不同浸水历时水泥乳化沥青砂浆动态受压试验

水泥沥青(CA)砂浆试件历经0,7,14,30,60d水浸泡后,在电子万能试验机上进行了应变速率1×10-5~1×10-2s-1的动态压缩试验,研究了水浸泡历时与应变速率对CA砂浆抗压强度、弹性模量、峰值应变以及应力-应变全曲线等动态特性的影响.结果表明:水浸泡历时和加载应变速率对CA砂浆的力学性能影响明显;CA砂浆的抗压强度和弹性模量随应变速率的增大而增大;相同应变速率下,CA砂浆的抗压强度和弹性模量均随水浸泡历时的增加先减小后增大;CA砂浆的平均抗压强度最大降低幅度为46.31%,平均弹性模量最大降低幅度为44.91%;CA砂浆的峰值应变随应变速率与水浸泡历时的增加呈增大的趋势,且水浸泡对峰值应变的影响大于应变速率对峰值应变的影响.     

加载速率效应对生土材料单轴抗压特性的影响研究

通过对生土块材在不同加载速率下进行单轴抗压试验,研究了生土材料抗压强度,弹性模量以及峰值应变随加载速率的变化规律,结果表明:当加载速率处于1～3mm/min时,生土材料表现出相对稳定的抗压特性,其抗压强度与弹性模量均随加载速率的增加先增大后减小,峰值应变随加载速率的增加逐渐减小。以切线模量的变化来量度试块的损伤,分析了生土试块损伤的演化规律和临界损伤应力随加载速率的变化规律。研究表明:随加载速率的增加,试块临界损伤应力呈先增大后减小的趋势,在相同的应力比条件下,试块的损伤随加载速率的变化规律不明显。     

应变速率和应力水平对CA砂浆动态抗压性能的影响

为了研究应变速率和应力水平对中国铁路轨道系统(CRTS)Ⅰ型板式无砟轨道水泥乳化沥青砂浆(CA砂浆)动态抗压强度、弹性模量和临界应变的影响规律,对0%,30%,60%和90%应力水平下的CA砂浆试件进行了应变速率为1×10-5~1×10-2s-1的单轴压缩试验.结果表明:应变速率和应力水平对CA砂浆的动态抗压性能影响显著;随着应变速率的增加,CA砂浆的动态抗压强度显著提高;随着应力水平的增大,CA砂浆的动态抗压强度明显降低,最大降低幅度为6.78%;CA砂浆的弹性模量随着应变速率和应力水平的增加呈增大趋势;CA砂浆的临界应变随应变速率的增加而增大,但随应力水平的增大而减小,且应变速率对临界应变的影响大于应力水平对临界应变的影响.     

CA砂浆力学性能与体积对温度的稳定性

研究了CA砂浆(水泥乳化沥青砂浆)力学性能和体积对温度的稳定性.结果表明:温度从-10℃增加到40℃时,CA砂浆的抗压强度和弹性模量均呈降低趋势;对采用SBS改性乳化沥青的CA砂浆而言,乳化沥青/水泥质量比越大,其抗压强度随温度升高下降越快;相同乳化沥青/水泥质量比条件下,随着温度升高,采用未改性乳化沥青的CA砂浆抗压强度下降幅度大于采用SBS改性乳化沥青的CA砂浆.CA砂浆热膨胀系数随水泥/砂质量比和龄期的增大而降低,随外加水用量和乳化沥青/无机材料(水泥+砂)体积比增大而升高;采用改性剂对乳化沥青进行改性,能够降低CA砂浆的热膨胀系数,改善CA砂浆体积对温度的稳定性,其中以SBS改性剂的改善效果最好.     

加载速率对不同温度状态石灰岩力学性能影响的试验研究

借助美国MTS810电液伺服材料试验机和高温炉,对常温和600℃两种温度状态下石灰岩试件进行不同加载速率下的单轴压缩试验,得到石灰岩力学性能随加载速率的变化规律。结果表明:常温时,石灰岩岩样在3×10-4³×10-3 mm/s的低应变率范围内,加载速率对峰值应力和弹性模量影响不大,在加载速率为3×10-33×10-3 mm/s的低应变率范围内,加载速率对峰值应力和弹性模量影响不大,在加载速率为3×10-3³×10-1 mm/s的区段内,峰值应力和弹性模量均呈明显上升趋势;600℃时,峰值应力和弹性模量随加载速率增加变化不大。常温时,不同加载速率下石灰岩岩样均为竖向劈裂破坏,且在3×10-33×10-1 mm/s的区段内,峰值应力和弹性模量均呈明显上升趋势;600℃时,峰值应力和弹性模量随加载速率增加变化不大。常温时,不同加载速率下石灰岩岩样均为竖向劈裂破坏,且在3×10-3³×10-1 mm/s的加载速率区段中,随加载速率的增加,劈裂面逐渐增多;600℃时,石灰岩岩样在不同加载速率下均为剪切破坏。     

CRTSⅠ型CA砂浆动态受压损伤试验

在电子万能试验机上对现场取样的水泥乳化沥青砂浆(CA砂浆)试件在应变率1×10-5～1×10-2S-1下进行动态单轴抗压试验,分析了动态荷载下CA砂浆的抗压强度、弹性模量及临界应变随应变率的变化规律.结果表明:CA砂浆的抗压强度随应变率的增加而增大,CA砂浆的抗压强度、弹性模量及临界应变与应变率之间呈幂函数关系,并给出了抗压强度、弹性模量及临界应变受应变率影响的经验公式.以切线模量的退化来度量CA砂浆的损伤程度,分析了CA砂浆动态损伤槛值随应变率的变化规律:当加载到相同的应变时,应变率越低,CA砂浆的损伤程度越严重;随着应变率的增大,CA砂浆损伤应力槛值及损伤应变槛值均增大;当应变率较高时,应变率对损伤应力槛值与平均抗压强度的比值和损伤应变槛值与平均临界应变的比值影响不大.     

加载速率对高温后大理岩动态力学性能的影响研究

利用100 mm分离式Hopkinson压杆装置,对经历不同高温后的大理岩进行不同加载速率下的冲击压缩试验,研究了峰值应力、峰值应变、弹性模量等与加载速率的关系。试验结果表明,高温后大理岩的峰值应力、峰值应变均表现出显著的加载速率强化效应,随加载速率的提高而近似线性增加,但800℃之后,峰值应力的加载速率强化效应明显减弱,而峰值应变的加载速率强化效应明显加强;高温后大理岩弹性模量的加载速率相关性并不明显,随着温度的升高,弹性模量逐渐减小,到1000℃高温时,随着加载速率的增加,弹性模量基本保持不变。结合岩石材料的微观结构特征、能量吸收以及受力状态等对岩石动态力学性能的加载速率强化效应机理进行了探讨。     

有压水环境下循环荷载历史对饱和混凝土动态力学特性的影响

为研究有压水环境中循环荷载历史对混凝土动态力学性能的影响,对历经不同荷载循环次数(0、25、50、100次)的水饱和混凝土试件(在2 MPa围压水环境中)进行了不同应变速率(10-5、10-4、10-3、10-2/s)下的常规三轴静动态压缩试验,分析了混凝土材料的峰值应力、峰值应变、弹性模量、吸能能力等基本力学参数的变化规律和机理。结果表明:同一加载速率下,水饱和混凝土的峰值应力、弹性模量和吸能能力均随循环次数的增长呈现出先增大后减小的规律,并且峰值应力和吸能能力增减的转折点随着应变速率的提高而向荷载循环次数增大的方向平移,峰值应变整体上呈减小的趋势;相同荷载循环次数后,峰值应力、峰值应变和吸能能力随着加载速率的增大而逐渐增大,并且荷载循环次数越大,率效应越显著,弹性模量随着加载速率的增大而逐渐较小。     

考虑应变率效应的混凝土材料单轴压缩特性尺寸效应研究

为了研究尺寸效应和应变速率对混凝土力学性能和变形能力的影响,对3种尺寸(70、100、150 mm)228个混凝土立方体试块分别在4种应变速率下(10^-5、10^-4、10^-3、10^-2/s),进行了试验研究。试验结果表明:同一应变率下,混凝土峰值应力随着尺寸的增大而减小,混凝土峰值应变随着尺寸增大而逐渐增大,并分析得出应变速率较大时,峰值应变由骨料弹性变形决定;应变速率较小时,峰值应变由水泥凝胶体黏性流动和混凝土裂缝扩展决定。同一尺寸下,混凝土峰值应力随着应变速率的增大而增大;混凝土弹性模量随应变速率的增大也呈现逐渐增大的趋势。指出动态加载下,混凝土弹性模量变化幅值不是一个确定的值,用静态下的弹性模量简单乘以一个放大或折减系数,不能满足计算动态加载下弹性模量的要求。通过线性回归分析,发现混凝土动态弹性模量和应变速率的对数成线性增长关系,对两者关系进行拟合,发现混凝土弹性模量与应变速率的关系曲线与试验结果吻合较好。     

乳胶粒径对聚合物改性水泥基材料性能的影响

合成了3种数均乳胶粒径分别为138,202,251nm的聚合物乳液,考查了乳胶粒径对聚合物在水泥表面吸附量、水泥净浆凝结时间、新拌砂浆流动度和含气量、硬化砂浆力学性能的影响.结果发现:在相同聚灰比(mP/mC)条件下,随乳胶粒径减小,聚合物在水泥表面的吸附量降低,水泥净浆的凝结时间变长,新拌砂浆流动度增大,硬化砂浆抗折强度提高,抗压强度下降;新拌砂浆含气量在mP/mC5%时随乳胶粒径减小而增大,在mP/mC≥5%时随乳胶粒径减小而减小;在饱和吸附量下单位质量水泥表面所吸附的3种聚合物覆盖面积与其粒径无关,分别为1 918,2 111,1 963cm2/g,比水泥的勃氏比表面积(3 530cm2/g)小.     

养护温度对水泥沥青砂浆强度发展的影响

试验研究了0,25,60℃这3种养护温度下不同沥青含量的水泥沥青砂浆(CAM)在3～120d龄期内的力学强度发展规律.结果表明:高温养护不利于低沥青含量CAM的力学强度发展,但有利于高沥青含量CAM的抗压强度发展;低温养护不利于任何类型CAM的强度发展;养护环境温度主要影响水泥的水化反应和沥青的破乳成膜过程,且对前者的影响大于后者.对不同类型CAM中后期现场养护方法提出了一些建议.     

Mode I reflection cracking resistance of strengthened asphalt concretes

This study was devised to evaluate the performance of polymer-modified asphalt mixtures and specially designed reinforcement techniques against reflection cracking for the typical asphalt pavement overlays. Selected polymers from previous studies were used as asphalt modifiers along with fibre; a polypropylene film (vinyl) and a grid were used as reinforcing materials. Using the reinforced asphalt mixtures with the optimum asphalt content from mix design, an asphalt mixture slab was made and cut into two specimens. A layer of grid or polypropylene film was placed at the bottom of each specimen to strengthen the pavement layer against cracking. Simulated-repeated loading was applied to the asphalt mixture specimens using a hydraulic dynamic loading frame. The asphalt mixture specimens were bonded to a cement concrete base which was cut to simulate a crack. Crack propagation under repeated loading was monitored and the effectiveness of the devised crack preventing techniques was evaluated. From the test results, a significant retardation of crack progress was monitored from some of the modified and reinforced asphalt mixtures.     

Framework for developing a static strength test for measuring deformation resistance of asphalt concrete mixtures

This study deals with a strength property which is showing high correlation with rutting resistance of asphalt mixtures. The test procedure was developed by applying a load to the compacted asphalt samples and calculating the strength by using the deformation of the mixture at the failure point. To evaluate the validity of this test, various mixtures were prepared with two aggregates and seven binders using four loading head types at the loading speed of 50.8 mm/min at 60 °C. Maximum load and deformation were recorded for each test and deformation strength, S_D, was calculated using a newly developed equation. For the same mixture, wheel tracking test was performed and two rut parameters, depth of rut and dynamic stability were obtained. The relationship between S_D and rut parameters was evaluated using regression analyses. In most cases, R² values were found to be over 0.9. This test procedure is still under development; however, current results indicate that it might be a simple test to predict the deformation resistance of asphalt mixtures at high temperatures.     

A model for dynamic creep evaluation of SBS modified HMA mixtures

The specimens, according to the Marshall Stability testing procedure, of hot mix asphalt (HMA) containing bitumen modified with styrene–butadiene–styrene (SBS) have been constructed in the laboratory and tested under dynamic loading for permanent deformation using Suleyman Demirel University Asphalt Tester equipment (SDU-Asphalt Tester). Analysis of data shows that the permanent deformation of the samples may be modeled in terms of the specimen’s characteristics in a very satisfactory manner. Benefits of adding styrene–butadiene–styrene (SBS) in variant quantities and in variant types of additive to asphalt cement (AC-60/70) were investigated. Initial research was done to determine the physical properties of asphalt cement and modifiers. Fifteen asphalt binder recipes were prepared with two types of gradation, six different contents of bitumen, four different contents of polymer, three different types of polymer. After that, Marshall samples were prepared by using the modified and unmodified control asphalt binders. The results of investigation indicate that asphalt mixtures modified by any SBS additive gives the best permanent deformation resistance in the tests carried out in this study, so that, this modification increases physical and mechanical properties of asphalt binder. In this study, total deformation of each sample was calculated using a newly developed equation containing variables of mixture characteristics. In addition to these, to develop a model that could fit the creep curve a new logarithmic model derived from first 100 preconditioning loading was developed instead of power law function model for first stage of permanent deformation curves.     

沥青混合料动态弹性模量场模型的建立与应用

为获得能表征不同工况下沥青混合料力学性能的本构方程,采用沥青混合料标准马歇尔试件的单轴压缩试验数据,获得以加载速率和应力状态为自变量的动态弹性模量场模型.基于ABAQUS/VUMAT编写了材料本构的用户子程序,依据试验数据分析了模型的可靠性.分别采用沥青混合料劈裂试验中压头的竖向位移数据和沥青混合料小梁弯拉试验中的弯拉强度数据验证动态弹性模量场模型在不同工况下的通用性.结果表明:采用动态弹性模量场模型的计算结果与不同加载速率下沥青混合料的单轴压缩、劈裂和小梁弯曲等工况下的试验数据吻合较好.动态弹性模量场模型能描述沥青混合料材料参数与受力状态和加载历史的依赖性,可为复杂受力状态下沥青混合料结构的力学分析提供一种方法.     

Performance of soft-hard-soft (SHS) cement based composite subjected to blast loading with consideration of interface properties

This paper presents a combined experimental and numerical study on the damage and performance of a soft-hard-soft (SHS) multi-layer cement based composite subjected to blast loading which can be used for protective structures and infrastructures to resist extreme loadings, and the composite consists of three layers of construction materials including asphalt concrete (AC) on the top, high strength concrete (HSC) in the middle, and engineered cementitious composites (ECC) at the bottom. To better characterize the material properties under dynamic loading, interface properties of the composite were investigated through direct shear test and also used to validate the interface model. Strain rate effects of the asphalt concrete were also studied and both compressive and tensile dynamic increase factor (DIF) curves were improved based on split Hopkinson pressure bar (SHPB) test. A full-scale field blast test investigated the blast behavior of the composite materials. The numerical model was established by taking into account the strain rate effect of all concrete materials. Furthermore, the interface properties were also considered into the model. The numerical simulation using nonlinear finite element software LS-DYNA agrees closely with the experimental data. Both the numerical and field blast test indicated that the SHS composite exhibited high resistance against blast loading.     

半刚性面层混凝土(SRPC)结构形成机理

结合水泥水化机理和软物质概念，论述了半刚性面层混凝土（SPRC）结构形成机理。认为水泥用量虽少，但使乳化沥青混凝土性能发生较大改变，克服了沥青混凝土柔性和水泥混凝土刚性过大的缺点。SRPC结构主要来源于乳化沥青颗粒与水泥颗粒构成的空间网状结构。提出水泥在SRPC结构形成过程中的四方面作用。分析了水泥、乳化沥青两种胶结料对SRPC结构形成影响之规律。     

焚烧飞灰颗粒对沥青混合料水稳定性的影响

为了实现焚烧飞灰(IFA)在沥青路面中的资源转化,将焚烧飞灰与水泥造粒以及与水泥、硅灰、粉煤灰造粒,研究掺有造粒颗粒沥青混合料的水稳定性以及冻融劈裂试验条件对其水稳定性的影响机制.结果 表明:焚烧飞灰造粒后,氯离子浸出率分别降低了56.76％、59.12％;冻融劈裂试验条件对焚烧飞灰/水泥颗粒沥青混合料水稳定性影响顺序为抽真空过程>冷冻过程>击实次数,抽真空过程破坏造粒颗粒表面沥青膜,导致可溶氯盐溶出,氯盐溶液在冻融过程中产生的冻胀、盐胀与腐蚀综合作用是导致沥青混合料内部结构受损关键因素;焚烧飞灰与水泥、硅灰、粉煤灰造粒的方法能有效改善沥青混合料的水稳定性.     

GTM沥青混合料低温性能影响因素研究

论述了以GTM设计的AC-16C改性沥青混合料为基础,在级配、油石比、粉油比变化的条件下,分别对混合料进行低温弯曲破坏试验。试验结果表明,对于沥青混合料的低温抗裂性能,4.75mm通过率、油石比、粉油比均存在最佳值。采用BBR试验进一步分析消石灰及水泥对胶泥低温性质的影响时发现,以部分水泥替代矿粉有利于提高沥青胶泥的低温性能。研究结论对道路沥青混合料配合比设计和施工控制具有一定的参考价值。     

Mechanical characterization of a bituminous mix under quasi-static and high-strain rate loading

There are various methods to determine the compressive and tensile strength of asphalt concrete under static loading conditions and most studies on asphalt strength and fracture have been conducted under such loading conditions. However, pavement materials also have to withstand a wide variety of loading and temperature conditions which may vary from quasi-static to high-strain rate impact, and pavement breakdown may occur due to fracture and/or fatigue failure. In the present study, a bituminous mix with 30% RAP has been characterized under quasi-static (10^?3–10^?4 strain/s) and high-strain rate (200–700 strain/s) regimes. The experimental studies have been performed to better understand the compressive, tensile and fracture response of bituminous mixes. Split Hopkinson pressure bar (SHPB) and its modifications were used for high-strain rate characterization of this bituminous mixture. It was observed that the mechanical properties of the hot mix asphalt (HMA) changed significantly under high-strain rate testing. Also, the failure mechanisms observed under the high-strain rate loading were found to be considerably different from those obtained in static testing, where failure of binder was a predominant mechanism. It was observed that high-strain rate loading caused trans-aggregate failures in the specimens; in addition to failure of the binder.