Rheological properties of warm mix asphalt binder by DSR test at medium temperature

The rheological properties including the complex modulus G＊ and the phase angle δof matrix and warm mix asphalt （WMA）binders were measured by using the dynamic shear rheometer （DSR ） test at the medium temperature ranging from 16 to 40 ℃,and the relationships between the fatigue factor G＊ sinδand the matrix binder property,WMA additive and test temperature were established.It is found that G＊ decreases with the increasing temperature while δincreases inversely,and G＊ of the asphalt binder with high WMA additive dosage is large,and δis small.G＊sinδexponentially decreases with the increasing temperature and linearly increases with the increase in additive dosage,and the amplitudes of variation are large at low temperatures and high additive dosages.The effect of WMA additive on the rheological property is more remarkable for the matrix asphalt binder with low G＊.Besides,aging has a great effect on the property of matrix asphalt binder,and a slight effect on the interaction between asphalt and additive.The high additive dosage can increase the fatigue cracking potential of the asphalt binder.

Long term performance of warm mix asphalt versus hot mix asphalt

The fatigue behavior, indirect tensile strength （ITS） and resilient modulus test results for warm mix asphalt （WMA） as well as hot mix asphalt （HMA） at different ageing levels were evaluated. Laboratory-prepared samples were aged artificially in the oven to simulate short-term and long term ageing in accordance with AASHTO R30 and then compared with unaged specimens. Beam fatigue testing was performed using beam specimens at 25 ℃ based on AASHTO T321 standard. Fatigue life, bending stiffness and dissipated energy for both unaged and aged mixtures were calculated using four-point beam fatigue test results. Three-point bending tests were performed using semi-circular bend （SCB） specimens at -10 ℃ and the critical mode I stress intensity factor K1 was then calculated using the peak load obtained from the load-displacement curve. It is observed that Sasobit and Rheofalt warm mix asphalt additives have a significant effect on indirect tensile strength, resilient modulus, fatigue behavior and stress intensity factor of aged and unaged mixtures.

Construction Technology of Warm Mix Asphalt Pavement in Cold High-Altitude Areas

With the continuous development of domestic highway construction,highway civil engineering and service level quality have attracted much attention.Good pavement quality and high-quality service make people feel comfortable and smooth when traveling.High-quality pavement can significantly reduce the probability of traffic accidents.At present,there is a direct relationship between pavement quality and pavement construction operations.Carrying out pavement construction operations in cold high-altitude areas requires a reasonable selection of construction equipment and methods.The application of warm-mix asphalt pavement construction technology can ensure pavement quality.Therefore,this paper analyzes the advantages of warm-mix technology,the environmental characteristics of cold high-altitude areas,and construction preparations,and discusses the construction technology of warm-mix asphalt pavement in cold high-altitude areas in detail,to improve the overall road quality of cold high-altitude areas.

Evaluation of asphalt mixture behavior incorporating warm mix additives and reclaimed asphalt pavement

Incorporation of warm mix asphalt （WMA） and reclaimed asphalt pavement （RAP） has benefited the asphalt industry in many ways such as reducing the demand for virgin materials, lowering energy requirement during the asphalt production and construction, in addition to reducing greenhouse-gas emissions. This study evaluated the effects of Evotherm and RH-WMA and RAP on mixtures＇ behavior in terms of the compaction energy index （CEI）, indirect tensile strength （ITS） and resilient modulus. The results showed that warm mix additives reduced the CEI, ITS and resilient modulus; while RAP increased the corresponding values. Statistical analysis showed that mixtures incorporating Evotherm and RAP had significant effects on CEI, while the effects of RH-WMA on the corresponding value were found to be statistically insignificant. General Linear Model showed that Evotherm, RAP and RH-WMA exhibited no significant effects on the ITS and resilient modulus. The one-way analysis of variance showed that Evotherm influenced mixture behavior significantly, while RAP and RH-WMA effects were found to be statistically insignificant. Regression equations with high accuracy levels were proposed to predict CEI, ITS and resilient modulus with respect to modification of mixture variables such as mix constituents （Evotherm, RH-WMA, and RAP） and compaction temperature.

Ageing and performance of warm mix asphalt pavements

This paper presents results from investigating the ageing behaviour and performance of different warm mix asphalt （WMA） pavement mixtures also called energy reduced pavements. The mixtures were either prepared in the laboratory or taken directly from a mixing plant. The study compared the rutting and fatigue behaviours of unaged material in comparison to long term laboratory aged material. In order to conduct the long term ageing, a special laboratory ageing protocol with different heating, cooling and watering cycles had been developed. The investigation revealed a quite controversial rutting behavior which could not be explained with the available data. While most aged energy reduced pavements showed increased rutting for other mixtures, lower rut depths could be found. As opposed to this finding, fatigue and stiffness of all aged energy reduced pave- ment samples compared to unaged samples improved significantly. The overall results led to the conclusion that the ageing of energy reduced pavement simulated in the laboratory is not very critical regarding their mechanical performance. Therefore, it was confrmed that the application of this type of pavement provides a good solution for saving on CO2 emissions. Another advantage is that by using energy reduced pavements the road con- struction season can be significantly prolonged.

Testing and assessing the performance of a new warm mix asphalt with SMC

Warm mix asphalt （WMA} is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. WMA has been widely tested and applied in the USA in the last decade, but it has just started in China. Recently, a new WMA using a new plastic- macromolecule-normal temperature additive, which was called ＂SMC＂ by the production company, was introduced as asphalt modifier. Based on discussing the strength forming process of this new WMA with SMC, a series of laboratory tests, including Marshall stability test （MST）, boiling test （BT）, modified immersion Marshall test （MIMT）, freeze-thaw split- ring test （FTST）, rutting test （RT）, low-temperature bending test （LTBT）, and abrasion loss test （ALT）, were conducted in this study to assess the performance of this WMA and the capability of applying it on low volume roads in China. SMC modified asphalt mixed under normal temperature is used in testing samples. It was found that this WMA product exhibited merits on its strength, which was about 6.7 kN bigger than the requirement of 5.0 kN in the JTG F40-2004, on high-temperature stability, which is about 1100 times/ram greater than the requirement of 600-1000 times/mm in the ）TG F40-2004, and on its storage stability. Based on these indicators, it is recommended that this product could be used for low volume low class roads construction. However, due to the relatively lower water resistance and low-temperature cracking resistance, this product is suggested to be applied first in the areas with warm weather and little rainfall. In order to improve the perfor- mance of this WMA with SMC, further research on this SMC asphalt modifier should be continued.

Warm-Mix Asphalt and Pavement Sustainability: A Review

Within the past two decades or so, the asphalt paving industry has responded positively to increasing global concerns over shrinking natural resource reserves and worsening environmental conditions through the development and deployment of warm-mix asphalt technologies. Such technologies make it possible to produce and place asphalt concrete at reduced temperatures compared to conventional hot-mix methods. Several studies have reported on the potential of warm-mix asphalt with regard to improved pavement performance, efficiency and environmental stewardship. This paper reviews several of those studies in the context of pavement sustainability. Overall, warm-mix asphalt provides substantial sustainability benefits similar to or, in some cases, better than conventional hot-mix asphalt. Sustainability benefits include lower energy use, reduced emissions, and potential for increased reclaimed asphalt pavement usage. Growth in utilization of warm-mix asphalt worldwide may, in the not-too-distant future, make the material the standard for asphalt paving. Regardless, there are concerns over some aspects of warm-mix asphalt such as lower resistance to fatigue cracking, rutting and potential water-susceptibility problems, particularly with mixes prepared with water-based technologies, which require further research to address.

Changes in Mixed Layer Depth and Spring Bloom in the Kuroshio Extension under Global Warming

The mixed layer is deep in January-April in the Kuroshio Extension region. This paper investigates the response in this region of mixed layer depth （MLD） and the spring bloom initiation to global warming using the output of 15 models from CMIP5. The models indicate that in the late 21st century the mixed layer will shoal and the MLD reduction will be most pronounced in spring at about 33~N on the southern edge of the present deep-MLD region. The advection of temperature change in the upper 100 m by the mean eastward flow explains the spatial pattern of MLD shoaling in the models. Associated with the shoaling mixed layer, the onset of spring bloom inception is projected to advance due to the strengthened stratification in the warming climate.

CHARACTERISTICS OF INTRASEASONAL VARIATIONS IN THE MIXED LAYER OF "WARM POOL" AREAS

Observational data obtained during the TOGA-COARE IOP in the "warm pool" area of the West-ern Tropical Pacific were used to analyze some characteristics of the intraseasonal variations in the mixedlayer. The influence of westerly burst and rainfall on SST, salinity. and mixed layer depth are discussed.There are two pairs of counteracting processes in the "warm pool" mixed layer: (1) The increase of mixedlayer depth caused by local westerly bursts and the decrease of mixed layer depth caused by larger scaleeasterly relaxation;(2) the vertical mixing by local wind and the strong stratification due to rainfall in themixed layer. Some possible mechanisms through the interactions between the intraseasonal time scale varia-tions of the oceanic mixed layer and atmospheric low frequency oscillations are revealed.

Warm asphalt rubber:A sustainable way for waste tire rubber recycling

Recycling end-of-life tire rubber as asphalt modifier is known as a sustainable paving technology with merits including enhanced pavement durability,waste tire consumption and noise reduction.However,the criticisms on the high construction emissions of asphalt rubber(AR)have limited its application.Warm mix asphalt(WMA)effectively reduces the mixing and compaction temperatures of conventional hot mix asphalt mixtures.The combination of AR and WMA,called warm asphalt rubber(WAR),is a promising paving material which achieves pavement sustainability from principles to practices.Many studies have demonstrated that WMA technologies work effectively with AR pavement in different ways,alleviating the concerns of potential higher emissions of AR by decreasing mixing and paving temperatures.A comprehensive literature review about WAR brings a better understanding of this promising paving technology.The findings of 165 publications were summarized in this review.It summarized the recent developments of WAR in various aspects,including rheological properties,mix design,mixture mechanical performance,field application,construction emission,and asphalt-rubber-WMA additive interaction.It is expected that this review is able to provide extensive information to explore further research development and application of WAR.

Salinity effects on the 2014 warm “Blob” in the Northeast Pacific

A significant strong, warm “Blob”(a large circular water body with a positive ocean temperature anomaly) appeared in the Northeast Pacific (NEP) in the boreal winter of 2013 2014, which induced many extreme climate events in the US and Canada. In this study, analyses of the temperature and salinity anomaly variations from the Array for Real-time Geostrophic Oceanography (Argo) data provided insights into the formation of the warm “Blob” over the NEP. The early negative salinity anomaly dominantly contributed to the shallower mixed layer depth (MLD) in the NEP during the period of 2012 2013. Then, the shallower mixed layer trapped more heat in the upper water column and resulted in a warmer sea surface temperature (SST), which enhanced the warm “Blob”. The salinity variability contributed to approximately 60% of the shallowing MLD related to the warm “Blob”. The salinity anomaly in the warm “Blob” region resulted from a combination of both local and nonlocal effects. The freshened water at the surface played a local role in the MLD anomaly. Interestingly, the MLD anomaly was more dependent on the local subsurface salinity anomaly in the 100-150 m depth range in the NEP. The salinity anomaly in the 50-100 m depth range may be linked to the anomaly in the 100-150 m depth range by vertical advection or mixing. The salinity anomaly in the 100-150 m depth range resulted from the eastward transportation of a subducted water mass that was freshened west of the dateline, which played a nonlocal role. The results suggest that the early salinity anomaly in the NEP related to the warm “Blob” may be a precursor signal of interannual and interdecadal variabilities.

On the Response of the Global Subduction Rate to Global Warming in Coupled Climate Models

The response of the global subduction rate to global warming was assessed based on a set of Intergovernmental Panel on Climate Change （IPCC） Fourth Assessment Report （AR4） models. It was found that the subduction rate of the global ocean could be significantly reduced under a warming climate, as compared to a simulation of the present-day climate. The reduction in the subduction volume was quantitatively estimated at about 40 Sv and was found to be= primarily induced by the decreasing of the lateral induction term due to a shallower winter mixed layer depth. The shrinking of the winter mixed layer would result from intensified stratification caused by increased heat input into the ocean under a warming climate. A reduction in subduction associated with the vertical pumping term was estimated at about 5 Sv. F^rther, in the Southern Ocean, a significant reduction in subduction was estimated at around 24 Sv, indicating a substantial contribution to the weakening of global subduction.

The Effect of Evotherm on Hot Mix Asphalt

There has been a paradigm shift globally from high combustion rates of all human activities that contribute to global warming. Environmental awareness has been increasing rapidly over the past years. In these regards, Evotherm, which is a Fatty-Amine derivative of the hydrocarbon chain, was investigated and used in the production of asphalt to examine the effect. The overall influence of the admixture and temperature was examined. Seven (7) Laboratory specimens with different additive contents of 0%, 0.25%, 0.5%, 0.75%, 1.0%, 1.25% and 1.5% were produced and compacted at different compaction temperatures of 100°C, 115°C, 130°C, 145°C and 160°C, to evaluate Marshall Stability parameters. The binder content for the control test and admix samples were all kept constant for the range of 5.0%, 5.5%, 6.0%, 6.5% and 7% by weight of total mix for all the trial mixes for proper and uniform observation and also for the determination of the optimal mix for the control and admix samples. For each specimen mix, two (2) Marshall cylindrical samples were compacted at heavy compaction level of 75 blows, which represent heavy traffic category, and the mean result obtained for accuracy. This was done for all the temperature categories. Therefore, for this research work, 350 cylindrical cubes of Marshall Samples were evaluated in the laboratory. The result shows that despite the modification on the asphalt by the Evotherm product, the admixed asphalt exhibited similar engineering properties as Hot Mix Asphalt even at lower temperature of 115°C, and could be used as a first step in the promotion of improved carbon print from Nigerian Asphalt pavements.

Seasonal variability in the thermohaline structure of the Western Pacific Warm Pool

Using the 28℃ isotherm to define the Western Pacific Warm Pool （WPWP）, this study analyzes the seasonal variability of the WPWP thermohaline structure on the basis of the monthly-averaged sea temperature and salinity data from 1950 to 2011, and the dynamic and thermodynamic mechanisms based on the monthly-averaged wind, precipitation, net heat fluxes and current velocity data. A△T=-0.4℃ is more suitable than other temperature criterion for determining the mixed layer （ML） and barrier layer （BL） over the WPWP using monthly-averaged temperature and salinity data. The WPWP has a particular thermohaline structure and can be vertically divided into three layers, i.e., the ML, BL, and deep layer （DL）. The BL thickness （BLT） is the thickest, while the ML thickness （MLT） is the thinnest. The MLT has a similar seasonal variation to the DL thickness （DLT） and BLT. They are all thicker in spring and fall but thinner in summer. The temperatures of the ML and BL are both higher in spring and autumn but lower in winter and summer with an annual amplitude of 0.15℃, while the temperature of the DL is higher in May and lower in August. The averaged salinities at these three layers are all higher in March but lower in September, with annual ranges of 0.41-0.45. Zonal currents, i.e., the South Equatorial Current （SEC） and North Equatorial Counter Current （NECC）, and winds may be the main dynamic factors driving the seasonal variability in the WPWP thermohaline structure, while precipitation and net heat fluxes are both important thermodynamic factors. Higher （lower） winds cause both the MLT and BLT to thicken （thin）, a stronger （weaker） NECC induces MLT, BLT, and DLT to thin （thicken）, and a stronger （weaker） SEC causes both the MLT and BLT to thicken （thin） and the DLT to thin （thicken）. An increase （decrease） in the net heat fluxes causes the MLT and BLT to thicken （thin） but the DLT to thin （thicken）, while a stronger （weaker） precipitation favors thinner （thicker） MLT but thicker （thinner） BLT and DLT. In addition, a stronger （weaker） NECC and SEC cause the temperature of the three layers to decrease （increase）, while the seasonal variability in salinity at the ML, BL, and DL might be controlled by the subtropical cell （STC）.

温拌SBS改性再生沥青混合料的路用性能研究

为研究再生SBS改性沥青混合料(RAP)掺量和温拌剂种类对温拌SBS改性再生沥青混合料的路用性能的影响,通过车辙试验、小梁弯曲试验和冻融劈裂试验分析了在RAP掺量为0,10%,30%,50%,Sasobit温拌剂掺量为3.0%和Evotherm温拌剂掺量为2.0%的温拌SBS改性再生沥青混合料的高温稳定性能、低温抗裂性能和水稳性能,并通过灰色关联度分析RAP掺量对两种温拌再生沥青混合料路用性能的影响。结果表明,RAP的掺入可以极大地改善温拌再生沥青混合料的高温性能,但不利于其低温抗裂性能和水稳定性能。不同RAP掺量的沥青混合料对各项路用性能影响程度大小排序均为:水稳定性能<低温抗裂性能<高温稳定性能。在RAP掺量为30%时,掺入Evotherm温拌剂的再生沥青混合料的高温性能、低温抗裂性能、水稳定性能优于掺入Sasobit温拌剂的再生沥青混合料。

Warm water wake off northeast Vietnam in the South China Sea

Due to orographic blockage, a weak wind wake occurs in summer off northeast Vietnam in the South China Sea. Under the wind wake, warm water is observed from both high-resolution satellite data and hydrographic observations. The wake of warm water forms in June, continues to mature in July and August, starts to decay in September, and disappears in October. The warm water wake also shows robust diurnal variation – it intensifies during the day and weakens in the night. Warm water wakes can be generated through wind-induced mixing and thermal（latent heat flux） processes. In this paper, a mixed layer model is used to evaluate the relative importance of the two processes on seasonal and diurnal timescales, respectively. The results demonstrate that thermal processes make a greater contribution to the wake than wind-induced mixing processes on a seasonal timescale, while the warm water wake is dominated by wind-induced mixing processes on a diurnal timescale.

沥青温拌技术分类及温拌效果的试验评价方法

沥青温拌技术日益广泛应用于路面工程,为了定量评价温拌沥青混合料在拌和生产过程中的温拌效果,提供试验评价方法,本研究自主开发了一种沥青混合料变速拌和试验装置,采用70^(#)基质和SBS改性两种沥青、自主研发的一种表面活性剂型沥青温拌剂(取名为Alube)和一种有机降黏型沥青温拌剂(取名为ACMP),以市场成熟产品Evotherm为参照,分别制备了温拌沥青及其AC-13C型混合料,测试了不同沥青和温拌沥青的三大指标、布氏黏度和动态剪切流变指标,分析了沥青的黏温曲线特性,通过混合料的变温击实试验和变速拌和试验,研究了沥青混合料的压实特性和拌和流动特性,提出了沥青混合料的拌和流动模型。研究结果表明,有机降黏型温拌剂减小了沥青的黏度,增大了沥青的流动性,改变了沥青的技术性能,如针入度、延度、相位角等增大,软化点、布氏黏度等减小,而表面活性剂型温拌剂不改变沥青的基本技术性能;黏温曲线法仅可表征有机降黏型温拌沥青的温度变化,等黏温度降低约9℃,变温击实法和变速拌和法则可以同时表征两大类温拌剂的温拌效果;沥青混合料的拌和流动性服从宾汉黏塑性模型,从流变理论上解答了混合料的拌和流动性及和易性,推荐采用变速拌和试验来评价温拌沥青混合料的温拌效果;综合考察现有沥青温拌技术可知,在常用温拌剂掺量下,温拌沥青的生产拌和温度可比热拌沥青混合料低20~30℃,符合常规认识。

SMC再生SBS沥青的流变性能和微观特性研究

【目的】探究新型温拌再生剂甲基苯乙烯共聚物(styreneic methyl copolymer,SMC)对老化苯乙烯系热塑性弹性体(styrene butadiene styrene,SBS)改性沥青的再生效果和再生机理。【方法】首先,在室内制备不同老化程度的沥青。然后,采用SMC再生剂对不同老化程度的SBS改性沥青进行再生。接着,对再生后的SBS改性沥青进行动态剪切流变和低温弯曲蠕变试验,以评价其流变性能。最后,开展红外光谱试验以揭示其作用机理,进行电镜扫描试验以验证SMC再生剂的再生效果。【结果】SMC再生剂会降低老化SBS改性沥青的车辙因子,降低老化SBS改性沥青的恢复率,同时会使老化SBS改性沥青的低温性能得到极大提升。SMC再生剂未与SBS改性沥青发生化学反应,两者仅为物理共混。同时,SMC再生剂能够弥补沥青因老化产生的裂缝。【结论】SMC再生剂对老化SBS改性沥青具有较好的修复效果,能够为沥青的再生提供一种新的途径。

聚乙烯蜡温拌再生沥青性能研究

聚乙烯蜡可提升沥青路用性能,同时具有良好的经济效益而受到研究人员的广泛关注。选取新聚乙烯蜡(NPEW)与回收聚乙烯蜡(RPEW)按照等比混掺的方式作为温拌剂(PEW),将PEW与再生剂(LBS)加入新旧共混沥青中制备了聚乙烯蜡温拌再生沥青,其中新旧共混沥青中分别含20%、30%、40%的老化SBS改性沥青(AAM),用于模拟实际路面再生过程中旧沥青比例。通过沥青三大指标、布氏黏度对不同PEW及AAM掺量下温拌再生沥青的感温性能、高低温性能及降黏效果进行分析。结果表明,AAM和PEW的添加可减少温拌再生沥青的温度敏感性;当温拌再生沥青中AAM掺量一定时,随着PEW掺量的增加,高温抗变形能力,低温抗裂性能均有显著提升;当温拌再生沥青中AAM掺量较低时,PEW的掺入可有效降低黏度;当AAM掺量30%,PEW掺量2%时,温拌再生沥青兼具最佳的路用性能及经济效益。

温拌再生沥青砂浆二次老化前后抗反射开裂性能评价

为研究温拌再生沥青路面的抗反射开裂性能,结合Overlay Tester(OT)试验与数字图像相关(Digital Image Correlation,DIC)技术,研究了长期老化后废旧沥青混合料(Reclaimed Asphalt Pavement,RAP)掺量对温拌再生沥青砂浆抗反射开裂性能的影响。研究结果表明:经过二次老化后,RAP掺量对温拌再生沥青砂浆的抗反射开裂性能影响显著,二者成负相关关系;在相同的老化条件下,不同RAP掺量的再生沥青砂浆裂缝扩展规律基本一致,二次老化后再生沥青砂浆的反射裂缝在初期开裂速度加快。