Dynamic mechanical behavior of polymer modified bitumen

The dynamic mechanical behaviour of bitumen (BIT) modified with styrene/butadiene/styrene block copolymer (SBS) were investigated. Dynamic mechanical analysis (DMA) were performed in the temperature range –80 to 60 °C. The primary viscoelastic functions were determined at the traffic frequency, 5 Hz. The BIT+SBS blends were investigated in creep fatigue regime at temperature 10, 20, 30, 40 and 50 °C. Dynamic mechanical behaviour of BIT+SBS blends depends on their morphological characteristics, number of phases, phase compositions and phase content in blend, as well as time and temperature. The curves of primary viscoelastic functions, storage modulus (E′), loss modulus (E′′) and loss tangent (tg δ) vs. temperature of polymer modified bitumen differ from unmodified bitumen and indicate the presence of the swollen polybutadiene and polystyrene phases in bitumen phase. The curve E′ vs. temperature of polymer modified bitumen show the rubbery plateau. With the increment of SBS content the rubbery plateau is shifted to high temperatures. At the constant load the creep values of BIT-SBS blends increase and those of creep modulus decrease over a period of time. These effect are more pronounced in samples with higer content of SBS. The time-temperature correspondence principle was applied to create master curves for the reference temperature 10 °C for the creep modulus of BIT + SBS blends. The data were analysed using WLF and Arrhenius equations. Electronic Publication     

改性沥青混合料拌和与压实温度确定方法综述

改性沥青混合料拌和与压实温度对沥青路面的设计和施工质量有很大影响,进而影响沥青路面的使用性能.介绍了4种具有代表性的确定改性沥青混合料拌和与压实温度的方法,分别为Yildirim法(Y法)、Bahia法(B法)、Shenoy法(S法)和Azari法(A法),阐明并论述了这4种方法的优缺点及适用范围.     

聚合物改性沥青高温抗变形特性实验研究

为研究短期老化作用、温度分别对3种聚合物改性沥青:SBS改性沥青(SMA)、橡胶粉改性沥青(RPMA)、复合改性沥青(CMA)抗变形能力的影响,利用动态剪切流变仪(DSR)分别对3种沥青原样及旋转薄膜烘箱老化(RTFOT)后的沥青试样进行重复蠕变恢复实验,利用抗变形指数HL与蠕变劲度的粘性部分GV对沥青高温变形性能进行评价;并利用扫描电子显微镜对各沥青试样的微观结构形态进行观察,从微观角度解释不同沥青抗变形能力存在差异的原因。结果表明,GV与HL可较好地评价高温下改性沥青的抗变形能力;短期老化作用使基质沥青与改性剂的微观结构发生变化,抗变形性能改变;温度对沥青抗变形能力的影响取决于沥青温度敏感性的强弱,RPMA在高温状态下表现最好。     

纤维铺放压紧力及预浸带加热温度对复合材料力学性能的影响

采用三因素四水平正交实验与单因素实验相结合, 通过力学性能测试及SEM和光学显微镜微观形貌观察研究了复合材料铺放过程中压紧力、 预浸带加热温度及芯模温度对复合材料力学性能的影响。实验结果表明: 压紧力与加热温度对层间剪切强度(ILSS)影响很大, 而芯模温度影响较小; 当压紧力为600 N、 预浸带加热温度为30℃、 芯模温度为18℃时, 复合材料综合力学性能达到最佳。微观形貌观察结果表明: 随着压紧力和预浸带加热温度升高, 纤维与树脂接触充分, 树脂与纤维分布均匀性较好, 层间富树脂区的厚度较小, ILSS逐渐增加; 但当预浸温度上升到40℃以后, 压紧力作用导致树脂与纤维的分布均匀性变差, 层间富树脂区的厚度较大, 从而导致ILSS下降。     

On the processing properties and friction behaviours during compaction of powder mixtures

ABSTRACT

Iron-based powder mixtures were prepared by dry and wet mixing method. The friction properties during compaction were tested by measuring the internal and external friction coefficient. The test results showed that the wet mixing process could realise the homogeneity of lubricant and improve the processing properties of the powder mixtures. With 0.6 wt-% lubricants, wet mixing powder mixtures have a flow rate of 29.6 s/50?g, an apparent density of 3.18?g?cm^–3, a repose angle of 35.5°, and the friction coefficient during the compaction is 0.223. An equation to calculate the total (both internal and external) friction forces during the compaction process is proposed, and then the factors influencing the friction coefficient during compaction were quantitatively analysed.     

盐冻循环条件下改性沥青的细观结构及低温流变性能

冬季由于低温路面经常会被冰雪覆盖,融雪盐是对路面进行融雪化冰的主要方式之一。为了研究盐冻循环前后的基质沥青、SBS（苯乙烯-丁二烯-苯乙烯嵌段共聚物）改性沥青和胶粉改性沥青的细观结构和低温流变性能变化,利用SEM和弯曲梁流变仪（BBR）对其测试。结果表明:改性剂以特定的结构形态存在于沥青中,二者具有良好的相容性,这种形态可以更好地吸附沥青,提高沥青的低温弹性或韧性,进而改善了沥青的低温性能。盐冻循环破坏了沥青的结构,影响了沥青的低温抗裂性能。经历盐冻循环后沥青的蠕变劲度模量增大、蠕变速率减小,低温抗裂和应力松弛能力降低,但改性沥青低温性能总体上优于基质沥青。因此建议北方等寒冷地区尽量选用改性沥青作为路面材料。      

Comparative binder efficiency modeling of dry granulation binders using roller compaction

Roller compaction parameters’ impact on granules and tableting properties of coprocessed Avicel^® DG [ADG], a physical mixture of the two components at the same composition present in ADG [PADCP], and microcrystalline cellulose and Kollidon^® VA-64 Fine physical mixture [KVA64] was quantified by analysis of variance (ANOVA) and multivariate methods. Roller force, roller gap, and roller speed levels were selected for evaluation. A 3³ full-factorial experimental design with three center points for roller force, roller gap, and roller speed was used. The response parameters studied were granule-to-fines (GF) ratio, compressibility index (CI), tablet thickness (TT), tablet friability (TF), tablet breaking force (TBF) and disintegration time (DT). A model acetaminophen tablet formulation was roller granulated and tableted at 10?kg scale. Principal component analysis of ADG and PADCP formulations were separated from KVA64 formulations, indicating different granule and tableting properties were binder dependent. This difference in binder performance was also confirmed by ANOVA. The ANOVA also showed that there were no statistical performance differences between coprocessed ADG and its comparable physical blend with the exception of TT. Principal component regression (PCR) analyses of ADG and PADCP revealed that these excipients exhibited a statistically significant negative effect on granules-to-fine (GF) ratio, TT, TBF, and DT. KVA64 demonstrated a positive effect on these parameters. The KVA64 physical mixture demonstrated an overall better performance and binding capability. This study strongly suggests that there is no performance advantage of coprocessed Avicel^® DG when compared to a physical mixture of the two components at the same composition.     

爆炸压实ZrB_2-SiC超高温陶瓷的密度与组织

为了研究炸药对ZrB2-SiC超高温陶瓷密度与组织的影响,采用爆炸压实工艺制备了SiC纳米颗粒和SiC晶须分别增韧的两类ZrB2基超高温陶瓷复合材料.研究发现：选择低速的硝酸铵或高速的黑索今时,两类ZrB2-SiC爆炸压实坯密度都比较低,而选择混合炸药时致密效果较好;采用225 g黑索今与75 g硝酸铵的混合炸药时,Z...     

基于黏弹性理论的多聚磷酸改性沥青低温性能

基于黏弹性理论,对不同质量分数(0.5wt%,1.0wt%,1.5wt%,2.0wt%)的多聚磷酸改性沥青及基质沥青进行低温弯曲流变试验(BBR),结合Burgers模型对低温弯曲梁流变试验得到的蠕变数据进行非线性拟合,利用Burgers模型的四个参数(E_1、η_1、E_2、η_2分别是Maxwell和Kelvin模型中弹性模量和黏性系数)确定出低温性能指标,对多聚磷酸改性沥青低温性能进行分析。结果表明:多聚磷酸的添加使沥青中的黏性和弹性都得到了一定的改善,沥青中松弛时间减少,储存能减少,耗散能增加,应力松弛能力得到提高。在相同温度下,多聚磷酸改性沥青延缓了沥青进入蠕变稳定期的时间,但随着温度的降低,达到蠕变稳定期的时间缩短。多聚磷酸改性剂的添加可以提高沥青低温性能,且随质量分数的增加,低温改善效果更好;但随着温度的降低,多聚磷酸对沥青的低温改善程度减小,且不同质量分数对其影响的差异也减小,在-24℃以上适合使用多聚磷酸改性,而在-24℃以下掺入多聚磷酸改性沥青意义不大。     

Homogenised elasto-viscoplastic material modelling of thick perforated plates at high temperature

Abstract

In this study, homogenised elasto-viscoplastic behaviour of thick perforated plates at high temperature was investigated for macro-material modelling. Homogenised stress–strain relations of a periodic unit cell of thick perforated plates subjected to simple and complex loading were analysed using a homogenisation method for periodic solids. The base metals of perforated plates were assumed to exhibit elasto-viscoplasticity based on Hooke’s law and Norton’s power-law, and the material parameters of modified 9Cr–1Mo steel at 550°C were employed. The resulting homogenised stress–strain relations were simulated using a recently developed elasto-viscoplastic macro-material model based on a general form of the quadratic equivalent stress. It has been shown that this macro-model successfully represents the macro-anisotropy and macro-volumetric compressibility that were revealed by the homogenisation analysis in uniaxial, biaxial and triaxial stress states.     

多聚磷酸改性沥青老化前后高温流变性能

基于动态剪切流变(DSR)试验,对老化前后三种改性沥青:多聚磷酸(PPA)改性沥青、苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青及SBS-PPA复合改性沥青的高温性能进行分析。结果表明:在不同温度及老化作用下,与SBS改性沥青相比,PPA改性剂对沥青高温流变性能的改善更为突出,沥青中黏性成分减小,弹性成分增加。在SBS改性沥青中添加PPA可以明显增强改性沥青的弹性,降低其黏性,SBS-PPA复合改性沥青的高温性能优于SBS改性沥青。在长期老化下,PPA和SBS-PPA复合改性沥青中由储存模量G′占主导作用转变为损失模量G″占主导作用的温度转化点都较高,温度转化点:PPASBS-PPASBS。对于SBS改性沥青,温度和频率比老化作用对复数模量G*和相位角δ的影响更大,而PPA和SBS-PPA复合改性沥青受老化影响较大,随着老化程度的加深,可以在较宽的温度和频率范围内保持一定的弹性来抵抗变形。PPA改性沥青在老化前后,不同温度和频率下都具有较高的车辙因子G*/sinδ,且老化后G*/sinδ增加的最多,高温抗车辙能力更强,其次是SBS-PPA复合改性沥青。     

抗低温地下混装乳化炸药工艺配方研究

针对低温对地下混装乳化炸药技术的影响,通过混装乳化炸药组分分析,进行系列化实验研究,确定抗低温地下现场混装乳化炸药工艺配方。即在常规地下混装乳化炸药工艺配方的基础上,往水相中加入析晶点调节剂A,油相中加入富含亲水基团且具立体结构组分B,敏化组分中加入冰点调节剂C。由实验验证和工业化应用表明,设计的工艺配方能够有效解决由低温引起的基质储存稳定性差、远距离输送压力高、敏化低效以及装药返药等问题,且具有良好的装药爆破效果。     

降黏型温拌胶粉改性沥青高低温性能试验

通过动态剪切流变试验(DSR)和小梁弯曲蠕变劲度试验(BBR),对添加不同掺量(1%、2%、3%)有机降黏剂(LP)的胶粉改性沥青(CR)高低温性能进行研究。结果表明:LP的添加使胶粉改性沥青的高温性能得到改善,复数剪切模量G*增大,相位角δ减小,且随着LP掺量的增加,其高温抗变形能力逐渐增强。对于低温性能,LP的添加可以提高胶粉改性沥青的低温性能,但不同温度下,随着降黏剂LP掺量的增加,其低温抗裂性能呈减小趋势,对改善胶粉改性沥青低温性能有一定的负面影响,且随着温度的降低,LP对胶粉改性沥青的低温性能改善效果减小,不同掺量对其影响相差不大。     

硅藻土与蒙脱土协同改善SBS改性沥青性能的研究

为探明硅藻土与蒙脱土协同使用对SBS改性沥青性能的影响,本文通过熔融共混法制备了不同配比的硅藻土/蒙脱土/SBS改性沥青。采用常规物理性能测试、动态剪切流变实验、压力老化和紫外老化实验对硅藻土/蒙脱土/SBS改性沥青的物理、流变和老化性能进行了评价,并利用傅里叶变换红外光谱(FTIR)分析了老化过程中改性沥青化学结构的变化。研究表明,硅藻土与蒙脱土协同使用,不仅提高了SBS改性沥青的软化点与黏度,改善了SBS改性沥青的高温抗变形能力,而且有效降低了蒙脱土对SBS改性沥青低温抗裂性能的不利影响,并能够明显减小压力老化和紫外老化对SBS改性沥青软化点和黏度的负面影响,大幅度提高其延度保留率。蒙脱土掺量为1.5%时,硅藻土的适宜掺量为6%。FTIR分析表明,硅藻土与蒙脱土协同使用抑制了SBS改性沥青压力老化和紫外老化后羰基指数的增加与丁二烯指数的降低,增强了SBS改性沥青的抗老化能力。     

新型包埋微生物材料-室温交联聚丙烯酰胺的合成

首先合成低分子量的聚丙烯酰胺，再用甲醛使其羟甲基化，最后羟甲基化聚丙烯酰胺和丙烯酰胺缩合得到可室温交联的聚丙烯酰胺。研究了反应物摩尔比、反应温度、反应时间和溶液pH值等因素对羟甲基化和缩舍反应的影响，确定了最佳反应条件。这种改性聚丙烯酰胺的水溶液和交联剂于室温可快速交联得到凝胶体。该工艺的优点是对微生物细胞无毒性，聚合（包埋）温度低，交联发生在侧链使抗水解性增强。     

纳米粘土/聚苯乙烯-丁二烯-苯乙烯嵌段共聚物复合改性沥青短期老化前后性能研究

为探究纳米粘土与聚苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)复合改性沥青的流变特性和抗老化性能,采用物理试验、动态剪切流变(DSR)、多应力蠕变回复试验(MSCR)和弯曲梁流变试验(BBR),对旋转薄膜烘箱加热老化试验(RTFOT)前后的不同纳米粘土掺量的纳米粘土/SBS复合改性沥青进行对比,探讨短期老化前后不同纳米粘土掺量下纳米粘土/SBS复合改性沥青的抗老化性能。结果表明:添加纳米粘土能明显地提高SBS改性沥青的高温、低温性能和抗老化性能;随着纳米粘土掺量的增加,纳米粘土/SBS复合改性沥青短期老化后的抗车辙因子、不可恢复蠕变柔量等性能指标不同程度改善;十六烷基三甲基溴化铵活化的纳米粘土表现出较好的化学活化效果和抗老化性能。     

Behaviour analysis of numerical solutions and simulation of coherent structures in compressible mixing layers

For understanding the correctness of simulations the behaviour of numerical solutions is analysed. In order to improve the accuracy of solutions three methods are presented. The method with GVC (group velocity control) is used to simulate coherent structures in compressible mixing layers. The effect of initial conditions for the mixing layer with convective Mach number 0.8 on coherent structures is discussed. For the given initial conditions two types of coherent structures in the mixing layer are obtained.     

Improved compaction and packing properties of naproxen agglomerated crystals obtained by spherical crystallization technique

Naproxen was crystallized from acetone-water in the presence of different concentrations of hydroxypropylcellulose (HPC). Naproxen particles recrystallized in the presence of HPC exhibited an obvious improvement in their packing, flow, and mechanical properties compared to naproxen recrystallized in the absence of the polymer (control particles). The results showed that the particle size distributions of the treated samples were broader than those obtained when HPC was absent. The agglomerates produced in the presence of 0.25% HPC displayed superior flow characteristics (displaying both a low angle of repose and Carr index) in comparison to samples produced in the presence of other concentrations of HPC. This was attributed to the spherical shape and smooth surface, since the area of contact in the powder bed for spherical agglomerates was smaller than that for other crystal shapes. However it was found that the tensile strength of tablets with the particles isolated in the presence of 1% HPC was increased to a greater extent than tablets produced using the spherical particles. Generally, the tensile strengths of the tablets increased with increasing concentrations of HPC present in the crystallization medium. Differential scanning calorimetry (DSC) and X-ray powder diffraction studies showed that naproxen particles, crystallized in the presence of HPC did not undergo structural modifications.     

Mix design considerations of foamed bitumen mixtures with reclaimed asphalt pavement material

In the present work, a mix design parametric study was carried out with the aim of proposing a practical and consistent mix design procedure for foamed bitumen mixtures (FBMs). The mix design parameters that were adopted in the study are mixing and compaction water content (MWC), compaction effort using a gyratory compactor and aggregate temperature. This parametric study was initially carried out on FBMs with virgin limestone aggregate without reclaimed asphalt pavement (RAP) material and a mix design procedure was proposed. This proposed methodology was also found to apply to FBMs with RAP. A detailed consideration was also given to characterising the RAP material so as to understand its contribution to the mechanical properties of FBMs. Optimum MWC was achieved by optimising mechanical properties such as indirect tensile stiffness modulus and indirect tensile strength (ITS-dry and ITS-wet). A rational range of 75–85% of optimum water content obtained by the modified Proctor test was found to be the optimum range of MWC that gives optimum mechanical properties for FBMs. It was also found that the presence of RAP influenced the design foamed bitumen content, which means that treating RAP as black rock in FBM mix design is not appropriate. To study the influence of bitumen and water during compaction, modified Proctor compaction and gyratory compaction were employed on mixes with varying amounts of water and bitumen. By this, the work also evaluated the validity of the total fluid (water + bitumen) concept that is widely used in bitumen–emulsion-treated mixes, and found it not to be applicable.