Using the surface free energy method to evaluate the effects of liquid antistrip additives on moisture sensitivity in hot mix asphalt

The objectives of this research are to evaluate the susceptibility of aggregates and asphalt binder with and without liquid antistrip (LAA) additives to moisture damage based on the properties that affect the adhesion bond between the aggregate and asphalt binder and the cohesion strength of the asphalt binder using the surface free energy (SFE) concept and laboratory testing. The percentage of the aggregate surface area that was exposed to water (P) due to each cycle was used as a screening parameter for evaluating the compatibility of the asphalt binder and aggregates in terms of the resistance to moisture damage. The results show that adding LAA causes the total SFE of the asphalt binder to increase, which results in a decrease in stripping between the aggregate and asphalt binder in the presence of water. Similar results were obtained from a dynamic modulus test. From the data obtained, we conclude that LAA caused a reduction of the magnitude of P that improves its resistance to moisture damage.     

Measurement of the specific free surface energy of solids

A set of equations is proposed that makes it possible to obtain calculation equations for experimental determination of the specific free surface energy of solids. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 68–69, October, 2007.     

Effect of warm mix additives on the interfacial bonding characteristics of asphalt binders

The quality of the interfacial bonding between asphalt binder and aggregates plays a significant role in determining the durability of asphalt mixtures. Warm mix asphalt (WMA) modifiers have been used extensively in the last decade primarily to reduce production and compaction temperatures as well as to improve workability of asphalt mixtures. This study aimed to provide better understanding of the effects of these WMA modifiers on the interfacial bonding between asphalt binders and aggregates. The evaluation focused on measuring surface energy of binders in unaged and aged states and aggregates and then calculating energy parameters that describe the potential of a given asphalt-aggregate combination to resist fatigue cracking and moisture damage. Results show that the combination of asphalt-WMA additive, as well as the content applied of WMA additive has a significant impact on the fatigue cracking and moisture damage resistance. The results suggest that it is poor practice to use a given type and percentage of WMA modifier without regard for binder type. Instead, test methods are recommended to evaluate the compatibility of asphalt binder, WMA additive type/content, and aggregates for improved performance at different conditions.     

润滑油对钢板胶接强度及环境腐蚀性能的影响

本文针对裸钢板及其涂润滑油的钢板表面进行接触角测试、表面自由能计算,进而研究润滑油对其界面粘合功与接头强度的影响;并在此基础上,分析润滑油对钢板单搭胶接接头在水浴环境中的抗腐蚀性能影响。结果发现:润滑油极大地提高了钢板与胶粘剂间界面结合能中的极性分量,从而略微提高了钢板胶接接头强度,改善了接头失效模式。在水浴环境下,由于扩散到界面处的水分子对氢键的破坏及对极性分子的溶解,接头强度急剧下降,界面失效面积增加。润滑油主要增加了界面结合能中极易被水分子破坏的极性分量,因而对钢板胶接接头水浴环境腐蚀性能影响较小。     

Examination of moisture sensitivity of aggregate–bitumen bonding strength using loose asphalt mixture and physico-chemical surface energy property tests

In this study, the moisture sensitivity of different kinds of aggregates and bituminous binders is examined by comparing the performance between five empirical test methods for loose mixtures – static immersion test, rolling bottle test (RBT), boiling water test (BWT), total water immersion test and the ultrasonic method – with more fundamental surface energy-based test data. The RBT and BWT results showed that limestone aggregates perform better than granite aggregates and that, for unmodified binders, stiffer binders provide better moisture resistance compared with softer binder. Both tests were sensitive to aggregate type, binder type and anti-stripping agent type. Ranking of the mixtures by RBT and BWT was in general agreement with the surface energy-based tests, especially for mixtures that performed worst or best in RBT and BWT. The magnitude of the work of debonding in the presence of water was found to be aggregate type dependent which suggests the physico-chemical properties of aggregates may play a fundamental and more significant role in the generation of moisture damage, than bitumen properties.     

State of the art: interface shear resistance of asphalt surface layers

Interface shear resistance is a measure of the bonding between two layers under shear loading. Adequate interface shear resistance and long-term bonding of the surface to the underlying pavement are critical to the performance of pavement structures. Interface shear strength is a function of adhesion, friction and aggregate embedment or interlock and is commonly modelled as a Mohr–Coulomb type envelope. Measurement of interface shear resistance can be performed in the field on full-scale pavements, in the laboratory on cores recovered from the surface or in the laboratory using samples prepared in the laboratory. However, laboratory testing of cores recovered from the field is likely to be more reliable and repeatable than field testing. There is a large range of test methods and procedures for the measurement of interface bond. These test methods are generally grouped into three main loading mechanisms; axial tension, torsional shear and direct shear. Direct shear tests offer a more comprehensive assessment of the full interface strength. The interface’s resistance to shear can be characterised by its strength, modulus/stiffness or work/energy. The results are affected by the test protocol, tack coat type and application rate, test temperature, applied normal stress and rate of loading, interface condition and post-construction trafficking. Of these, the test temperature is the most influential factor. A number of studies have reported contradictory and conflicting conclusions with regard to the importance of various factors and conditions on the different measures of interface shear resistance. Such inconsistent findings likely stem from the complicated interaction between the various interface conditions and testing protocols. The fundamental factors affecting monotonic interface strength are now reasonably well understood. The focus of future research is expected to be on shear fatigue performance of interfaces.     

Ultrasonic Analysis of the Degree of Cure and Cohesive Properties of the Adhesive in a Bond Joint

Acoustic techniques have been used to monitor cure of thermoset adhesive during cure reaction and to evaluate cohesive properties of the material in the adhesive joint after cure. Longitudinal sound velocity and attenuation as well as adhesive's elastic moduli were monitored to investigate molecular network development during reaction at different temperatures. The ability of high-resolution acoustic microscopy to study development of adhesive microstructure during cure reactions was also demonstrated. Correlations of the value of sound velocity with cohesive properties of the material and with joint performance were demonstrated. This approach can be used to monitor development of the cohesive strength of the joint during the cure process in manufacturing.     

新型聚合物水泥胶浆界面剂粘结性能及作用机理研究

采用新型聚合物水泥胶浆作为界面剂以提高新旧混凝土之间的粘结性能,通过拉拔粘结强度与劈裂抗拉粘结强度实验对5种不同类型的聚合物水泥胶浆界面剂的粘结性能进行了测试,并利用扫描电镜(SEM)分析研究了丁苯聚合物水泥胶浆的界面增强机理。实验结果表明,5种聚合物乳液中,丁苯聚合物水泥胶浆具有较好的拉拔粘结性能,当优选m(水泥)∶m(DB-1乳液)=3∶2时,其7d、28d拉拔粘结强度分别达到1.83MPa、2.41MPa,相比水泥净浆空白样分别提高了144%、96%;在劈裂抗拉粘结强度方面,水平方向浇筑时劈裂抗拉粘结强度相对较高,当聚合物水泥胶浆的优选m(水泥)∶m(DB-1乳液)=3∶2,水平浇筑时其28d劈拉粘结强度达到2.96MPa,明显高于不掺界面剂的试样以及掺加其它配比界面剂的混凝土试样;经过微观测试分析,丁苯DB-1聚合物水泥砂浆内部界面过渡区(ITZ)相比空白样明显致密,表明丁苯聚合物的加入有效填充了水泥基材料内部的宏观与微观缺陷,提高了界面过渡区的密实程度。     

两种新型无机复合阻燃改性沥青的流变性能及其阻燃机制

针对目前沥青阻燃剂存在的毒性大、造价高及耐热性差等问题,制备了两种由金属氧化物和金属氢氧化物组成的新型无机复合阻燃剂.通过动态剪切流变试验、弯曲梁流变(BBR)试验和Brookfield旋转黏度试验,深入研究了两种新型阻燃改性沥青的高温流变性能、低温流变性能以及黏度特性.在此基础上,借助DSC试验探究了两种复合阻燃改性沥青的阻燃机制,并对比了两种无机复合阻燃剂与常用阻燃剂的经济效益.试验结果表明:两种无机复合阻燃剂阻燃的抑烟效果良好,可显著改善沥青的高温抗车辙性能,提高沥青胶浆的低温性能,增加沥青黏度;两种无机复合阻燃改性沥青的抗车辙因子与温度呈现良好的相关性; 将两种复合阻燃剂加入到沥青中,能使沥青相态变化需要更多能量,改性沥青在受热过程中更加稳定.     

Comparison between the fatigue response of hot and warm mix asphalts based on the dissipated energy approach

This study focused on the fatigue behaviour of warm mix asphalt (WMA) based on the dissipated energy (DE) approach. Two conventional binders consisting of 60/70 and 85/100 penetration-grade bitumens were used to prepare the control mix. WMA was prepared by incorporating 2% Sasobit by weight of bitumen. First, the basic properties of WMA containing optimum bitumen content were compared with those of control hot mix asphalt (HMA). The main laboratory programme included four-point flexural fatigue test that was accomplished at different strain levels of 250, 500, 750 and 1000 microstrain. The studied WMA had comparable Marshall stability and indirect tensile strength to those of control HMA. Furthermore, based on the resilient modulus test results, the temperature susceptibility of WMA was slightly more than that of the control mix. Fatigue lives of studied mixes were evaluated using the conventional fatigue curves that were developed based on the initial strain level. Comparison between these curves revealed the predominant fatigue behaviour of WMAs at different examined strain levels. The initial DE and the cumulative DE of WMAs were lower than those of HMAs. The latter issue justifies the predominant fatigue response of WMA. By considering the DE curve, the ratio of dissipated energy change (RDEC) was calculated. Afterward, the plateau value (PV) was determined using the moving average of fatigue data in the plateau stage of the RDEC curve. Finally, PV-based fatigue models were developed which could precisely estimate the fatigue life regardless of the mix type and testing condition.     

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.     

基于表面能理论的老化温拌SBS改性沥青结合料的粘附性

在SBS改性沥青中添加Sasobit与Evotherm温拌剂制备得到温拌沥青,对3种SBS改性沥青进行旋转薄膜烘箱老化(RTFOT)与压力老化(PAV),采用接触角法检测了老化前后温拌SBS改性沥青与蒸馏水、甘油和甲酰胺等3种液体的接触角,探讨了短期老化与长期老化对温拌SBS改性沥青接触角的影响。基于表面自由能理论,得到了温拌SBS改性沥青的表面能及其色散分量和极性分量,研究了老化对温拌SBS改性沥青表面能的影响。结果表明:随着老化程度的加强,温拌SBS改性沥青与水的接触角逐渐增大,疏水性变化明显;原样与Evotherm温拌SBS改性沥青的总表面自由能及其分量均随着老化程度的加强呈降低趋势,其在短期老化阶段的表面自由能下降较为严重;经长期老化,Sasobit温拌SBS改性沥青的极性分量有增大趋势。     

Future climates: Markov blankets and active inference in the biosphere

We formalize the Gaia hypothesis about the Earth climate system using advances in theoretical biology based on the minimization of variational free energy. This amounts to the claim that non-equilibrium steady-state dynamics—that underwrite our climate—depend on the Earth system possessing a Markov blanket. Our formalization rests on how the metabolic rates of the biosphere (understood as Markov blanket''s internal states) change with respect to solar radiation at the Earth''s surface (i.e. external states), through the changes in greenhouse and albedo effects (i.e. active states) and ocean-driven global temperature changes (i.e. sensory states). Describing the interaction between the metabolic rates and solar radiation as climatic states—in a Markov blanket—amounts to describing the dynamics of the internal states as actively inferring external states. This underwrites climatic non-equilibrium steady-state through free energy minimization and thus a form of planetary autopoiesis.     

水镁石粉体表面改性及表面能测算

水镁石粉体是聚合物的常用填料,但水镁石极性较大,与基材的相容性也较差,因此必须通过表面改性,降低水镁石粉体表面能,增强亲油疏水性,从而增加与聚合物之间的相容性,而阴离子表面活性剂是合适的改性剂之一。水镁石粉体改性后的表面性能,可以用固体表面能数值的变化来表征,本文选择丙三醇、水、1-溴代萘为探针液体,用直接测定法与Washburn方程间接计算法获得了改性前后水镁石的接触角,通过Lifshitz-van der Waals acid base三参数法计算其表面能。研究结果表明,不同的阴离子基团中,羧酸类、磷酸较之磺酸类硫酸类改性效果有明显优势,表面能的碱分量γ-S和酸分量γ＋S降为0;随着改性剂中非极性链烃的碳原子个数增加,表面能非极性分量γLSW下降很多,最终导致总表面能下降,接触角增加,疏水性增强。     

基于表面理论的温拌SBS改性沥青-集料体系的粘附性

采用躺滴法检测了掺加1.5%、3%的Sasobit和0.5%、1%的Evotherm 3G制备得到的温拌SBS改性沥青与蒸馏水、甘油和甲酰胺3种液体的接触角;基于表面自由能理论,对比了温拌SBS改性沥青在无水条件下的表面自由能和粘聚功以及在有水条件下的剥落功;同时,考察了温拌SBS改性沥青和石灰岩质集料的粘附功和配伍率。结果表明:采用躺滴法可以准确检测温拌SBS改性沥青与常用检测液体的接触角;以粘聚功、粘附功、剥落功、配伍率作为评价指标可用于表征温拌SBS改性沥青-集料体系的粘附性;温拌SBS改性沥青的表面自由能及其分量、粘聚功、配伍率随着Sasobit掺量的增大而减小,但随着Evotherm温拌剂掺量的增加而增大;水的参与降低了温拌剂对SBS改性沥青-集料体系粘附性影响的差异;Evotherm温拌剂有助于改善温拌SBS改性沥青的水敏感性,Sasobit温拌剂增加了温拌SBS改性沥青的水敏感性。     

The effect of adding nano-SiO2 and nano-Al2O3 on properties of high calcium fly ash geopolymer cured at ambient temperature

This article presents the effect of adding nano-SiO₂ and nano-Al₂O₃ on the properties of high calcium fly ash geopolymer pastes. Nano-particles were added to fly ash at the dosages of 0%, 1%, 2%, and 3% by weight. The sodium hydroxide concentration of 10 molars, sodium silicate to sodium hydroxide weight ratio of 2.0, the alkaline liquid/binder ratio of 0.60 and curing at ambient temperature of 23 °C were used in all mixtures. The results showed that the use of nano-SiO₂ as additive to fly ash results in the decrease of the setting time, while the addition of nano-Al₂O₃ results in only a slight reduction in setting time. Adding 1–2% nano-particles could improve compressive strength, flexural strength, and elastic modulus of pastes due to the formation of additional calcium silicate hydrate (CSH) or calcium aluminosilicate hydrate (CASH) and sodium aluminosilicate hydrate (NASH) or geopolymer gel in geopolymer matrix. In addition, the additions of both nano-SiO₂ and nano-Al₂O₃ enhances the shear bond strength between concrete substrate and geopolymer.     

聚氨酯-含氟丙烯酸酯防水防油性复合乳液的制备及性能

以自乳化自交联的阳离子水性聚氨酯乳液(PU)为种子乳液进行含氟丙烯酸酯(FA)、苯乙烯(St)和丙烯酸丁酯 (BA)等乙烯基单体的自由基共聚合,制得阳离子聚氛醋-含氟丙烯酸酯(FPUA)复合乳液.通过红外光谱分析、接触角测试、表面自由能计算、粒径及粒径分布测试及透射电镜测试对聚合物乳液及其膜结构与性能进行了表征.结果表...     

Adhesive interactions of geckos with wet and dry fluoropolymer substrates

Fluorinated substrates like Teflon^® (poly(tetrafluoroethylene); PTFE) are well known for their role in creating non-stick surfaces. We showed previously that even geckos, which can stick to most surfaces under a wide variety of conditions, slip on PTFE. Surprisingly, however, geckos can stick reasonably well to PTFE if it is wet. In an effort to explain this effect, we have turned our attention to the role of substrate surface energy and roughness when shear adhesion occurs in media other than air. In this study, we removed the roughness component inherent to commercially available PTFE and tested geckos on relatively smooth wet and dry fluoropolymer substrates. We found that roughness had very little effect on shear adhesion in air or in water and that the level of fluorination was most important for shear adhesion, particularly in air. Surface energy calculations of the two fluorinated substrates and one control substrate using the Tabor–Winterton approximation and the Young–Dupré equation were used to determine the interfacial energy of the substrates. Using these interfacial energies we estimated the ratio of wet and dry normal adhesion for geckos clinging to the three substrates. Consistent with the results for rough PTFE, our predictions show a qualitative trend in shear adhesion based on fluorination, and the quantitative experimental differences highlight the unusually low shear adhesion of geckos on dry smooth fluorinated substrates, which is not captured by surface energy calculations. Our work has implications for bioinspired design of synthetics that can preferentially stick in water but not in air.     

双金属冷压焊固相结合强度的分析和计算

分析了表面状态及金属性能对双金属冷压焊结合强度的影响，运用金属-金属界面结合力的计算方法，对冷压焊固相结合强度进行了分析和研究。     

基于表面能理论研究盐冻循环对沥青-矿料界面粘附性的影响

根据表面能理论,采用接触角测量法测定盐冻循环前后苯乙烯-丁二烯-苯乙烯（SBS）、废胎胶粉（CR）和复合胶粉（CCR）3种聚合物改性沥青、石灰岩、玄武岩和花岗岩的表面自由能参数,分别计算出盐冻循环前后沥青-矿料系统的粘附功和剥落功,从而确定盐冻循环对沥青-矿料系统粘附和剥落特性的影响。结果表明:盐冻循环前后,沥青与矿料的粘附过程以及水侵入沥青-矿料界面的剥落过程的比表面自由能变化均为负值,说明沥青与矿料的粘附过程和剥落过程均自发进行;随着盐冻循环次数和盐浓度的增加,沥青-矿料系统粘附功逐渐减小,剥落功逐渐增大,粘附性和抗水损害能力逐渐减弱;当沥青种类相同时,沥青与石灰岩的粘附功最大,剥落功最小,沥青与花岗岩的粘附功最小,剥落功最大;当矿料种类相同时,CCR改性沥青与矿料的粘附功最大,剥落功最小,SBS改性沥青与矿料的粘附功最小,剥落功最大。