Performance evaluation of new warm mix asphalt and water stability of its mixture based on laboratory tests
Introduction
Asphalt pavement has the advantages of driving comfort and convenient maintenance, which has been widely applied to highway construction. However, high mixing and compaction temperatures of asphalt mixture require a large amount of energy, and the asphalt emission, dust particle, nitrogen oxide and greenhouse gases will be emitted [1], [2]. Asphalt pavement construction has become one of the industries with high energy consumption and pollutant emissions, which deviates from the social theme of energy conservation and emission reduction in China. The high production temperature also accelerates the aging rate of asphalt and limits the construction time of asphalt pavement at low temperature in cold plateau areas. How to reduce the construction temperature of asphalt mixture without damaging the road performance gradually caught the attention of engineers and technicians. Warm mix asphalt technology reduces the high temperature viscosity of asphalt binder during production, so the construction temperature of warm mix asphalt mixture can be lower by 20 °C–30 °C when compared with hot mix asphalt mixture [3]. The low production temperature extends the construction time of asphalt mixture in cold plateau regions, which has good economic and social benefits [4], [5], [6].
For the performance of warm mix asphalt, Zheng et al. [7] studied the influence of warm mix additive on high and low temperature property of SBS high viscosity asphalt and examined the improvement effect of EC-120 on temperature sensitivity. EC-120 is the wax-based additive developed by Haichuan Company, which main component is long-chain aliphatic polymer. Wang et al. [8] investigated the influence of Sasobit, RH and Advera on high temperature rheological property of asphalt rubber. Among which, the main component of RH warm mix additive is polyethylene wax. The rutting resistance of asphalt rubber was enhanced by several warm mix additives. Tan et al. [9] reported that the penetration of asphalt binder decreases due to the addition of Sasobit, and the indexes of softening point and rutting factor increase. Other researchers obtained similar results [10], [11]. Liu et al. [12] revealed that the viscosity of graphene oxide (GO) modified asphalt containing waste cooking oil (WCO) and Sasobit decreases significantly. The difference of high and low temperature properties among different warm mix asphalt is obvious. Roja et al. [13] conducted the shear rate sweep test and steady shear test to reveal the viscosity reduction effect of Evotherm and Sasobit. Yang et al. [14] suggested that Deurex additive significantly reduces the viscosity and enhances high temperature property of SBS modified asphalt. Ferrotti et al. [15] carried out the laboratory tests to evaluate the influence of chemical warm additives on asphalt performance and confirmed that the viscosity susceptibility of polymer modified bitumen (PMB) can be reduced by chemical additive.
For the road performance of warm mix asphalt mixture, Kataware et al. [16] found that the warm mix additives of FT, WB and CS can lower the construction temperatures, and enhance the rutting resistance of asphalt mixture. The similar conclusion was also confirmed by Ghabchi. [17]. Yang et al. [18] discovered that the crumb rubber modified warm mix asphalt mixture (CR-WMA) containing Evotherm has good mechanical property. Saberi et al. [19] revealed that the fatigue resistance and rutting resistance of rubberized asphalt mixtures mixed with high RAP and Sasobit are superior to the control mixture. Roja et al. [20] reported that the wax-based warm mix additive increases the rutting resistance of asphalt mixture, but the chemical-based warm mix additive has some adverse effect. Sanchez-Alonso et al. [21] carried out the static and dynamic tests and found that the mechanical property of asphalt mixture containing silica gel is similar to the mixture mixed with zeolite. Ma et al. [22] confirmed that Sasobit improves the rutting resistance but may damage the low temperature cracking property and moisture resistance of CR-WMA. Rodriguez-Alloza et al. [23] realized that the organic warm mix additives lower the construction temperature of asphalt mixture and have little adverse influence on volume parameter and compaction characteristic.
Warm mix technology significantly improves low temperature workability of asphalt mixture, but the reduced construction temperature may result in the water damage of asphalt pavement. You et al. [24] investigated the moisture susceptibility of foamed asphalt mixture and found that the water damage usually occurs due to the weak interaction between asphalt and aggregate. Yu et al. [25] studied the water stability of CR-WMA containing E3G and the anti-stripping agent was recommended to improve the water stability of asphalt mixture. Kassem et al. [26] also demonstrated that warm mix additive has some adverse influence on interfacial bonding between asphalt and aggregate. Nakhaei et al. [27] evaluated the influence of ethylene-bis-stearamide (EBS) and polyethylene (PE) on water stability of warm mix asphalt mixture and realized that EBS can reduce the water damage of asphalt pavement. Ji et al. [28] found that the asphalt mixture containing organic wax additive of RH is more sensitive to water damage. According to the research report of NCAT (National Center for Asphalt Technology) [29], [30], the mechanical strength of warm mix asphalt mixture decreases significantly under low temperature conditions, and is prone to water damage.
The existing studies confirmed that the warm mix technology significantly reduces the construction temperature of asphalt mixture, but there is also some negative effect on road performance, especially the water stability of asphalt mixture. In addition, the related studies mostly focus on short-term water stability of asphalt mixture, and rarely considered the influence of freeze–thaw cycles on water stability in cold plateau regions. Qualified water stability of warm mix asphalt pavement cannot avoid the water damage such as looseness and stripping in cold plateau regions. The water damage has become the main obstacle to the application of warm mix asphalt technology [31], [32]. Therefore, it is important to develop a kind of new warm mix additive with good road performance. The long-term water stability of warm mix asphalt mixture also needs to be studied by considering the climatic characteristic of freeze–thaw cycles in cold plateau regions.
To confirm the reliability of self-developed ZYF-1 warm mix additive and provide some references for the promotion and application of ZYF-1, firstly, the self-developed warm mix additive of ZYF-1 and commonly used warm mix additives of Sasobit and Aspha-min were selected in the paper. The conventional test and SHRP test of SK90# asphalt and SBS modified asphalt containing different warm mix additives were conducted to analyze the influence of warm mix additive on asphalt performance. The reasonable dosage of ZYF-1 was determined based on the variation of asphalt performance. Then the splitting test and Cantabro test of warm mix asphalt mixture before and after freeze–thaw cycles were conducted to evaluate the long-term water stability. The difference and deterioration law of water stability for warm mix asphalt mixture were also analyzed. Finally, the beam fatigue test and Wheel Tracking test were carried out to verify other road performance of asphalt mixture with ZYF-1.
Section snippets
Asphalt
The SK90# asphalt and SBS modified asphalt were used in this paper. The starting binder of SBS modified asphalt is SK90# asphalt made by SK company in Korea, which penetration varies from 80 dmm to 100 dmm. The modification agent is Styrene-Butadiene-Styrene modifier, and the dosage is 4%. The method of binder mixing with SBS modifier was wet process, which was performed by FLUKO FM300 high shear dispersing emulsifier. The preparation process and parameters of SBS modified asphalt are shown in
Conventional indexes of asphalt
The influence of ZYF-1, Sasobit and Aspha-min on penetration, softening point and ductility of SK90# asphalt and SBS modified asphalt is shown in Table 4.
As shown in Table 4, the penetration of SK90# asphalt and SBS modified asphalt varies to different degrees after the addition of warm mix additives. After mixed with Sasobit and Aspha-min, the penetration of SK90# asphalt and SBS modified asphalt decreases to various extents, and the penetration of asphalt binder containing Sasobit decreases
Conclusions
The performance variation law of SK90# asphalt and SBS modified asphalt after the addition of warm mix additive is consistent. ZYF-1 greatly improves the low temperature property of asphalt and has little adverse effect on high temperature performance. Sasobit and Aspha-min enhance the rutting resistance of asphalt binder, but the two have some adverse influence on low temperature property. Aspha-min and ZYF-1 have little effect on fatigue resistance of asphalt binder, while Sasobit improves
CRediT authorship contribution statement
Ke Zhang: Data curation, Writing - original draft. Yaofei Luo: Conceptualization, Methodology, Supervision, Funding acquisition. : . Fei Chen: Visualization, Investigation, Validation. Feifei Han: Writing - review & editing.
Acknowledgments
The study is supported by National Natural Science Foundation of China (NSFC) (51008031), Provincial Natural Science Foundation of Anhui (1908085QE217, 1908085MF207), Key project of Natural Science Research of Anhui Provincial Department of Education (KJ2018A0668), Open Fund of National Engineering Laboratory of Highway Maintenance Technology (Changsha University of Science & Technology) (kfj180108), Open Fund of Key Laboratory of Road Structure & Material Ministry of Transport (Chang’an
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