Flexible Pavement Design Research Articles

Evaluation on Deformation Behavior of Granular Base Material during Repeated Load Triaxial Testing by Discrete-Element Method

Granular base material (GBM) is widely used as the base/subbase course of pavement structure. In the mechanic–empirical design of flexible pavement, both the resilient modulus and permanent deformation are the major deformation properties of base materials, related to early-stage distresses of the surface layer under traffic loading. However, since the microscopic interaction between aggregates of the GBM is quite complex, the deformation behavior was not to be understood merely empirically. This study aims to evaluate the macroscopic and microscopic behavior of the GBM under repeated load triaxial (RLT) testing by the discrete-element method. Both the size gradation and the aggregate shape were considered in numerical simulations. The modeling technology of a heterogeneous structure was developed and verified by laboratory results. The results showed that the resilient modulus measured by the developed simulation was in good agreement with that of laboratory tests, within errors of 5.0%. The deformation behavior of the GBM presents the stress-hardening characteristic that the resilient modulus of the GBM increases from 94.03 to 337.71 MPa with the growth of the volume stress and deviator stress. The microstructure of the GBM maintain a relatively stabilization in dynamic response and anisotropy changes during the cyclic loading and voids within aggregates play a role in buffering the change in internal stress. The principal contact normal trends to the direction of maximum bulk stress through small motions, and rotations of aggregates during the loading. It provides a robust mechanism for the resistance to deformation, which results in dispersing more stresses into the skeleton.

Reduction of pavement thickness using a subgrade layer treated by different techniques

A range of stabilisers for poor quality subgrade soils have been developed to promote road constructions. Many of them are becoming more popular depending on their effectiveness. The purpose behind this research is to identify the relative efficacy of many physical and chemical stabilisation techniques for enhancing the properties of three types of local Iraqi subgrade soils. The comparison of the samples is based on the CBR tests. The AASHTO (1993) flexible pavement design was used to compute the pavement thickness requirements. The soil samples A, B and C have a natural CBR values of 3.8, 3.9 and 4, respectively, on which the physical stabilisers of Powdered rock (PR), grained recycled concrete (GRC), and recycled crumb rubber grains (CR) were employed, while Quicklime (QL) and activated fly ash (AFA) were both utilised as chemical stabilisers. The stabilisation with 15 % of AFA proved to be the most applicable method for soil types A and B for reducing the pavement thickness requirements by 51 % and 32 %, respectively, with a reasonable financial feasibility for both. The same feasibility is proven when stabilising soil type C with 15 % of GRC, which reduces the pavementthickness by 25.7 %.

A Study of Cost Comparison of Flexible Pavement Using Different Soils

India is home to the world’s second-largest road network. It has a diverse range of soil types, each with its own set of conditions and characteristics, on which the road network is built. IRC: 37-2018 was used for the Design and Cost Analysis of Flexible Pavement for five distinct types of soils: Black cotton soil, Alluvial soil, Sandy soil, Red Laterite soil, and Murram soil. The Resilient modulus which depends on CBR value of the soil has been found to influence the pavement thickness, strength and performance. The project’s cost is determined by the pavement thickness, which again is determined by the soil’s CBR value. By employing a soil with a high CBR value, the project’s pavement thickness and cost will be decreased. On poor or problematic soils, soil stabilisation techniques should be employed to improve CBR value and save project expenses. According to the findings, employing the CBR value improves the pavement’s strength and hence saves time when planning a pavement.

Effect of several fillers on some basic mechanical properties of asphalt concrete

Filler is one of the mandatory ingredients in asphalt mixture. It also plays a very significant role in influencing the properties and behavior of asphalt concrete. This paper presents the results of laboratory experiments to determine the influence of 4 different fillers (including conventional stone powder, Portland cement, rice husk ash, and fly ash) on some mechanical properties of asphalt concrete with Dmax of 12.5 (AC12.5). The content of filler used in the study was 5% of the total volume of aggregate. The results show that the designed AC with different fillers have the mechanical properties (air void, Marshall stability, flow, and retaining stability) that meet the specification requirements of Vietnam Ministry of Transport Decision No. 858/2014. In which the mechanical properties of AC using conventional stone powder filler are achieved with an overall better and stable effect. Although rice husk ash and fly ash filler also have certain improvements in Marshall stability and air void, AC using rice husk ash and fly ash filler does not meet the requirement of elastic modulus recommended in the Vietnam standard for flexible pavement design 22TCN 211 -06.

Effect of several fillers on some basic mechanical properties of asphalt concrete

Filler is one of the mandatory ingredients in asphalt mixture. It also plays a very significant role in influencing the properties and behavior of asphalt concrete. This paper presents the results of laboratory experiments to determine the influence of 4 different fillers (including conventional stone powder, Portland cement, rice husk ash, and fly ash) on some mechanical properties of asphalt concrete with Dmax of 12.5 (AC12.5). The content of filler used in the study was 5% of the total volume of aggregate. The results show that the designed AC with different fillers have the mechanical properties (air void, Marshall stability, flow, and retaining stability) that meet the specification requirements of Vietnam Ministry of Transport Decision No. 858/2014. In which the mechanical properties of AC using conventional stone powder filler are achieved with an overall better and stable effect. Although rice husk ash and fly ash filler also have certain improvements in Marshall stability and air void, AC using rice husk ash and fly ash filler does not meet the requirement of elastic modulus recommended in the Vietnam standard for flexible pavement design 22TCN 211 -06.

Effect of several fillers on some basic mechanical properties of asphalt concrete

Filler is one of the mandatory ingredients in asphalt mixture. It also plays a very significant role in influencing the properties and behavior of asphalt concrete. This paper presents the results of laboratory experiments to determine the influence of 4 different fillers (including conventional stone powder, Portland cement, rice husk ash, and fly ash) on some mechanical properties of asphalt concrete with Dmax of 12.5 (AC12.5). The content of filler used in the study was 5% of the total volume of aggregate. The results show that the designed AC with different fillers have the mechanical properties (air void, Marshall stability, flow, and retaining stability) that meet the specification requirements of Vietnam Ministry of Transport Decision No. 858/2014. In which the mechanical properties of AC using conventional stone powder filler are achieved with an overall better and stable effect. Although rice husk ash and fly ash filler also have certain improvements in Marshall stability and air void, AC using rice husk ash and fly ash filler does not meet the requirement of elastic modulus recommended in the Vietnam standard for flexible pavement design 22TCN 211 -06.

DESIGN OF FLEXIBLE PAVEMENT USING THE C.B.R. METHOD

California bearing ratio is an empirical test and over the world, it is used for designing the flexible pavement. This method was developed by California Highway Department in 1928. The tests results are used in pavement design, in the duration of second world war. Aim of the study: the main aim of the study is design of flexible pavement using the C.B.R. method Material and method: Tests including Atterberg's (liquid and plastic) limits, shrinkage limits, differential free swelling and swelling pressure as well as OMC and MDD as well as the UCS have all been done to develop the flexible pavement utilising black cotton soil and slurry of Kota stone. Conclusion: Tests are also used to establish the engineering characteristics. The Atterberg's limits (Liquid Limit, Plastic Limit, Plasticity Index), sieve analysis, standard proctor test, and California Bearing Ratio are used to investigate the behaviour of black cotton soil with varying percentages of Kota stone slurry

Implementación del espectro de curvas de diseño ramcodes de suelos no saturados de subrasantes en el diseño de pavimentos flexibles

The design process for a pavement structure assumes that the subgrade will saturate at some point during the service life, however, the saturation of the subgrade depends on the conditions depending on the region in which it is located. Therefore, it is necessary to study design conditions for partially saturated subgrade. The present research aims to implement the spectrum of RAMCODES design curves for unsaturated subgrade soils, applied to the design of flexible pavements under environmental and traffic conditions associated with the Oyon-Ambo highway. To construct the RAMCODES design curves, CBR tests were performed by varying compaction energies and moisture contents. Likewise, using the OriginPro 2019 program, the curves were obtained and a mathematical model was used to predict the variation of the degree of saturation in the subgrade over time. Subsequently, the seasonal CBR were obtained and correlated to obtain the resilient moduli. Finally, two flexible pavement structure designs were carried out, one using the traditional subgrade characterization methodology and the other according to the proposed methodology. From the results obtained, it is interpreted that the consideration of the unsaturated behavior of the subgrade optimizes the pavement design since the bearing capacity of the subgrade is increased by 28.8%, which means that the thickness of the subbase layer is reduced by 25%.

Development of Expert System for Flexible Pavement Design in Sabah

Flexible pavement covers three quarters of the total local roads including Sabah. An ideal flexible pavement should have sufficient thickness to distribute the load to subgrade but not overdesign which cause extra cost. This research paper is conducted to develop an expert system for flexible pavement design in Sabah. It is aimed to reduce the hu-man error during the design phase in order to ensure the road quality. Sabah is selected as the location as Sabah is developing state that involve many on-going highway and flyover construction. Besides, expert system is important in this modern era to replace manual calculation that waste time and energy. Information about flexible pavement is collected through literature review from previous research papers and from human experts who have years of experiences in road construction. The information obtained is analysed and coded using Visual Basic Net. programming language on Microsoft Visual Studio. An expert system for flexible pavement design in Sabah is developed with a given name, ES-FPD. For validation test, comparison is made between results obtained from ES-FPD and manual calculation by expert evaluator. The results show ES-PFD passed both evaluation test and validation test. ES-FPD is considered to be verified and can be used.

Impacts of Lightweight Aggregate Interlayers for Air Convection Embankment on Pavement Thermal Profile and Pavement Performance in Alaskan Permafrost Regions

Crushed-rock air convection embankment (ACE) has been used to mitigate pavement distresses caused by climatic extremes in permafrost regions for more than three decades. This study proposes using lightweight aggregates as cost-effective alternative materials to overcome the shortage of desired crushed rocks needed for ACE in interior Alaska. This paper presents an investigation of the performance of six selected pavement structures: an asphalt pavement typical of the northern region of Alaska and five pavements reinforced with different paving interlayers (i.e., silty sand/gravel, crushed rocks, cellular concrete aggregate, foam glass aggregate, and lightweight expanded clay aggregate). Pavement thermal analyses using Temperature Estimate Model for Pavement Structures (TEMPS) program and ANSYS Fluent software were performed to predict heat transfer patterns and thermal performance for each case. Pavement performance analyses using viscoelastic-based FlexPAVE™ and the elastic-based Alaska Flexible Pavement Design (AKFPD) program were conducted to evaluate the long-term performance and structural stability of subgrade soil with different types of interlayers. The results showed that the lightweight aggregate ACEs improved cooling performance more effectively than the crushed-rock ACE. The lightweight aggregate interlayers could maintain desired thermal insulation in summer and enhance the cooling effect in winter. The modeling results identified the high potential of using lightweight aggregates as alternative ACE materials to improve pavement service life and subgrade stability.

Project on Preparation of Plastic Road Using Single Used Waste Plastic

Abstract: Plastics are non-biodegradable materials and means to degrade our environment. The waste plastic and its disposal are a major threat to the environment, which results in pollution and global warming. The utilization of plastic waste in bituminous mixes enhances its properties and also its strength. In addition, it will also be a solution to plastic disposal & various defects in pavement i.e., pot holes, corrugation, ruts, etc. the waste plastic used are poly-ethylene, poly-styrene, poly-propylene. There are two processes available for the mixing of plastic in bituminous mix such as wet process and dry process. The waste plastic is shredded & coated over aggregate & mixed with hot bitumen and resulted mix is used for pavement construction is known as the dry process. But in wet process waste plastic is ground and made into shredded form; various percentage of plastic is mixed with the bitumen and study the durability of the roads laid out with shredded plastic waste is much more compared with roads with asphalt with the ordinary mix which is the objective of the present study. The use of the innovative technology not only strengthened the road construction but also increased the road life as well as will help to improve the environment and also creating a source of income. It’s economical and eco-friendly. In this project, we have discussed about the bitumen with plastic properties to be considered in design of pavement, pavement design, and process of construction flexible pavement. Keywords: plastic waste, flexible pavement, strength, eradication of pot holes

Impact of Subgrade Strength on Pavement Performance

Based on the standard design of flexible pavement structure conducted in Turkey, only subbase course layer is affected by the variation of subgrade strength and other pavement layers (wearing course, binder course, asphalt concrete (AC) base course, and crushed stone base course) are not influenced by the variation of subgrade strength. Therefore, the aim of this study is to investigate the impact of subgrade strength on flexible pavement distresses. To achieve the objectives, firstly, three different flexible pavement structures designed using the Turkish Flexible Pavement Design Guide 2008 were chosen and secondly, the effect of variation of subgrade strength [5 to 50 California Breading Ratio (CBR)] on pavement performance (rutting and fatigue cracking) for three different traffic levels [5000, 10000, and 15000 average annual daily truck traffic (AADTT)] for climatic condition of Izmir region using AASHTOWare Pavement ME Design v2.5.5 were analyzed. The results of the study show that, reducing subgrade CBR values from 50 to 5 CBR resulted in an increase by 3.7mm in total rutting depth and 5.6% in alligator cracking magnitude. Also, results demonstrated that the influence of subgrade strength on rutting within asphalt concrete layers (AC rutting) is negligible. By contrast, increasing subgrade CBR value from 5 to 50 resulted in a significant increase (65.1 to 314.7 m/km) in longitudinal cracking magnitude while thermal (transverse) cracking is not sensitive to the variation of subgrade CBR values. This study can assist highway agencies and individual pavement designers in the design a more practical pavement.

DMRB Flexible Road Pavement Design Using Re-Engineered Expansive Road Subgrade Materials with Varying Plasticity Index

Pavement thickness is a very vital component during the design stage of a road construction project. Pavement design helps to determine the costs of the project over a certain period to ascertain how the cost of road pavement construction affect the life cycle cost of the road. Road pavements are designed based on the type of subgrade material and the expected traffic load to help clients and decision-makers make decisions on the project. In this study, expansive road subgrade materials were improved using lime and cement and their California Bearing Ratio (CBR) was used in road pavement design. The study used the Design and Manual for Roads and Bridges (DMRB) as a guide to investigating the effect of stabilised expansive road subgrade with varying CBR values on road pavement design. The mineral structure, characteristics, Atterberg limit, compaction CBR, swell and microstructural analysis (scanning electron microscopy (SEM) and Energy Dispersive X-ray (EDX)) of stabilised subgrade materials were investigated. The results show an increase in California Bearing Ratio (CBR) values and a reduction in swell values while curing age increased for stabilised subgrade materials. Treated samples show high Calcium Silicate Hydrate (C-S-H) gel formation after 7 and 28 days of curing. The thickness of road pavement was observed with an increase in CBR values. The study established that the thickness of road pavement and overall construction cost can be reduced using cement and lime as additives in subgrade stabilisation.

Resilient Characteristics of Polymer Emulsion-Treated Sandy Soil

The current pavement design guidelines, for example, Mechanistic-Empirical Pavement Design Guide (MEPDG), heavily rely on the resilient moduli of pavement materials. Some locally available pavement materials may not meet the design requirements and often require the application of efficient stabilizers. Therefore, the characterization of natural and treated subgrade soils using resilient modulus is important for the design of durable flexible pavements. A research study was designed and conducted to investigate the effect of polymer emulsion treatment on the resilient characteristics of sandy soil, which is used in constructing highways and airport surfaces. A commercially available polymer emulsion was used to stabilize cohesionless soil, and an attempt was made to understand the influence of polymer emulsion dosage and curing time on the strength and resilient characteristics of treated soil mixtures. Several laboratory tests were conducted on mixtures prepared with different dosages and curing times to evaluate the improvement in unconfined compressive strength and resilient moduli properties of treated sandy soil. Multiple regression analyses were conducted on resilient moduli test results using two- and three-parameter models and identified the best model exhibiting a good fit with the experimental data. A case study was demonstrated using the resilient moduli of untreated and polymer emulsion-treated soil to determine the thickness of airfield pavement. Overall, the outcome of the study is expected to assist the state and federal agencies in stabilizing and using problematic sandy soils for constructing various pavement structures.

Modify Design of Flexible Pavement to Enhance Its Strength for Indian Road Conditions

Abstract: Now a days, disposal of plastic waste has became issue of great concern for environmental engineers due its non biodegradable characteristics and health hazard. The reasons due to which bitumen is mostly used as a binding material are its excellent binding characteristics, waterproofing properties and low cost as compared to other binders. Due to the critical shortage of natural aggregate, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. The application of recycled aggregate has been started in many countries for construction projects. Recycled coarse aggregate (RCA) obtained from crushed concrete rubble, instead of being stored, can be reused in building industry. The main aim of this project is to add various types of disposal plastic to modify design for enhance road strength. Keywords: Flexible Pavement, Marshal Stability, Plastic Waste, Bitumen, Aggregate, Plastic-bitumen-aggregate mix.

Quantifying the Benefits of Geosynthetics Reinforcement in Flexible Pavement Design Using Cyclic Plate Load Testing

Development of pavement design over the past decades has focused on moving from empirical design equations to more powerful and adaptive design schemes. The AASHTO mechanistic–empirical pavement design guide (MEPDG) has been developed to model pavement structure and predict its service life more accurately. Although MEPDG has been widely implemented to design conventional pavement, it is not yet capable of predicting the service life of pavement reinforced with geosynthetics. Given the above concerns, seven full-scale test sections that were constructed at Louisiana Transportation Research Center-Pavement Research Facility (LTRC-PRF) were devoted to a structural experiment to investigate the performance of geosynthetic reinforced pavements. The benefits of using geosynthetics to enhance the performance of pavements constructed over soft subgrades was evaluated using cyclic plate load testing. Cyclic load at a frequency of 0.77 Hz was applied through a 305 mm diameter steel plate. The test results clearly show the benefits of geosynthetics in significantly reducing pavement rutting. The test section with double geosynthetic layers performed better than the other six sections studied. After eliminating the effect of variations in construction, the benefits of geosynthetic reinforcement are quantified within the context of the AASHTOWare Pavement ME Design Guide. The developed design procedure is capable of quantifying the contribution of geosynthetics in pavements to base reinforcement as well as subgrade stabilization. A design methodology is proposed that falls within the context of MEPDG.

Contribution to the flexible pavement design guides evaluation used in tropical zone: Application to lateritic materials of Bamougoum (West, Cameroon)

The choice of any materials in the realization of sustainable road infrastructures for the well-being of populations must be made using reliable criteria. In this work, classic geotechnical characteristics and experimental Young's modulus determination of the Bamougoum lateritic materials were put together in order to raise the non-exhaustive limits of pavement design guides used in tropical zone. The results show that the Bamougoum materials are very plastic silty materials, made up mainly of the fine fraction (33.49% and 76.41%) with plasticity indices between 9.49 and 36.88. The CBR values vary from 11 to 38 and the behavior of materials is qualified as fair to poor. For compression forces of 18.30–25.45 KN, and longitudinal deformations of 0.007–0.02, Young's modulus values varies from 72 to 221 MPa with an increase percentage less than 20 from age 3–7 days. The compliance of studied materials to road pavement standards for tropical countries and technical guides indicate that they can be used in sub-base of flexible pavements of medium or low traffic. However, relying mainly on these criteria can be misrepresentative as materials characteristics vary considerably based on laboratory test procedures, climate and parent rock not considered in the different manuals. Then, the experimental Young's modulus association with the existing classical selection criteria of material to be used in road pavement could contribute to the reduction of early roads degradation in tropical countries. Moreover, the use of pre-established modulus values has a negative impact on the infrastructure durability.

A Novel Approach to the Design of Geogrid-Reinforced Flexible Pavements

A Novel Approach to the Design of Geogrid-Reinforced Flexible Pavements

Influence of Seed Layer Moduli on Backcalculation Procedure and on Overlay Design of Flexible Pavements

The seed moduli selected for backcalculation analysis of multilayer flexible pavement can have significant effects on the performance of backcalculation software and, sometimes, the final solutions of the overlay designs. Therefore, this paper aims to analyze the variability of the resilient moduli (MR) obtained by backcalculation programs, taking different seed moduli as input data. To this end, data obtained from non-destructive structural evaluation (falling weight deflectometer [FWD]) were used in three different regions of Brazil. Thereafter, the deflection basin values and the seed moduli were inputted into the two backcalculation methods: linear elastic and finite element. By varying the RM seed of one of the layers by 100%, the percentage differences in the backcalculated moduli were computed within the range of typical resilient modulus (MR) values for paving materials, and close to the upper and lower thresholds of the usual moduli in Brazil. Furthermore, with the data provided by backcalculation software and crack monitoring, these were inputted into the flexible pavement design software (MeDiNa) to also analyze the influence of the seed moduli variability on the pavement overlay design, through the cracked area percentage parameter. Therefore, it was found that the seed moduli have a high influence on the backcalculated moduli, with percentage differences of up to 68.30%, mainly for the base and subbase layers of pavement. Even with the differences obtained in the values of the backcalculated moduli, it was found that the seed moduli did not cause a significant impact on the overlay design in which the percentage difference between the cracking predicted for the surface layer was less than 2.5%.

Rotation of Stresses in French Wheel Tracking Test

The main function of a pavement is to distribute the traffic-induced load over its different layers. While the flexible pavement design methods are based on a linear elastic calculation, the real behavior of the different layers is highly non-linear and elastic. They can also, in some cases, be plastic and viscous. This research aims to develop a three-dimensional numerical model that is closely similar to the test FWTT conditions. The model will have a real geometry wheel footprint (rather than a rectangular shape). As a substitute for incremental loading, the wheel movement during its passage over the specimen will be simulated by a horizontal displacement. These important characteristics of the model represent the novelty and the major difference between the current research and previous studies. The current model, which is based on the finite elements method, uses Abaqus software and a viscoelastic constitutive model. The materials' viscoelastic properties have been described by the Prony series, also called the relaxation modulus, which is a function of time. This parameter can be defined in most computer-aided engineering (CAE) software. The procedure for calculating the Prony series from experimental data is explained. The results obtained agree with the stress signal amplitude, the stress rotation principal, and the total displacement rotation when the load approaches the node considered and located in the middle of the specimen. Doi: 10.28991/CEJ-2022-08-03-03 Full Text: PDF