7. Previous work reports of dynamic loads on fatigue properties of asphalt concrete

At the car speed of more than 30 km/h the surface load process at the reference point d during a small time interval can be represented as the static load F affecting on the definite blanket volume on the base under the harmonic vibrations. With account of the before mentioned assumption, the authors used the developed in the university (VGASU) method of the prediction of asphalt concrete operational properties based on the results of testing of the beams 4 4 16 (cm) on the vibration exciter (Figure 14).

Vibration exciter provides the production of a frequency and vibrational amplitude from 10 up to 100 Hz and from 0.1 to 5 mm respectively gradually regulated during the operation time. The load onto the sample can change from 2 to 60 kg.

Figure 14. Vibration exciter at the moment of asphalt concrete beams testing.

Analytical dependences able to determine operation period duration under simulation load were taken as the base of method.

The vibrations similar to the harmonic form are modeled on a vibration exciter:

$$A = A\_0 \sin\left(\omega t + \varphi\_0\right) \tag{8}$$

E<sup>∂</sup> ¼ σ=ε<sup>m</sup> (12)

ð Þ� <sup>n</sup><sup>1</sup> � <sup>n</sup><sup>2</sup> <sup>5</sup> � <sup>10</sup>�<sup>6</sup> (14)

N<sup>Э</sup> ¼ NпрK1K<sup>2</sup> (16)

(15)

101

<sup>2</sup>bh<sup>2</sup> (13)

http://dx.doi.org/10.5772/intechopen.76877

<sup>σ</sup> <sup>¼</sup> <sup>3</sup>Pl g <sup>þ</sup> <sup>4</sup>A0π<sup>2</sup><sup>f</sup>

The final formula for dynamic module of elasticity determination is written down as:

<sup>E</sup><sup>∂</sup> <sup>¼</sup> <sup>3</sup>Pl g <sup>þ</sup> <sup>4</sup>A0π<sup>2</sup><sup>f</sup>

The assessment of operation reliability caused by operating –climatic effect (T) is implemented

<sup>T</sup> <sup>¼</sup> Np N<sup>Э</sup>

where Np - number of asphalt concrete loading cycles up to its dynamic elasticity module abatement in two times; design number of wheels loading application during the year of road

where Nnp – equated movement intensity; K1 – coefficient of a car track overlapping; K2 –

For the investigation of asphalt concrete cyclic fatigue in a laboratory, the following factors were taken: asphalt concrete water saturation as physical-climatic; aging after heating during

Cyclic fatigue under dynamic loads is tested on the specially constructed diagnostic tester in the laboratory providing load application with frequency of 868 min�<sup>1</sup> in the regime of cyclic bending of the 2.5 � 4 � 16 cm size test beams at the fixed deformation amplitude. The test temperature is 20�С. The fatigue deformation amplitude was registered by the moment of destruction. The

The use of shungite powder instead of standard mineral powder promotes the growth of asphalt concrete fatigue life especially in the conditions of asphalt concrete water saturation.

One of the important properties of asphalt concrete predetermining its durability (during the destruction) is its structural stability in the changing humidity regime and temperature conditions. At water saturation adsorption aqueous layers simplify the formation of new surfaces in asphalt concrete during its deformation reducing the surface energy (Rehbinder's effect). Wedge effect of aqueous layers separating mineral grains and exfoliating bitumen strengthens the destruction effect. The mechanism of accelerated fatigue destruction of water saturated asphalt concrete at surface operation in the regime of cyclic dynamic loads is conditioned by the appearance of hydrodynamic pulsations in filled with water porous. This fact was investigated by Rudensky [17].

5 h at t 150�C as chemical; asphalt concrete composition formula as internal ones.

deformation amplitude while testing was 0.0021 (the test beam kink was equal to zero).

coefficient considering portion of design cars in a flow (0.3–0.4).

It may be connected with the higher adhesion of shungite powder.

2bh<sup>2</sup>

by the formula:

blanket service.

<sup>2</sup>

The Enhancement of Asphalt Concrete Surface Rigidity Based on Application of Shungite-Bitumen Binder

<sup>2</sup> Km

where A – vibrational amplitude at the time moment t:

Ао – maximal amplitude;

φо – initial form.

ω ¼ 2πf - cyclic frequency, where ƒ – vibrational frequency of vibration exciter.

direction of the forces, effecting on asphalt concrete test beam in relaxation stage can be represented in Figure 14 as:

where F1 – static load weight influencing the asphalt concrete beam.

F2 – elastic force in asphalt concrete beam;

F3 – inertial force during vibration exciter vibrations;

d – arbitrary point of load application.

The process of asphalt concrete fatigue fracture usually has three stages: internal fractures accumulation accompanied by a significant elasticity module reduction; microcracks appearing at small velocity of module elasticity reduction; propagation and progressive development of cracks with strong reduction of elasticity module [3].

The tension acting in the beam section in the bridge span center was calculated by the formula:

$$
\sigma = \frac{\Im P\_{\eth} l}{2bh^2} \tag{9}
$$

where P<sup>∂</sup> - dynamic load; l – span between piers; b, h – section size. The value of the relative deformation was defined by the formula:

$$
\varepsilon\_m = \frac{(n\_1 - n\_2)}{\text{K}m} \cdot 5 \cdot 10^{-6} \tag{10}
$$

where n1 и n2 - strain transducer registration for the sample without loading and vibration, and after the loading and vibration; Кm– coefficient of strain-sensitivity of a strain transducer.

The values of relative deformation were defined by a strain transducer registrations should be close to the design ones received by the formula:

$$
\varepsilon\_p = \frac{6\hbar}{l^2} \tag{11}
$$

At adherence to the situation ε<sup>p</sup> ¼ ε<sup>m</sup> the module of elasticity is defined by the formula:

The Enhancement of Asphalt Concrete Surface Rigidity Based on Application of Shungite-Bitumen Binder http://dx.doi.org/10.5772/intechopen.76877 101

$$E\_{\partial} = \sigma / \varepsilon\_{m} \tag{12}$$

$$\sigma = \frac{3Pl\left(g + 4A\_0 \pi^2 f^2\right)}{2bh^2} \tag{13}$$

The final formula for dynamic module of elasticity determination is written down as:

Analytical dependences able to determine operation period duration under simulation load

A ¼ A0sin ωt þ φ<sup>0</sup>

direction of the forces, effecting on asphalt concrete test beam in relaxation stage can be

The process of asphalt concrete fatigue fracture usually has three stages: internal fractures accumulation accompanied by a significant elasticity module reduction; microcracks appearing at small velocity of module elasticity reduction; propagation and progressive devel-

The tension acting in the beam section in the bridge span center was calculated by the formula:

<sup>σ</sup> <sup>¼</sup> <sup>3</sup>P∂<sup>l</sup>

where P<sup>∂</sup> - dynamic load; l – span between piers; b, h – section size. The value of the relative

where n1 и n2 - strain transducer registration for the sample without loading and vibration, and after the loading and vibration; Кm– coefficient of strain-sensitivity of a strain transducer. The values of relative deformation were defined by a strain transducer registrations should be

> <sup>ε</sup><sup>p</sup> <sup>¼</sup> <sup>6</sup>fh l

At adherence to the situation ε<sup>p</sup> ¼ ε<sup>m</sup> the module of elasticity is defined by the formula:

<sup>ε</sup><sup>m</sup> <sup>¼</sup> ð Þ <sup>n</sup><sup>1</sup> � <sup>n</sup><sup>2</sup>

(8)

<sup>2</sup>bh<sup>2</sup> (9)

Km � <sup>5</sup> � <sup>10</sup>�<sup>6</sup> (10)

<sup>2</sup> (11)

The vibrations similar to the harmonic form are modeled on a vibration exciter:

ω ¼ 2πf - cyclic frequency, where ƒ – vibrational frequency of vibration exciter.

where F1 – static load weight influencing the asphalt concrete beam.

opment of cracks with strong reduction of elasticity module [3].

were taken as the base of method.

Ао – maximal amplitude;

represented in Figure 14 as:

F2 – elastic force in asphalt concrete beam;

d – arbitrary point of load application.

deformation was defined by the formula:

close to the design ones received by the formula:

F3 – inertial force during vibration exciter vibrations;

φо – initial form.

100 Modified Asphalt

where A – vibrational amplitude at the time moment t:

$$E\_0 = \frac{3Pl\{g + 4A\_0 \pi^2 f^2\} K\_m}{2bh^2(n\_1 - n\_2) \cdot 5 \cdot 10^{-6}}\tag{14}$$

The assessment of operation reliability caused by operating –climatic effect (T) is implemented by the formula:

$$T = \frac{N\_p}{N\_\oplus} \tag{15}$$

where Np - number of asphalt concrete loading cycles up to its dynamic elasticity module abatement in two times; design number of wheels loading application during the year of road blanket service.

$$N\_{\ominus} = N\_{np} K\_1 K\_2 \tag{16}$$

where Nnp – equated movement intensity; K1 – coefficient of a car track overlapping; K2 – coefficient considering portion of design cars in a flow (0.3–0.4).

For the investigation of asphalt concrete cyclic fatigue in a laboratory, the following factors were taken: asphalt concrete water saturation as physical-climatic; aging after heating during 5 h at t 150�C as chemical; asphalt concrete composition formula as internal ones.

Cyclic fatigue under dynamic loads is tested on the specially constructed diagnostic tester in the laboratory providing load application with frequency of 868 min�<sup>1</sup> in the regime of cyclic bending of the 2.5 � 4 � 16 cm size test beams at the fixed deformation amplitude. The test temperature is 20�С. The fatigue deformation amplitude was registered by the moment of destruction. The deformation amplitude while testing was 0.0021 (the test beam kink was equal to zero).

The use of shungite powder instead of standard mineral powder promotes the growth of asphalt concrete fatigue life especially in the conditions of asphalt concrete water saturation. It may be connected with the higher adhesion of shungite powder.

One of the important properties of asphalt concrete predetermining its durability (during the destruction) is its structural stability in the changing humidity regime and temperature conditions. At water saturation adsorption aqueous layers simplify the formation of new surfaces in asphalt concrete during its deformation reducing the surface energy (Rehbinder's effect). Wedge effect of aqueous layers separating mineral grains and exfoliating bitumen strengthens the destruction effect. The mechanism of accelerated fatigue destruction of water saturated asphalt concrete at surface operation in the regime of cyclic dynamic loads is conditioned by the appearance of hydrodynamic pulsations in filled with water porous. This fact was investigated by Rudensky [17].


Mineral powder from shungite (Medvezhjegorskoe deposit) differs from the traditional one from dolomite by bigger porosity of the surface and high developed micropores system and also bitumen of the grade БНД 60/90 of Ryazan НПЗ was investigated. The dispersed raw under study will be correct to test for accordance with the demands [5] asphalt concrete mixes mineral powders. Characteristics of under research fillers proper-

The Enhancement of Asphalt Concrete Surface Rigidity Based on Application of Shungite-Bitumen Binder

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103

Mineral powder meets the requirements. But the porosity of the material 20–25% higher than the porosity of lime stone filler and the value of specific surface at the same grain metric proportion is 60–70% higher. So the conclusion is the system of micropores of under research

The results of the experimental researches of asphalt concrete binding agent. From our point the most informative method of studying the method "bitumen-mineral powder" is the investigation of asphalt concrete binding agent characterized by greater homogeneity of the structure and stability of the properties. Asphalt concrete binding agent was produced from according to the standard method with the before bitumen amount batching. Thus for the mineral powder from shungite the index is 16.2% which is 26% more than traditional lime stone mineral powder has. These data are correlated with the indexes of bitumen proportion in powders. The research results of the physical chemical properties of asphalt concrete binding agent with optimal amount of bitumen are given

Coefficient of composite thermal stability and its water resistance are the most interesting among all the data. Therefore, the index of heat resistance of shungite is 14.3% more than while using the traditional mineral powder from lime stone or dolomite. Thermal resistance of mixes and asphalt concrete is characterized by the coefficient of thermal resistance defined as the ratio of ultimate compression strength at t-20C to the ultimate stress

As the under research, raw material is porous; the water can penetrate inside the shungite grains and decompose the asphalt concrete binding agent on the bitumen- mineral powder interface if binding agent covers mineral powder surface partially or if the adhesion bonds

Names of the characteristics Mineral powder МП-2 Demands of the standard

Not less than 95 from 80 to 95 not less 60

shungite

100 98 80

Porosity, % 37 Not more 40 Indexes bitumen capacity, g 48 Not more 80 Humidity, % on mass 0.55 Not more 2.5

ties are shown in Table 5.

in Table 6.

limit at t = 50C.

Grain proportion, % on mass:

Table 5. Characteristics of under research illers properties.

are weak.

Smaller 1.25 mm <0.315 mm <0.071 mm

carbon containing raw material is more developed.

Table 4. Values of fatigue durability of asphalt concrete samples.

The assessment of asphalt concrete by the method of dynamic effect on the water saturated samples is more corresponding to the operation conditions of the material in road construction than the known methods based on statistic water action. That is why the tests of comparison fatigue of asphalt concrete durability were conducted on dry and water saturated samples. Water saturation of asphalt concrete samples was 1.65–1.66% by volume. Values of fatigue durability of asphalt concrete samples were given in Table 4.

The application of shungite material instead of the lime stone mineral powder promotes the growth of asphalt concrete fatigue durability especially in the conditions of water saturation. It connects with high adhesion activity of shungite carbon with shungite carbon containing material [21].

The increase of asphalt concrete fatigue durability with the application of shungite mineral powder as a result of aging (after the heating for 5 h) demonstrates the properties stability under temperature effect. It is clear that it connects with oil migration from pores in carbon containing materials and bitumen film rejuvenation during aging.
