Potential of recycled fine aggregates powder as filler in asphalt mixture

The main objective of this study is to investigate the potential of using recycled fine aggregates powder (RFAP) as filler in asphalt mixtures. RFAP is a by-product of the production of Recycled Concrete Aggregate (RCA). The disposal of RFAP may cause many serious environmental problems. It is necessary to find potential usage to avoid these problems.In this study, RFAP is used as filler in asphalt mixture by totally replacing conventional limestone powder (LP). Firstly, the properties of RFAP is studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). Then the indirect tensile strength and modulus tests, three-point bending tests, dynamic creep tests and fatigue tests are conducted to compare the properties between asphalt mixtures with RFAP and traditional asphalt mixture with LP. Results indicate that RFAP can improve the properties of asphalt mixture, such as including water sensitivity and fatigue resistance. However, it may cause a little decrease of the low-temperature performance. All the results indicate that the RFAP can be used in asphalt pavement, especially in hot regions.     

Experimental investigation on related properties of asphalt mastic containing recycled red brick powder

Some properties of asphalt mastic containing recycled red brick powder (RBP) were investigated in this paper. RBP was used as filler in asphalt mastic. The investigated mastic consisted of asphalt and filler at a mass ratio of 1:1. Penetration, softening point and high-temperature viscosity were tested. Dynamic Shear Rheometer (DSR) was used to conduct frequency sweep test of asphalt mastic. The introduction of RBP resulted in reduced penetration, increased softening point, apparent activation energy, complex shear modulus in the low frequency area and high-temperature viscosity. It indicates that RBP may have some positive effect on high-temperature properties but some negative effect on low-temperature properties of asphalt mastic. It is also believed that the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing limestone mineral filler (LMF).     

高温下橡胶沥青胶浆特性及矿料级配优化分析

为改善橡胶沥青混合料的高温性能,提出以橡胶沥青胶浆和矿料级配为主要研究对象的优化思路。通过室内试验,首先研究粉胶比对橡胶沥青胶浆抗车辙因子和相位角的影响;然后结合橡胶沥青的特异性,对其橡胶沥青混合料的矿料级配进行选择和调整,将动稳定度和相对变形作为混合料高温性能评价指标,得出优化后的矿料级配。研究结果表明,提高橡胶沥青混合料高温稳定性的措施有:适当调整粉胶比,控制在1.2左右为宜;以水泥取代矿粉作为混合料的填料;以传统SMA级配为基础,对混合料级配作出调整,适当降低填料比例,能够实现橡胶沥青混合料高温稳定性的优化。     

Evaluation of marble waste dust in the mixture of asphaltic concrete

In the study the use of marble dust collected during the shaping process of marble blocks has been investigated in the asphalt mixtures as filler material. The samples having marble dust and limestone dust filler were prepared and optimum binder content was then determined by Marshall test procedure. Dynamic plastic deformation tests were carried out by using the indirect tensile test apparatus. Optimum filler content was then determined considering the filler/bitumen ratio and filler ratio. Test results showed that plastic deformation of marble waste is between the upper and the lower limits of grounded marbles. The study showed that marble wastes, which are in the dust form could be used as filler material in asphalt mixtures where they are available and the cost of transportation is lower than ordinary filler materials.     

Utilization of municipal solid waste incineration ash in stone mastic asphalt mixture: Pavement performance and environmental impact

The objective of this study is to the use of municipal solid waste incinerator (MSWI) fly ash as a partial replacement of fine aggregate or mineral filler in stone matrix asphalt (SMA) mixture. For saving natural rock and reusing solid waste, basic oxygen furnace slag (BOF slag) was used as part of coarse aggregate. And this makes SMA mixtures contain more than 90% solid waste materials by mass. A comparative study of the performance of two mixes designed using superior performance asphalt pavements (SUPERPAVE) and Marshall mix design procedures was carried out in this research. Samples from both mixes were prepared at the design asphalt contents and aggregate gradations and were subjected to a comprehensive mechanical evaluation testing. These tests included Marshall stability, water sensibility, resilient modulus, fatigue life and rutting. In all the performed tests SUPERPAVE mixtures proved their superiority over Marshall mixtures. TCLP test for environmental impact indicated that asphalt is an effective stabilization and solidification agent for heavy metal in MSWI ash. The heavy metal leachates in TCLP tests have great positive correlation with their initial concentration in waste. But Ni is an exception that lower initial concentration leaded to higher cumulative leaching rate.     

考虑集料-胶浆粘附性能的钢渣沥青混凝土体积稳定性改善研究

采用XRD分析了钢渣的矿物相特征以调整沥青胶浆的组成来增强钢渣-沥青胶浆粘附性,利用沥青胶浆包裹的钢渣集料颗粒进行水煮试验以分析钢渣-胶浆粘附作用的强弱,并开展了钢渣沥青混凝土浸水膨胀试验以确定其体积稳定性水平.试验结果表明采用钢渣粉替代传统的石灰石矿粉与沥青制备而成的胶浆与钢渣集料具有优良的粘附性能,可显著提高钢渣沥...     

The role of industrial by-products in self-compacting concrete

The development of self-compacting concrete is considered as a milestone achievement in concrete technology due to several advantages. In order to be self-compactable the fresh concrete must show high fluidity besides good cohesiveness. For the purpose of evaluating these properties, several concrete mixtures were prepared with a water to cement ratio of 0.45 in the presence of an acrylic-based superplasticizer at a dosage ranging from 1% to 2% by weight of very fine material fraction (maximum 150 μm). Either limestone powder or fly ash or recycled aggregate powder (that is a powder obtained from the rubble recycling process) were used as mineral addition, in order to assure adequate rheological properties, in terms of cohesiveness, in the self-compacting concretes. Preliminary rheological tests were carried out on cement pastes containing these mineral additions. In some cases, recycled instead of natural aggregate was used by substituting either the coarse or the fine aggregate fraction. The fresh concrete properties were evaluated through slump flow, L-box test and segregation resistance. Compressive strength of concrete was determined at 1, 3, 7 and 28 days of wet curing. Results obtained showed that an optimization of self-compacting concrete mixture seems to be achievable by the simultaneous use of rubble powder and coarse recycled aggregate with improved fresh concrete performance and unchanged concrete mechanical strength.     

掺活性矿粉片麻岩沥青混凝土在湖北大广北高速公路的应用

采取掺入活性矿粉、用石灰岩石屑代替片麻岩石屑等综合措施,进行了片麻岩沥青混合料性能指标的室内试验,研究了活性矿粉对SBS改性沥青和湖改性沥青片麻岩沥青混合料的改善效果,并进行了试验段的铺筑。结果表明:采用活性矿粉可以有效提高片麻岩沥青混合料性能,在确保沥青混合料性能的前提下降低工程造价。     

锰渣矿粉沥青混合料抗腐性能研究

利用锰渣矿粉替代沥青混合料中的石灰岩矿粉配制成锰渣沥青胶浆和锰渣矿粉沥青混合料,进行锰渣沥青胶浆直剪试验、吸持性能试验及锰渣矿粉沥青混合料马歇尔试验、浸水马歇尔试验、冻融劈裂强度试验,测试不同替代量锰渣沥青胶浆粘附性能和锰渣矿粉沥青混合料抗腐性能的变化.结果表明,利用锰渣矿粉替代沥青混合料中的石灰岩矿粉能有效地改善和提高沥青胶浆粘附性能和沥青混合料抗腐性能.同时,通过锰渣矿粉改善和提高沥青胶浆粘附性能和沥青混合料抗腐性能的性能机理分析,揭示锰渣矿粉替代量影响沥青胶浆粘附性能和沥青混合料抗腐性能变化的原因.     

Laboratory comparison of the crumb-rubber and SBS modified bitumen and hot mix asphalt

The use of crumb rubber (CR) recycled from waste tires using an ambient grinding process was evaluated at two stages in asphalt formulation. First, bitumen modified with crumb rubber was evaluated by rotational viscometery (RV), dynamic shear rheometry (DSR) and conventional binder tests. Hot asphalt mixtures including crumb-rubber-modified bitumen were then evaluated by determining the permanent and fatigue characteristics and stiffness moduli of control and modified mixtures. The properties of the crumb-rubber-modified bitumen and asphalt mixtures were compared to different contents of styrene–butadiene–styrene (SBS) modified-bitumen and asphalt mixtures. The tests showed that to achieve the same performance, as with SBS-modification, the CR-content must be used at much higher than SBS. 8%-CR modification was determined as the most suitable content according to both binder and mixture tests.     

煤矸石粉沥青胶浆路用性能及微观机理研究

为了拓宽煤矸石加工再利用的途径,探究其在道路工程中的应用前景,采用5种粉胶比制备了分别掺入煤矸石粉(CWP)、煤矸石灰(CWA)和石灰岩(LS)3种填料的沥青胶浆,对其路用性能进行了对比研究,并对煤矸石粉沥青胶浆的微观机理进行了分析.结果表明:与矿粉相比,煤矸石粉尤其是煤矸石灰颗粒更细,比表面积更大,表面更粗糙,并且含有更多的活性矿物成分和孔隙结构,提高了与沥青的黏结力;煤矸石粉和煤矸石灰的孔隙吸收了沥青中的轻质组分,使胶质和沥青质的相对含量增大,从而显著提高了沥青胶浆的高温稳定性能,并改善了感温性,但其低温性能有所降低.     

建筑固废物再生粒料基层混合料的性能研究

在研究天然集料(NA)、再生混凝土集料(RCA)、再生砖渣与混凝土集料(RBCA)物理力学性质的基础上,开展了不同RCA掺量(质量分数,下同)及掺30%砖渣的混合料CBR(California bearing ratio)试验,探讨了压实度、含水率对混合料动回弹模量的影响.结果表明:RCA掺量越大,混合料CBR值与动回弹模量均越大;掺入30%砖渣后,混合料CBR值与动回弹模量均降低明显,表明工程应用中应适当控制砖渣掺量;压实度对RCA混合料的动回弹模量影响最大,对RBCA混合料的影响次之,对NA混合料的影响最小;含水率对NA混合料的动回弹模量影响较小,而对RCA、RBCA混合料的影响较大.该研究可为建筑固废物混合料用作道路结构层提供参考.     

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.     

添加剂对凝灰岩沥青混合料粘附性能影响

为改善凝灰岩沥青混合料的粘附性能,以掺水泥和抗剥落剂凝灰岩沥青混合料为研究对象,选取石灰岩沥青混合料为对比试样,通过水煮法试验、老化前后水稳定性试验,对凝灰岩沥青混合料的粘附性能研究。结果表明:掺入适量添加剂可使凝灰岩集料的粘附等级显著提高,并接近石灰岩集料等级;掺水泥对凝灰岩沥青混合料老化后残留稳定度和冻融劈裂强度比的提升效果均优于掺抗剥落剂,与不掺添加剂的凝灰岩沥青混合料相比,水泥掺量2%、3%下,凝灰岩沥青混合料的老化后残留稳定度分别提高了21.5%、21.7%,冻融劈裂强度比分别增大了16.7%、15.3%,均接近于石灰岩沥青混合料。掺液体抗剥落剂对凝灰岩沥青混合料的冻融劈裂强度比提升效果欠佳。     

掺合料对再生混凝土三孔砖力学及抗冻性能的影响

利用废弃黏土砖制备再生混凝土三孔砖,通过改变粉煤灰、矿粉的掺量,研究单掺、复掺掺合料裹骨料对再生混凝土三孔砖的抗压强度和冻融循环后强度损失及质量损失的影响。结果表明:采用粉煤灰、矿粉裹骨料搅拌工艺制备再生混凝土三孔砖,改善了混凝土三孔砖的力学及抗冻性能,使混凝土三孔砖达到国家承重墙体材料的标准要求。复掺矿粉、粉煤灰的改性效果优于单掺掺合料改性效果,当矿粉掺量为20%,粉煤灰掺量10%时,改性效果最优,混凝土28 d抗压强度达到最大值47.2 MPa,抗冻性最好,其抗冻质量损失最低为0.3%,强度损失最低为8%。     

热拌及温拌再生SMA沥青混合料疲劳性能分析

设计了RAP质量分数分别为0%,20%,30%的6种热拌及温拌再生SMA沥青混合料,并对其进行四点梁弯曲疲劳试验,采用耗散能法分析了RAP掺量、拌和方式对热拌及温拌再生SMA沥青混合料疲劳性能的影响.结果表明:热拌及温拌再生SMA沥青混合料的疲劳寿命与累积耗散能的关系不会随RAP掺量、拌和方式的变化而变化,疲劳寿命与累积耗散能在双对数坐标下,均表现出良好的线性关系.同时,还发现了热拌及温拌再生SMA沥青混合料的累积耗散能与RAP掺量、拌和方式之间的变化规律.     

Study on properties of recycled tire rubber modified asphalt mixtures using dry process

To minimize waste tires pollution and improve properties of asphalt mixtures, properties of recycled tire rubber modified asphalt mixtures using dry process are studied in laboratory. Tests of three types asphalt mixtures containing different rubber content (1%, 2% and 3% by weight of total mix) and a control mixture without rubber were conducted. Based on results of rutting tests (60 °C), indirect tensile tests (−10 °C) and variance analysis, the addition of recycled tire rubber in asphalt mixtures using dry process could improve engineering properties of asphalt mixtures, and the rubber content has a significant effect on the performance of resistance to permanent deformation at high temperature and cracking at low temperature.     

Laboratory evaluation of fatigue characteristics of recycled asphalt mixture

This paper presents the results of a laboratory study of evaluating the fatigue characteristics of hot-mix asphalt (HMA) mixtures using different testing methods. In this study, the fatigue performance of HMA mixtures was evaluated with the Superpave indirect tension (IDT) tests and beam fatigue test. The HMA mixtures containing 0%, 10%, 20%, and 30% of recycled asphalt pavement (RAP) were plant prepared with one source of aggregate, limestone, and one type of binder, PG 64–22. The fatigue properties tested included indirect tensile strength (ITS), failure strain, toughness index (TI), resilient modulus, DCSE_f, energy ratio, plateau value, and load cycles to failure. The results from this study indicated that both Superpave IDT and beam fatigue tests agreed with each other in ranking the fatigue resistance of mixtures when proper procedures were followed.     

Investigation into the properties of asphalt mixtures containing magnesium hydroxide flame retardant

In this study, horizontal burning, limiting oxygen index (LOI) and direct burning tests were conducted to evaluate the effects of magnesium hydroxide (MH) on flame retardancy for asphalt. The influence of MH on the mechanical properties of the asphalt mixtures was also evaluated using a Marshall stability test and an indirect tensile strength test. The results indicate that MH improves the thermal stability of asphalt. The presence of MH reduces the horizontal burning classification of asphalt from FH-3 to FH-1, and the LOI is also increased. Reductions in the average burning time and mass loss were observed. The volume of flammable volatiles released from asphalt was reduced. By replacing some of the mineral filler in asphalt with equal quantities of MH, the Marshall stability was increased, its loss decreased. Similarly, the indirect tensile strength (ITS) was increased, but the ITS loss increased slightly. It is concluded that MH can be used as flame retardant for asphalt mixtures without significantly reducing the original pavement performance. This may provide a novel and safer road material, especially for use in tunnel roadways.     

纤维沥青混合料低温性能研究

对三种常用路用纤维的沥青胶浆及混合料进行低温性能试验，分析其低温特性，并与普通的沥青胶浆和沥青混合料进行对比，指出纤维沥青混合料具有较好的低温性能，聚酯纤维和矿物纤维在抗低温损坏方面表现突出。