利用表面自由能法对添加消石灰的WMA水稳定性的研究

温拌沥青混合料在摊铺行业应用越来越多。尽管温拌沥青有许多优点,水稳定性是温拌沥青混合料潜在的不利因素之一,所以有必要在这一领域进行更多的研究,以提高温拌沥青性能。在研究中,熟石灰作为改善沥青混合料的水稳定性的抗剥落剂,用表面自由能法对集料和沥青之间的粘结性进行了分析。该实验采用了石灰岩和花岗岩两种类型的集料,并用asphamin作为温拌剂,熟石灰作为抗剥落剂。结果表明,熟石灰增加了沥青对集料的浸润性,提高了沥青和集料之间的附着力。添加消石灰的样品,沥青-集料与水-集料的表面自由能相差不大。这说明如果发生剥落则需要更多的能量,也就是消石灰提高了温拌沥青混合料的抗水损害性能。     

Estimation of resistance to moisture destruction in asphalt mixtures

Moisture damage in asphalt mixtures refers to loss in strength and durability due to the presence of water. The level and the extent of moisture damage, also called moisture susceptibility, depend on environmental, construction, and pavement design factors; internal structure distribution and the quality and type of materials used in the asphalt mixture. In order to assess the moisture destruction, the current study bears out an analytical approach based on surface energy. Two types of bitumen represent very different chemical extremes (AC-10 and AC-20) and the three aggregates represent a considerable range in mineralogy (limestone, siliceous gravel, and granite) were evaluated during the course of this study. Repeated compressive test was conducted on samples in dry and wet conditions under controlled temperature and moisture destruction was monitored as a change in dynamic modulus with load cycles. Further, mixtures including the two types of bitumen with or without hydrated lime were evaluated to determine quantity improvement of hydrated lime on moisture destruction. The result show that AC-20 have less moisture induced damages compared to AC-10 and dynamic modulus values for mixes with AC-20 were higher than the one with AC-10 for all the aggregate types. Hydrated lime increased the dynamic modulus values and wet/dry ratio stiffness. Addition of lime for river gravel samples showed significant difference between two types of bitumen but no major differences were found in crashed granite.     

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.     

Material-specific effects of hydrated lime on the properties and performance behavior of asphalt mixtures and asphaltic pavements

This study evaluates hydrated lime-treated hot-mix asphalt (HMA) mixtures through various laboratory tests, including the dynamic modulus test and performance tests to characterize permanent deformation and fatigue damage resistance both in displacement-controlled and force-controlled modes. Two different asphalt mixtures — the asphalt concrete mixture and the fine aggregate asphalt matrix mixture — which differ only in the amount of additional hydrated lime (0.5–3.0%), are tested. Test results demonstrate material-specific damage characteristics of hydrated lime and the existence of a more appropriate amount of hydrated lime to be added to the HMA mixtures than the current typical application rate such as the addition of 1.0% lime to dry or pre-moistened aggregates. In addition, the newly released Mechanistic-Empirical Pavement Design Guide (MEPDG) is used for predicting pavement performance related to hydrated lime content. The MEPDG analysis results show that damage prediction models implemented in the current MEPDG are limited to accurately predicting material-specific damage characteristics. Mechanistic models that consider material-specific crack phenomenon and fracture behavior should be pursued.     

外加材料对乳化沥青再生水泥稳定碎石混合料性能的影响

通过室内试验评价了水泥、消石灰和消石灰矿渣粉3种外加材料对乳化沥青再生水（泥）稳（定）碎石混合料（乳化沥青再生混合料）路用性能的影响,利用扫描电镜观察了水泥乳化沥青胶浆与水稳碎石再生集料界面的微观结构,分析了乳化沥青再生混合料的强度形成机理.结果表明：水泥对乳化沥青再生混合料劈裂强度、水稳性和疲劳寿命提高最大,消石灰矿渣粉次之,消石灰最小.乳化沥青再生混合料中除乳化沥青外,水泥或消石灰矿渣粉也具有明显的胶结材料的作用,但消石灰不具有胶结材料的作用.水泥和乳化沥青水化产生的水化产物,在提高水泥乳化沥青胶浆黏度的同时,能与再生集料上的旧水化产物直接黏结,增大乳化沥青再生混合料中水泥乳化沥青胶浆与再生集料界面的黏结强度.     

沥青路面水损害分析

针对沥青路面水损害问题,运用轴对称有限元方法分析了标准轴栽作用下沥青路面层内孔隙水压力的变化规律及其对沥青路面结构应力状态的不利影响。研究结果表明,孔隙水压力致使沥青与集料剥离,并引起沥青路面内部开裂,从而造成沥青路面过早破坏。     

Investigation of the use of strip-prone aggregates in hydraulic asphalt concrete

A study is made of the suitability of strip-prone aggregates for use in asphalt concrete water barriers in embankment dams. Standard boiling tests were used for ranking various aggregate types with respect to water susceptibility and aggregate-bitumen adhesion. Indirect tension tests (splitting tests) were used to study the effects of aggregate-bitumen adhesion on asphalt concrete tensile strength. The test results show the significant detrimental effects of using strip-prone aggregates for open-grade porous asphalt (air void 4–10%), but that aggregate-bitumen adhesion and tensile strength could be increased by adding amine or hydrated lime to the asphalt mix. However, a similar test series on dense-grade hydraulic asphalt (air void 2–3%) shows no detrimental effects of using strip-prone aggregates. Furthermore, there were no significant differences in compressive strengths or beam bending strengths and strains at failure between specimens with or without strip-prone aggregates and with or without amine added. This was the case even for specimens having been cured by exposure to 100 freeze–thaw cycles at +25 °C to −25 °C. For hydraulic asphalt, which is virtually impervious with a significant bitumen film thickness covering the aggregate particles, it does not seem required to use additives to improve the aggregate-bitumen adhesion properties. However, further testing should be done to study any long-term effects of using strip-prone aggregates.     

考虑钢渣表面特征的沥青混凝土水稳定性改善研究

钢渣经过水洗和陈化处理后可作为粗集料铺筑沥青路面。但钢渣表面有杂质粉尘包裹,高压水洗难以去除,陈化后钢渣表面依然对沥青混凝土水稳定性有显著影响。为促进钢渣在工程中应用,本研究以生产线大批量制备的工程用钢渣集料为研究对象,采用SBS改性沥青及硅酸盐水泥填料调整沥青胶浆的组成来增强钢渣与沥青胶浆的粘附,改善钢渣沥青混凝土的水稳定性。首先采用XRD对钢渣及钢渣表面矿物相成分分析,从理论上验证改善方案的可行性;然后对沥青胶浆包裹的钢渣集料进行水煮试验,分析改善措施对粘附性的提升效果;最后对钢渣沥青混凝土进行冻融劈裂试验和浸水马歇尔试验,确定其水稳定性变化。结果表明,改善措施能使水稳定性能得到改善,建议SBS改性沥青和硅酸盐水泥复合使用。     

高模量沥青混合料基础层路面施工总结

指出高模量沥青混凝土就是在沥青内添加SBS或EVA类聚合体改性剂或者在骨料拌和中直接掺加添加剂,来得到的高模量、抗车辙和耐水性较好的沥青混凝土。根据阿尔及利亚东西高速公路高模量沥青混凝土路面施工经验,对本项目高模量沥青混凝土配合比设计及施工进行总结。     

Rutting evaluation of hydrated lime and SBS modified asphalt mixtures for laboratory and field compacted samples

The purpose of this study is to evaluate permanent deformation for hydrated lime and SBS modified asphalt mixtures. Control (C), 2% hydrated lime (2L), 5% SBS polymer mixtures and 2%hydrated lime–5%SBS (2L5SBS) mixtures were prepared. The Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracker, also known as French Rutting Tester were realized with two different stages. Same LCPC slabs were produced. Original LCPC compactors and also field cylinder were used separately. LCPC rutting values were determined with left and right wheel loadings. Also averages were obtained with calculation. Repeated creep tests were used for these mixtures and permanent deformations were plotted for two different moisture conditioning that water immersion and freeze and thaw cycles. Diameter samples (100 mm and 150 mm) were studied in repeated creep tests. In the result that LCPC tracking values were compared with repeated creep tests in terms of sample diameters. LCPC wheel-tracking test results show that 2L5SBS mixtures reveal utmost performance according to the other mixtures types. Polymer modification increased rutting resistance of lime modified ones. Both original LCPC compactor and field cylinder compaction showed resemble results. 150 mm samples showed highest correlation (higher than R² = 0.80) between LCPC test and repeated creep test for different compaction types and different moisture conditionings.     

Duroflex~改性剂对沥青混合料性能影响研究

介绍了Duroflex改性剂的作用机理,分析了改性剂在不同掺量下对沥青粘度及沥青混合料水稳定性、高温稳定性、抗疲劳性能的影响,理论上得出Duroflex改性剂在混合料中的合理掺量为0.4%;对比试验分析了掺Du-roflex改性剂沥青混合料与SBS改性沥青混合料的性能,结果表明AC-25C型混合料中掺0.3%的Duroflex改性剂与SBS改性沥青混合料的水稳定性相当,但SBS改性沥青的高温稳定性具有一定优势。     

Use of basalt in asphalt concrete mixes

One of the main reasons behind the appearance of early distresses in Jordan roads and the low surface skid resistance is the use of marginal quality limestone aggregate. Large quantities of good quality basalt are available in the Northeastern parts of Jordan. In this research, the possibility of improving the properties of local asphalt concrete mixes by replacing different portions of the normally used limestone aggregate by basalt was investigated. The replacement included total replacement of the limestone by basalt, replacing the coarse aggregate, and replacing the fine aggregate. Results showed that the optimal mix was the mix that had basalt coarse aggregate and limestone fine aggregate. In order to overcome the stripping potential of the optimal mix, 20% of the filler portion of the aggregate, material smaller than 0.075 mm, was replaced by lime. The optimal mix showed superiority, over the tested mixes, in all the evaluated properties, which were Marshall Stability, indirect tensile strength, stripping resistance, resilient modulus, dynamic creep, fatigue, and rutting.     

Mechanistic analysis of ST and SBS-modified flexible pavements

This paper deals with the viability of using starch (ST) and styrene–butadiene–styrene (SBS) as an additive in stone matrix asphalt (SMA) mixtures. A 5% of ST and SBS by weight of bitumen were blended with (70/100)-paving grade asphalt. Unmodified and modified bitumen were subjected to physiochemical tests. The performance tests including, Marshall stability, tensile strength, tensile strength ratio and resilient modulus were carried out on unmodified and modified SMA mixtures. A mechanistic-empirical design approach was used for estimating the improvement in service life of the pavement or reduction in thickness of SMA and base layer for the same service life due to modification the SMA mixtures. The analyses of test results show that the moisture damage and temperature susceptibility can be reduced by the inclusion of ST and SBS in the asphalt mixture. The results also revealed that ST-modifier can be used as anti-stripping agent, and reduced plant emissions and energy consumption by 30%, as well as it shows resistant to fuels, most common chemicals and solvents. The results of multi-layer elastic analysis presented herein indicate that the pavement consisting of ST and SBS-modified SMA as a surface layer is beneficial in reducing the construction materials. In addition, the safe pavement design criteria of unmodified and modified SMA mixtures based on the anisotropic elasticity analysis through finite-element simulation were obtained and reported herein.     

Effect of aggregate properties on asphalt mixtures stripping and creep behavior

The purpose of this paper is to look at some aspects of the effects of aggregate chemical and physical properties on the creep and stripping behavior of hot-mix asphalt (HMA). Two types of aggregates evaluated in this study were limestone and basalt. The effects of the aggregates type were evaluated on three different aggregate gradations and two types of asphalt used in preparing the HMA. The percent of increase in static creep strain of HMA due to conditioning was utilized in this study to assess the stripping.Test results indicated that unconditioned HMA specimens prepared using basalt aggregate resist creep better than those prepared using limestone. However, after conditioning, mixes prepared using basalt were less resistant to creep strain than those prepared using limestone aggregate. Percent absorbed asphalt was found to be directly related to stripping resistant. Also, mixes prepared using aggregate following ASTM upper limit of dense aggregate gradation presented the highest resistance to stripping. The results of the calculated adhesion work were able to detect the effect of stripping on creep behavior for mixes prepared.     

沥青混合料中掺加消石灰粉替代部分矿粉施工质量控制

为改善沥青与石料黏附性,提高沥青路面的抗水损害能力,在连盐高速公路下面层结构沥青混凝土混合料中,以消石灰替代部分石灰岩矿粉(总量不超过混合料质量的2%)进行施工。介绍了消石灰粉替代部分矿粉进行施工的工序、配合比设计、压实方案和施工控制要点,最终沥青混合料总体质量得到控制。     

矿渣消石灰粉乳化沥青混凝土性能与微观机理

研究了矿渣消石灰粉用量对乳化沥青混凝土稳定度、抗压强度、抗压回弹模量和劈裂强度的影响,使用红外光谱、X衍射和扫描电镜分析了矿渣消石灰粉改善乳化沥青混凝土强度的微观机理.结果表明,添加矿渣消石灰粉能显著提高乳化沥青混凝土力学性能;在消石灰的碱性激发作用下,矿渣粉与乳化沥青中的水相发生了水化反应,生成了水化硅酸钙凝胶,它和乳液破乳后的沥青通过物理过程形成了复合胶结料,改善了沥青胶浆微观结构,增大了胶浆黏度,增强了胶浆与集料界面的黏结,从而提高了乳化沥青混凝土的力学性能.     

Comprehensive analysis of surface free energy of asphalts and aggregates and the effects of changes in pH

Moisture damage is a major factor in the deterioration of asphalt pavements. In order to combat this problem, it is essential to understand the effects of moisture on the adhesive and cohesive bonds in asphalt concrete mixtures. These effects can be quantified through the use of surface free energy, which is a thermodynamic material property that has been successfully used to select asphalt binders and aggregates that have the necessary compatibility to firm strong bonds and resist moisture damage.This study aimed at understanding the effects of material characteristics and additives on surface energy and the resulting bond between asphalt binders and aggregates. As such, the study involved measuring the surface free energy of 37 neat and polymer modified asphalt binders and 11 aggregates were measured. In addition, the surface free energy was measured for three asphalt binders after two anti-strip agents were added separately (six binder-anti-strip agent combinations) and for nine asphalt binders that were both short and long-term aged. The study also examined the effect of water pH on surface energy and water-aggregate adhesive bond. It was found that anti-strip agents, in general, reduced the cohesive bond energy of asphalt binder, allowing better wetting and adhesion to aggregates and increase in resistance to moisture damage. Aging of the asphalt either increased or decreased the cohesive bond depending upon the chemical composition of the unaged asphalt binder. Statistical analysis was conducted to rank the moisture resistance of asphalt binders and asphalt–aggregate combinations, respectively. The results showed that the pH of the water increased slightly due to contact with the aggregates, but did not significantly alter the total surface tension of the water or surface free energy components of the asphalt binder.     

集料形态特征对集料-沥青黏附及水稳定性的影响

为评价集料形态特征对集料-沥青黏附性及其体系水稳定性的影响,提出了一种定量测试集料-沥青黏附性的新方法.借助集料图像测量系统(AIMS)测试了5种集料的形态特征,并对不同形态集料沥青混合料的水稳定性进行评价,建立了集料形态特征与集料-沥青黏附性及水稳定性的关系,同时基于灰色关联法分析了集料形态特征对集料-沥青黏附性及水稳定性的影响排序.结果 表明:提出的集料-沥青黏附性定量测试方法简单、可靠;沥青混合料水稳定性最佳的棱角性为2500～3000,球度为0.65～0.75;随着集料表面纹理的增大,沥青混合料的水稳定性增强;集料表面纹理对集料-沥青黏附性的影响最大,棱角性对沥青混合料浸水飞散损失指标的影响最大,球度对沥青混合料冻融劈裂强度比、浸水车辙变形拐点指标的影响最大.     

Rheological properties and storage stability of bitumen/SBS/montmorillonite composites

Styrene–Butadiene–Styrene triblock copolymer is commonly used for modifying physical, mechanical and rheological properties of bitumen. Because of the poor compatibility between SBS and bitumen, SBS modified bitumen is not storage stable at high temperature. To obtain more compatibility between SBS and bitumen, several methods have been suggested. In this study, organophilic montmorillonite/SBS modified bitumen mixtures were prepared by melt intercalated blending. Physical and rheological properties of polymer modified bitumen were compared before and after adding nanoclay to the bitumen. Results showed that the presence of nanoclay improves the storage stability of PMB significantly without adverse effect on other properties of it. The structure of OMMT/SBS/bitumen blend was characterized by XRD. The spectra indicated that proper dispersion of OMMT in SBS led to a homogenous blend which is named exfoliated structure. The result of storage stability test showed that the difference in softening point was in good accordance with ASTM standard limitation which means that OMMT can improve the storage stability of PMB. Also morphological analysis confirmed storage stability results.     

水性环氧树脂改性乳化沥青作为雾封层材料的应用性能研究

沥青路面雾封层预养护主要选用普通乳化沥青、SBS改性乳化沥青等材料,本研究采用水性环氧树脂乳液作为改性剂对乳化沥青进行改性,将其试用于沥青路面雾封层施工,经检测路面防水抗渗功能明显提高,松散细集料得到有效固结。结果表明,水性环氧树脂改性乳化沥青作为沥青路面雾封层材料,具有良好的路用性能。