Abstract
In this paper, the ultra-thin layer (UTL) is defined as the dense framework structure mixture made of asphalt binder, fine aggregate with nominal maximum aggregate size (NMAS) not greater than 13.2 mm and possible additives (mineral or organic), thickness of 2–4 cm. The study aims to investigate comprehensive performance of UTL asphalt mixture. The method of impact freeze thaw split test and the index of impact freeze–thawing damage degree (IFTDD) are proposed to reflect the durability. The indoor tire-rolling-down test system and accelerated abrasion machine are used to simulate the tire-pavement interaction and test road noise and skid resistance, respectively. Though evaluating the influencing factors (pavement thickness, gradation, asphalt binder type, and the content of KS additive) on durability, the optimum parameters with excellent durability are recommended. Combined with the test of noise and skid resistance, the factors affecting the surface function are analyzed. Moreover, the prediction mathematical model of skid resistance and the long-term safety benefit value Eeff are put forward. Results indicate that pavement thickness is the most significant factor effecting on durability, and gradation is the most significant factor affecting noise. Compared with KS additive, gradation has a greater influence on skid resistance index of Texture Depth (TD), whereas, KS additive is the most significant factor affecting British Pendulum Number (BPN). Furthermore, with the addition of asphalt rubber (AR), IFTDD and noise are reduced by 29.17% and 1.6 dB, and BPN and TD increase by 0.7 and 0.03 mm, remarkably. Compared with different asphalt types, the noise of UTL asphalt rubber mixture with 13.2 mm NMAS (UTL13 AR) is the lowest. Additionally, when KS content increases by 0.6%, the noise increases by 3 dB. Furthermore, on the basis of the calculation results of Eeff, UTL13 AR mixture with 0.5% KS has the best long-term benefit of pavement safety and is recommended for field project.
Highlights
In addition to the traditional requirements of rutting resistance, cracking resistance and moisture susceptibility, the durability, safety and environmental protection of pavement are being paid more and more attention
With the addition of asphalt rubber (AR), impact freeze–thawing damage degree (IFTDD) and noise are reduced by 29.17% and 1.6 dB, and British Pendulum Number (BPN) and Texture Depth (TD) increase by 0.7 and 0.03 mm, remarkably
According to the phenomenon that micro cracks appeared on the top of the test piece but the structure at the bottom was complete, it could be inferred that top-down crack was one of the failure forms of ultra-thin layer (UTL) asphalt pavement with reasonable structural strength
Summary
In addition to the traditional requirements of rutting resistance, cracking resistance and moisture susceptibility, the durability, safety and environmental protection of pavement are being paid more and more attention. Tire/road noise is one of the major environmental problems of modern society [1]. How to construct asphalt pavement with excellent using function under limited financial and material resources is one of the main problems faced by highway development. Because of the prominent economic and social benefits and good performance, the thin layer surfacing asphalt pavement has been popularized rapidly. The influence factors of pavement durability are very complex. Traffic load and environmental conditions are the two most important factors. There are many researches on the durability of Materials 2020, 13, 4260; doi:10.3390/ma13194260 www.mdpi.com/journal/materials
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