磨碎玻纤增强环氧树脂应变片基底材料的研究

以表面改性的磨碎玻纤为增强材料制备了环氧树脂薄膜作为传感器应变片的基底材料。考察了玻纤表面改性及添加量对材料性能的影响。结果表明,随着偶联剂用量、玻纤填充量的增加材料的拉伸强度和拉伸模量均先增大后减小。薄膜微结构表明,填充20wt%的改性玻纤增强材料中纤维能够更好的分散在树脂中,玻纤在材料内部比较集中的区域能够互相交叠。随着改性玻纤含量的增加材料的玻璃化温度和抗蠕变性能明显改善。结果证实,填充20wt%的1wt%KH-550偶联剂改性的磨碎玻纤的增强环氧树脂材料具有最佳的力学强度、耐热性和抗蠕变性能。     

可扩链双马来酰亚胺对聚氨酯-环氧树脂基体的改性及性能表征

采用可扩链的双马来酰亚胺(BMI)和聚氨酯改性环氧树脂在4，4’-二氨基二苯基甲烷存在下固化制备了MBI改性聚氨酯-环氧树脂内部交联网络聚合物，通过红外光谱分析证实了聚氨酯在环氧骨架上的接枝，并对改性材料的力学性能、热性能和形态学进行了研究。由力学性能及热性能的研究结果表明聚氨酯与环氧树脂的复合提高了环氧树脂的机械强度，但同时也降低了玻璃化转变温度和热稳定性，而BMI与聚氨酯-环氧树脂体系的复合提高了材料的热稳定性、拉伸强度和弯曲强度，降低了材料的冲击强度和玻璃化转变温度。我们还利用扫描电子显微镜分别研究了聚氨酯改性环氧树脂和可扩链的BMI改性聚氨酯-环氧树脂体系的表面形态。     

可膨胀石墨对环氧树脂的阻燃改性

本文利用环氧树脂E-51和固化剂聚醚胺WHR-H023(质量比为3∶1)制成树脂基体。采用H_2SO_4和HNO_3对颗粒尺寸为80目的可膨胀石墨进行表面酸化处理,制备亲水性酸化可膨胀石墨;并将酸化处理的可膨胀石墨及未经酸化处理的可膨胀石墨分别对上述树脂基体进行阻燃改性,石墨添加量为5%、10%和15%。借助红外光谱分析仪检测酸化处理的可膨胀石墨表面羧基、羟基等官能团的接枝情况;利用极限氧指数分析仪和万能材料试验机分别测试改性树脂基体材料的极限氧指数(LOI)及拉伸性能;采用扫描电子显微镜(SEM)观察改性树脂基体材料的断面。研究结果表明,酸化可膨胀石墨比未经酸化处理的可膨胀石墨对环氧树脂基体的阻燃效果更佳,且拉伸性能下降更少。     

水性环氧树脂乳化沥青在高温、低温和浸水条件下的粘结性能

以水性环氧树脂(WER)为改性剂,通过其与固化剂的物理-化学交联反应对乳化沥青进行改性,制备成一种理想的路面粘层材料——水性环氧树脂乳化沥青(WEREA)。采用剪切和拉拔试验,在不同温度、层间纹理和浸水时间条件下,将不同WER掺量的WEREA与普通乳化沥青和SBS改性乳化沥青进行对比试验,研究了WEREA的高温、低温和浸水粘结性能。结果显示,在试验研究范围内,随着WER掺量的增加,WEREA的层间性能显著改善;温度越高,粘层材料粘结性越差,但高温、低温条件下,WEREA的抗剪、抗拉强度均大于对照试验组。可以认为,WER通过交联作用有效改善了粘层材料的强度和层间粘附性,减缓了WEREA粘结性随浸水时间延长而降低的速率,显著提高了粘层材料的浸水粘结性。     

水性环氧乳化沥青桥面防水粘结层的性能研究

为保证粘层材料具有足够的力学强度、防水性能以及与铺装层较好的变形协调能力,研制了一种高粘结水性环氧乳化沥青防水粘层材料.制备4种不同环氧掺量的粘层材料,试验研究-15,0,25,50,70℃5种温度下粘层材料试件的拉拔、剪切以及断裂拉伸等力学性能的变化规律,并对比分析了水性环氧乳化沥青、乳化沥青稀浆封层、AC-5沥青砂和4.75 mm同步碎石4种常用防水粘层材料的渗水性能.结果 表明:环氧树脂含量对水性环氧乳化沥青粘层材料的断裂拉伸性能、剪切和拉拔性能影响显著,低环氧树脂掺量的粘层材料对温度敏感程度更高,且随着试验温度的升高其力学性能逐渐降低.层间界面的材质和粗糙程度对粘结效果影响较大,新粘层材料用于沥青混凝土和水泥混凝土界面的粘结效果明显优于钢质材料的界面粘结,拉拔强度提高3倍,剪切强度提高1倍.在70 cm水头高度下测试水性环氧乳化沥青粘层材料不渗水,明显优于其他3种材料的渗水性能.开发的高粘结水性环氧乳化沥青防水粘层材料具有良好的力学性能和抗渗水性.     

受阻酚封端聚氨酯/环氧树脂共混物阻尼材料的结构与性能EI北大核心CSCD

制备了系列受阻酚封端聚氨酯/环氧树脂(EP)共混物阻尼材料,研究了组成比和云母对共混物动态力学性能和拉伸性能的影响。结果表明,EP的加入显著拓宽了阻尼温域和改善了阻尼性能,随着EP用量的增加,共混物的拉伸强度显著增加,但断裂伸长率降低。加入填料云母后,材料的阻尼性能和拉伸性能均有所提升。     

沥青路面超疏水抗凝冰涂层设计及性能

超疏水涂层具有超强的疏水性能,用于沥青路面表面可以延缓路面结冰,具有良好的抗凝冰效果,但涂层存在易脱落、耐磨性差的缺点,导致融冰雪功能耐久性不足.为了提高超疏水抗凝冰涂层的表面稳定性和耐久性,本工作采用"功能层+粘结层"的复合式设计方案,通过试验研究了功能层和粘结层的材料构成及配比,并对复合式涂层的抗凝冰效果和表面稳定性进行了试验和评价.通过研究和分析,建议功能层采用疏水SiO2和Fe3 O4进行纳米复合改性,以改善超疏水涂层耐磨性差及易反光的问题,并基于接触角和滚动角的测试结果,推荐抗磨耗填料SiO2和颜色调配料Fe3 O4的最佳掺量分别为涂层浆体质量的2％和2.5％;建议粘结层采用环氧树脂混合体系以提高涂层与路面的附着力,并基于附着力试验结果,确定了混合体系中环氧树脂、固化剂及环氧增韧剂的最佳质量比为2:1:0.2.同时,通过SEM分析了各层的微观形貌,阐述了各层材料的作用机理.最后,复合式超疏水抗凝冰涂层的路用性能测试结果表明,复合式涂层稳定性和耐久性好,能够抵抗动水冲刷和冻融循环,且具有良好的抗凝冰性能.     

化学处理和吸湿水对剑麻纤维及其与树脂界面性能的影响

使用KMnO₄、NaOH、阻燃剂、硅烷对剑麻纤维进行表面处理。采用单丝拉伸和微脱粘方法分别测试了剑麻纤维的拉伸性能及其与改性丙烯酸酯、环氧树脂的界面性能,考察了吸湿水对剑麻纤维表面形貌、拉伸性能及其与树脂界面粘结的影响,分析了相应的破坏模式。结果表明,经过表面化学处理后剑麻纤维的拉伸强度和模量均有不同程度的下降,其中经KMnO₄和硅烷处理后,纤维拉伸强度下降了44%,经NaOH处理后其拉伸强度降低了27%,阻燃剂处理对剑麻性能的影响不明显。表面化学处理还会降低剑麻纤维与改性丙烯酸酯的界面粘结强度,其下降的幅度与纤维拉伸强度下降程度不一致,阻燃剂处理的剑麻/改性丙烯酸酯的界面强度最低,仅为2.0 MPa,较未处理剑麻纤维复合体系下降了80%。经硅烷处理后,剑麻纤维的吸水率下降,吸水后其拉伸性能保留率高于未处理剑麻纤维。湿态条件下未处理剑麻纤维与环氧树脂的界面强度为6.6 MPa,高于硅烷处理剑麻/环氧树脂的界面强度,其断口形貌表明硅烷处理可导致微纤之间的弱粘结,从而降低了剑麻纤维自身及其与树脂的界面性能。     

新型快通修补材料与道面混凝土基材粘结性能研究

为解决现有道面混凝土修补结构在使用一段时间后粘结面易出现裂缝,进而造成修补混凝土损坏的问题,该文综合考虑修补材料的表面粗糙度、粘结剂和养护龄期等因素,对一种新型混凝土路面快速修补材料的适用性和使用性能进行评价。设计三因素四水平正交试验进行系统研究,用劈裂抗拉试验和直剪试验测定复合试样的粘结强度。通过分析试样的剪切滑移特性,了解组合试件的实际粘结性能。结果表明,劈裂抗拉强度为1.21～2.43 MPa,直剪强度为2.84～5.92 MPa,粘结强度与表面粗糙度和养护龄期有较好的相关性;高表面粗糙度混凝土的滑移距离几乎是低表面粗糙度混凝土的3倍。该文研究的快速修补材料具有与旧混凝土良好的粘结性能,能够在早期产生较高的粘结强度,满足机场道面快速修补的要求。     

环氧树脂复合材料的制备及隔声性能

以硅烷偶联剂改性的空心玻璃微珠(HGB)为功能填料,端羧基液体丁腈橡胶(CTBN)为增稠剂和增韧剂,环氧树脂为基体,甲基六氢苯酐为固化剂,2-乙基-4-甲基咪唑为促进剂,通过自转/公转搅拌机将混合物混匀、脱泡处理,再经过改变温度的分段固化技术制备了环氧树脂/端羧基丁腈橡胶/空心玻璃微珠(EP/CTBN/HGB)复合材料,并研究了复合材料的隔音性能。实验结果表明,CTBN和HGB均能提升EP材料的隔音性能,CTBN填充量为12%的EP/CTBN比纯EP的平均隔音量高115%,而填充30%HGB的EP/CTBN/HGB复合材料的平均隔音量又较EP/CTBN提高了30%。在填料和CTBN的添加量及试样厚度均相同的条件下,添加空心玻璃微珠的环氧基复合材料的隔音性能优于实心玻璃微珠复合材料。     

Experimental investigation on skid resistance of asphalt pavement under various slippery conditions

The skid resistant performance of slippery pavement is one of the most important pavement surface characteristics, as it is associated with both pavement serviceability and traffic safety. Through simulating different pavement conditions in the freezing laboratory, skid resistance of asphalt pavement under various slippery conditions is measured with pendulum friction coefficient tester. Then, the effects of pavement temperature on skid resistance of dry, wet, icing and snowy pavements are quantitatively analysed. Furthermore, factors exerting effects on test results are taken into account, such as thicknesses of ice and water film on pavement. Through quantitative analysis, empirical evaluation model of pavement friction coefficient (PFC) under different conditions is established. To facilitate practical engineering application, reference standard values of PFC are recommended. Finally, the PFC is classified into seven levels, which illustrates the corresponding relationships of friction rank, skid resistance assessment, PFC range and pavement conditions.     

Development of degradation model for urban asphalt pavement

There is a lack of a profound understanding of urban pavement deterioration pattern. This is due to the complexity of traffic conditions and the variety of pavement structures in urban roads. The lack of a suitable deterioration model for the urban pavements limits the possibility of making any scientific and cost-effective repair and maintenance strategy. There is a need for a better understanding of the long-term behaviour of urban pavements by which predictive pavement condition models can be derived and consequently a suitable maintenance management system can be built. In response to this need, a comprehensive field study was performed in three Iranian cosmopolitan cities. Pervasive pavement damages were defined and an urban pavement condition index was established. A deterioration model was developed by monitoring and analysing the conditions of road pavements in a period of four years. This model varies as the structural and loading conditions of the pavement change. The efficiency and practicability of the model in predicting the conditions of the pavements were illustrated.     

绿色道路胶凝材料的研究现状及发展趋势

主要介绍了国内外公路的发展现状,通过对水泥路面和沥青路面的比较,以及对水泥工业发展、沥青资源利用和碱胶凝材料研究进展的分析,浅谈了绿色道路胶凝材料的发展趋势.充分利用工业废渣制备性能优良的道路胶凝材料,符合科学发展观的原则,符合推动资源节约型和环境友好型行业建设,实现交通可持续发展的战略.     

Back-calculation of transition probabilities for Markovian-based pavement performance prediction models

This paper presents a new technique to estimate the transition probabilities used in the Markovian-based pavement performance prediction models. The proposed technique is based on the ‘back-calculation’ of the discrete-time Markov model using only two consecutive cycles of pavement distress assessment. The transition probabilities, representing the pavement deterioration rates, are the main elements of the Markov model used in predicting future pavement conditions. The paper also presents a simplified procedure for evaluating the pavement state of distress using the two major pavement defect groups, namely cracking and deformation. These two defect groups are to be identified and evaluated for pavement sections using visual inspection and simple linear measurements. The extent of these two major defect groups is measured using the defected pavement areas (or lengths) and the defect severity is measured based on the average crack width and average deformation depth. A case study is presented to demonstrate the ‘back-calculation’ of transition probabilities. In particular, the impacts of the pavement section length on the distress rating and on the estimation of the transition probabilities have been investigated. The results have indicated that the estimated transition probabilities become highly unstable as the section length gets larger and the sample size becomes smaller.     

An assessment of the skid resistance effect on traffic safety under wet-pavement conditions

Pavement-tire friction provides the grip that is required for maintaining vehicle control and for stopping in emergency situations. Statistically significant negative correlations of skid resistance values and wet-pavement accident rates have been found in previous research. Skid resistance measured with SCRIM and crash data from over 1750 km of two-lane rural roads in the Spanish National Road System were analyzed to determine the influence of pavement conditions on safety and to assess the effects of improving pavement friction on safety. Both wet- and dry-pavement crash rates presented a decreasing trend as skid resistance values increased. Thresholds in SCRIM coefficient values associated with significant decreases in wet-pavement crash rates were determined. Pavement friction improvement schemes were found to yield significant reductions in wet-pavement crash rates averaging 68%. The results confirm the importance of maintaining adequate levels of pavement friction to safeguard traffic safety as well as the potential of pavement friction improvement schemes to achieve significant crash reductions.     

Evaluating pavement management treatment selection utilising continuous deflection measurements in flexible pavements

The objective of this study was to develop a new structural index based on rolling wheel deflectometer (RWD) deflection data to describe pavement structural capacity and to improve pavement management treatment selection. To achieve this objective, pavement conditions including surface cracking, rutting, roughness and asphalt layer thicknesses were categorised and sorted according to their AC layer thickness and divided into various subgroups. The cumulative distribution function of the new RWD index in each subgroup was generated so that various percentiles were calculated and used to define the boundary between structural and functional rehabilitation. Results showed that the Louisiana criteria may recommend structural rehabilitation for pavements with sound pavement structure (Type I error) and functional rehabilitation to pavements with weak pavement structure (Type II error). Therefore, the state pavement management system should consider both pavement structural indices and surface distress indices currently available when making recommendations for pavement preservation and rehabilitation. RWD testing technology and indices derived from its data are one of the most promising candidates to fulfil this need.     

Experimental investigation on preparation and performance of clear asphalt

Abstract

Coloured micro-surfacing technology has become increasingly popular in pavement construction because of its economic benefit and ability to accept traffic quickly. The main goal of this study was to produce a clear asphalt with superior performance that can be easily emulsified. Two types of resin that are easy to emulsify and one kind of extract oil were used to synthesise the clear asphalt. The clear asphalt was mixed with a styrene butadiene styrene (SBS) modifier at different proportions using a mechanical agitator. The physical properties of the samples were determined via conventional bitumen tests and the optimum formula was obtained by changing the mixture ratio through orthogonal experimentation. The thin-film oven test evaluated the ageing property of the clear asphalt. The surface energy components corresponding to the advancing process and the receding process were determined using the Wilhelmy plate method. The surface free energy (SFE) of the aggregates was measured with a gravimetric sorption analyser. The adhesive bond energies between asphalt samples and aggregates were calculated using their SFE components to evaluate their properties of fracture and healing. Results show that depending on the amount and type of resin added, different synthetic clear asphalts can be obtained. Further, the clear asphalt mixed with SBS is capable of synthesising better properties at high or low temperature. The clear asphalt with aggregates had fracture and healing properties similar to common base asphalt.     

Sensitivity of flexible pavement design to Michigan’s climatic inputs using pavement ME design

Climate condition is an important factor that affects the performance of pavements and distress predictions using mechanistic-empirical analyses. This study aims to analyse the sensitivity of flexible pavement distress predictions to climatic inputs using the AASHTOWare Pavement ME Design software in the state of Michigan. Typical traffic parameters, pavement structures and material properties for the state of Michigan were used as inputs for the analysis of flexible pavement performance. Six representative sites geographically distributed throughout Michigan and two typical traffic levels (high and medium) were incorporated in a comprehensive analysis of the effects of climate on flexible pavement performance predictions. A normalised sensitivity index was adopted to quantitatively evaluate the sensitivity of distress predictions to the five individual climatic variables: temperature, wind speed, precipitation, percent sunshine and relative humidity. The results of this study showed that the prediction of flexible pavement performance in Michigan is most sensitive to changes in temperature with other climatic factors such as wind speed, percent sunshine, precipitation and relative humidity impacting predictions to a lesser extent. Higher temperature and percent sunshine at a given location increased rutting and International Roughness Index (IRI) predictions, but reduced the likelihood of fatigue cracking. An increase in wind speed or precipitation reduced rutting and IRI predictions, but increased fatigue cracking predictions. Ambient relative humidity had a negligible effect on all flexible pavement distress predictions. These findings provide insights into the sensitivity of flexible pavement designs under different climate conditions. The sensitivity results are also beneficial for the Michigan Department of Transportation as they seek to improve the existing climatic files in PMED through evaluation of new climatic data sources.     

Multi-scale computational model for design of flexible pavement – part II: contracting multi-scaling

A computational multi-scale procedure for designing flexible pavements is developed in this, the second of a three-part series. In this study, computational analyses are performed on sequentially smaller length scales, termed contracting multi-scaling. The model is constructed by utilising the finite element method on each length scale, thereby creating a one-way coupled multi-scale algorithm that is capable of accounting for the effects of cyclic loading on the initiation and evolution of cracks on multiple length scales within the roadway. For example, the algorithm can be utilised to predict the effects of small-scale design variables such as aggregate volume fraction, as well as the effects of large scale design variables such as asphalt concrete thickness on pavement cracking due to external loading. The model for predicting roadway cracking is briefly described herein, including the experimental properties required to deploy the cracking model within a computational framework. The article concludes with demonstrative examples intended to elucidate the power of this predictive technology for the purpose of designing more sustainable roadways.     

Mechanical and fracture–mechanical properties of geosynthetic reinforced asphalt systems

Geosynthetic interlayers in asphalt systems have become a convenient technology for lifetime prolongation in road construction engineering. Established testing methods for characterizing construction materials can be used to describe and evaluate these innovative systems. This study compares three groups of asphalt interlayer systems (stress absorbing membrane interlayer = SAMI, asphalt reinforcement, SAMI + asphalt reinforcement) represented by 10 different geosynthetic interlayers in terms of crack growth resistance and strength. The results will be presented in relation to asphalt reference systems without interlayer. The mechanical and fracture–mechanical properties were determined by means of the wedge splitting test (WST) according to Tschegg and partially by the pull‐out test. Due to temperature dependences of the material properties of asphalt, the tests have been performed at ?10 °C, 0 °C and +10 °C specimen temperature.