Surface treatment is technological process the construction of wear layers of the closing layer of the coating or the creation of a rough surface by pouring viscous bitumen and scattering strong stone materials on it with dimensions of 5 ... 25 mm.

Single surface treatment is arranged on asphalt concrete mix pavements of types C and D of all grades, types B and G grades II and III , as well as on coatings arranged by the impregnation method or from soils treated with organic (inorganic) binders.

Surface treatment is carried out on a clean, dry and dust-free coating at an air temperature of at least + 15 ° C.

Viscous bitumen grades BND (BN) 60/90, BND (BN) 90/130, BND (BN) 130/200 are used as a binder, and crushed stone is used as a mineral material, mainly cubic-shaped fractions 5 ... 10, 10. ..15, 15...25 mm from hard-to-grind rock with a strength of at least 120 MPa. Crushed stone must be clean, free of dust and dirt.

The pouring temperature of bitumen grades BND (BN) 60/90, BND (BN) 90/130 - 130 ... 160 ° C, grades BND (BN) 130/200 - 100 ... 130 ° C.

Better surface treatment is carried out using black crushed stone with fractions of 10...15, 15...20 mm. Black crushed stone is laid with a bituminous crushed stone distributor of the RD-701 type with a strip of 3.5 m with a technical capacity of up to 4000 m 2 / h.

However, both of these methods of surface treatment have significant drawbacks.

1. Crushed stone, difficult to grind, cube-shaped, with a strength of 120 MPa, is a scarce material.

2. Insufficient service life, high traffic noise, intensive tire wear.

3. Torn-out grains of crushed stone reduce the safety of traffic, especially when they hit the windshield.

Surface treatment from sand-rubber-bitumen mixture eliminates the above disadvantages, eliminates shear deformations and improves road operation in winter.

The mixture can be prepared on conventional asphalt plants with the addition of a unit for supplying crumb rubber to the mixer.

The composition of the mixture:

river fraction sand 0.5 mm - 78%;

mineral powder (fly ash) - 15%;

crushed rubber with a size of 0 ... 1.5 mm - 7%;

viscous bitumen grades BND 60/90, BND 90/130 - 11.5% of the total mass.

Sand heated to 220 ° C, mineral powder, rubber crumb are mixed for 30 s.

Next, bitumen is fed into the bunker with a temperature of 150 ... 160 ° C and the mixture is mixed for 1 min. The finished mixture with a temperature of 160 ... 170 ° C is laid with an asphalt paver (bitumen-spreader) with a layer thickness of 1.0 ... 1.5 cm on a primed coating with liquid bitumen SG (MG) 70/130 at the rate of 0.5 ... 0, 8 l/m2.

Compaction of crushed stone (mixture) is carried out by heavy rollers weighing 10 ... 18 tons in 4 ... 6 passes along one track.

Raising the roughness and compaction of the coating can be achieved by embedding black crushed stone into the freshly laid top layer of the coating from a low-gravel or sandy mixture - the site. The top layer of the coating is pre-rolled by a self-propelled roller weighing 6...8 tons in 2...4 passes. Crushed stone is distributed by a crushed stone distributor based on:

fractions 5...10 mm - 12...14 kg/m2,

fractions 10...15 mm - 15...17 kg/m2 and fractions 15...20 mm - 18...21 kg/m2.

Embedding black crushed stone into the top layer of the coating is carried out by a self-propelled roller weighing 6 ... 8 tons in 2 ... 4 passes. Further compaction of the top layer of the coating is carried out by heavy rollers weighing 10...18 tons in 12...18 passes.

When using a surface treatment device using foamed bitumen, the same grades of bitumen and crushed stone are used. Foamed bitumen is a conglomerate consisting of bubbles of an air-steam mixture, the walls of which are composed of bitumen films. Foaming occurs when water is supplied to the bitumen in an amount of 1 .... The optimal amount of water is determined empirically for each specific case. Surface treatment with the use of foamed bitumen is carried out at an air temperature of at least +10 °C.

Bottling of foamed bitumen is carried out by an asphalt distributor or a chipped bitumen distributor of the RD-701 type, equipped with a foaming system.

Benefits of using foamed bitumen:

improving the quality of bottling (the layer is thinner, continuous, uniform in thickness);

reduction in binder consumption;

the ability to spill the binder in wet weather;

better adhesion with stone material and coating.

The bitumen temperature when pouring into a container is 170...190 ° C, and when pouring 150...170 ° C.

The RD-701 machine can operate in the bitumen filling mode with simultaneous scattering of crushed stone, or these operations are performed independently, separately. During breaks in work with the supply of crushed stone, 2 ... 3 m before stopping, the bitumen is blocked, the remnants of the system drain and fall asleep with crushed stone.

Following RD-701, a team of 4 ... 5 road workers corrects emerging defects in surface treatment. Rolling is carried out by rollers weighing 10...13 tons in 3...5 passes at a speed of 2...4 km/h.

On roads with intensive heavy traffic, rough layers 1.5, 2.0, 2.5 cm thick are arranged as wear from hot crushed stone (50 ... ...0.5 l/m2. The mixture is distributed by an asphalt paver and compacted at a temperature of 120...140 ° C by rollers weighing up to 9 tons on a pneumatic track in 8...12 passes and by heavy smooth-rollers weighing 10...18 tons in 6...10 passes. The consumption of the mixture depends on the size of the crushed stone and ranges from 30 to 60 kg/m.

Double surface treatment is used for significant damage to asphalt concrete and cement concrete pavements.

Crushed stone, not treated with binders, is allowed to be used on roads with a traffic intensity of not more than 1000 vehicles / day.

The device for surface treatment on old coatings is started after all damages and deformations (potholes, subsidence, etc.) have been eliminated, and the coating has been thoroughly cleaned from dust and dirt. The construction technology of various types of surface treatment of the coating is set out in Table. 61, 62, and fig. 17, possible disadvantages and ways to eliminate them in table. 63.

Table 61

The technology of the device for single surface treatment of the coating using various materials and machines

Note. Bitumen is poured according to the rate of 1 ... 1.3 l / m 2 according to the fractions of white crushed stone, and according to the norm of 0.8 ... 0.9 l / m 2 - according to the fractions of black crushed stone.

Table 62

Technology of double surface coating device using different materials and machines

Note. Bitumen consumption (1.0 ... 1.6), (0.8 ... 0.9) l / m 2 is provided for white crushed stone, and (0.8 ... 0.9), (0, 6 ... 0.7) l / m 2 for black gravel.

Table 62

Disadvantages and ways to eliminate them in the device for surface treatment of the coating

Quality control of work

1. The bitumen temperature in each asphalt distributor is checked.

2. Constantly check the uniformity and purity of crushed stone, the uniform distribution of bitumen and crushed stone on the surface.

3. At least once per shift, the adhesion of the binder to the surface of crushed stone grains is checked in accordance with GOST 12801-84.

SURFACE FINISHING

rubble

Crushed surface treatment transfers the load from traffic to the surface, serves as a wear layer and increases the grip between the road and the car wheel.

In order to provide a complex of these functions, crushed stone must be durable, of a certain shape, not sensitive to frost and have good adhesion to the coating and the surface of the mineral material.

The characteristics of crushed stone depend either on the choice of deposit (internal characteristic) or on the method of their production. Internal properties meet the needs of fatigue strength, wear resistance and durability in a complex of own or acquired characteristics.

Three tests fundamentally determine these internal characteristics:

• impact resistance;
• Wear resistance due to friction;
• Durability (micro-roughness) is measured by the accelerated polishing factor.

To these three tests it is desirable to add a fourth:

• A test of crushed stone homogeneity, which makes it possible to detect the presence of elements of different volumetric mass, the study of the nature and proportions of which can help to accept crushed stone or refuse it.

Four criteria determine the quality of crushed stone.

Grading

The granulometric composition determines the roughness and uniformity of the surface treatment.

Commonly used crushed stone is divided into the following grain classes (European standards):

2/4 - 4/6 - 6/10 - 10/14; these common sizes are standardized. Very rarely a different grit is used; however, in any case, it is desirable to follow the rule: d 0.6D (d and D represent the thresholds of granularity of crushed stone d/D)

2/4 is an exception to this rule, which, on the other hand, is difficult to achieve purity.

The d0.6D rule limits the expansion of the particle size distribution and allows to achieve a uniform surface finish. Aggregate, in addition to determining d / D, must have its particle size curve included in the graph of its grit class.

Angle formula

Crushed stone for surface treatment, extracted from mountain ranges and gravel pits, is carefully crushed. If it comes from gravel pits, it should represent a crushing ratio of 4 or more. Due to economic feasibility and for non-intensive traffic, it is possible, however, to use parts of an even larger ratio. The crushing ratio is the ratio of the smallest size of the naturally occurring material subjected to crushing to the largest size of the resulting fine material.

The form

The shape of the crushed stone should be as cubic as possible, flat (tiles) and elongated (needles) elements are fragile and do not fit well on the coating. The following rules must be observed:

L= Length (largest size)
G= Value (diameter of the smallest ring through which gravel can be passed)
E = Thickness (the minimum spread of two parallel planes between which crushed stone can be placed).

Necessary:

A) that the inequality L˂G6E be true for 90% of the crushed stone elements
B) so that the percentage of crushed stone elements, for which the G / E ratio is higher than 1.56, does not exceed:

20-25% if traffic is light;
15% if traffic is heavy;
10% if the traffic is very heavy.

Purity

Crushed stone of surface treatment must be very clean, which causes it to be thoroughly washed during production. Depending on whether the movement is heavy or not, the proportion in weight of the particles passing through the 0.5 mm sieve should be less than 0.5, 1 or 2% (including particles associated with fine material). In addition, the proportion of fine particles below 5 microns should be less than 0.05% total weight fine-grained material. The presence of clay, even in very low proportions, is highly undesirable: clay is extremely hydrophilic, and the strong swelling that occurs in the presence of water tends to break the binder-crushed stone bond.

Cationic emulsion

The role of the bituminous emulsion in surface treatment is to stick the crushed stone to the pavement and make the pavement waterproof.

The choice of bituminous emulsion intended for surface treatment is determined depending on the type of pavement structure to be laid, on the profile of the road, on environment, on the climate, on the period of work, on the nature of transportation and on the timing of the resumption of traffic.

Produced at a temperature of +80°C approximately, and poured at +20°C...+70 °C, bituminous emulsion is classified as a "cold binder".

The advantages of emulsified bitumen are numerous compared to those of anhydrous binders (thinned bitumen, diluted, etc.).

For example:

• Produced and distributed at a lower temperature, it consumes fewer calories;
• It does not require complexities in warehousing and distribution;
• It does not pose a flammable hazard, is non-toxic during handling;
• Less demanding on atmospheric conditions, it allows you to extend the period of work from the beginning of spring to the end of autumn;
• It achieves its final qualities not by evaporation, but by a gap between the bitumen and the water phase, which gives it better stability during laying in cold and wet periods;
• It does not harden upon contact with the ground;
• It has maximum adhesion to the aggregate due to the excellent wetting of the latter in the water phase;
• It cannot soften the base, preventing the crushed stone from sinking into the coating or the binder from escaping to its surface.

The emulsions used for surface treatments are mainly cationic emulsions.

Concentration

In surface treatments, the useful binder is the residual binder after the breakdown of the emulsion, accompanied by evaporation and release of water. The percentage of bitumen in emulsions used for road technologies can be from 60 to 69%. 69% emulsion most suitable for surface coatings. It is quite viscous at normal ambient temperatures so as not to run into depressions in the road surface if severely deformed or damaged. It allows you to get enough residual “binder” in one pouring to ensure the laying of large-sized crushed stone in one layer.

Viscosity

The viscosity should be such that the bituminous "binder" does not flow into low areas (depressions), and is easily distributed by conventional asphalt distributors.

Penetration (permeability) of bitumen depending on temperature:

For bitumen subjected to the same treatment, the viscosity of the emulsion is directly related to its penetration. The viscosity will be lower the lower the penetration; this can be seen in the example of the produced 69% emulsion, made on the basis of bitumen penetration 60/90, or bitumen 100/130: the second is less viscous than the first.

It should be noted that cooling at a given temperature is accompanied by an accelerated increase in the viscosity of the emulsion with a high percentage of bitumen, as shown by the difference in the slope of the viscosity curves corresponding to 65 and 69% emulsions.

Modern dispensing machines allow filling of 69% emulsions at a temperature of approximately +20°C, however, it is preferable to distribute them at a higher temperature (+40...+70°C), which allows better film formation, faster cooling which prevents outside leakage. The calculation shows that an emulsion sprayed between +70 and +80°C on a pavement with an ambient temperature of 20°C cools on contact with the road to a temperature of approximately +35°C due to the instantaneous exchange of calories with the contact surface.

The viscosity of the emulsion varies depending on the bitumen penetration and temperature, as well as depending on the formulation, on the spraying of the binder and on the percentage of bitumen in the emulsion.

Effect of temperature on the rate of decomposition of cationic emulsions:

At a temperature of +20°C, a 65% emulsion has a viscosity of 6° to 10°E (Angler's degree), while a 69% emulsion has 12-20°E.

Emulsions are called liquid if their viscosity is below 6°E, semi-fluid if the viscosity varies between 6 and 15°E, and viscous if the viscosity is above 15°E. The degree of Engler is easily converted into GOST indicators for viscosity in seconds.

Decay rate (decay time)

The rate of disintegration of cationic emulsions is a function with numerous parameters. The first of these parameters is the emulsification formulation. The choice and dosing of the emulsifier makes it possible to obtain different qualities of emulsions. Emulsions are classified according to international standards, based on their decay rate in 4 categories (in Russia - EBC 1,2,3):

• Emulsions with fast disintegration,
• With a semi-rapid decay
• With slow decay
• Super stabilized emulsions.

It can also be observed that temperature plays an important role in the decay rate. The rate of disintegration of an emulsion dispensed at +50°C will be twice as fast as that of an emulsion of the same formulation dispensed at +20°C. The increase in disintegration rate associated with the increase in viscosity during cooling allows the emulsion to be distributed without overspending, regardless of the transverse and longitudinal slope, the deformation of the coating or the thickness of the applied layer.

The disintegration time depends on the degree of moisture of the road and gravel, and has a direct effect on the disintegration of the emulsion. Wet highway or wet gravel require a reduction in decay time. In humid regions, recipe adjustments take place to reduce this time to a minimum.

The porosity of crushed stone, which is expressed in an increase in the specific surface area, contributes, on the contrary, if it is highly developed, to a significant decrease in the decay time.

Laying surface treatment at low temperature or at elevated temperature

Before the advent of cationic emulsions, surface treatments were subjected to the phenomenon of "baldness" for a long time. The latter occurred either due to insufficient adhesion at the “binder-crushed stone” boundary, or due to the fragility of the “binder” film at low temperature.

Indeed, the permeability of bitumens that are part of emulsions decreases rapidly when the temperature drops.

So, for bitumen emulsion 100/130, poured at a temperature of +10°C, the penetration of the residual “binder” will be 30, but if the temperature drops to 0 or -5°C after the spill, the penetration will reach 10 and 7, respectively. Low temperature permeability will obviously be even lower with harder bitumens. In any weather, the change in the volume of binder in crushed stone resembles mercury in a thermometer - the expansion coefficient of the binder is 30-50 times higher than the expansion coefficient of the mineral material.

Ignoring the brittle point, which for bitumen occurs at -25°C...-30°C, and below which any movement becomes impossible, the viscosity at 0°C is such that dynamic impact can lead to the most unfortunate consequences.

For example, when snow falls on a salted road at 0°C, the pavement surface temperature drops sharply to -15°C. There is a real thermal shock: very viscous bitumen at 0°C quickly shrinks and cracks, while softer bitumen can shrink without cracking. The rupture of the "binder" film, when this occurs, is an open gap for water, which leads to the destruction of the coating in a short time.

Since the "mosaic" is not formed, that is, because the crushed stone does not lay down as it should under the influence of movement, and is supported by the interconnection of its sides, the coating remains fragile, especially at low temperatures. However, it should be noted that the time during which the coating remains brittle will be much shorter when it comes to multi-layer coating.

In order to speed up the fixation of the crushed stone in the binder and prevent the phenomenon of “baldness” at low temperatures, the base bitumen of cationic emulsions can be diluted with some solvent when poured. Its amount depends on the laying temperature and is chosen so that the penetration of the residual binder emulsion is, at the laying temperature, approximately equal to the penetration that the base bitumen had at +25°C.

Based on this, it is possible to lay coatings at relatively low temperatures (up to +5°C approx.).

The small amount of solvent contained in the residual binder quickly evaporates and the bitumen returns to its original characteristics, which eliminates any danger of sweating it out during the warm period.

The use of solvents completely eliminates the phenomenon of baldness, allows you to minimize the release of crushed stone from the surface treatment layer to the roadside.

If the paving is to be laid in extremely hot conditions, bitumen should be used with the highest possible viscosity. At this time, road foundations are usually not strong enough, with the exception of foundations made of high-gravel materials. Fine-grained surface treatment material tends to sink into the pavement under the influence of the wheels of heavy vehicles, unless its movement is stopped by a rigid base or slowed down in summer by the use of a binder of viscous bitumen. Therefore, depending on the season, the choice of viscosity of the binder introduced into the emulsion is the result of a compromise between laying conditions and extreme temperatures encountered.

Storage stability

The storage stability of high concentration, high viscosity cationic emulsions is better than the stability of less concentrated emulsions.

Cationic emulsions for surface treatment can easily be stored for about seven days, and if necessary, have a longer storage. Even for very fast breaking emulsions, the emulsifier protection of the bituminous micelles is sufficient to prevent any coalescence during such storage period.

Tear resistance

Cationic emulsions adhere to any clean gravel, whatever its structure. Crushed stone should not be treated with a binder (blackened). However, sticking depends on a certain number of parameters, and in particular on chemical properties emulsifier, the introduction of modifiers, as well as the pH of the emulsion.

It has been found that a low pH value (strong acidity) provides less good adhesion than a pH close to 3 or 4; however, at a lower pH, the stability of the emulsion is increased and the processing of materials with a binder is facilitated. in technology stabilization it was decided to use low pH emulsions.

In technology surface treatments what is sought is certainly not a high emulsion stability, but above all a good tear resistance and a fast disintegration rate. The trend is thus to introduce modifiers to counteract the adverse effects of low pH.

Surface Treatment Formulations

Formulation development is necessary to optimize the characteristics of the coating structure, the nature and granulometric properties of the mineral material, the properties of the binder, as well as their respective dosages.

It is determined by the following parameters:

• The physical characteristics of the bases - the structure (of the old pavement - asphalt concrete), the quality of its components (type of aggregate and binder), the state of the surface (stiffness, uniformity, cracking) and the geometry of the road (its longitudinal and transverse profiles);
• Characteristics of road load requirements - traffic (number of cars per day, percentage of heavy trucks, speed limit), and operating conditions (winter maintenance, traffic in more than 2 lanes);
• Environmental conditions - climatic region, vegetation, urbanization, atmospheric conditions during the surface treatment device;

Structure selection

There are several surface treatment structures:

• Single layer coating;
• Single-layer coating with a double layer of crushed stone;
• Two-layer coating;
• Covering "sandwich", or SCHVShch (crushed stone-astringent-crushed stone).

The structure is selected mainly depending on the type of loads and the condition of the foundation.

single layer structure is the most common. Most often, it is arranged from the material of the fraction 5/10.

When traffic is heavy and/or the base is not uniform, it is preferable to lay two-layer coating, it will provide better tightness of the old road, deformations will be better distributed. You can also give, with some precautions, easy repurposing.

An interesting compromise, especially common in modern times - single layer structure with double distribution crushed stone (clearing), which is especially well suited for roads with intensive and heavy loads, provided that it is laid on a good "hard" base.

Finally, covering "sandwich", can be compared to a single-layer - double-scatter coating. It is used for roads of secondary, local importance.

mineral material

Properties of mineral materials

They are driven by economic and technical considerations.

From a technical point of view, it is necessary to have a stone material whose quality meets the specifications listed above, and the cost, depending mainly on the distance of transportation, will force one to choose a mineral material that is often located as close as possible to the construction site.

At construction sites where surface treatments are carried out on a non-main road network, local materials are used that do not meet the requirements of official specifications in quality. In these cases, it should always be remembered that any violation of the technology in relation to the quality of the material, and in particular to their purity and their form, leads to the risk of failure in this delicate technology.

The choice of particle size distribution

Various parameters must be taken into account for the selection:

• Obtaining good roughness;
• Operational qualities (noise, driving comfort);
• Provided type of coating structure;
• Environmental conditions.

The most applicable fraction is 5/10, but stronger roughness can be achieved with a 10/15 fraction. In a single coat with a double coat of crushed stone, 10/15 will mate well with 2/5, the difference in grit will, in experience, be such that will lead to a better result.

While the 10/15 grit offers the advantage of higher roughness, at the same time it increases the risk of crushing the crushed stone into the soft pavement due to the concentration of traffic-induced forces on a more limited number of crushed stone "tops".

Of the two possible fractions, one should choose the one that represents the least inconvenience in a particular situation.

In areas with increased use, the noise will be much stronger with aggregate that has an increased grain size. In this case, it is better to use a fraction of 5/10, or even 2/5, to provide a thinner coating, but if a double distribution of crushed stone is necessary, then it is better to use a combination of fractions of 5/10-2/5.

In the case of two-layer coatings, the difference in grit between the two layers is just as desirable as for a single-layer coating with two layers of crushed stone; it allows you to get a better laying of the "mosaic" of the second layer.

Practical dosing of mineral material and theory

Theoretical dosing of crushed stone

In the case of single layer coatings, it is ideal to obtain a uniform monogranular layer.

Numerous developers have tried to determine the ideal dosing based on a theoretical shape placeholder: either a regular geometric shape such as a sphere, cube, or tetrahedron, or trying to replicate observations at a construction site. In reality, the aggregates included in the same fraction are different, and there is usually a tendency to take into account the concept of average size:

As with other types of surface treatments, for single-layer coatings, in most cases it is necessary to determine in advance the covering power of the mineral material of the accepted particle size distribution.

Single coat

The dosages used for monogranular layers can be:

6 to 7 l/m² for 2/5
8 to 9 l/m² for 5/10
11 to 13 l/m² for 10/15

A weak release of rubble when opening the movement is inevitable.

Attempts to increase these dosages in order to achieve a flawless mosaic should be avoided. The result of an overdose of mineral material does not lead to an acceleration of the formation of a homogeneous "mosaic", but to the destruction of the emerging monogranular layer.

Single layer coating with two layers of gravel

The goal is to obtain a primary mesh from coarse gravel, allowing you to cover 1/3 of the area of ​​the distributed binder, and dosing a fine fraction allows you to fill these "voids", leaving the tops of coarse gravel protruding.

These dosages should provide an effective mosaic with very good drainage. It will also prevent the tires from sticking to the binder.

Typically, these conditions are met in the following dosing ranges:

10/15-2/5 10/15 7 to 9 l/m²
2/5 4 to 5 l/m²

5/10-2/5 5/10 5 to 7 l/m²
2/5 3 to 4 l/m²

Double layer coating

By definition, these coatings are a superposition of two layers, the applied dosages for the first layer are slightly less than for a single layer coating. A slight underdosing of the first layer does not cause problems, and moreover, on the contrary, it avoids a surge that would interfere with the installation of the second layer.

Coating "sandwich"

The end result is usually comparable to appearance single-layer coating with two layers of crushed stone, as a result of which it would be necessary to state comparable dosages. In fact, this method of arrangement, consisting of covering the tops of coarse gravel with fine gravel, requires even distribution of fine gravel over the entire surface in order to allow road vehicles to pass without sticking to their tires. The dosage of this second layer will be slightly larger than the dosage of the second layer of a single-layer pavement with double distribution of crushed stone.

Emulsion dosing

The dosing of the emulsion for surface treatment is estimated by the dosing of the residual binder.

It is a mistake to think that the thicker the binder film that binds the crushed stone, the better.

But, we know that after spilling and setting the crushed stone, the binder rises under the influence of rolling and traffic along the inner parts of the voids formed by the adjacent faces of the crushed stone. Simultaneously under the action traffic flow crushed stone is turned over, crushed and pressed into the underlying coatings. Consequently, excessive dosing adversely affects the quality of the surface treatment.

Binder dosing must meet two conditions:

• Be sufficient so that the adhesive film of the binder can resist the stresses caused by movement;
• Do not completely fill the gaps, so as not to float to the surface and cause the phenomenon of sweating of the binder above the surface of the surface treatment layer.

Theoretical reasoning

Most developers say that the percentage of voids when distributed in the granular bed is in the range of 42-52%, the percentage at the end of rolling is brought to 30%, at the end after stabilization by traffic, the amount of voids reaches 20%.

It is calculated that the residual binder should occupy 2/3 of the voids of the mosaic. Thus, it is possible to calculate the theoretical dosing for a particular fraction by applying formulas, taking into account, of course, the density of the binder.

However, in practice, a rule called "1/10th" is usually applied, which consists in applying a final binder dosage equal to 1/10th of the crushed stone dosage, measured in liters (based on the average size rule).

Condition and nature of the foundation

Foundation - an element of paramount importance, the knowledge or ignorance of the state of which can be the cause of failure or success.

The condition of the surface can be easily assessed: one can distinguish between a greasy and smooth road, a dense and rough road, or a very rough, porous one, but this lightness is only apparent, since homogeneous roads are rarely found.

In the case of smooth and greasy roads, a reduction in the dosage of the binder of the order of 10-20% or the use of larger fractions of crushed stone can be applied.

Sand patch measurements can provide an accurate indication of the surface condition of an existing pavement.

It should also be taken into account the usual porosity of microcracking or the rigidity of the base, which could contribute to the immersion of crushed stone in an overly “soft” coating layer.

Movement aggressiveness

It is characterized by the amount of heavy trucks, and is also a function of the direction and profile of the road as individual waypoints, such as junctions.

Outside the zone of intersections and bends, where significant tangential forces develop, transportation by heavy trucks, usually passing along the same lane, contributes to the compaction of the mosaic, that is, to the acceleration, under the influence of vibrations, of crushed stone indentation into the coating layer. Thus, the appropriate rows should not be brought up to the dosage of the binder by 10-15%.

On the contrary, on high-speed sections of roads with 2x2 lanes, four lanes, or on the central part of a three lane highway, an additional dosage of 10-15% is necessary.

If the movement is not intense, good fixation of crushed stone in the binder is possible only by overdosing, which can reach up to 20%, and in this case there is practically no risk of sweating.

Form and nature of crushed stone

Despite the careful distribution of crushed stone, it is always necessary to clarify its average thickness and adjust the dosage of the binder. The spread cannot exceed 10-15%.

The origin, physico-chemical nature of the crushed stone must also be taken into account, but only the established experience is an element of the assessment. Usually it can be stated that crushed stone obtained from sedimentary rocks requires an overdose of 5% in relation to crushed stone of the same fraction from rock masses.

Combination of amendments

Combining different corrections in dosing, made depending on various parameters, can lead to a significant deviation from the average dosing.

It is difficult to calculate allowable limits: in fact, experience has shown that a deviation of +30% usually allows for correct processing, especially on roads with little traffic, on the other hand, with a high level of lane loading, underdosing should not exceed a value of 20%.

Laying and preliminary work

road cleaning

Sweeping is necessary to ensure a good adhesion of the coating to the substrate. The coating will not stick due to its own weight alone or the adhesion of its own elements. It is necessary that the layer of dust does not play the role of talc between the base and the coating.

On roads already covered with hydrocarbon material, it is necessary to carry out under throwing in order to clean them from dirt and foreign bodies and, especially, to free the edges from the dust that always collects on them. If the surface to be coated consists of a gravel-sand mixture or treated with a hydraulic binder, or macadam macadam, the surface should be cleaned—without breaking it—to allow the binder to form bonding points with large elements.

Sweeping operations should be done early enough so as not to slow the pace of the crew, and late enough to prevent any new build-up of contamination before the binder is spilled.

Emulsion distribution

The distribution should be carried out in such a way that the dosage is equal to the set value, that the longitudinal and transverse distribution is uniform and that individual points (joints, recesses) do not represent weak points in the finished work.

Compliance with the prescribed dosing

Depending on the selected emulsion and the width of the used ramp, the driver determines, using the adjustment elements of the asphalt distributor (nomogram, computer), the necessary ratio between the speed of movement and the number of revolutions of the pump, which determines the dosing of the binder onto the coating. During distribution, the ratio between vehicle speed and pump revolutions is kept constant, either by automatic tracking or by direct reading of the tachometer and rev counter by the driver.

The laying described above is possible and reliable only if the equipment used is in a condition that meets the designer's tolerance standards and is kept in a state of great cleanliness. In fact, any contamination, whether on the delivery machines, or occurring in the emulsion production cycle, or any change specifications emulsions lead to changes in the amount of liquid in the system, which makes dosing unreliable.

Uniform longitudinal distribution

The quality of the longitudinal distribution of the binder is a function of the spill team's strict adherence to the paving parameters defined above, taking into account unforeseen changes in working width.

Uniform transverse distribution

The bottling team must adhere to the prescribed ramp height for each type of ramp, and certain adjustments depending on the number of diffusers used. In addition, the ramp should be kept as parallel as possible to the transverse profile of the road. Poor position of the ramp in height leads to “combing out” of the binder, which will contribute to pulling out the crushed stone from the grooves depleted in binder.

Example of adjusting brush diffusers:

The brush-like jet from the nozzle has an angle of 40°, the diffusers are located at a distance of 12.5 cm from one another, a good distribution uniformity is achieved by tilting all diffusers in the same direction by 15° in relation to the vertical plane of the ramp, and fixing the level of the latter at a height of 25 cm from the treated coating.

Careful processing

At the beginning of each cycle of work on the construction site, it is desirable to have, from the beginning of the covered length, a paper tape; this belt will take the binder, a few decimetres, until the asphalter reaches its steady speed. Thus, the transverse joints will be clean and tidy, without overdosing and underdosing in individual parts. This technology can also be extended to the stop zone of the asphalt distributor at the end of the operation.

At the junction of two adjacent strips of the emulsion to be dispensed (longitudinal seam), the application must be precisely defined and carried out with care in order to strictly adhere to the defined dosing. This overlap is necessary to prevent underdosing, since the end nozzles of the ramp do not overlap each other with their jets, like the nozzles of the central part of the section.

During the installation of multilayer coatings, the longitudinal and transverse joints of each layer should be shifted.

The emulsion, being a product of very strong adhesion, requires that the plugs of control manholes, keyed hatches and other accessories on the road be protected so that they remain easy to open after the coating is applied.

crushed stone distribution

Like an emulsion, the crushed stone must be distributed in accordance with the given dosage, with the most uniformity possible, both in the transverse and longitudinal directions. Thus, the best accuracy is achieved by using hard and granular materials.

In order to achieve the dosing accuracy prescribed by the granulometric composition in accordance with the recipe, the team distributing the crushed stone must observe the following rules:

The good condition and reliability of the technology guarantee the uniformity of the transverse and longitudinal dosing. Also, the state of the machine must be systematically checked, taking into account that the passage of crushed stone causes rapid wear in the area of ​​the shutters, sluice gates and the dosing roller (cell dosing).

Adapt settings to specific type crushed stone prescribed by the documentation of a particular object. Since even within a given size of crushed stone, the size ratios fluctuate.

Strictly follow the rules of laying

Crushed stone should be distributed as soon as possible after the spill of the binder. The chip spreader should follow the distributor no later than in 20-40 seconds. This period must be observed the more strictly, the faster the disintegration of the emulsion occurs, or if the emulsion has been spilled on a deformed highway and, therefore, can drain into low points.

All surfaces covered with binder must be treated with crushed stone. Particular attention should be paid to the joints: the crushed stone that did not seize during the processing of the first strip should be swept away before the joint is coated with an emulsion of the second strip.

It is necessary that the person responsible for the distribution of crushed stone be able to assess with his own eyes the quality and density of the distributed materials.

By demonstrating the need to cover the emulsion with crushed stone as early as possible, one can understand the importance of the crushed stone distribution process and the speed of laying aggregate, which ensures productivity and daily output at the construction site.

Coating seal

The compaction of the surface treatment ensures the laying of the aggregate and its fixation on the pavement by means of a binder film. Pneumatic tire seals provide these features superbly. They adapt to the unevenness of the road and do not destroy the gravel. The desired effect is fully achieved with a tire pressure of seven to eight bar for a load of two to two and a half tons per wheel through three to five passes at a speed set at three kilometers / hour for the first, and ten kilometers / hour for the latter.

Covered roads, which resumed traffic immediately after the works, are provided with full compaction. However, for a short time, it should be carried out at a limited speed. In the case of a single-layer coating with a double layer of crushed stone, compaction should also be carried out after the distribution of the first layer of aggregate.

In the case of a multi-layer coating, it is preferable not to compact the first layer before laying the subsequent ones. In fact, too careful application of the first layer may prevent satisfactory adhesion of subsequent layers. Compaction of the multi-layer coating should be carried out after the complete installation of the latter. This complete laying must be fast enough so that compaction can be carried out before the emulsion begins to break.

Selection of discarded rubble

The ejection is defined, on the one hand, by rolling aggregate that has not set well or not set, and, on the other hand, by fine-grained material torn out or thrown out when the movement is opened.

It makes sense to pick up this discarded rubble as soon as possible, because, in addition to being dangerous for road users, it can interfere with the formation of a mosaic and interfere with the normal flow of water by clogging the sewage.

As a consequence, from the moment the discharge appears at the road edge and along the axis of the rows, the discharge is swept up, sucked up and removed.

Control measures

Preliminary control of equipment

The control measures mainly apply to the uniformity of distribution in the longitudinal direction in the transverse direction, as well as compliance with the dosing of binder asphalt distributors and chip spreaders.

Binder spreaders must be tested on a test bench.

Defects and deviations

Destruction in a short time

Common rubble uprooting

Common chipping

The immediate release is abnormally high and constant.

The binder does not seize the aggregate. Destruction extends to all coverage.

Possible reasons:

Error in technology

• The conditions of use are above the reasonable limit of the use of surface coatings (too intense horizontal loads).

Recipe errors

• The binder is not adapted to traffic conditions;
• Dosing of the binder does not match the location, the actual geometric characteristics of the aggregate, the condition of the base surface and the traffic conditions;
• Insufficient general mechanical adhesion at the binder-crushed stone interface;
• Very fragile structure for traffic conditions.

supply errors

• Components that do not meet the characteristics provided by the formula (properties, size, shape, purity of aggregates).

Installation errors

• The technique and means used do not correspond to the properties of the components or the pace at the construction site;
• Loading error resulting in the use of binder or aggregates instead of those that should have been laid (for example, blackened crushed stone).

Disadvantages of the implementation of work

• The ambient temperature is very low, which does not allow the implementation of work;
• The road surface is too wet or too cold;
• Incorrectly distributed amount (underdose of binder, excessive distribution of crushed stone);
• Drainage of the binder to the edge (slow disintegration emulsion);
• Late distribution of crushed stone, carried out after the breakdown of the emulsion;
• Insufficient compaction;
• Premature resumption of movement
• Precipitation occurring before a detour is established to protect the freshly covered area.

The separation of elements of fine-grained material from one another occurs in "spots" in more or less significant zones.

Possible reasons:

Disadvantages in coating preparation

• Individual underdoses of binder due to poor surface geometric condition created due to runoff into adjacent zones;
• Absorption of the binder by the coating due to repair work where exposed asphalt concrete was used.

Disadvantages of work

• Heterogeneity of aggregate in terms of quality, granularity or purity (contaminated warehouses, which leads to the loading of earthen clods);
• Uncovered areas of the surface.

Combing

The separation of the elements of fine-grained material from one another occurs by parallel grooves on the edge of the road.

Possible reasons:

• Poor distribution of the binder on the road due to damage to the distribution ramp (clogged nozzle nozzles, poor adjustment of the distribution of jets to the ground).

Removing the coating from the base

Baldness

Most of the surface treatment gravel is separated from the coating by spots of more or less significant size.

Possible reasons:

• Insufficiently cleaned base, silt and contaminated during emulsion spill;
• Traces of binder not filled with gravel on the road, sticking to pneumatic tires, which causes even more tearing, especially in the wake of traffic.

Other destruction

The coating is partially or completely destroyed in various zones

Possible reasons:

• Significant efforts that destroy the still fragile mosaic (sudden braking, sudden change in the direction of movement of the roller);
• Dirt (oil stains).

Destruction in time

Ejection with the first cold snap

After seemingly stabilizing without problems, the coating begins to lose its aggregate in a systematic way (chipping)

This destruction is always intensified in winter period road conditions (sprinkling with salt) and because of the peculiar driving conditions (pneumatic tires with spikes). It corresponds to periods of high humidity, numerous zero crossings and cold weather.

Possible reasons:

Recipe errors

• Underdosing of binder;
• Base bitumen too brittle at low temperatures.

Errors in the work

• Late distribution of crushed stone after disintegration, which does not allow obtaining satisfactory wetting of the aggregate;
• Excessive distribution of crushed stone, preventing the formation of a mosaic.

summer blowout

It occurs due to extreme heat, when the binder softens too much under the influence of temperature. .

sweating

Destruction occurring mainly in warm weather, which is characterized by the appearance of spots, smudges or streaks of the binder on the surface due to either the actual rise of the binder or the surface depletion of the aggregate.

Sweating due to the rise of the binder

Recipe errors

• The theoretical binder dosing is too high for the grain size or actual shape of the materials;
• The theoretical dosing of the binder is poorly adapted to the nature or condition of the base, the level of traffic;
• Heterogeneity of aggregates in terms of quality or grain size;
• Poor ground preparation;
• Too saturated dosing during previous work;
• Dirt (oil stains).

Destruction in time

The damage already mentioned may develop with some delay, in particular if traffic or atmospheric conditions suddenly become too unfavorable.

Local overdoses of binder due to poor geometrical condition of the road, which contributes to the accumulation of binder at low points (potholes, ruts).

Styling errors

• Accidental overdoses of astringent;
• Underdoses of gravel.

Sweating due to ejection

Any release leads to depletion of the surface of the coating by the filler, this depletion corresponds to a relative overdose of the binder.

Pseudo-sweating is formed due to the indentation of crushed stone into the coating under the action of transport.

This destruction develops mainly in the lanes of heavy trucks. The immersion of the aggregate into the coating results in the depletion of the surface treatment with crushed stone and the rise of the binder to the surface.

Technology errors

• Application conditions that are outside the reasonable limits of the use of surface treatments (too intense vertical loads in relation to the rigidity of the base).

Recipe errors

• Poorly adapted to the intensity of traffic structure.
• The crushed stone is too small in relation to the hardness of the pavement and the intensity of traffic.

Note

Indentation of aggregate elements into the pavement can occur in very limited areas:

• A strong change in the longitudinal profile (steep vertical curves), causing significant dynamic overloads of the pavement under the action of the traffic flow;
• Limited changes in the nature of the pavement (sealed trenches, widening along the edge, various repairs).

Baldness

The totality of surface treatment components (binder-crushed stone) is separated from the coating by more or less significant spots.

This phenomenon occurs in warm weather due to sweating when heavy traffic is heavy. Excess binder, softened, sticks to car tires. The coating is torn off from the base in pieces and glued again in other places, forming non-uniform irregularities on the coating.

metal spikes

Under the influence of repeated impacts, the aggregate may be crushed or exposed. Then there is increased wear of the upper layer pavement, accompanied by tearing out of the material (binder and aggregates).

Various pollution

Various types of pollution can be detrimental to coatings. The destruction they cause remains, however, very limited in significance.

Organizational measures at the site of surface treatment

patching

Pothole repair is a very common technology, the purpose of which is to repair the upper layers of the road surface, in some places.

Pothole repair can be carried out:

• With the help of bituminous emulsion and crushed stone of granulometric composition;
• Using materials treated with bituminous emulsion;
• With the help of non-storable dense materials treated with bituminous emulsion.

A car repairer usually has a thermally insulated container for the emulsion, a distribution device for pneumatic application (trunk, rod with a nozzle) of emulsion and crushed stone, and one or two bunkers for different fractions of crushed stone.

Usually in the technology of patching two fractions are used - a larger 5/10, 10/15 for the lower layer and a fine 2/5 for the upper layer. Sometimes one fraction is used. Usually 2/5 and 5/10.

The emulsion used should be cationic, fast disintegrating EBK-1, with a bitumen content of 60-65%. The temperature of the emulsion during operation is from +30ºС to +60ºС.

The dosage of the emulsion is calculated in relation to the stone material 4-5% of the emulsion.

Emulsion recipe for patching:

1. Bitumen BND 60/90 or 90/130 - 60-65%
2. Adhesive additive () - 0.05-0.15% - consumption depending on the type of stone material.
3. Kerosene - 0.9-3% - the lower the air temperature, the more it is desirable to introduce kerosene: usually up to + 10ºС - this is 3%, the higher the lower the dosage.
4. Latex (Butonal NS198) - up to 2% - it is desirable to introduce when using the emulsion on loaded road sections.
5. Emulsifier () - 0.25-0.35%
6. Hydrochloric acid - up to pH 2.5 ± 0.3
7. Water up to 100%.

This is a classic patching recipe for any type of patching machine. The bitumen content is adjusted according to the resulting emulsion viscosity and is determined by the convenience of work (excessive spatter). The content of the adhesive additive is determined by the adhesion to the stone material used.

The use of latex is mainly on loaded roads with high traffic intensity, at intersections.

Kerosene is dosed in the cold season for better engraftment.

SURFACE TREATMENT TECHNOLOGY "CHIP FORCE"

"CHIP POWER" is a surface treatment in which the synchronous distribution of bituminous emulsion and graded stone material occurs. It is used to maintain in working condition and extend the durability, as well as to improve the transport and operational characteristics of roads.

From the history

Rough surface treatment device technology with synchronous distribution of binder and stone material according to technology "CHIP POWER" originates in 1960. Chuvash specialists developed a proposal to replace the traditional laying technology with a new one with synchronous distribution. Several prototypes were made in repair shops, but this technology did not receive further development. And in 1985, the French company "Secmair" began to use this technology in the construction of French roads. In 1999-2001, FSUE SNPTS "ROSDORTECH" developed and in 2001 approved by Rosavtodor "Methodological recommendations for the installation of a single surface treatment by equipment with synchronous distribution of bitumen and crushed stone." SNPTS "ROSDORTEKH" together with French company"Secmair" has developed a Russian analogue of the machine "Chipsealer - 26". About 40 years have passed from the moment of development to the introduction of this technology on the roads of Russia.

Conditions for the surface treatment device "CHIP SEAL"

The main condition for the production of work on the device SHPO is the ambient temperature. When using a bitumen emulsion as a binder, the temperature should not be lower than +5°C, and when using bitumen, it should not be lower than +15°C. However, based on experience, there are the following restrictions on the performance of work due to weather conditions:

• The air temperature in spring should not be lower than +15°С;
• Work must not be carried out if within 48 hours after the installation SHPO the temperature is expected to drop to +5°C and below;
• In August, work on the device SHPO should be produced at an air temperature not lower than +20°С;
• The surface of the coating must be smooth and free from dust and dirt;

Preparatory work before the device

With the device of surface treatment according to technology "CHIP POWER" potholes and cracks should be sealed in the existing pavement. As a rule, cracks with an opening of more than 3 mm are subject to mandatory sealing. It should be noted here that the use of cold asphalt mixes in the subsequent installation SHPO by technology "CHIP POWER" Not recommended. In addition, the repaired surface of the asphalt concrete pavement must be smooth, dry (when used as a binder bitumen) and cleaned of dust and dirt (free from any loose materials, ending with the pouring of the binder). Therefore, preparatory work should include:

• Removal of thermoplastic road markings by demarcation, as lack of adhesion between thermoplastic and distributing bitumen emulsion (bitumen) leads to defects such as “bald patches” and chipping;
• Sealing cracks with hot bitumen or mastic with sand powder;
• Repair of the existing pavement in places of peeling and chipping of the roadway;
• Sealing potholes using hot mix asphalt repair technologies;
• Elimination of rutting;
• Cleaning the road surface from dust and dirt with a combined road machine.
• Device SHPO

After all preparatory work the optimal length of the work site is determined and the installation is filled with stone material and binder. Crushed stone for surface treatment is pre-cleaned and moistened. The content of clay in lumps is not allowed, and the content of dusty and clay particles should not exceed 0.5%. Failure to comply with these requirements can lead to a rupture of the binder-crushed stone bond.

Synchronous pouring of binders and scattering of crushed stone is carried out by a special machine - "Chipsealer - 41".

The main stages of the device ShPO

• Stage 1: Synchronous distribution of binders and crushed stone by a special machine - "Chipsealer - 41".
• Stage 2: compaction of rough surface treatment with pneumatic rollers.
• Stage 3: after 2 - 3 days from the moment of laying, the unfixed crushed stone is swept away by a combined road machine.
• Stage 4: the opening of traffic and the application of road markings in at least 0.5 - 2 hours with a speed limit of up to 40 km / h for 7 days.

When performing work on the device SHPO the joints of the laid strips are arranged by analogy with traditional surface treatment. To ensure the quality of the longitudinal joint, the distribution of bitumen emulsion (bitumen) from the side of the joint is 0.20 - 0.25 m wider than the distribution of crushed stone, which is achieved by closing the extreme damper of crushed stone. When arranging an adjacent strip, the distribution of bitumen emulsion (bitumen) is carried out with a double overlap on an adjacent strip with a width of 0.20 - 0.25 m and the distribution of crushed stone on the resulting joint. In this way, an even longitudinal conjugation is obtained.

The "carpet" of the rough surface treatment should have a uniform texture. In order to ensure uniform texture and give each gravel a state of "rest", compaction is used. SHPO pneumatic rollers. In case of formation of local defects (crushing of crushed stone, sweating of bitumen emulsion, etc.), they must be eliminated.

Advantages of the ShPO device using the "CHIP SEAL" technology

• Security;
• Durability;
• Closing and preventing the formation of cracks;
• Facilitate the organization and coordination of work due to synchronism;
• Coating protection;
• Reducing the period of work;
• Profitability;
• High performance.

Disadvantages of the ShPO device using the "CHIP FORCE" technology

• Possibility of car damage by rubble;
• Increased noise level;
• Rigid dependence on weather conditions and temperature conditions;
• Temporary speed limit.

OUTPUT: Device for rough surface treatment by technology "CHIP POWER" as a preventive method of maintaining not yet destroyed asphalt concrete layers, as well as restoring worn layers, it is increasingly attracting the attention of customers due to the increase in transport and operational characteristics, as well as the service life of roads. And based on the technical and economic analysis this method much more profitable than traditional milling with further laying of a new layer of coating. This technology Not recommended for use in residential areas.

Since 2012 the company "TechDorGroup" rough surface treatment was carried out on such roads as:

1. Sverdlovsk region. Highway R-242 Perm - Yekaterinburg km 187+000 - km 197+000.
2. Sverdlovsk region. Highway R-351 Ekaterinburg-Tyumen km 280+000 - km 289+820.
3. Khanty-Mansiysk autonomous region- Yugra:
- Highway R-404 Tyumen - Tobolsk - Khanty-Mansiysk km 827+000 - km 830+000;
- Highway R-404 Tyumen - Tobolsk - Khanty-Mansiysk km 899+000 - km 903+000.
4. Khanty-Mansi Autonomous Okrug - Yugra. Highway road R-404 Tyumen - Tobolsk - Khanty-Mansiysk km 932+000 - km 939+000, in the Khanty-Mansiysk Autonomous Okrug-Yugra.
5. Sverdlovsk region. Highway R-242 Perm - Yekaterinburg km 239+000 - km 260+000.
6. Perm region. Highway R-242 Perm - Yekaterinburg km 154+000 - km 160+046.
7. Sverdlovsk region. Highway R-242 Perm - Yekaterinburg km 232+000 - km 239+000.
8. Sverdlovsk region. Highway R-351 Yekaterinburg - Tyumen km 191+000 - km 218+000.
9. Sverdlovsk region.

— Highway R-242 Perm — Yekaterinburg km 169+000 — km 187+000.
— Highway R-242 Perm — Yekaterinburg km 260+000 — km 269+000.

10. Sverdlovsk region.

— Highway R-351 Ekaterinburg-Tyumen km 67+000 — km 80+000;
— Highway R-351 Ekaterinburg-Tyumen km 261+000 — km 280+000;
— Highway R-351 Ekaterinburg-Tyumen km 225+000 — km 233+000.

11. Sverdlovsk region. Highway R-242 Perm – Yekaterinburg km 187+000 – km 205+000
12. Sverdlovsk region. Highway R-242 Perm - Yekaterinburg km 205+000 - km 232+000.
13. Sverdlovsk region:

— Highway R-351 Yekaterinburg — Tyumen km 174+200 — km 191+000;
— Highway R-242 Perm — Yekaterinburg km 232+000 — km 239+000;
— Highway R-242 Perm — Yekaterinburg km 239+000 — km 260+000.

14. Device for double surface treatment of the roadway with crushed stone treated with organic binder in the installation:

— Bolshaya Sosnova — Frequent km 27+000 — km 33+000;
- Nytva - Grigoryevskoye - Ilyinsky km 4+500 - km 19+000;
- Nytva - Grigoryevskoye - Ilyinsky km 22+000 - km 25+200;
- Nytva - Grigoryevskoye - Ilyinsky km 26+700 - km 31+700;
- Dybki - Tabory - Okhansk km 11+800 - km 19+000;
– Ocher – Vereshchagino – Siva km 3+900 – km 10+300;
- Ocher - Vereshchagino - Siva km 15+000 - km 24+310.