Sustainable Construction Materials 2012

The South African government plans to create a low carbon industry whilst simultaneously creating new jobs through industrial development. These plans coincide with the released UN publication: "Towards a Green Economy: Pathways to Sustainable Development and Poverty Eradication". National policies are underway to ensure execution of these environmental and social objectives within the industry. The industry consists of many disciplines of which the road pavement sector is a major role player. The aim of this paper is to establish whether the road construction industry is equipped to implement such proposed policies. The institutional obstacles are reviewed in order to identify key issues that are prevalent in developing countries. The sustainability of some current road construction practices are assessed with regard to climate change mitigation. In addition the importance of the implementation of strategic objectives and the formulation of clear goals are investigated. This paper will show the necessity of a paradigm shift by role players and stakeholders in order for the country to reach long term sustainable goals.

In this paper the use of slags, from ferro- and silicomanganese alloy production as well as from the production of Pt-group element concentrates in blended cements, is discussed. The properties of the mixtures depend on the cement type, the mixtures, and the different manufacturers. Some cement performs better than others. The results are promising, but show variable behavior depending on slag and cement composition. Compressive strength tests as well as heat flow curves showing the hydration behaviour, indicate that 10-20 % addition of these slags to ordinary Portland cement is possible. These slags can be used as additions to cements to produce composite cements fulfilling the requirements up to 42.5N MPa class. By the addition of slag, the amount of calcium carbonate necessary for clinker production is reduced and, therefore, CO2 emissions are decreased. Also, large slag stock piles can be avoided.

Continuously reinforced concrete pavements (CRCP) are frequently applied on motorways and also on other heavily trafficked roads in Belgium, mainly because of the confidence in its durability. An exposed aggregate surface is used to reduce the traffic noise. The durability, the sustainability, the low maintenance and the low traffic noise production of CRCP lead to long-lasting applications in Belgium. This paper presents the observations and findings from the monitoring of three CRCP test sections constructed on the motorway E17 near the city of Ghent, Belgium in August 2011. The three test sections have a reinforcement rate of 0.75%, 0.70% and 0.65% + 20 kg/m3 steel fibers, respectively. Right from the moment of construction, the behavior of the pavements was monitored for the concrete temperature, the crack spacing and the crack width, and the development of the crack pattern in time. The temperatures within the concrete were evaluated using thermocouples. The crack spacings were measured with a distance measuring wheel. The width of a number of cracks was measured with a microscope and the movements within the CRCP were also measured with a linear variable differential transformer (LVDT) across a number of cracks. Major observations and findings from the monitoring of the CRCP test sections include: the effect of longitudinal reinforcement on the early-age cracking; the effect of time of construction during the day on the early-age cracking; and the effect of curing time of concrete on the early-age cracking.

Houben has developed a model concerning the transversal cracking in non-jointed plain concrete pavements using equations from the standard Eurocode 2 for the time-dependent concrete properties and shrinkage. For properties that are not available in standards, Houben made assumptions based on engineering judgment. After that, Pradena and Houben studied those assumptions more in depth, including the maturity method. The results were compared with field measurements and a new equation for the relaxation factor was proposed. The objective of the present paper is to apply those findings for analysis of the longitudinal cracking process in non-jointed plain concrete pavements taking into account different conditions. The calculation results include the time of occurrence of longitudinal crack(s), if any, the variation of the crack widths and the maximum pavement width that can be constructed without any longitudinal joint. In the cases that a longitudinal crack occurs, it is always only one crack which occurs at early age. Because differences in the relaxation at this age are fundamental, future analyses need to concentrate at early age. The new approach confirms the complexity of this kind of modelling, improves the analysis from a theoretical point of view, and yields new insights for future investigations.

Cement asphalt mortar (CA mortar) is the key component in the structure of Shinkansen slab track and serves as the elastic shock-absorber. CA mortar is a composite material with cement and asphalt emulsion and acts as a cushion layer in the structure of slab track. The workability and homogeneity quality of fresh CA mortar is governed by its rheological behavior. Influences of cement type, emulsified asphalt type and superplasticizer dosages on the rheological parameters were analyzed by means of a rheometer. The rheological model was also explored. The results show that the CA mortar is a non Newtonian fluid and it shows thixotropic flow behaviour. The fresh CA mortar behavior is better described by the Herschel-Bulkley model. From the point of thixotropic behavior, the cement C-3 and emulsion A-1 may be beneficial for higher static and dynamic segregation resistance.

The main objective of this paper presents a study of the effect of engineering properties of expansive soil as subgrade when stabilized by using different percentage of hydrated lime on thickness of pavement structural system. A series of physical tests in terms of sieve analysis, liquid limit, plastic limit and plasticity index as well as dry density, moisture content relationship also mechanical tests in term of and CBR test was conducted before and after adding three percentages of lime (2%, 4% and 6%) by weight of expansive soil with curing time of 24 hour to evaluate the effect of hydrated lime on behavior of expansive soil as subgrade on thickness of flexible pavement structural system. The results shows that the lime provides better physical properties in term of liquid limit, plastic limit and plasticity index and shows that the lime increases the CBR value to 52%, 27% and 44% when adding 2%, 4% and 6% percentages of lime, respectively, for untreated soil (CBR=1%). Also, the lime decreases swelling from 4% in untreated soil to 1.20%, 0.01% and 0.20% when adding 2%, 4% and 6% lime percentages, respectively. The design of pavement thickness shows that the adding of lime decreases the thickness from 92.5 cm when using untreated expansive soil as subgrade to 45cm, 35cm, and 35 cm when using 2%, 4%, and 6% percentages of lime respectively in stabilization of expansive soil as subgrade. The results suggest that the lime content 6% is optimum percentage were that given a highly strength, lowest swelling and small thickness of pavement.

In preventative maintenance, it is very significant to accurately recognize the void beneath the cement concrete pavement. However, there are quite a few defects in the current NDT technologies of void recognition. Based on ground penetrating radar (GPR), the void investigation is carried out on several typical highway sections in Anhui Province. Then, the reflected wave profile is obtained by "Reflex-Win" so as to ascertain whether there is void at the bottom of these pavement slabs. Next, falling weight deflectometer (FWD) is utilized to carry out multi-level load deflection test. So, the "load-deflection" regression models can be established by the test results. Additionally, extension evaluation is adopted to recognize the void and its index system comprises the regression model's slope, intercept as well as the maximum deflection. Finally, comparing to the detection results of GPR, by way of adjusting the section domains of these indexes, the classical domains of different void status and their weight coefficients scientifically, relatively higher recognition ratio and relatively lower misjudgment ratio can be acquired. The study shows that under this improved method, the void ratio of the typical highway sections is 33%, approximately to the result of GPR (35%). Moreover, this method's recognition ratio is 88.6% and its misjudgment ratio is merely 6.1%. The superior accuracy of void recognition shows that the improved method is able to satisfy the demands of engineering detection, recognition and structural evaluation.

For the sake of developing new cementitious materials with high toughness and excellent workability, an extensive research programme was set up to investigate the properties of self-compacting concrete (SCC) with waste tyre rubber particles and emulsified asphalt in fresh state and hardened state. The effects of rubber particles and emulsified asphalt on strength, dynamic elastic modulus, stress-strain response and impact toughness of hardened SCC were analyzed in detail. Results indicate that rubber particle and emulsified asphalt remarkably influence mechanical properties of SCC. Incorporating rubber particles together with emulsified asphalt is conducive to improve self-compactability of fresh SCC. The strain capability and toughness of SCC can be greatly enhanced by addition of rubber particle and emulsified asphalt. A combination of rubber particles and emulsified asphalt is an effective way to prepare new self-compacting concrete with excellent dynamic mechanical properties.

Based on the FLAC3D software, this paper is devoted to researching the numerical simulation analysis of slope stability under rainfall infiltration. Based on the shear strength and seepage of unsaturated soils, it should add matric suction and soil-water characteristic curve to FLAC3D. So, in this way, FLAC3D can be applied to the field of saturated-unsaturated seepage. Simulation analysis of the seepage of the slope and the change of security variation in the condition of rainfall can be done. It achieved the hazardous area of slope after rainfall and put forward the concept of "small slip failure occurred in the toe of slope". And in this paper, the relationship between coefficient of permeability, rainfall duration, rainfall intensity, slope height, slope and slope stability after the rainfall was researched by the written procedures 1. This paper provides a basis for stability analysis of unsaturated soil slopes under rainfall infiltration.

In the western region of Croatia, small fractions of recycled aggregate have similar properties like small fractions of crushed natural aggregate regarding grain shape and fines content. The focus of this research was to analyze possibilities of using small fractions of recycled aggregate in the cases where only poor quality natural sand is available for production of concrete. The research is based on available data from concrete production in wider region of western Croatia and also on experimental research carried out on several series of mortar samples prepared with recycled and natural fine aggregate. Influence of two-phase mixing method on mortar properties in fresh and hardened state was analyzed. Based on the results of testing, it is concluded that small recycled concrete aggregate may be suitable for use in the concrete production. In concrete mix design, it is recommended to decrease absolute aggregate absorption determined according to HRN EN 1097 and to use double-mixing method, due to its positive effect on the consistency and strength.

Due to the relatively longer length of Continuously Reinforced Concrete Pavement (CRCP), CRCP can be regarded as a long slab on the elastic foundation. According to the slippage assumption of shearing stress and maximum principal stress theory, the analytical solutions of the displacement, tensile stress, and shearing stress in CRCP under thermal load are deduced in this study. The following results are acquired from the analysis. Maximum thermal displacement, thermal tensile stress, and shearing stress have relations with the temperature difference, resistance coefficient of friction between slab and base, the thickness, modulus and length of slab. And they are in proportion to temperature difference. The influence of resistance coefficient of friction is significant to maximum thermal displacement and stress. In conclusion, reducing the resistance coefficient of friction is a preferential choice to decrease the maximum thermal displacement and maximum thermal stress.

In order to determine the domains of Chaboche model of cement concrete fatigue damage under high stress ratios, first, the probability densities of general monotonic random variables including cement concrete fatigue life are deduced. And then, the probability density of Chaboche fatigue damage model is deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of Chaboche model can be obtained, considering different stress ratios. Substituting load cycles into the functions, the cement concrete fatigue reliabilities based on Chaboche model can be acquired through integral operation. Finally, on the basis of cement concrete fatigue reliability analysis, the critical values of load cycle of Chaboche model under different high stress ratios can be made certain and the model's domains corresponding to these stress ratios can be obtained. The obtained results also show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines gradually from almost 100% to 0%. No matter under any stress ratio, in the initial stage of load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the phase diminishes gradually and the load cycle corresponding to reliability of 0% also decreases. In descent phase of reliability, the higher stress ratio is, the lower cement concrete reliability is for the same load cycle.

The carbonation resistance of concrete with or without Mg(OH)2 as a carbon immobilizer is investigated in this study. The carbonation rate of the concrete is evaluated with the accelerated carbonation tests. The results show that 4.8% of Mg(OH)2 in the binder of concrete can reduce the carbonation depth to about 50%. Microstructural analysis show that the Mg(OH)2 reacts with CO2 and water to form the hydromagnesite, via which the CO2 is immobilized.

A new type of electrically conductive concrete with double-layered stainless steel fiber (DSSF) for deicing of pavements is developed in this study. The concrete is designed as a multi-layer structure with stainless steel fibers placed in two separate layers. The concrete matrix is modified with graphite particles or steel fibers. The mechanical properties and resistivity of the DSSF concrete are tested. The results have shown that the electrically conductive concrete with DSSF has low electric resistivity, making it suitable for the purpose of deicing.

The price of metakaolin is one of the constraining factors to large-scale applications in concrete. In this paper, 6 grade kaolins have been applied in the experiment to seek one that has high performance-cost ratio. All grade kaolins were treated by the same calcination system that heated treating of 750¢C for 4 hours to produce metakaolin. Techniques of X-ray diffraction (XRD) and scanning electron microscopy (SEM) were further employed to identify the composition and microstructure of metakaolin. Then mortar was prepared by replacing10% Portland cement with different grade metakaolin to study the relative strength. The results show that all the compressive strength ofmortar which contain metakaolin are higher than that of mortar without metakaolin, but the clay that the content of the particle size below 2 μm is 50% can be the best choice to use in concrete comprehensively considered from the strength enhancing efficiency and economic efficiency. The price of the clay is low and the intension rising rate is also high. The relative strength rising rate can be more than 20% at 7 day and 28 day.

The performance of concrete pavements depends to a large extent upon the satisfactory performance of the joints. Most jointed concrete pavement failures can be attributed to failures at the joint, as opposed to inadequate structural capacity (FHWA, November 30, 1990). Distresses that may result from joint failure include faulting, pumping, spalling, corner breaks, blow-ups, and mid-panel cracking. Characteristics that contribute to satisfactory joint performance, such as adequate load transfer and proper concrete consolidation have been identified through research and field experience. The incorporation of these characteristics into the design, construction, and maintenance of concrete pavements should result in joints capable of performing satisfactorily over the life of the pavement. Regardless of the joint sealant material used, periodic resealing will be required to ensure satisfactory joint performance throughout the life of the pavement. Satisfactory joint performance also depends on appropriate pavement design standards, quality construction materials and good construction and maintenance procedures. This research aims at structurally analyzing the effect of misalignment of dowel bars in rigid pavement joints on the joints performance and suggesting practical remediation.

Macroscopic traffic flow models play an important role in the planning, design, and operation of transportation facilities (Easa, 1980). In the last decades, the importance of highways as transportation facilities has been increased. However, there is lack of research about the performance of traffic flow in tunnels. Furthermore, building and operating costs of tunnel segments are much expensive than free highway segments. Therefore, reliable realization of traffic performance in tunnels is of great importance for economical planning of tunnels. Moreover, speed-flow relationship has more gradual slope with constant speed for higher levels of flow (Singh, 1999). In the light of recent research dealing with speed-flow models, this research aims at: (a) Investigation of speed-flow relationship in two-lane two-way Austrian tunnels during normal operating conditions; (b) Investigation of the effects of heavy traffic on the rate of speed reduction with the increase of traffic volume in tunnels and reviewing the passenger car equivalent factors that are used to convert traffic volume to passenger car units; (c) conducting of a speed-density relationship; and (d) estimation of lane capacity by transforming speed-density model to speed-flow relationship.

This paper investigates the self-healing behavior of Polyvinyl Alcohol Engineered Cementitious Composites (PVA-ECC) with the addition of other microfibers, including steel fiber and rock wool fiber. Four-point bending tests were used to precrack ECC beams at the age of 7 and 28 days, respectively. The precracked samples were then cured in water to promote the occurrence of self-healing and in air for control. The addition of microfibers help tighten the crack width greatly, resulting in enhanced flexural stiffness for the water cured samples. Furthermore, the additive effect also promotes larger extent restoration of deflection capacity, despite much lower initial deflection capacity for the mixtures 2a and 3a. The self-healed samples were also examined under light microscope and environmental scanning electrical microscope (ESEM) to reveal the products of self-healing.

Engineered cementitious composite (ECC) is a kind of composite reinforced with moderate fiber volume fraction, typically 2% by volume. Of special interest is the capability of ECC material to deform to high tensile strains, commonly over 3%, while maintaining very tight crack width. In this study the rubber powder is used in ECC to partially replace fine silica sand, thus enhancing the greenness of ECC. Two particle sizes of rubber powder (450 μm and 200 μm on average) are used in this research. Furthermore, there are three different dosages (0, 10%, 15% by volume replacing silica sand) for each rubber powder size. The influence of rubber powder on the ECC mechanical properties is revealed via flexural deformation, crack width and compressive strength. In this paper, it is found that the addition of rubber powder into ECC decreases its first cracking strength with the trend of enhancing deformation capacity. With the increasing volume of rubber powder, the crack width gets lower. The deformation capacity gets enhanced and compressive strength decreases when the dosage of rubber powder is 15%. The study results prove that it feasible to produce ECC by replacing silica sand partially with rubber powder, thus greatly promoting the greenness of ECC.

The pressure to reach sustainability favours the development of ternary composite cement. The synergistic effect on mechanical behaviour at 28 days between limestone powder (LP) and pozzolanic additives, i.e. fly ash (FA) and blast furnace slag (BFS), has been documented. In order to better understand the synergistic effect, this article investigated the effect of LP on the microstructure of PC-FA and PC-BFScementitious system. The mineralogy and pore structure were determined after 28 days of curing at 20°C and 95% relative humidity. The mineralogy in pastes was identified by means of X-Ray diffraction (XRD) and thermogravimetry (TG). The pore structure was evaluated by Mercury intrusion porosimetry (MIP). The results showed that neither monosulfoaluminate nor ettringite was found in any of the XRD patterns. Instead, carboaluminate was observed. Hemicarboaluminate produced in FA-PC or BFS-PC system transformed into monocarboaluminate with the addition of LP. The porosity was enlarged compared with LP-free paste system. It seems that both the physical and chemical effect of LP contribute to the synergistic effect on mechanical behaviour of cementitious system hydrated up to 28 days.

Scrap tires form a major part of the world's solid waste management problem. In recent years, the waste tire problem has become so acute that there is an urgent need to find an optimum and effective way to use scrap tires in asphalt mixtures.This paper investigates used tire rubber as an asphalt modifier and its potential prospects to enhance bitumen physical and asphalt mixture properties in a hot climate like Sudan. Bitumen grade 60/70 blended with a different percentage of crumb used tire rubber. Engineering and physical properties of bitumen and bitumen/rubber mortar were evaluated. Marshall Mix was designed and used to evaluate the bituminous mixtures properties. Extensive laboratory studies and tests have been done to evaluate the effect of crumb tire rubber on bitumen and bituminous mixture concrete. The laboratory results indicated that crumb rubber modifier provides better engineering properties in terms of rheological properties, penetration, softening point, specific gravity flash and fire point tests. They furtherindicated that crumb rubber modifier decreases the stability and density, increases the flow, and slightly increases the air voids and the voids of mineral aggregate. The study recommended that further studies should be conducted in mixing time and temperatures as well as a field test on rubberized constructed section.

Runway surfaces are optimally designed to meet specific mechanical requirements. These specific requirements mainly include surface friction, resistance to raveling, and resistance to chemicals such as de-icing and fuel. Hence, in the Netherlands, Belgium, Germany and other countries, an additional anti-skid thin surface layer is often applied to provide enough surface friction and avoid hydroplaning. These anti-skid surfaces are specially designed to ensure high friction during a long service life. Until recently, tar-containing material was used as binder. Tar is toxic and not environmentally friendly. For this reason, it is necessary to develop new binders to replace these tar-containing binders. This paper gives a brief introduction on the design approach that was developed to evaluate potential binders and to answer the question if they are qualified to be used for antiskid surfaces on runways. The test methods include Dynamic Shear Rheometer tests (DSR) and Dynamic Mechanical Analysis tests (DMA) on original binders, as well as weather-aged and oxygen-aged binders. Newly designed pull and shear tests were introduced to determine the bonding strength between anti-skid layer and substrate layer.

To evaluate the recycling potentials of the aged styrene-butadiene-styrene (SBS)-modified asphalt binder, effects of the short-term and long-term oxidative aging on the physical properties, rheological properties and microstructure characteristics of the aged SBS-modified binder were investigated. Results showed that the aging of SBS-modified binder consists of two parts: (i) the oxidative aging of the asphalt components and (ii) the degradation of the SBS modifier. The aging inevitably leads to a hardening and brittle binder. By characterizing the aging behaviors of SBS-modified binder, the recycling of aged SBS-modified binder was conducted by adding a recycling agent and a modifying additive. The recycling agent is normally used in unmodified binder for rejuvenation. The modifying additive can benefit the asphalt mixture performance. Results indicated that the commonly used recycling agent may not enhance the performance of the recycled polymer modified asphalt when it is used alone. The rejuvenation of aged polymer modified asphalt requires new additive with well-balanced modification effect. It is found that the recycling agent together with a modifying additive MATM are proved to be capable of restoring the durability of SBS-modified binder and eventually satisfying the desired road performance. Therefore, compound rejuvenation method of polymer modified asphalt was recommended.

Durable and sustainable asphalt pavements require high-quality asphalt materials. In pavement design, the tensile strength of asphalt concrete is a fundamental engineering property. Due to the characteristics of bitumen, the tensile strength is a function of temperature and loading rate. In the past, some regression equations were developed to predict the tensile strength of asphalt concrete. However, these equations are only valid for narrow temperature and strain rate ranges and do not relate to the material properties. This paper proposes a new general equation for the prediction of the tensile strength, which is based on tension tests performed at different test conditions and relates to the complex modulus of the bitumen. By means of the Dynamic Shear Rheometer (DSR), frequency sweeps were done to obtain a master curve for the complex modulus of the bitumen. Uniaxial tensile strength (UTS) tests were conducted to get the tensile strength of the asphalt mixture at different temperatures and loading rates, respectively. In this paper, an S-shaped prediction curve is used to link the tensile strength of the mixture and complex modulus of the bitumen to each other. The test results indicate that the proposed prediction model has a low relative error, which means that it gives a realistic description for the tensile strength of an asphalt mixture.

Compared with the unmodified asphalt, aged SBS modified asphalt is harder to extract. It is difficult to completely remove the residual solvents and mineral powder in the recovery process. The objective of this research is to develop a procedure to evaluate the properties of aged and recycled binder without extraction and recovery, and to determine the species and amount of recycling agent. Properties of artificially aged mixture and asphalt were tested. Bending test of small beam was taken to evaluate the aged mixture and the regenerated mixture. The test data included limit flexural tensile strength and fracture energy. The test results showed that the aged mixture became harder and more brittle. The species and amount of recycling agent could be determined by fracture energy. The properties of regenerated mixture designed in the new way were better than those designed in the traditional way on high temperature and fatigue performances. The low temperature performances of regenerated mixtures designed in the two ways were both qualified.

In order to be able to make a realistic life cycle analysis for porous asphalt (PA) surface layers, it is very important to be able to predict the PA surface layer properties during service life. As ageing of these very high voids content mixes will change properties dramatically and initiate ravelling as the major cause of failure, in depth knowledge of the field ageing of a PA layer is needed. In this paper a study is reported to develop a laboratory ageing procedure for PA mixtures. The aim was to realize approximately 10 years of field ageing in 10 days in a laboratory ageing procedure with standard laboratory equipment. Conventional empirical (penetration, softening point ring and ball), sophisticated fundamental rheological tests (DSR), chemical tests (FTIR) and adhesion tests (Wilhelmy plate) were conducted on binders recovered from field cores and on binders recovered from specimens aged in the laboratory. Several ageing methods were tried, resulting in two promising ageing procedures: one for the mortar in PA and one for the loose PA mix. To accomplish the same ageing of the bitumen as for a 10-year period in the field, the mortar has to be heated in an oven for 2 hours at 165°C and then be placed in a PAV at 90°C for 7 days under air pressure of 2.1 MPa. The loose PA mix was heated for 44 hours at 135°C to accomplish the same degree of ageing.

The combination of load repetitions and severe environmental conditions (aging, moisture ingression, etc.) are causing ravelling (losing of the stones at the top) of porous asphalt. Ravelling has a strong influence on the service life, especially in the slow lane. The service life of porous asphalt can be extended by improving the self-healing capability in time. In this paper, the rejuvenation approach is described to upgrade the self-healing capability during service life. With this approach, the porous asphalt is rejuvenated from outside at the top in order to regain the self-healing capability. Experience with some test trials is described. After the treatment with rejuvenators, the beams from the single-layer porous asphalt show a higher bending stiffness in the 3-point bending test. The beams from the two-layer porous asphalt show a lower bending stiffness after treatment. The results of Rotating Surface Abrasion Test (RSAT) indicate that the rejuvenators can improve the ravelling resistance of porous asphalt. The rejuvenation approach can be very cost-effective not only for porous asphalt but also for other (noise-reducing) thin-surface layers and asphalt concrete containing highly aged reclaimed asphalt.

The study is focused on the fatigue life prediction of Road System of Thermal Energy Collector and Release (RSTECR) using the finite element method. The pavement structure was modeled as two-dimensional, four-layer stratum using ANSYS finite element soft. The maximum tensile strain or stress of asphalt layers was calculated in order to predict the fatigue life of the system. Especially, the different load position and installed tube's direction were considered. The results show that no matter where the traffic direction is vertical or parallel to the installed tube's direction, the tube must not be installed in the top layer. The most adverse load position is that the single wheel is upon the installed tube when the load direction is parallel to traffic direction. And the most adverse load position is that two wheels are upon the installed tube when the load direction is vertical to traffic direction. Finally, the simulating method of the system was put forward and the study is expected to be able to provide road engineers with some design basis.

Bitumen is widely used in road construction, but it is an organic mixture with complex compounds and chemical structures which will change after exposed to heat, oxygen, and ultraviolet radiation (UV) and make the physical properties worse, especially at low temperature. In this paper, different aging levels (TFOT, UV-6days) of asphalt binders with various mass ratio of layer clay powder to asphalt (0,3%,5%) were considered to investigate the low temperature rheological properties of aged asphalt binders and low temperature strength as well as fatigue properties. Dynamic Shear Rheomoter (DSR) and Universal Testing Machine (UTM) were used to evaluate low temperature properties of bitumen and mixture. The ageing evaluation shows that the ageing resistance of bitumen and its mixture is improved and this improvement at low temperature properties can be better maintained compared to base asphalt.

In this study, the objective was to dedicate to the application of coal tar pitch in road engineering construction. The present application situation of the coal pitch was discussed. The asphalt and the asphalt mix were designed. Appropriate adjustment of the proportion of coal pitch and petroleum asphalt improved the technical indexes of asphalt. The optimal bitumen-aggregate ratio based on the closest skeleton-interlocking dense condition principle is selected. Results indicated that the mix with modified coal tar pitch and the designed optimal bitumen-aggregate ratio had good performances, involving high temperature stability, low temperature cracking resistance and water stability. Besides, it was also found that the construction temperature can be reduced by the warm mix asphalt additive decreasing the volatile of polycyclic aromatic hydrocarbon which was a carcinogenic substance in coal pitch. The conclusion of this paper is valuable for the further application of coal tar pitch.

When using the batch asphalt mixing plant for thermal regeneration of RAP, to a certain extent, the performance of the recycling mixture depends on the degree of diffusion permeation of the regeneration agent in the aging asphalt. Based on the analysis of the structure and working principle of mixer, the mathematical model was established, which is related with the use parameters and operating parameters of stirrer, and the time that the recycling agent uniformly distributed required was determined. Based on solute solvent diffusion theory, the time that regeneration agent diffusion penetration required was identified by test. Last, the thermal regeneration process of ready mixed hot asphalt mixture was obtained.

During application process of the bitumen, along with aging, there also exists the volatile phenomenon at the non-high temperature condition. This paper simulated different circumstances in the laboratory-based environment: Infrared (IR), Ultraviolet Radiation (UV) and Vacuum (Va), to investigate the effects of volatile organic compounds (VOC) emission from different asphalts on the performances of the bitumen. Mass changes, chemical compositions, soften point as well as penetration test were conducted to analyze the experimental results. Basic tests were used to evaluate the colloidal structure and temperature-sensitive property of the bitumen. Temperature sweep, frequency sweep tests, as well as stress and strain scanning test were introduced in this paper to investigate the effects on rheological properties by Dynamic Shear Rheomoter (DSR). Results in this paper show that asphalt can volatile at the non-high temperature circumstance and performances of the asphalt are influenced by VOC emission conditions.

The paper presents the research results and discussions of a sustainable maintenance solution for porous asphalt (PA) pavements through a rejuvenation technology. A specially designed rejuvenator (as a form of emulsion) is developed and applied by means of a spraying truck on the asphalt pavement surface. The rejuvenator is able to drain via the voids and migrate into the aged bitumen, and eventually to activate and restore the flexibility of old asphalt pavements. This paper firstly gives a brief introduction to the theoretical background and research approach. Then a theoretical model has been proposed to predict the lifetime of the treated asphalt pavement. Afterwards some laboratory and field test results and the LCA investigation results are presented and discussed. The results of the rejuvenation treatment do not only show the improvement in the mechanical performance and functional requirements, but also exhibit an environmental benefit (LCA analysis) as compared with the current maintenance option. Finally, the conclusions have been drawn, followed by the recommendation for a sustainable pavement maintenance strategy based on this rejuvenation technology.

In this study, the importance of reducing tyre/road noise is stated. Different types of noise-reducing pavement and prediction models are introduced. A new method of modeling is forwarded which links the difference of the tyre/road noise level to the variation of the mixture properties. The model concentrates on certain type of road surface. In the current research, thin layer surface layers are taken into account. Measurements are carried out to collect data of material properties and road surface characteristics. A modeling process is also shown using the existing database. The result model is closely related to practical engineering and can be easily used for estimating the tyre/road noise level changes.

Styrene-butadiene-styrene tri-block copolymer (SBS) and waste polyethylene (WPE) were combined to modify the base asphalt in order to improve the performance of asphalt. In the presence of special stabilizer (mainly sulfur), SBS/PE combined asphalts showed much better storage stability at high temperature and no visible phase separation was observed under optical microscope observation. The physical properties and dynamic mechanical properties (including viscosity change and rheological characteristics) of SBS/PE combined asphalt with and without sulfur were studied respectively. SBS/WPE combined asphalt with sulfur should be recommended to be used and was a member in high modulus asphalt.

The Libyan climate which, characterized by hot arid climatic region (high variation in daily temperatures, high solar radiation, low humidity, low rainfall intensity, wind and dust storms), lies between 15° and 45° both north and south. Asphalt pavement roads are the main and only source of the Libyan overland transportation system for most passengers and goods. Most of Libyan deteriorated roads are passing through a hot arid climatic region (Libyan Desert); Libyan roads expected design life is 20 years, but these roads do not last so long due to aging rapid deterioration and cut down of service life. The tendency for the asphalt binder to harden and age under atmospheric influences has been known and studied for many years. Therefore, high solar radiation in hot arid climate region in Libya with presence of oxygenaccelerate and increase the physical, chemical, and photochemical process in the asphalt binder, while the pavement in midday of summer season can be heated by the solar radiation to more than 70 °C,it may be cooled down in some extreme cases to freezing temperatures during night. This swinging and fluctuation of solar radiation and temperatures induces thermal stresses and causes fast aging in the asphalt pavement layers. Therefore, the deterioration in the form of thermal cracking became a problem in cold regions as well as in hot, arid climate regions with great variation in daily temperatures. The aim of this paper was to estimate the solar radiation energy and present the influences of Libyan climate conditions on road deterioration.

This paper evaluated the stiffness characteristic and rutting resistance of warm-mix asphalt (WMA) mixtures containing different percentages of reclaimed asphalt pavement (RAP) through laboratory performance tests. The WMA mixtures were plant-produced with a commonly-used foaming technology in the U.S. RAP content ranged from 15% up to 40%. Laboratory performance tests included resilient modulus test, dynamic modulus test, and asphalt pavement analyzer (APA) rutting test. For comparison purpose, HMA mixtures containing 15% and 30% RAP were also evaluated and compared to WMA. Based on the laboratory test results, WMA mixtures with RAP showed high rut resistance and were expected to perform satisfactorily in terms of rutting.