# Study on the Properties and Benefits of a Composite Separator Layer in Airport Cement Concrete Pavement

^{1}

^{2}

^{3}

^{4}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Experiments

#### 2.1. Micro-Surfacing Ingredients

#### 2.1.1. Emulsified Asphalt

#### 2.1.2. Aggregates

#### 2.2. Resilient Modulus Test

#### 2.3. Shearing Test

^{2}. In the synchronous macadam layer, the amount of emulsified asphalt used was 1.0 kg/m

^{2}. The total coverage rate of macadam in the synchronous macadam layer is 60%. The total thickness of the separator layer was about 20 mm. As soon as the separator layer was finished, a 5 cm thick concrete layer was constructed. Core samples of diameter 150 mm were obtained after 28 days to use as the objects of the shearing test.

#### 2.4. In Situ Erosion Test

## 3. Numerical Simulations

#### 3.1. Model Description

#### 3.2. Resilient Modulus of Separator Layer

#### 3.3. Contact Characteristic

_{S}) and normal stress (S

_{N}) is shown in Equations (2) and (3). The equations show the shear force between the separator layer and concrete consists of two parts. One part is the Coulomb friction proportional to normal pressure. The other part is considered provided by the tension of asphalt. The picture of the fracture interface (Figure 11) shows the contribution of asphalt coherence to the total shear force.

_{S}= 171.44 S

_{N}+ 51.70, R

^{2}= 0.99 (without separator layer. Unit: MPa)

_{S}= 96.02 S

_{N}+ 27.34, R

^{2}= 0.99 (with separator layer. Unit: MPa)

_{s}in the elastic stage can be obtained from the slope of the tested curves. In the stable stage, the k

_{s}is 0, and the shear stress is a fixed number. Another important parameter is the turning point determining whether the shearing relationship has reached a stable state. For Form 1, the turning point is the shearing force of the peak, while for Form 2, the turning point is the relative slide at the intersection of the elastic state and stable stage. Overall, the constitutional relationship was established using k

_{s}, turning point values, and stable shear force. To simplify the model, the k

_{s}in the elastic stage under different normal stress is taken as the same value.

_{s}is the interlayer shear stiffness; Δγ interlayer relative displacement increment.

## 4. Validation of FEM Simulation

^{3}.

^{2}.

## 5. Results and Analysis

#### 5.1. Influence of Separator Layer on the Contraction Stress before Joint Sawing

#### 5.2. Results of In Situ Erosion Test

#### 5.3. Benefit of Separator Layer When Voids Occur

## 6. Benefits on Pavement Longevity

_{cm}is the flexural strength of concrete; σ

_{p}is the calculated concrete tensile stress.

_{ei}is the cumulative loading times of a certain type of aircraft; N

_{ei}is the permissible loading times of a certain type of aircraft.

## 7. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 17.**Maximum tensile stress difference between the “without separator layer-void” condition and “with separator layer-no void” condition.

Properties | Test Results | ||
---|---|---|---|

Micro Surfacing | Synchronous Macadam | ||

Demulsification Speed | Slow-Breaking | Rapid-Breaking | |

Remaining percentage on the sieve (1.18 mm sieve) | 0.45% | 0 | |

Particle charge | Cationic | Cationic | |

Engler viscosity | 5.4 | 17.6 | |

5d storage stability | 7.40% | 0.20% | |

Evaporation residue content | 60% | 65% | |

Evaporation residue properties | Penetration (100 g, 25 °C, 5 s) | 55 | 62 |

Ductility (5 °C) | 14.7 | 23.1 |

Properties | Requirements | Tested Value |
---|---|---|

Coarse aggregate apparent relative density (g/cm^{3}) | ≥2.5 | 2.8 |

Water absorption (%) | ≤3 | 1.4 |

Needle-like particle content (%) | ≤20 | 4.5 |

Fine aggregate apparent relative density (g/cm^{3}) | ≥2.5 | 2.67 |

Ingredients | Wt/% |
---|---|

Emulsified asphalt | 11.0 |

Aggregates | 84.7 |

Water | 3.4 |

Cement (PO32.5) | 0.9 |

Components | Dimensions | Properties |
---|---|---|

Portland cement concrete slab | Regular slab: 5 m × 5 m Length of long slab: 5 m × 50 m~150 m Thickness: 0.36 m | Elastic modulus: 42 GPa Poisson’s ratio: 0.15 Linear expansion coefficient: 10 × 10 ^{−6}/°C |

Cement stabilized macadam | Horizontal dimension: the same as all slabs and joints all together Thickness: 0.36 m | Elastic modulus: 7 GPa Poisson’s ratio: 0.20 |

Subgrade | Elastic foundation (dimension not needed) | Foundation reaction modulus: 70 MN/m^{3} |

Joint | 8 mm wide Spring unit (dimension not needed) | Joint stiffness: 1000 MN/m^{3} (distributed among nodes) |

Separator layer | Horizontal dimension: the same as all slabs and joints all together Thickness: 0.02 m | Elastic modulus: from results of 2.2 Bond to concrete slab: from results of 2.3 Bond to base layer |

Temperature | 0.1 Hz | 0.5 Hz | 1 Hz | 5 Hz | 10 Hz | 20 Hz |
---|---|---|---|---|---|---|

0 °C | 748 | 826 | 878 | 944 | 978 | 1010 |

10 °C | 491 | 561 | 596 | 665 | 685 | 714 |

20 °C | 383 | 439 | 460 | 517 | 549 | 585 |

30 °C | 280 | 312 | 355 | 391 | 433 | 460 |

40 °C | 176 | 203 | 221 | 260 | 281 | 303 |

Interlayer | Load Location | Measurement Location | Strain from Measurement (με) | Strain from Simulation (με) | Error (%) |
---|---|---|---|---|---|

With separator layer | Middle of longitudinal joint | Slab top | 6.5 | 6.97 | 7.2 |

Slab bottom | −8.0 | −8.47 | 5.9 | ||

Corner of slab | Slab top | 4.5 | 4.78 | 6.2 | |

Slab bottom | −6.0 | −6.10 | 1.7 | ||

No separator layer | Middle of longitudinal joint | Slab top | 6.5 | 6.31 | 2.9 |

Slab bottom | −8.0 | −7.78 | 2.8 | ||

Corner of slab | Slab top | 5.0 | 4.66 | 6.8 | |

Slab bottom | −6.5 | −5.96 | 8.3 |

Void Location | Load Transfer Ability (Joint Stiffness) | Maximum Tensile Stress (MPa) (Without Separator Layer-Void) | Maximum Tensile Stress (MPa) (With Separator Layer-No Void) |
---|---|---|---|

Slab edge | Good (1500 MN/m^{2}) | 2.702 | 2.610 |

Fair (1000 MN/m^{2}) | 2.981 | 2.857 | |

Poor (250 MN/m^{2}) | 3.236 | 3.089 | |

Very bad (25 MN/m^{2}) | 3.301 | 3.154 | |

Slab corner | Good (1500 MN/m^{2}) | 1.746 | 1.543 |

Fair (1000 MN/m^{2}) | 1.986 | 1.560 | |

Poor (250 MN/m^{2}) | 2.750 | 1.584 | |

Very bad (25 MN/m^{2}) | 3.371 | 1.590 |

Airplane Type | Scenario | Permissible Loading Times |
---|---|---|

B737-800 | No separator layer + no voids | 5760521 |

No separator layer + voids | 1776803 | |

Separator layer + no voids | 3274549 | |

B767-300 | No separator layer + no voids | 95138211 |

No separator layer + voids | 25018911 | |

Separator layer + no voids | 44012764 | |

B777-200 | No separator layer + no voids | 2272068 |

No separator layer + voids | 617682 | |

Separator layer + no voids | 1086613 |

With Separator Layer | Without a Separator Layer—Assume Voids Appear Beneath the Slab in a Specific Year after the Pavement Construction | |||||||
---|---|---|---|---|---|---|---|---|

2nd Year | 10th Year | 11th Year | 15th Year | 20th Year | 22nd Year | 25th Year | ||

Pavement Life (years) | 35 | 29 | 30 | 31 | 32 | 33 | 34 | 35 |

Extra life | - | 6 | 5 | 4 | 3 | 2 | 1 | 0 |

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**MDPI and ACS Style**

Lu, H.; Zhao, C.; Yuan, J.; Yin, W.; Wang, Y.; Xiao, R.
Study on the Properties and Benefits of a Composite Separator Layer in Airport Cement Concrete Pavement. *Buildings* **2022**, *12*, 2190.
https://doi.org/10.3390/buildings12122190

**AMA Style**

Lu H, Zhao C, Yuan J, Yin W, Wang Y, Xiao R.
Study on the Properties and Benefits of a Composite Separator Layer in Airport Cement Concrete Pavement. *Buildings*. 2022; 12(12):2190.
https://doi.org/10.3390/buildings12122190

**Chicago/Turabian Style**

Lu, Hang, Ce Zhao, Jie Yuan, Wei Yin, Yanhai Wang, and Rui Xiao.
2022. "Study on the Properties and Benefits of a Composite Separator Layer in Airport Cement Concrete Pavement" *Buildings* 12, no. 12: 2190.
https://doi.org/10.3390/buildings12122190