# Steady-State Creep of Asphalt Concrete

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Bitumen

#### 2.2. Asphalt Concrete

#### 2.3. Sample Preparation

#### 2.4. Test

## 3. Results and Discussion

#### 3.1. Creep Curve

#### 3.2. Steady-State Creep

_{1}< t ≤ t

_{2}).

#### 3.3. Defining Relations for Steady-State Creep of Asphalt Concrete at Complex Stressed Condition

_{хх}> 0, σ

_{yy}= σ

_{zz}= σ

_{хy}= σ

_{yz}= σ

_{zx}= 0. Therefore, from Equation (13), we have

## 4. Conclusions

- -
- For creep curve stage II, the asphalt concrete deformation occurred at a constant rate. The strain rate for this stage is dependent on the stress, and this dependence is satisfactorily described by a power function. The stress has a great influence on the strain rate where the increase of stress by one order increases the strain rate approximately by four orders;
- -
- The dependences were constructed for the start point, end point, and the duration of the stage of steady-state creep on the stress. The stress also impacts greatly on the specified time characteristics, where the increase of stress by one order increases these characteristics for 4.3–4.5 orders;
- -
- The values of viscosity for asphalt concrete were determined at various stresses. The dependence was defined for viscosity on the stress and can also be satisfactorily described by a power function. In particular, the increase of stress by one order reduces the viscosity by three orders;
- -
- Assuming that asphalt concrete is an incompressible material, then the stress deviator is proportional to the strain rate deviator. Hence, there is a functional relationship between the stress intensity and the strain rate intensity, which does not depend on the type of stress condition. The defining relations were formulated for the steady-state creep of asphalt concrete under complex stressed conditions.

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 14.**Curve of asphalt concrete strain during cyclic loading, green line: creep under load; blue line: recovery of strain after unloading; red cross: failure.

**Figure 15.**Plastic strains (the depth of the rut is more than 60 mm) in asphalt concrete layers of the highway “Ekaterinburg-Almaty” (km 1903.1—Karaganda Region, Kazakhstan).

Indicator | Measurement Unit | Requirements of ST RK 1373 | Value |
---|---|---|---|

Penetration, 25 °С, 100 gr, 5 s | 0.1 mm | 101–130 | 104 |

Penetration Index PI | - | −1.0, … ,+1.0 | −0.34 |

Tensility at temperature: | cm | - | - |

25 °С | - | ≥90 | 140 |

0 °С | - | ≥4.0 | 5.7 |

Softening point | °С | ≥43 | 46.0 |

Fraas point | °С | ≤−22 | −25.9 |

Dynamic viscosity, 60 °С | Pa·s | ≥120 | 175.0 |

Kinematic viscosity | mm^{2}/s | ≥180 | 398.0 |

Indicator | Measurement Unit | Requirements of ST RK 1284 [20] | Value | |
---|---|---|---|---|

Fraction 5–10 mm | Fraction 10–20 mm | |||

Average density | g/cm^{3} | - | 2.55 | 2.62 |

Elongated particle content | % | ≤25 | 13 | 9 |

Clay particle content | % | ≤1.0 | 0.3 | 0.2 |

Bitumen adhesion | - | - | satisf. | satisf. |

Water absorption | % | - | 1.93 | 0.90 |

Indicator | Measurement Unit | Requirements of ST RK 1225 | Value |
---|---|---|---|

Average density | g/cm^{3} | - | 2.39 |

Water saturation | % | 1.5–4.0 | 2.3 |

Voids in mineral aggregate | % | ≤19 | 14 |

Air void content in asphalt concrete | % | 2.5–5.0 | 3.8 |

Compression strength at temperature | MPa | - | - |

0 °С | - | ≤13.0 | 7.0 |

20 °С | - | - | 3.4 |

50 °С | - | ≥1.3 | 1.4 |

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**MDPI and ACS Style**

Iskakbayev, A.; Teltayev, B.; Oliviero Rossi, C.
Steady-State Creep of Asphalt Concrete. *Appl. Sci.* **2017**, *7*, 142.
https://doi.org/10.3390/app7020142

**AMA Style**

Iskakbayev A, Teltayev B, Oliviero Rossi C.
Steady-State Creep of Asphalt Concrete. *Applied Sciences*. 2017; 7(2):142.
https://doi.org/10.3390/app7020142

**Chicago/Turabian Style**

Iskakbayev, Alibai, Bagdat Teltayev, and Cesare Oliviero Rossi.
2017. "Steady-State Creep of Asphalt Concrete" *Applied Sciences* 7, no. 2: 142.
https://doi.org/10.3390/app7020142