Flexible Pavements

Appropriate design and use quality materials for pavement construction is important in construction of cost-efficient flexible road pavements, where the highest stresses are imposed by the traffic's wheel loads, with a gradual decrease in material quality through the pavement, the poorest quality materials being used deeper in the pavement where the stresses are much reduced [1]. Flexible pavements are the most common type of pavements used in almost all road networks in Jima Zone. And they do have two sources of materials (aggregate) for wearing course. Therefore, this research initiated to determine or to recommend better source of aggregate for wearing course for road construction projects in Jima zone. aggregates from Babu aggregate production site better for road construction projects.

Abstract The performance implications of laboratory asphalt loose mixture aging at 135 °C were evaluated by comparing the performance of mixtures subjected to long-term aging at 95 °C and 135 °C to yield the same rheology. Although the rheology of the mixtures aged at 135 °C and 95 °C matched, their chemistry differed. Performance test results suggest that the chemical changes induced by aging at 135 °C can negatively impact performance. The relationship between binder chemistry and rheology was unaffected by aging temperatures at or below 95 °C. The rate of oxidation increased with an increase in temperature, and thus, the optimal loose mixture aging temperature is 95 °C.

This paper presents the mechanical, durability and microstructure characteristics of cement treated recycled asphalt (CTRA) bases and sub-bases material produced by varying the percentage of virgin aggregate (VA), recycled asphalt aggregate (RA), and cement content. Modified proctor method of compaction was used to prepare cylindrical specimens at 2.5, 5.0, 7.5, and 10.0% cement contents (% by wt. of aggregate) with different blends of VA and RA. Durability tests were carried out to evaluate the performance of mixtures under repeated wetting and drying in the tropical climate. Experimental results revealed that the addition of cement in CTRA had more effect on mechanical and durability properties compared to RA content. The CTRA mixtures were found to be more ductile albeit lower values of elastic modulus. Scanning Electronic Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis manifest that large amount of Ettringite and higher the Si/Ca ratio in CTRA compared to cement treated mixtures without RA. The higher proportion of these products signify the detrimental effect in mechanical properties. Cost analysis for a typical pavement section demonstrate that the cost-saving of the pavement section with CTRA mixtures observed to be in the range of 26–32% under varying cement and RA contents compared to the pavement section without CTRA. It was found that these mixtures can be used as a replacement for granular bases and sub-bases in flexible pavements and/or bases for concrete pavements instead of roller-compacted concrete.

Most of the road network in India has a significant level of deterioration and therefore requires major rehabilitation projects; in general, most of these rehabilitation activities involve a new asphalt layer on the original pavement structure; knowledge and analysis of structural capacity of the pavement is essential to perform a durable and economical rehabilitation design. The determination of the structural capacity of flexible pavements as a function of the deflections produced by the application of a load. The techniques most used in many countries to measure pavement deflections are the Falling Weight Deflectometer (FWD) and the Benkelman beam, the first one works under dynamic loading and the second device under static loading. The use of devices under static loading has not been recommended by several design methodologies, including AASHTO, but these are still used widely in many countries including India, for this reason it is necessary to compare the deflections by Benkelman beam and falling weight deflectmeter. In this study deflections measure by BBD and FWD techniques on 30 deflection observation points on selected 1.5 km flexible urban highway stretch. Both test are perform simultaneously on marking points. And data collected by booth test are as per IRC: 81-1997 and IRC: 115-2014.

Flexible pavements get distress during their service
life because of increase in traffic particularly commercial
vehicles. The present study focuses on finding the increase of
magnitude of deformations from 2008 to 2015 traffic data
using ANSYS for which the BRTS stretch in Visakhapatnam is
considering five locations along the stretch.

Now days, worldwide population density increases, which enhance production of plastic waste on daily basis. It may be beneficial to society, when it is biodegradable and eco-friendly economical material.  But, some plastic polymer act as hazardous product, as it is non-biodegradable waste material affects environment badly. It is unwanted environmental hazard which increases all three types of pollution i.e. soil, air and water pollution.

As India is rapidly developing country, these types of problems we have to eradicate completely.  There is enormous scope to use plastic waste in flexible road construction. As due to extensive rain in India, lots of economical waste is occur every year. Due to use of waste plastic in flexible pavement, drainage capacity of road surface increases efficiently. We can use plastic in road construction in marshy land area as well as area of high rainfall intensity, to enhance lifespan of roads and economy in construction.

Also, large amount of economy of government is wasted every year i.e. million of rupees are wasted in treatment of waste plastic material. Some techniques are available for disposal of plastics like landfill and incineration. But, incineration method produces lots of air pollution which affects the human health. Lifespan of plastic waste is very large. Also, plastic material is available in different forms like plastic bags, papers and utensils. So, we can use this plastic waste in shredded form in road construction by wet process and dry process. This increases durability and drainage efficiency of roads.

Tens of thousands of aging, bridge-class, RC box culverts are in service in the United States. Within the context of establishing load rating for in-service RC box culverts, this paper introduces, calibrates, and applies a system-level pavement-stiffness model to a production-simplified, soil–structure interaction model used for calculating load demands. The proposed pavement-stiffness model uses system-level pavement data to account for the additional stiffness provided by the pavement structure to attenuate live load. The full cover-soil depth is modeled using linear-elastic finite elements per the production-simplified soil–structure interaction model, and the additional stiffness provided by the pavement structure is modeled using beam elements across the top row of finite-element nodes. Equivalent beam-modulus values for the system-level pavement-stiffness model were calibrated against results from a research-intensive, full-pavement model for various pavement types. A parametric study using the proposed model showed that the inclusion of pavement stiffness could increase the load ratings for both asphalt pavements with an intermediate thickness and concrete pavements, for both direct-traffic and low-fill RC box culverts. The effects of the system-level pavement-stiffness model on predicted live-load moment response were further evaluated using measured live-load moments from field live-load tests on in-service culverts. From these comparisons , the system-level pavement-stiffness model showed improved accuracy and precision of the live-load demand prediction. Finally, load-rating analyses performed for an illustrative sample of 24 in-service Texas RC box culverts under various pavement types showed improved rating factors from the system-level pavement-stiffness model compared to the production-oriented soil–structure interaction model without pavement stiffness and the AASHTO-recommended structural-frame model. The inclusion of the pavement stiffness when modeling in-plane live-load attenuation improves the RC box culvert load-rating results and can be implemented for systemwide infrastructure management.

In this present time, it has become very important to provide a good and better road network to meet the increasing rate of development and population, but also designing better roads which are economic and environmentally friendly is of utmost importance. Disposal of waste rubber and waste plastics has become a very serious problem and these wastes are burnt for apparent disposal which causes environmental pollution. Use of waste plastics such as carry bags, plastic bottles etc. in bitumen mixes has proven to enhance the properties of the mix as well as solving pollution problems. The aggregate mix is heated to about 170°C and the shredded waste plastic is melted with it to form a uniform coat over the aggregate. This plastic-coated aggregate (PCA) is mixed with hot bitumen of about 160°C and the resultant mix is used for flexible pavement construction. PCA-Bitumen mix has a high Marshall stability value of 18-20 KN and its bearing capacity is increased by 100%. PCA-Bitumen mix has improved binding properties and less wetting properties. Study proves that plastic paved road has been known to perform well and they are both Ecofriendly and economical. The bitumen modified with crumb rubber in suitable percentage enhances the properties of the bitumen. This reduces the pollution occurred due to waste rubber as well as minimizes the use of natural aggregate, which help in reducing global warming as well as health problems.

Over the last two decades, the production and appliance of asphalt mixtures used for road construction have been improving, particularly to achieve economic and environmental objectives. Recently, the improvement has paid more attention to the reduction of energy consumption throughout the process, without changing the in-service mechanical performance of asphalt mixtures.

There is  a  growing international pressure on  the reduction of fossil fuels consumption and the emission of greenhouse effect gases (GHG), such as CO2(carbon dioxide), SO2 (sulphur dioxide), NOx etc. Unfortunately, the production of hot-mix asphalt (HMA) for pavements is attributed towards a significant percentage of the energy consumption and the release of pollutant gases. This is a consequence of drying and heating mineral aggregates, bitumen and at temperatures above 150˚C, mixing of these ingredients to produce hot bituminous mixtures.

If a significant temperature decrease could be  achieved within the production practice of asphalt mixtures, while the workability of the material is adequate and mechanical performance attained is the same as or even better than HMA, the gain  for the environment and the society in general would be significant.

Therefore, the scientific and technical community have developed a number of new technologies for asphalt materials, generally referred to as warm mix asphalt (WMA), half warm mix asphalt(HWMA), and cold mix asphalt (CMA) which require lower production temperatures and application. As a result, since these technologies consume less energy than traditional HMA, they significantly contribute to achieve the aforementioned objectives.

WMA is the recent technology getting the attention of industry towards it in our country.

Warm Mix Asphalts are again subdivided into two categories i.e.
• WMA prepared with additives (chemical or organic).
• WMA prepared without additives called as Half Warm Mix (HWMA) or foamed bitumen technology.

WMA prepared with additives has a temperature range of 100 to 140˚C while those prepared without additives also termed as “Half-Warm Mix Asphalt (HWMA)” has temperature range from 70 to 100˚C. The temperature decrease is around 30˚C for the first case and can attain up to 80˚C for the second case as compared to HMA.

HWMA are those mixes in which the bituminous binder is either a bitumen emulsion or foamed bitumen, which is manufactured and mixed with warm aggregates (about 100˚C), laid and compacted a temperature between 80-90˚C.

HWMA is the recent technology developed for aggregate, which is to be available in our country and reveled out to be used at its peak so that can be useful for society which not only reduces the cost for road construction but also reduces the pollution in environment and helps in reducing greenhouse effect.

In this paper the design methodology for developing emulsion based half warm mixes (HWMA) using waste aggregates will be discussed. Based on the laboratory study, the achieved production and application temperature with respective to design parameters will be presented in detail.

Many researches on PMA mixture have been conducted for the past two decades. Although addition of virgin polymers to asphalt for the purpose of enhancing the properties of asphalt over a wide temperature range in paving applications was contemplated quite some time ago, recycled polymer added to asphalt have also shown almost the same result in improving the road pavement performance as compared to virgin polymers This paper is a review of the use of polymers in asphalt pavement. In this study, a critical review on the history and benefits of using waste and virgin polymer in asphalt is presented followed by a review of general studies on using polymers in asphalt in order to improve the properties of pavement. (C) 2012 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0950061812000323

Flexible Road pavement plays an essential role in developing an effective, economic, and safe operation
road network of any country. In Vietnam, a developing country, the selection of a suitable flexible pavement structure
is always a challenge due to fiscal limitations. The traditional determinant method (TDM) by which pavement
structures are selected mainly on the basis of initial construction costs and traffic load has been used for many years
in the nation. This paper presents the use of Monte Carlo simulation to analyze the entire flexible pavement life cycle
cost. Data including initial and maintenance costs and road user costs were collected from several different types of
existing flexible pavement in Nghe An province, Vietnam. Random variations of several main inputs were explored
in order to develop density distribution functions. These functions then were used as the bases for Monte Carlo
simulation. One million simulation runs were implemented and the Net Present Values (NPVs) among pavement
types were compared under the light of risk analysis. Research results showed that TDM method provided bias and
uncertain results compared to that of Monte Carlo one. In terms of long- term pavement performance, a low-cost
pavement structure should not always be considered as a wise selection. Some other suggestions for a developing
country as Vietnam were also included.

Keywords: Pavement life cycle cost, Monte Carlo simulation, flexible pavement

A mechanistic roughness performance model that takes into account vehicle dynamics was developed for use in flexible pavement design and evaluation. The model was developed in the form of a relation between roughness and number of load repetitions, axle load, and asphalt layer thickness. The model is completely mechanistic and uses vehicle dynamics analysis to estimate the dynamic force profile and finite element structural analysis to estimate the change of pavement surface roughness for each load repetition. The model makes use of the fact that pavement roughness changes the magnitude of the vehicle dynamic forces applied on the pavement and that the dynamic forces change the road roughness. The developed mechanistic roughness performance model can be used to estimate the 80-kN (18-kip) equivalent single-axle load for mixed traffic. The model can also be used to design pavement so that it will last for a certain number of load repetitions before reaching a predetermined roughness ...

Rutting is one of the most important deteriorations in flexible pavements which a significant amount of maintenance and rehabilitation funds are consumed for repairing it annually. On the other hand lack of a simple test to determine specimen resistance to permanent deformation as the main reason for asphalt rutting is sensible in Superpave first level mix design which owes considerable advantages in comparison with the marshall method. Prevalent methods of evaluating rutting potential of asphalt mixtures are usually expensive and time consuming. Mentioned parameters illustrates the necessity of developing a simple method, not only having fine precision but also be able to predict specimens rutting performance in the short term in laboratory. In this research two types of aggregates (silica and calcareous base), two types of gradation, two types of bitumen, two types of filler and three bitumen contents were used to prepare specimens. After modeling gyratory shear stress, the model and gyratory compaction slope parameters were used to develop two mathematical models to estimate specimen wheel Track apparatus rut depth. These models were validated using ANN and GA and make it possible to evaluate rutting potential while preparing specimens in laboratory to determine optimum bitumen content. Hence not only expensive instruments for rutting test aren't necessary but a considerable reduction in mix design procedure time is gained.