# Developing and Testing of the Principle Prototype for Efficient Micro-Damage Fine Stripping of Asphalt on the Surface of Reclaimed Asphalt Pavement

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## Abstract

**:**

## 1. Introduction

## 2. Structure Design of RAP Surface-Asphalt-Stripping Principle Prototype

#### 2.1. Structural Composition of Asphalt Mixture

#### 2.2. Functional Analysis and Structural Scheme of the Stripping Structure

#### 2.3. Modeling of the Principle Prototype

## 3. Simulation of the Prototype Based on EDEM

#### 3.1. Basic Theory of DEM

#### 3.1.1. Introduction to DEM

#### 3.1.2. Equation of Motion—Newton’s Second Law

#### 3.1.3. Time Step

#### 3.2. Configuration of the DEM Simulation Model

#### 3.2.1. Contact Model Selection

#### 3.2.2. Material and Geometry Parameter Settings

#### 3.2.3. Aggregate Model Setting

#### 3.2.4. Establishment of the Simulation Model

#### 3.3. Numerical Simulation and Analysis

## 4. Test of the Principle Prototype

#### 4.1. Mechanical Test of Single Particle Asphalt Stripping

#### 4.2. Treatment Process of the Principle Prototype

#### 4.3. Test Scheme and Preparation

_{0}and m

_{1}are the masses of coarse aggregates before and after treatment.

## 5. Results and Discussion

#### 5.1. Change in Surface Morphology of Coarse Aggregates

#### 5.2. Changes in Asphalt Content of Coarse Aggregates

#### 5.3. Particle Size Ratio of Each Grade

## 6. Conclusions

- (1)
- The principle prototype with fine aggregate blasting and coarse aggregate self-grinding has a satisfactory treatment effect, which can realize the stripping of asphalt on the surface of coarse aggregates without damaging the grading of coarse aggregates. The reliability of the prototype is also preliminarily verified.
- (2)
- The shot-blasting effect and the self-grinding effect lead to satisfactory asphalt stripping. When the blasting process is not applied, the asphalt-stripping efficiency is low because only the self-grinding contributes. With both processes active, the asphalt content on the aggregate surface can reach the lowest achievable amount in the shortest time.
- (3)
- With the application of the blasting process, increasing the treatment time and projectile size can increase the asphalt-stripping rate and reduce the residual aged asphalt content on the aggregate surface. The effect of 2.36–5 mm projectiles and 60 min treatment is the best; the highest stripping rate can reach 41.5%, and the lowest asphalt content can be reduced to 1.35% after treatment. Considering that the energy consumption of 60 min treatment is doubled compared with a 30 min treatment, while the improvement of the treatment effect is limited, different process parameters should be selected according to the actual working conditions.

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

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**Figure 2.**Structure and working principle. (

**a**) Vertical shaft spiral mixing structure; (

**b**) shot-blasting machine.

**Figure 7.**Velocity of the coarse aggregates in the treatment chamber. (

**a**) Overall velocity of aggregates; (

**b**) X-axis view of aggregate velocity; (

**c**) Y-axis view of aggregate velocity; (

**d**) Z-axis view of aggregate velocity.

**Figure 9.**The stripping test of a single particle asphalt. (

**a**) Test configuration; (

**b**) aggregate comparison before and after asphalt stripping; (

**c**) force and displacement curve of 8 tests; (

**d**) total stripping force in 8 tests.

**Figure 11.**Surface morphology of coarse aggregates before and after treatment. (

**a**) Surface color of coarse aggregates before treatment; (

**b**) surface color of coarse aggregates after treatment.

Material Type | Poisson’s Ratio | Shear Modulus (Pa) | Density (kg/m^{3}) |
---|---|---|---|

Aggregate | 0.25 | 2.3 × 10^{10} | 2700 |

Steel | 0.3 | 7 × 10^{10} | 7850 |

Relation of Contact | Coefficient of Recovery | Coefficient of Static Friction | Coefficient of Sliding Friction |
---|---|---|---|

Aggregate–Aggregate | 0.10 | 0.60 | 0.24 |

Aggregate–Steel | 0.10 | 0.80 | 0.24 |

Specification of Aggregate (mm) | Aggregate Grade Ratio (%) |
---|---|

4.75–9.5 | 30.57 |

9.5–13.2 | 23.65 |

13.2–16 | 29.66 |

16–26.5 | 16.12 |

Scheme | Coarse Aggregates Mass/kg | Projectiles Size/mm | Processing Time/min |
---|---|---|---|

1 | 40 | 0 | 30 |

2 | 40 | 0 | 60 |

3 | 40 | 0–4.75 | 30 |

4 | 40 | 0–4.75 | 60 |

5 | 40 | 2.36–4.75 | 30 |

6 | 40 | 2.36–4.75 | 60 |

Scheme | m_{0}/kg | Projectiles Size/mm | Processing Time/min | m_{1}/kg | P/% |
---|---|---|---|---|---|

1 | 40 | 0 | 30 | 28.45 | 28.88 |

2 | 40 | 0 | 60 | 25.10 | 37.25 |

3 | 40 | 0–4.75 | 30 | 25.40 | 36.50 |

4 | 40 | 0–4.75 | 60 | 23.90 | 40.25 |

5 | 40 | 2.36–4.75 | 30 | 25.00 | 37.50 |

6 | 40 | 2.36–4.75 | 60 | 23.40 | 41.50 |

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**MDPI and ACS Style**

Zhou, L.; Wang, S.; Zhang, J.; Zou, B.; Wang, M.; Zhang, W.; Lv, X.; Meng, D.; Hu, X.; Yao, Z.;
et al. Developing and Testing of the Principle Prototype for Efficient Micro-Damage Fine Stripping of Asphalt on the Surface of Reclaimed Asphalt Pavement. *Machines* **2023**, *11*, 367.
https://doi.org/10.3390/machines11030367

**AMA Style**

Zhou L, Wang S, Zhang J, Zou B, Wang M, Zhang W, Lv X, Meng D, Hu X, Yao Z,
et al. Developing and Testing of the Principle Prototype for Efficient Micro-Damage Fine Stripping of Asphalt on the Surface of Reclaimed Asphalt Pavement. *Machines*. 2023; 11(3):367.
https://doi.org/10.3390/machines11030367

**Chicago/Turabian Style**

Zhou, Long, Shanshan Wang, Jizhe Zhang, Bin Zou, Meng Wang, Wenwu Zhang, Xin Lv, De’an Meng, Xueliang Hu, Zhanyong Yao,
and et al. 2023. "Developing and Testing of the Principle Prototype for Efficient Micro-Damage Fine Stripping of Asphalt on the Surface of Reclaimed Asphalt Pavement" *Machines* 11, no. 3: 367.
https://doi.org/10.3390/machines11030367