers) materials, ready-made mixtures
- mixture before laying (density, temperature)
- laying quality (thickness, density, evenness)
- coefficient of adhesion of asphalt concrete to a car wheel.
What “pavement” consists of:
- sand layer
- crushed stone layer
- base layer
- intermediate layer
- finish coating
- 28 years - for earthworks
- 28 years - on the base and undercoat (asphalt)
- 5 years - on the top layer of the coating (asphalt concrete).