Bamboo Fiber Modified Asphalt Mixture Proportion Design and Road Performances Based on Response Surface Method

In order to comprehensively utilize the remaining bamboo residue of bamboo products,this paper presents a research on recycling the bamboo fibers from bamboo residue for improving the performance of the asphalt mixtures.First of all,the basic performance parameters of sinocalamus affinis fiber,phyllostachys pubescens fiber,green bamboo fiber were tested and analyzed,and the optimal content and length were put forward.Then,the mix ratio design of the bamboo fiber modified asphalt mixture was further designed through the response surface method,and was verified the rationality of the mix ratio.Finally,the mixture specimens were made according to the experimental design mix ratio,and the high temperature,low temperature performance and moisture susceptibility of the bamboo fiber modified mixtures asphalt were tested.The results showed that the high temperature performance,low temperature performance and moisture susceptibility of bamboo fiber modified asphalt mixtures were improved compared with the performance of SBS modified asphalt mixture.When the length of bamboo fiber is 7.25 mm and the content of 0.22%,the road performance of the asphalt mixture was optimal.Consequentially,the decomposition of bamboo residue into bamboo fiber and its application in asphalt pavement can improve the reuse of bamboo waste,with remarkable environmental benefits and great promotion value.

Dynamic Mechanical Characterizations and Road Performances of Flame Retardant Asphalt Mortars and Concretes

To research the dynamic mechanical properties and road performances of flame retardant asphalt mortars and mixtures, four different asphalt mortars/mixtures were prepared: a reference group and three asphalt mortars/mixtures containing composite flame retardant materials(M-FRs) of different proportions. Temperature sweep, frequency sweep, repeated creep test, force ductility test and bending beam rheological test were carried out to research the dynamic mechanical properties of asphalt mortars containing M-FRs; wheeltracking test, low-temperature bending test and freeze-thaw split test were used to study the road performances of asphalt mixtures containing M-FRs. The results show that high-temperature performances of the three flame retardant asphalt mortars improve greatly, while low-temperature cracking resistances decline. Both hightemperature performances and water stabilities of asphalt mixtures containing M-FRs are quite good and exceed the specification requirements. However, their low-temperature performances decline in different degrees. In summary, besides their good flame retardancy, the flame retardant asphalt mortars and mixtures also exhibit acceptable road performance.

Preparation and Analysis of Carbon Fiber-Silicon Carbide Thermally Conductive Asphalt Concrete

An experimental investigation into the thermal conductivity of CF-SiC two-phase composite asphalt concrete is presented.The main objective of this study was to verify the possibility of using SiC powder instead of mineral powder as the thermal conductive filler to prepare a new type of asphalt concrete and improve the efficiency of electrothermal snow and ice melting systems accordingly.The thermal conductivity of asphalt concrete prepared with different thermally conductive fillers was tested by a transient plane source method,and the related performances were measured.Then the temperature rise rate and surface temperature were studied through field heating tests.Finally,the actual ice melting efficiency of the thermally conductive asphalt concrete was evaluated using an effective electrothermal system.As shown by the experimental results,the composite made of SiC powder and carbon fiber has a high thermal conductivity.When SiC replaces mineral powder,the thermal conductivity of the asphalt mixture increases first and then decreases with the increase of carbon fiber content.In the present study,in particular,the thermal conductivity attained a peak when the carbon fiber content was 0.2%of the aggregate mass.

Evaluating Contractors’ Safety Record and Its Influence on Performance of Road Infrastructural Projects

A number of studies conducted in Kenya and internationally indicated that most of the construction firms and contractors do not seem to strictly observe safety administration in construction industry, hence compromised performance at implementation stage of projects and even later in the post implementation or post-delivery stage. The study aimed to examine the influence of contractors’ safety record on road performance. This is to create better understanding of how the safety record of contractors could either positively or negatively influence performance of roads during post-delivery stage. The study used both descriptive survey research design and correlation design based on a pragmatic mixed method approach. Through stratified sampling and proportionate sampling, a sample of 210 was drawn from a population of 460 comprising of registered contractors and Public Service Vehicles (PSV) drivers within Nairobi County in Kenya. Questionnaires were distributed using simple random sampling. The questionnaires returned were 153 in total representing 72.8% of all questionnaires distributed to the respondents. Data was descriptively analyzed using percentages, frequencies, means and standard deviations for measuring central tendency and variability. Inferential analysis was done by use of correlation and regression. The descriptive analysis revealed that safety policy management system, insurance policy, and adequacy of standards in addressing safety outcome are to some extent practiced and adhered to. However, compliance behavior to safety procedures is still weak and requires improvement. The null hypothesis was tested and the results obtained from a simple linear regression indicated that, R = 0.657, R2 = 0.431, B = 0.359, t = 10.703, F (1,151) = 114.558, p = 0.000 < 0.05. This means that contractors’ safety record has a strong positive and significant relationship with road performance and that 43.1% of variation in performance is explained by safety record. This study recommends that contractors’ safety record should be part, and parcel of the evaluation criteria used in selection of a suitable road contractor to ensure road performance is achieved even after construction is completed. The study is significant in that it contributes to the body of knowledge by providing empirical data on the need for safety procedures in urban road construction and beyond.

Development and road performance of clear asphalt with high transparency and adhesion

Clear asphalt(CA)currently used in light-colored asphalt mixtures(LCAM)exhibits poor transparency and adhesion.Therefore,a highly transparent CA(HCA)modified using a silane coupling agent(KH550)was prepared.Furthermore,LCAM was prepared by mixing CA and limestone aggregates.The properties of the HCA and ordinary CA(OCA)were characterized using conventional asphalt tests,optical tests,pull-off tests,ultraviolet aging tests,dynamic shear rheometry,Fourier-transform infrared spectroscopy,differential scanning calorimetry,and scanning electron microscopy.Whereas Marshall,moisture resistance,wheel tracking,trabecular bending,and British pendulum tests were employed for the LCAM.The transmittance and spectral reflectance of the HCA were 123.30 and 3.74 times greater than those of the OCA,respectively.The complex modulus and viscosity-aging index of the HCA were 48%and 53%less than those of the OCA,respectively.After modification with KH550,the Marshall stability ratio,tensile strength ratio,and flexural strain of the HCA-prepared LCAM increased by 12.92%,25.06%,and 23.90%,respectively.However,the rutting resistance of the HCA-prepared LCAM was 14.3%less than that of the OCA-prepared LCAM.The comprehensive performances of the HCA and HCA-prepared LCAM were 49.2%and 10.3%greater than those of the OCA and OCA-prepared LCAM,respectively,indicating a high application value in the future.

Investigating the influence of segmentation in estimating safety performance functions for roadway sections

Safety performance functions（SPFs） are crucial to science-based road safety management.Success in developing and applying SPFs, apart data quality and availability, depends fundamentally on two key factors： the validity of the statistical inferences for the available data and on how well the data can be organized into distinct homogeneous entities. The latter aspect plays a key role in the identification and treatment of road sections or corridors with problems related to safety. Indeed, the segmentation of a road network could be especially critical in the development of SPFs that could be used in safety management for roadway types, such as motorways（freeways in North America）, which have a large number of variables that could result in very short segments if these are desired to be homogeneous. This consequence, from an analytical point of view, can be a problem when the location of crashes is not precise and when there is an overabundance of segments with zero crashes. Lengthening the segments for developing and applying SPFs can mitigate this problem, but at a sacrifice of homogeneity. This paper seeks to address this dilemma by investigating four approaches for segmentation for motorways, using sample data from Italy. The best results were obtained for the segmentation based on two curves and two tangents within a segment and with fixed length segments. The segmentation characterized by a constant value of all original variables inside each segment was the poorest approach by all measures.

Review on application of phase change materials in asphalt pavement

Phase change materials(PCMs)can regulate the temperature in asphalt pavement and minimize temperature-related problems,such as rutting and thermal cracking,because of their ability to store and release latent heat.Suitable PCMs can also enable additional road surface functions,such as snow melting ability,freeze-thaw cycle resistance,and heat island reduction.These functions are helpful in achieving intelligent,green,and sustainable transportation systems.Although the research on PCMs for asphalt pavement has been carried out for more than 10 years,a systematic material system and mature application technology have not yet been formed.The main reasons for restricting the development of this technology include the lack of suitability between the PCMs and asphalt pavement,the quantitative characterization of phase change temperature regulation property,and the evaluation of the effect of phase change energy storage on improving pavement performance.Although the published review has made a comprehensive summary of the existing research,it has yet to identify the key restricting the development of this technology and carry out a review and discussion based on it.To grasp the development status of the application of PCMs in asphalt pavement,sort out the development needs and break through the technical barriers,this study systematically summarizes the preparation and performance of PCMs for asphalt pavement,compares the performance and evaluation methods of asphalt mixtures with different PCMs,and summarizes the numerical simulation methods of phase change asphalt mixtures.Finally,this study presents potential approaches to address critical technical issues and discusses possible future research.

A comprehensive review of bio-oil, bio-binder and bio-asphalt materials: Their source, composition, preparation and performance

To promote the application of bio-materials and provide a direction for their further researches,this paper comprehensively summarizes the research progress of biomaterials in recent years.The review results show that bio-oil is a mixture obtained from different biomasses through pyrolysis,alcoholysis,acidolysis,high liquefaction,etc.,and those biomasses mainly include wood fiber type,waste oil type and animal manure type.Biobinder refers to the product of bio-oil processed by distillation,extraction oxidation and polymer modification,and it can be served as a modifier,diluent or substitute material of asphalt;the main chemical components of bio-oil include ethers,esters,aldehydes,ketones,phenols,organic acids,alcohols and sugars.Bio-asphalt is obtained by adding biobinder into the petroleum asphalt for modification or blending,and the shear temperature and shear rate of bio-asphalt derived from wood fiber type and waste oil type are usually higher than that of bio-asphalt derived from swine manure.Compared with petroleum asphalt,bio-asphalt binder usually shows lower high-temperature performance as well as higher low-temperature performance and aging resistance.Also,bio-asphalt mixture generally exhibits lower high-temperature stability,higher low-temperature crack resistance and water stability than petroleum asphalt mixture.Future studies should be conducted combining with the source,composition,preparation,properties and oil production rate of bio-oil.First,how to raise the bio-binder content in bio-asphalt as much as possible while ensuring the sufficient performance becomes the focus of future researches.Second,the micro reaction mechanism between bio-binder and petroleum asphalt should be illustrated in depth.Moreover,developing a complete and unifying technical standard and application specification of bio-asphalt technology is necessary for future researches.Furthermore,determining the optimum bio-binder potentially used as the substitute of petroleum asphalt is also an interesting topic.

Testing and assessing the performance of a new warm mix asphalt with SMC

Warm mix asphalt （WMA} is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. WMA has been widely tested and applied in the USA in the last decade, but it has just started in China. Recently, a new WMA using a new plastic- macromolecule-normal temperature additive, which was called ＂SMC＂ by the production company, was introduced as asphalt modifier. Based on discussing the strength forming process of this new WMA with SMC, a series of laboratory tests, including Marshall stability test （MST）, boiling test （BT）, modified immersion Marshall test （MIMT）, freeze-thaw split- ring test （FTST）, rutting test （RT）, low-temperature bending test （LTBT）, and abrasion loss test （ALT）, were conducted in this study to assess the performance of this WMA and the capability of applying it on low volume roads in China. SMC modified asphalt mixed under normal temperature is used in testing samples. It was found that this WMA product exhibited merits on its strength, which was about 6.7 kN bigger than the requirement of 5.0 kN in the JTG F40-2004, on high-temperature stability, which is about 1100 times/ram greater than the requirement of 600-1000 times/mm in the ）TG F40-2004, and on its storage stability. Based on these indicators, it is recommended that this product could be used for low volume low class roads construction. However, due to the relatively lower water resistance and low-temperature cracking resistance, this product is suggested to be applied first in the areas with warm weather and little rainfall. In order to improve the perfor- mance of this WMA with SMC, further research on this SMC asphalt modifier should be continued.

An investigation on modification mechanism of CH2O-modified low temperature coal tar pitches

Rising oil price has brought huge cost pressure for low grade highway construction, and it is urgent to find alternative resources. At the same time, there are nearly 50000-60000 tons of low temperature coal output in inner Mongolia region, China, which has high toxicity and high polluting. To make the low temperature coal be applicable for road constructions, the formaldehyde is used as cross linking agent, the concentrated sulfuric acid is used as catalyst, and the chemical modification of low temperature coal tar pitch in Inner Mongolia region is investigated. The road performance （softening point, penetration and ductility） of modified low temperature coal are tested. Results shown that the road performance of modified low temperature coal is increased significantly. Modification mechanism of low temperature coal is studied by Scanning Electron Microscopy and other analytical tools. Results show that, in the modified low temperature coal, resin content increases and the resin fiber diameter becomes larger with the increasing of formaldehyde content.

Evaluating the safety benefit of retrofitting motorways section with barriers meeting a new EU standard:Comparison of observational before-after methodologies

The road safety barriers are today designed and installed in compliance with the European standards for Road Restraint Systems （EN 1317）, which lays down common requirements for the testing and certification in all EU countries. The introduction of the European Union （EU） regulation for safety barriers, which is based on performance, has encouraged Euro- pean road agencies to perform an upgrade of the old barriers installed before 2000, with the expectation that there will be safety benefits at the retrofitted sites. Due to the high cost of such treatments, a benefit-cost analysis （BCA） is often used for site selection and ranking and to justify the investment. To this aim a crash modification factor （CMF） has to be applied and errors in the estimation of benefits are directly reflected in the reliability of BCA. Despite the benefits of empirical Bayes before-after （EB-BA） analysis or similar rigorous methods are well-known in the scientific world, these approaches are not always the standard for estimating the effectiveness of safety treatments. To this aim, the dif- ferences between the EB-BA and a naive comparison of observed crashes before and after the treatment are presented in the paper. Crash modification factors for total and target crashes are estimated by performing an EB-BA based on data from a motorway in Italy. As expected the results suggest a strong safety benefit for the ran-off-road crashes by reducing the number of severe crashes （fatal and injury）. The statistical significance of results ob- tained by the EB-BA approach show that the retrofits are still cost-effective. Thecomparison pointed out as selection bias effects can overestimate the safety benefit of the retrofits when a naive approach is used to estimate the CMF and how those can signifi- cantly affect a benefit-cost analysis.