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Open AccessArticle

The Rejuvenating Effect in Hot Asphalt Recycling by Mortar Transfer Ratio and Image Analysis

State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
Hebei Reach Traffic Engineering Consulting Co., Ltd., Shijiazhuang 050010, China
School of Resource and Civil Engineering, Wuhan Institute of Technology, Wuhan 430073, China
Authors to whom correspondence should be addressed.
Academic Editor: Marco Morreale
Materials 2017, 10(6), 574;
Received: 9 January 2017 / Revised: 17 May 2017 / Accepted: 17 May 2017 / Published: 24 May 2017
Using a rejuvenator to improve the performance of asphalt pavement is an effective and economic way of hot asphalt recycling. This research analyzes the rejuvenating effect on aged asphalt by means of a Mortar Transfer Ratio (MTR) test, which concerns the ratio of asphalt mortar that moves from recycled aggregates (RAP aggregates) to fresh added aggregates when aged asphalt is treated with a regenerating agent and comes into contact with fresh aggregates. The proposed MTR test analyzes the regeneration in terms of the softening degree on aged asphalt when the rejuvenator is applied. The covered area ratio is studied with an image analyzing tool to understand the possibility of mortar transferring from RAP aggregates to fresh aggregates. Additionally, a micro-crack closure test is conducted and observed through a microscope. The repairing ability and diffusion characteristics of micro-cracks can therefore be analyzed. The test results demonstrate that the proposed mortar transfer ratio is a feasible way to evaluate rejuvenator diffusion during hot recycling. The mortar transfer ratio and uncovered area ratio on fresh aggregates are compatible, and can be used to quantify the contribution of the rejuvenator. Within a certain temperature range, the diffusing effect of the rejuvenator is better when the diffusing temperature is higher. The diffusion time of the rejuvenator is optimum when diffusion occurs for 4–8 h. When the rejuvenator is properly applied, the rough and cracking surface can be repaired, resulting in better covered aggregates. The micro-closure analysis visually indicates that rejuvenators can be used to repair the RAP aggregates during hot recycling. View Full-Text
Keywords: rejuvenator; mortar transfer ratio; micro-cracks; preventive maintenance rejuvenator; mortar transfer ratio; micro-cracks; preventive maintenance
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MDPI and ACS Style

Wang, F.; Wang, Z.; Li, C.; Xiao, Y.; Wu, S.; Pan, P. The Rejuvenating Effect in Hot Asphalt Recycling by Mortar Transfer Ratio and Image Analysis. Materials 2017, 10, 574.

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