**7. Bifurcation**

5 × 5 × 5 cm have been prepared from these samples, and they have been tested for direct compression at the same temperatures. Three asphalt concrete samples have been tested at each temperature. The results of the initial tests of the asphalt concrete samples at cyclic bending have been represented in **Table 3**, and their further test at direct compression—in **Figure 13**. As it is seen, the asphalt concrete has a high residual compression strength after the cyclic bending to failure, comparable with the strength of a new asphalt concrete (**Figures 9** and **12**).

**Figure 13.** Residual strength of the asphalt concrete at compression after cyclic bending at various temperatures.

As it is known, the self-organization phenomenon occurs in complicated open thermodynamics systems and new structures occur in them in critical conditions such as Benar's cells, separated cells of living organisms, laser ray, and so on. Occurrence of specific dissipative structures in critical low-temperature conditions on the asphalt concrete pavement has been shown in the works [15–17, 47]. The provided above staging of the fatigue failure for the asphalt concrete pavement, possibility in principle for occurrence of dissipative structures in it at critical conditions as a result of self-organization of its structural elements, significant dependence of single loading, cyclic and long-term strength of the asphalt concrete on deformation type (stressed condition) and existence of residual strength at another deformation

*Fatigue failure of an asphalt concrete pavement under repeated load impact is realized according to the consequently changing stages in every of which pavement parts function as specific dissipative structures with characteristic deformation type, which interchange in the sequence of:* 

**6. Principle of consequential change of deformation types**

type after failure allow formulating of a new regularity for the fatigue failure:

*tension-bending-compression.*

74 Modified Asphalt

The principle of consequential change of deformation types at fatigue failure for an asphalt concrete pavement formulated earlier can be explained on the basis of provisions for thermodynamics of irreversible processes and nonlinear dynamics (synergetics).

In short description of the examples for dissipative structure occurrence—Benar's cells and cell separation, it has been mentioned earlier that the action of systems in critical conditions in both cases is a benefit for them: liquid flow along the hexagonal cells allows including additional convective mechanism of heat exchange with environment; separation of the cell into two saves it from "death."

We also consider that the realization of the fatigue failure according to the consequent stages, changing deformation type from "tension" into "bending" and from "bending" into "compression" at the continuous mechanical impact is a benefit to the asphalt concrete pavement, as:


Such staged failure with consequential change of deformation type prolongs the existence time ("life cycle") of separate parts of the asphalt concrete pavement.

The formulated principle can be visually demonstrated by the bifurcation scheme proposed (**Figure 14**).

In thermodynamics and synergetics, it is accepted to consider that the system away from the equilibrium condition acquires new properties. The system in the strong nonequilibrium condition becomes more active and all substructural elements of the system work jointly, consistently, fluctuations are synergized and new structures occur at the critical moment [18–26, 48]. In addition, the system has a choice in critical conditions—what scenario of evolution to follow further.

In accordance with the proposed bifurcation scheme, the asphalt concrete pavement works as continuous medium under scheme of volumetric stressed-deformed condition since the moment of starting of operation to the moment of losing of the tension resistance (0–1). At the time moment of the complete losing of the tension resistance (point 1), the thermodynamics system (substructural elements of the asphalt concrete pavement) has a choice—which thermodynamics branch (branch А and branch B)—to function further. If the system in point of bifurcation chooses the thermodynamics branch A, the parallel cracks occur on the patch lines in point 1, and the asphalt concrete strips work as a long beam between points 1 and 2, and they are deformed under the scheme of bending. The transverse cracks occur in point 2, long asphalt concrete strips are divided into more short parts, each of the obtained parts for the period of

from other types of cracks, three levels for their development have been determined, but

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77

**2.** Fatigue failure of the asphalt concrete pavement is realized stage by stage. Change of stages for failure occurs under mechanism of self-organization for the substructural elements of the pavement material—asphalt concrete in critical conditions. Similar to the known phenomena of self-organization—Benar's effect and biological cell separation, it is proposed to consider the parts of the asphalt concrete pavement as specific dissipative structures. They work as specific dissipative structures on each stage of the fatigue failure.

**3.** Comparison of the results for the performed and known tests of the asphalt concretes for determination of single loading, cyclic, long-term and residual strength for tension, bending and compression has shown that the strength at bending is always more than at ten-

**4.** The determined staged character of the fatigue failure for the asphalt concrete pavement, possibility in principle for occurrence of dissipative structures in it, dependence of asphalt concrete strength on deformation type (stressed condition), moreover, its increase in the sequence of "tension-bending-compression," and also the existence of residual strength for the asphalt concrete at compression after failure at tension have served as a basis for formulating of a new regularity for the fatigue failure: *fatigue failure of an asphalt concrete pavement under repeated load impact is realized according to the consequently changing stages in every of which pavement parts function as specific dissipative structures with characteristic defor-*

*mation type, which interchange in the sequence of tension-bending-compression.*

[1] CN RK 3.03-19-2006. Design of flexible pavements. Astana; 2007. 87 p

[2] Ivanov NN, editor. Design and Calculation of Flexible Pavements. Moscow: Transport;

[3] Hveem FN. Pavement defections and fatigue failures. Highway Research Board.

[4] Saal RNJ, Pell PS. Fatigue of bituminous road mixes. Kolloid-Zeitschrift. 1960;**171**:61-71 [5] Taylor IF, Pell PS. Could fatigue be a problem in flexible pavements? Roads and road

the relation is not considered between these levels.

sion; and it is more at compression than at bending.

Address all correspondence to: bagdatbt@yahoo.com

Construction. 1969;**47**(560):236-243

Kazakhstan Highway Research Institute, Almaty, Kazakhstan

**Author details**

Bagdat Teltayev

**References**

1973. 328 p

Bulletin 114

**Figure 14.** Bifurcation scheme at fatigue failure of an asphalt concrete pavement.

2–3, work as a short beam, and it is also deformed under the scheme of bending. In point 3, the number of the occurred cracks increases and for the period of 3–4, separate failure fragments of pavement work under scheme of direct compression. Complete failure of the asphalt concrete pavement occurs at the time moment 4. The road section of the highway "Karagandy-Shakhtinsk," described earlier can serve as an example of the practical realization for the fatigue failure of the asphalt concrete pavement according to the thermodynamics branch A.

If the system in point of bifurcation 1 chooses the thermodynamics branch B, then, first, the transverse cracks occur on pavement, then longitudinal fatigue cracks occur between them, and for the period of time 1–5, separate pavement blocks function as big and short slabs, and they are deformed under scheme of bending. Additional transverse and longitudinal cracks occur in point 5, grids of cracks become more intensive until each of the pavement fragments is not deformed under scheme of direct compression (time period 5–6). Complete failure of the asphalt concrete pavement occurs in time moment 6. The road section of the highway located in Sharjah city (UAE) can serve as an example of the practical realization for the fatigue failure of the asphalt concrete pavement under the thermodynamics branch B.
