嵌入式胶粉复合SBS改性沥青的结构与性能

通过螺杆高温挤出使胶粉预先脱硫降解,然后嵌入分散在苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青中,研究了胶粉的降解程度、种类、含量及交联稳定工艺对复合改性沥青结构与性能的影响.结果表明:降解胶粉易微细化嵌入SBS改性沥青中,明显提高了SBS改性沥青的低温延度和耐老化性能,且不明显增加复合改性沥青的施工黏度.嵌入式胶粉复合SBS改性沥青经过交联稳定后热贮存稳定性能良好.     

耦合老化作用下混合料中SBS改性沥青的老化行为研究

通过动态剪切流变试验(DSR)和弯曲流变试验(BBR),测试了老化前后苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青的复数模量G*、相位角δ、劲度模量S和蠕变速率m,对比研究了热、紫外光、荷载3种环境因素两两耦合老化对SBS改性沥青性能的影响,并用红外光谱(FTIR)分析了经不同耦合老化方式作用后SBS改性沥青的官能团变化情况.结果表明:光热耦合作用对SBS改性沥青老化程度的影响相对严重,其余2种耦合老化下沥青老化程度较小;3种耦合方式对SBS改性沥青官能团的影响不同,光热耦合老化后的沥青主要表现为丁二烯键的断裂和羰基增加,热荷耦合老化主要使沥青中羰基增加,光荷耦合老化主要使沥青中部分丁二烯基的降解和羰基微量增加.     

老化作用下沥青混合料的疲劳及自愈合性能

通过四点弯曲疲劳试验,分析了老化作用下苯乙烯-丁二烯-苯乙烯三嵌段共聚物(SBS)改性沥青混合料和基质沥青混合料的疲劳及自愈合性能.结果表明:老化作用显著削弱了沥青混合料的抗疲劳性能,SBS改性沥青混合料的抗疲劳性能优于基质沥青混合料;老化程度和损伤程度对沥青混合料的自愈合能力影响最为显著;适当延长愈合时间和适宜的愈合温度可以提高沥青混合料的愈合率,但老化程度和损伤程度会削弱其自愈合能力;未老化条件下,基质沥青混合料的自愈合能力大于SBS改性沥青混合料,而老化条件下SBS改性沥青混合料表现出较强的自愈合能力.因此选用SBS改性沥青混合料作为路面材料可以提高沥青路面的抗疲劳及自愈合性能.     

沥青混合料损伤愈合性能的多尺度评价

采用宏观与细观相结合的方法评价了沥青混合料的损伤愈合性能,以半圆弯拉试验为基础,同时使用数字散斑相关法(DSCM)研究了老化程度、损伤度、愈合时间和愈合温度对沥青混合料损伤愈合性能的影响.结果表明:宏观与细观指标的变化规律表现出相似特征;随着老化程度的加深,苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青混合料的损伤愈合性能逐渐变差,基质沥青混合料损伤愈合性能变化不明显,长期热老化后沥青混合料的愈合率与经过紫外复合老化后的沥青混合料接近;随着损伤度的加深,基质沥青混合料与SBS改性沥青混合料的损伤愈合性能明显降低,基质沥青混合料的损伤愈合性能优于SBS改性沥青混合料,SBS改性沥青混合料的损伤愈合性能受损伤度的影响更显著;愈合温度越高,愈合时间越长,沥青混合料的损伤愈合性能越好.     

基于凝胶渗透色谱法的改性沥青中SBS降解行为研究

为了探明改性沥青中SBS(苯乙烯-丁二烯嵌段聚合物)在施工及使用过程中的老化行为,通过对改性沥青在RTFOT、PAV老化前后的凝胶色谱分析研究了SBS的降解过程.结果表明:改性沥青经历RTFOT老化后有少量SBS交联结构发生降解,对沥青仍具有较好的改性效果:改性沥青经历PAV老化后SBS发生严重降解,平均分子质量显著下降,部分SBS丧失对沥青的改性效果:线性和星型2种类型SBS的老化程度不同;荧光显微观测试验结果与GPC分析结论一致,证明GPC分析方法能有效表征SBS的降解过程.     

时间和温度对短期老化SBS改性沥青官能团的影响

为探究老化时间、老化温度对老化SBS改性沥青微观结构的影响,通过旋转薄膜烘箱(RTFOT)对基质沥青、SBS改性剂、糠醛抽出油、稳定剂制备的SBS改性沥青进行不同时间(1.5h、3h、4.5h)、不同温度(163℃、173℃、183℃)的短期老化,然后采用红外光谱(FTIR)对其进行了官能团分析。结果表明:不同老化条件下的老化SBS改性沥青亚砜基特征峰、亚砜基指数增大,丁二烯基特征峰、丁二烯基指数减小;随着RTFOT老化时间、温度的增长,沥青老化程度不断加深,SBS改性剂持续降解;老化温度提高10℃的RTFOT老化SBS改性沥青老化程度大于老化时间延长1.5h的RTFOT老化SBS改性沥青。     

基于DNN改性沥青中SBS含量的预测模型

为准确预测苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青中SBS的含量,采用傅里叶变换红外光谱(FTIR)采集了不同SBS含量改性沥青的FTIR图谱,建立了基于深度神经网络(DNN)改性沥青中SBS含量的预测模型,并研究了不同因素对模型预测精度的影响,对比评价了模型的预测精度、敏感性及适用性.结果 表明:数据的降维、降噪预处理使SBS含量预测模型的均方误差降低了70％;基于DNN改性沥青中SBS含量预测模型的精度高于标准曲线法和随机森林方法,其对改性沥青中SBS含量的预测具有较好的敏感性及适用性.     

基于介电性质的沥青抗老化性能量化表征与分析

通过对热氧老化前后的90^#基质沥青、苯乙烯-丁二烯-苯乙烯嵌段共聚物（SBS）改性沥青进行三大指标、布氏黏度、频率扫描、线性振幅扫描和介电常数测试,研究了老化前后沥青基础指标、流变学指标、疲劳性能及沥青组分的变化情况,量化了短、长期老化后各指标的变化情况,并建立了沥青组分与性能指标之间的量化关系.结果表明：采用三大指标描述沥青老化程度时,针入度指标评价最为合理;基质沥青的黏度、温度敏感性、复数剪切模量主曲线和抗疲劳性能受热氧老化的影响大于SBS改性沥青;基质沥青的黏度和温度敏感性在短期老化过程中变化更明显,SBS改性沥青的黏度和温度敏感性在长期老化过程中变化更明显;2种沥青的抗疲劳性能和复数剪切模量的衰减主要发生在长期老化过程中;采用介电常数对沥青组分进行划分,并以此关联沥青老化前后性能变化的分析方法是可行的.     

SBS改性沥青的复合老化机理

通过考察沥青的纳米微观形貌、化学官能团和宏观力学指标,研究了复合老化条件下苯乙烯丁二烯苯乙烯嵌段共聚物(SBS)改性沥青的老化规律和机理.结果表明：复合紫外（UV）老化对SBS改性沥青的影响远大于短期老化,且复合UV老化对低温性能的影响更大;复合老化引起沥青“蜂形结构”数目和面积发生改变,复合老化后SBS改性沥青微观表面的杨氏模量和黏附力发生显著变化;复合老化后SBS改性沥青红外光谱中966、1376、1601cm-1处的基团发生了明显变化.     

不同试验方法的老化沥青疲劳性能研究

通过旋转薄膜烘箱试验(RTFOT)和压力老化试验(PAV),对70~#基质沥青、苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青、高黏沥青(HV)和基于化学改性原理的SBS/橡胶复合改性沥青(SRC)进行短期老化和长期老化,采用温度扫描试验、时间扫描试验、多重应力蠕变恢复(MSCR)试验和线性振幅扫描(LAS)试验对4种沥青的疲劳性能进行了研究.结果表明:SRC沥青的疲劳性能和抗老化能力最佳;温度扫描试验不能很好地区分不同沥青的疲劳性能差异;时间扫描试验可有效表征4种沥青的疲劳性能,但其耗时较长;MSCR试验中出现了平均弹性恢复率(R_(0.1)和R_(3.2))在长期老化之后大于短期老化之后的情况,其指标规律性和适用的沥青范围尚不明确;LAS试验可以表征沥青在重复荷载作用下的累积损伤发展过程,得到的损伤特征曲线和疲劳方程可有效评价各种沥青的疲劳性能.     

Effects of thermal oxidative ageing on dynamic viscosity,TG/DTG,DTA and FTIR of SBS- and SBS/sulfur-modified asphalts

Thermal oxidative ageing as an inevitable process in the practical application of road asphalt has a great effect on the properties of polymer-modified asphalts (PMAs). In this article, the influences of short-term and long-term thermal oxidative ageing on the dynamic viscosity, thermal stabilities, and infrared spectra of styrene–butadiene–styrene (SBS)- and storage-stable SBS/sulfur-modified asphalts were studied respectively. Although the addition of sulfur improved the dynamic viscosity and the thermal stability of SBS-modified asphalt significantly due to the formation of a chemically crosslinked polymer network structure, the improved properties declined evidently after ageing and the losses of properties became very severe with the ageing aggravated and the binder with sulfur showed a visible viscous behaviour compare with the corresponding binder without sulfur after ageing due to the severe degradation of vulcanized SBS, therefore SBS/sulfur-modified asphalt was more susceptible to ageing. Besides, the SBS structure also had a great effect on the properties of binders before and after ageing. In infrared spectra analysis, the structural evolutions of binder under different ageing modes were characterized by using right ageing index and the conclusions of thermal analysis and dynamic viscosity tests were confirmed further by the changes of butadiene and carbonyl indexes.     

Micro-structural and rheological characteristics of SBS-asphalt blends during their manufacturing

Two styrene–butadiene–styrene block (SBS) copolymers which differ in weight average molecular weight and two base asphalts (from local crude source, Argentina) had been blended under different experimental conditions. Rotational viscosity, fluorescence microscopy, size exclusion chromatography (SEC) and FT-IR spectrometry were used in order to study the rheological and morphological changes of the blends during their manufacturing. Our results show that the high shear rate and temperature used during this procedure induce the SBS copolymer degradation and the degradation fragments distribution into maltenic asphalt phase. These events are responsible for the observed changes. The optimal time which produces the best rheological properties of modified asphalt depends on the blend composition and on the shear rate used.     

Storage stability and compatibility of asphalt binder modified by SBS graft copolymer

The performance of styrene–butadiene–styrene (SBS) triblock copolymer modified asphalt binder at high temperature can be improved significantly with the addition of SBS-g-M grafted with vinyl monomer under γ-rays irradiation. The dynamic mechanical properties of SBS modify asphalts binder before and after graft has been characterized by use of dynamic shear rheometer. It has been found that the added content of SBS-g-M has great effect on the rheological properties of the binder and its high temperature performance was improved while its temperature susceptibility was reduced in compare with SBS modified asphalts binder. It also has been confirmed that the morphology observed by fluorescence microscopy revealed the compatibility between SBS-g-M and asphalt and the storage stability of binder was improved significantly compared with SBS modified asphalt binder. As a consequence, the use of SBS grafted with polar monomer can be considered a suitable alternative for modification of binder in pavement.     

基于MSCR试验的改性沥青高温性能评价

应用多应力蠕变恢复(MSCR)试验,对SBS改性沥青、胶粉改性沥青和高强沥青在不同温度下的不可恢复蠕变柔量Jnr与应力敏感性指标Jnr-diff进行了分析,依据AASHTO MP19-10标准对3种改性沥青进行了交通分级,并采用改性沥青混合料三轴动态蠕变试验进行了验证.结果表明:在非线性范围内应力和温度对改性沥青抗永久变形能力的影响具有等效性;随着温度的升高,改性沥青流变性能的线性范围逐渐变窄,应力敏感性更为显著;胶粉改性沥青在低应力区间的高温性能优秀,但是其线性范围很小,当应力或温度提高时胶粉改性沥青的流变性能迅速进入非线性范围,高温性能急剧衰减;不同应力和温度下改性沥青高温性能的排序发生改变,基于AASHTO MP19-10标准的交通分级能够反映改性沥青的这一特性.     

Influence of aging on the evolution of structure,morphology and rheology of base and SBS modified bitumen

The influence of aging on the evolution of structure, morphology and rheology of base bitumen and SBS modified binders was investigated by Fourier transform infrared (FTIR), atomic force microscopy (AFM) and dynamic shear rheometer (DSR), respectively. Two laboratory simulation aging methods, named standard rolling thin film oven (RTFO) test and pressure aging vessel (PAV) test were applied in this study. The aging temperature of PAV was selected at 60 °C, which is considered to be consistent with the real high temperature within an asphalt pavement in the field. After aging, it was found that more carbonyl and sulphoxide groups but less chain segments of butadiene were available. With the oxidation of base bitumen and the degradation of SBS segments, obvious asphaltene micelles appeared in both binders, consistent with the changes of softening point and rheology of base bitumen and SBS modified binders.     

The effects of using lime and styrene–butadiene–styrene on moisture sensitivity resistance of hot mix asphalt

This study focuses on determining the effects of styrene–butadiene–styrene (SBS) and using mineral filler with lime on various properties of hot mix asphalt especially moisture damage resistance. The asphalt cement was modified with 2%, 4% and 6% SBS. The lime treated mixtures containing 2% lime by weight of the total aggregate as filler. The physical and mechanical properties of polymer modified binder and binder–aggregate mixes were evaluated through their fundamental engineering properties such as dynamic shear rheometer (DSR), rotational viscosimeter (RV) for binders, Marshall stability, stiffness modulus, indirect tensile strength and moisture susceptibility for mixes. The retained Marshall stability (RMS) and tensile strength ratio (TSR) values were calculated to determine the resistance of mixtures to moisture damage. To investigate clearly the effective of SBS and lime seven freeze–thaw cycle was applied to specimens at TSR test. The results indicate that application of SBS modified binders and lime as mineral filler one by one improves the stability, stiffness and strength characteristic of hot mix asphalt. According to retained Marshall stability it is concluded that addition of only 2% lime have approximately same effect with addition of 6% SBS. Using lime together within the SBS modified mixes exhibit high accordance and exacerbates the improvement of properties. Specimens containing both 2% lime and 6% SBS, have the highest stiffness modulus which is 2.3 times higher than those of the control mixture and showed the least reduction in tensile strength ratio while maintaining 0.70 tensile strength ratio after seven freeze–thaw cycle.     

Starch as a modifier for asphalt paving materials

This paper investigates the viability of using starch (ST) as a new modifier for asphalt paving materials. Different ratios of ST (2.5, 5.0, and 7.5% by weight of asphalt) were blended with 70/100 paving grade asphalt. Unmodified and modified asphalt binders were subjected to physicochemical, alkali, acid and fuel resistance tests. The performance tests including, Marshall stability, Marshall Quotient (MQ), tensile strength, tensile strength ratio, flexural strength, rutting resistance and resilient modulus (MR) were carried out on unmodified and modified stone matrix asphalt (SMA) mixtures. The analyses of test results show that the performance of ST-modified asphalt mixtures are better than conventional and styrene–butadiene–styrene (SBS)-modified mixtures. The rutting potential, moisture susceptibility and temperature susceptibility can be reduced by the inclusion of ST in the asphalt mixture. The laboratory MR values are lower than the calculated ones using the empirical equations. The results also revealed that this modifier can be used as anti-stripping agent. It also shows resistance to fuels and most common chemicals. A ST content of 5% by weight of asphalt is recommended for the improvement of the performance of asphalt concrete mixtures similar to that investigated in this study.