Road Pavement Layers Research Articles

Stabilisation of lateritic soil with pulverised ceramic waste for road construction

Lateritic soil is used for the construction of road pavement layers in the tropics. The engineering properties of lateritic soil can be improved by using additives in order to make it suitable for road pavement construction. Such additives can be agricultural waste or other suitable materials. In this research, the influence of adding varying proportions of pulverised ceramic waste (PCW) to lateritic soil was evaluated. The materials used for the study were lateritic soil and PCW samples. The control and lateritic soil samples with addition of 5%, 7.5%, 10% and 12.5% PCW were considered for specific gravity, grain size analysis, Atterberg limits, compaction, California bearing ratio and unconfined compressive strength tests. The plasticity index reduced from 12.17% to 11.98% from the control (0%) to 12.5% addition of PCW; the maximum dry density increased from 1.76 to 1.95 kN/m3 while the corresponding optimum moisture content of the lateritic soil decreased from 14.76% to 11.63%. The specific gravity of the lateritic soil and PCW were 2.63 and 2.82 respectively. The addition of 12.5% PCW increased the California bearing ratio and the unconfined compressive strength of the lateritic soil by 129% and 175% respectively.

Investigation of influence of the rubber crumb, as a stabilizing additive, on the properties of stone-mastic asphalt

Problem It is noted that ensuring uniformity of crushed stone-mastic asphalt mixtures (SMA) at the stage of their preparation and use is one of the conditions that significantly affects the properties and durability of arranged layers of road pavement. Ensuring uniformity as a technological characteristic, the criterion of which is the binder runoff index, can be carried out by introducing stabilizing additives of various origins into the composition of SMA. The stability over time is uniform, and its concentration in the composition of mixtures of a certain type depends on the effectiveness. Goal. The article presents the results of experimental studies based on the effect of the stabilizing additive "Myactive 75", which is a rubber crumb that is crushed from old truck tires, on the uniformity index of SMA-15 and the properties of stone-mastic asphalt (SMA) of the SMA-15 form. Results. It was found that with an increase in the concentration of rubber crumb, as a stabilizing additive, in the composition of SMA-15, an increase in the uniformity of the mixture at technological temperatures is observed. It has been shown that to ensure the same binder runoff rate in SMA-15, it is necessary to introduce 1,5 times more "Myactive 75" stabilizing additive as compared with the “Viatop-66” stabilizing cellulose additive. Under these conditions, SMA-15 in terms of physical and mechanical properties and frizz resistance is absolutely not inferior to SMA-15, which contains 0,4% by weight of the mineral part of the stabilizing additive “Viatop-66”.

Clarification of the stress-strain state of the superstructure with orthotropic slab taking into account solar radiation

The purpose of this work is to clarify the stress-strain state of the superstructure under the influence of solar radiation using the results of a non-contact pyrometer and contact thermometer. Full-scale measurements of the temperature of the superstructure elements with orthotropic slab during daylight at extremely high temperatures and exposure to solar radiation were carried out. Temperature readings on two measuring instruments were taken at the designated points of the asphalt pavement and main beams. Verification of the non-contact pyrometer according to the readings of the contact thermometer was performed. The analysis of the results of full-scale measurements showed that when measuring the temperature of the superstructure elements using a non-contact pyrometer, an error in the results may occur in comparison with a contact thermometer. With the help of a special software package, a detailed temperature distribution was determined by the thickness of the layers of road pavement, orthotropic slab and the height of the main beams for various cases of solar radiation exposure. With the help of the developed finite element model of the superstructure, 2 variants of calculating the stress-strain state were performed: (1) in accordance with the readings of the non-contact pyrometer; (2) in accordance with the readings of the contact thermometer. The results of calculations obtained on the basis of the contact thermometer and non-contact pyrometer are compared. The results of numerical studies have shown that when calculating the stress-strain state of the span structure, there is a discrepancy between the results of the initial data of the pyrometer and the thermometer. In full-scale temperature measurements under the influence of solar radiation to clarify the results, it is recommended to specify the readings of the non-contact pyrometer according to the readings of the contact thermometer.

Properties of mineral-cement emulsion mixtures based on concrete aggregates from recycling

The article presents selected problems connected with the development of road innovations for national roads and motorways. The main aim of the research work was to analyze possibilities of application of reclaimed concrete obtained from the demolition waste from the existing roads to produce new layers of road pavements. The article presents selected test results which show the influence of the cement and emulsion binders contents on the strength parameters of the mineral-cement emulsion mixtures (MCE). Analysis of the standard MCE mixtures design process has been indicated. It has been suggested that new tests methods and criterions should be implemented to this process, when reclaimed concrete is used in mixtures. The application of reclaimed concrete in conventional MCE mixtures made it possible to achieve positive economic and environmental effects.

Influence of replacement Portland cement with white limestone powder from Madura as filler on hot asphalt mixture (hot mix) Asphalt Concrete Wearing Course (ACWC) on Marshall characteristic

Road pavement layers are essential road construction that supports traffic loads, and as infrastructure that connecting one place to another and used by society should have good quality pavement, excellent performance and comfort serviceability to human movement in transportation. As is known filler has term and condition specification in Bina Marga General Specification (Edited Version 3) (2010), the added filler requirements consist of limestone dust, Calcium Carbonate, CaCO3, or lime dust by AASHTO M303-89 (2006). While the lime powder that has used as filler is according to the test results from the chemical engineering laboratory, ITS Surabaya pure white limestone Madura is a waste of natural lime rock containing Calcium Carbonate (CaCO3) as much as 58.46%. It will be seen from the value of stability and flow by using Marshall Test Performance by combines mixture of asphalt-aggregate with filler of white lime powder of Madura with difference of asphalt content 5,5%, 6% and 6,5% and variation of content filler 0%, 1%, 2% 3% and 4% on mixed Asphalt Concrete Wearing Course (ACWC). From the result of the testing and analysis of Marshall, the replacement Portland cement with white limestone powder on asphalt concrete wearing course layer are finding combine of asphalt content 5,5 %, 6,0% and 6,5% and higher levels of filler in asphalt mixture shows the higher value stability while the value of flow decrease with increasing value of filler content in the asphalt mixture. Based on the value of the variation filler that meets specifications Marshall 4% white limestone Madura and 6% asphalt content as the proportion that meets all of Marshall parameter value.

EXPERIENCE ON DESIGN AND CONSTRUCTION OF ROAD PAVEMENTS USING THE CLAUSES OF EUROPEAN STANDARDS ON HYDRAULICALLY BOUND MATERIALS

Hydraulically bound mixtures (HBM) are most effectively applied in the base layers of flexible road pavements to enhance their load bearing capacity and also in the base layers of rigid road pavements in the case of weak soils of the sub-grade. The evaluation of Ukrainian standards which are identical to European standards relating HBM leads to the point of subsequent implementation of new requirements trough design and construction of motor roads in Ukraine. The by European standards stated requirements and classification of HBM provide a modelling regime closer to the performance of bound pavement layer and give the wider range of HBM designations with different strength properties. Thus, this article reviews such aspects of design and construction of road pavements with HBM layers which are distinguished from the conception approved now in Ukraine. The reviewed clauses on design and construction concern road pavements which, in accordance with the European practice, are classified as flexible pavements or semi-rigid pavements and are comprised of flexible (bitumen-bound) upper layers laid on a HBM base. The reviewed types of road pavement constructions are most eligible to emphasize the possibilities of implementation of new standard requirements in the Ukrainian road building industry. As it was concluded, the European standards state classification of HBM by compressive strength RC and classification by tensile strength in combination with elastic modulus Rt, E. These methods of classification are equivalent with no correlation intended between them and have been successfully used during design and construction of road pavement constructions comprised of bitumen-bound layers laid on a HBM base. When designing the motor roads with the above mentioned pavement construction to be loaded with high traffic, HBM of strength classes RС from С8/10 to С9/12 shall be contributed where classes of strength are determined by the type of a hydraulic binder and can be accorded to the categories by ”Rt, E” values not less than T3 (from T3 to T5). Keywords: hydraulically bound mixtures, classification by values of mechanical properties, compressive strength, base layers from hydraulically bound mixtures.

Evaluation of The Modification Efficiency of Bituminous Binders with SBS Polymer Based on Changes in Strain Energy in the Ductility Test

Road pavement layers in many cases are done of hot mix asphalt (HMA). It is mixture of mineral aggregate and asphalt binder. The content of the bituminous binder is not very significant (several percent). In fact, asphalt binder decides about every properties of hot mix asphalt in significant range. Traffic condition is still changing (traffic is growing and trucks are heavier). It is reason to find better solution to asphalt pavement and improve parameters asphalt binder. One of important attribute is sensitivity for temperature. Searching for a way to improve cohesion, viscosity and adhesion to mineral aggregate is one of the directions research. One of solution is use application of modifier. The most popular are polymers. Most frequently used copolymers to modify asphalt binder are thermoplastic elastomer styrene - butadiene - styrene (SBS). Thermoplastic polymers are used in practice, which soften upon heating and harden during cooling (reversible process), reminding in this respect the behaviour of asphalts. In article, authors have present tests results of modified asphalt binder by SBS polymer. Tests were made on two types of bitumen, one of them was distilled asphalt, second oxidised. Amount of modifier was variable and was from 0% to 6%. Results of test confirmed usefulness SBS polymer to modify asphalt. In every cases noticed increase penetration index (PI) and change structure of bitumen from sol-gel to typical gel. Effect of this is reduce thermal sensitivity. Resistance to changing of temperature is better. After tests and analyses, the authors stated that amount of polymer above 2% clearly changes asphalt parameters both hard and soft.

Estudo da aplicação da cinza de caldeira a coque nas camadas de base e sub-base de pavimentos

Este estudo apresenta a caracterização de cinzas obtidas do processo de beneficiamento do níquel em usina siderúrgica, tendo como objetivo principal, avaliar sua aplicabilidade para estabilização de solos em camadas de base e sub-base de pavimentos rodoviários, através da mistura destas a um solo regional e cal. Foram realizados ensaios de caracterização química, física e mecânica, para o solo puro e para o mesmo solo com a adição de diferentes teores de cinzas e cal em diferentes tempos de cura a fim de se verificar a ocorrência de reações pozolânicas, tais que resultassem em aumento da rigidez do solo. A análise mecânica constituiu de ensaio de módulo de resiliência em corpos de prova contendo 10%, 15% e 20% de cinza em substituição a massa seca do solo e 8%, 13% e 18% de cinza e 2% de cal em substituição a massa seca da cinza. Como resultados, encontrou-se que a cinza de caldeira a coque provoca acréscimo da rigidez das misturas com aumento do tempo de cura, podendo ter seu efeito potencializado pela ação da cal, efeito observado através dos ensaios triaxial de cargas repetidas. Os resultados obtidos para todos os teores de cinza foram satisfatórios, ressaltando o emprego positivo do material para aplicação em camadas de pavimentos em vias de baixo a médio tráfego.

The study of strength of sandy soils reinforced with cement with the addition of «DorZem Ds-1», for use in the construction of foundations of roads

Currently, road organizations are faced with the problem of increasing the bearing capacity of the layers of road pavement. This problem can be solved by using new design solutions, technologies and materials. The use of local road construction materials, industrial waste, stabilization and strengthening of soils in the foundations of the pavement will increase the bearing capacity of the pavement, reduce transportation costs for the delivery of materials and reduce the cost of construction. Strengthening of soils – a set of measures to improve their strength and water resistance. In the process of strengthening the soils for use in the foundations of the pavement the main task is to obtain a new building material with the desired structural and mechanical properties. The process of strengthening is a process of structure formation, new connections are created by influencing the soil structure-forming binders (cement, lime, organic binders, etc.). When stabilizing the properties of soils, mainly the content of water in the soil, use stabilizers. They usually are water-repellent additives. When strengthening the soil can use different types of modifiers: Russian and foreign. We used the modifier «Dorzem DS-1». It is a powdery substance. The use of «Dorzem DS-1» fundamentally changes the process of crystallization. The mechanism of binding of soil particles changes from «bonding» to the «plexus» – when hitting the «Dorzem DS-1» in the ground begin to form crystalline dlinnorylye of communication, which «envelop» all the elements. On the strength of they, like Kevlar thread (strong, flexible). Due to this, strong, wear-resistant structures are obtained (cement, lime, organic binders, etc.). Several years in a row on the instructions of road construction organizations of the city of Bryansk employees of the Department «Roads» BGITU conducted research to strengthen clay soils. Recently, road organizations began to prefer sandy soils. They are enough in the Bryansk region, but they are mostly fine-grained and dusty. Performing the task of LLC «Bryansk road construction company №1», we have previously been installed grain composition of sandy soil. Its density and humidity were determined. From the silty sand specimens have been fabricated reinforced soil using Portland cement grade 400, modifiers the «Palace area DS-1» and water for mixing, tested. The samples had cuboid shape with dimensions: 10х10х10 cm and 7х7х7 cm. The compressive strength was determined as the average value of four samples in a series made from a mixture of one composition. The Age of the samples during the tests was 28 days, which corresponds to the brand strength of the main mineral binder of the 1st type (Portland cement) – GOST23558-94 p. 6.1. Laboratory tests of samples from the soil treated with cement and cement plus the additive «Dorzem DS-1» showed that the greatest strength can be achieved by adding to the soil 12 % of the cement over the weight of the soil and 3 % of the additive. The strength obtained in this case is 4,882 MPa, i.e. about 5 MPa. In the manufacture of samples of hardened soil cement with one (12 % in excess of the weight of the clay) strength is much lower 3,712 MPa. This pattern is observed in other formulations of recipes. The use of additives «Dorzem DS-1» in strengthening the soil can improve the performance of water resistance and frost resistance, eliminate the formation of cracks.

Gradation Analysis of Reclaimed Asphalt Pavement from National Road as Asphalt Concrete Layer

One of the assets of land transportation infrastructure that obtained attention now is the road. Road construction can support the developing economy, industry, trade, people and good mobility, regional development. Management of road infrastructure assets require to prioritize natural resources managements efficiently as possible. Reclaimed Asphalt Pavement (RAP) is the result of dredging material with aggregate gradation condition that are not in accordance with the needs of the gradation envelope. Utilization of RAP as a pavement layer is an effort to converse the use of natural materials. The efficiency aspect of RAP aggregate use needs to be done by determining the road pavement layer that is most appropriate to the condition of the RAP aggregate so that the addition of new aggregates is kept to a minimum. The aim of this study was to obtain a suitable pavement layer determination based on the aggregate gradation of RAP and standard specifications. The method used literature study from previous research and RAP aggregate sieve analysis from national roads in East Java Province. The results showed that the utilization of RAP from national roads based on the RAP aggregate conformance value were AC-WC layer of 82.292%, AC-BC layer of 68.75% and AC-Base layer of 41.667%. Based on the gradation analysis, it is found that the RAP aggregate is best suited for the AC-WC layer, because it requires optimal RAP aggregate and the most efficient of additional aggregate.

Alkali-activation of recycled construction and demolition waste aggregate with no added binder

The alkaline-activation of aluminosilicate compounds present in fine particles of unselected construction and demolition waste (UCDW) aggregates is investigated here. The aim is to stabilize UCDW aggregates by adding an alkali-activating solution (AAS) composed of sodium hydroxide and sodium silicate and then assess their potential employment in stabilized base/subbase road pavement layers. Contrary to the practice in other studies, no industrial–waste by-products (i.e., fly ash, slag precursor) or other components containing silica-aluminates were added to the material. Workability, strength, and stiffness values were evaluated at laboratory temperature (around 25 °C) for 7, 28 and 60 days. The resulting mixtures were compared with those containing pure water and a diluted AAS (50% of pure AAS and 50% of water). The resilient modulus of UCDW aggregates compacted with pure AAS was considerably higher than those containing both diluted AAS and water only. Similar conclusions were drawn for the unconfined compressive strength and indirect tensile strength parameters, which for UCDW with pure AAS were comparable to those for ordinary cement-stabilized granular materials. These results demonstrate the potential offered by the alkali-activation of aluminosilicate compounds present in fine particles of UCDW. The microstructural observation, carried out by Field Emission Scanning Electron Microscopy, coupled with an elemental analysis performed by Energy Dispersive Spectroscopy, supported the successful alkali-activation of UCDW fines.

EXPERIENCE ON IMPLEMENTATION OF HOT IN-PLACE RECYCLING OF ASPHALT CONCRETE IN UKRAINE

Rehabilitation of asphalt concrete layers of road pavements using HIR technologies enables effective elimination of surface defects (rutting, cracking, raveling, bleeding (flushing)) including defects caused by the non-conformity of asphalt concrete to the standard specifications. Due to the economical and ecological advantages, HIR technologies belong to the present-day effective alternative methods of rehabilitation of asphalt concrete pavements. In Ukraine, HIR technologies were first applied on intermediate repair works on an area of the international road I-01 “Kyiv-Chernihiv-Novyye Yarylovichi” in the 2013. Now, HIR technologies have been applied on repair works on numerical objects including areas on such state motor roads as I-01, I-06, N-09, R-10, R-67. The presented paper analyzes the results of monitoring of materials and technologies which was aimed on HIR performance investigation supported by State Road Agency of Ukraine (Ukravtodor) throughout 2014-2018. The results of monitoring of HIR technologies including laboratory evaluation of materials and also field testing of the rehabilitated pavements led to the conclusions fitted by the world-wide experience on implementation of HIR technologies. 1. Being applied to the structurally sound pavements, HIR provides effective elimination of surface defects of flexible pavement to a depth of (50-60) mm including defects caused by the non-conformity of asphalt concrete to the standard specifications. However, HIR is not suitable for existing asphalt pavements which have too much variation in asphalt concrete composition and thickness within the project limits. 2. The efficiency of asphalt pavement rehabilitation using HIR technologies largely depends on precise engineering consideration which determines the efficiency of preparatory (repair) works including some special works such as: – correction of cracks in case of cracking that extends below the depth of hot recycling; – re-compaction of an unbound base layer(s) in case of the insufficient compaction causing “alligatored” network-like cracking of asphalt pavement. 3. Proper technical and working conditions of the rehabilitated pavement during the nominal life cycle could be maintained by overlaying the surface treatment using bituminous emulsion materials or by single-pass overlaying a new hot-mixed asphalt concrete layer. Investigations accomplished during the implementation of HIR technologies allow enhance quality of recycled materials and also promote the entire adaptation of HIR technologies to the Ukrainian standards. Keywords: asphalt pavement rehabilitation, hot in-place recycling, recycled asphalt concrete, field testing, road pavement strength measurement, rutting measurement.

Application of recycled concrete aggregate in mineral-cement-emulsion mixtures

The article presents selected problems connected with the accomplishment of the research grant ‘Application of reclaimed materials’ as part of the joint project Development of Road Innovations (RID) co-financed by the National Centre of Research and Development as well as the General Directorate for National Roads and Motorways. The main aim of the project was to analyse possibilities of application of reclaimed concrete obtained from the demolition waste from the existing roads to produce new layers of road pavements. The article presents selected test results which show the influence of the reclaimed concrete content on the strength parameters of the MCE mixtures. Significant variation of the tested MCE mixtures properties depending on the percentage of the reclaimed material has been indicated. It has been suggested that new tests should be implemented in the process of MCE mixtures design process. An optimal content of reclaimed concrete has been determined in order to obtain required values of the analysed parameters. The application of reclaimed concrete in conventional MCE mixtures made it possible to achieve positive economical and environmental effects.

Steel Aggregate Swelling Potential in Layers of Road Pavements

AbstractSteel slag, one of the by-products from the production of steel, is crushed, sized properly, and treated in relation to its volume swelling potential to be used as a highly resistant aggreg...

The Impact of Long-Time Chemical Bonds in Mineral-Cement-Emulsion Mixtures on Stiffness Modulus

Deep cold in-place recycling is the most popular method of reuse of existing old and deteriorated asphalt layers of road pavements. In Poland, in most cases, the Mineral-Cement-Emulsion mixture technology is used, but there are also applications combining foamed bitumen and cement. Mineral-Cement-Emulsion mixtures contain two different binding agents – cement as well as asphalt from the asphalt emulsion. Asphalt creates asphalt bonding (responsible for flexible behaviour), whereas cement generates hydraulic bonds (responsible for stiffness of the layer). Final properties of Mineral- Cement-Emulsion mixtures are a result of a combination of both binding agents. While the stiffness of the material is unaffected by asphalt bonding, an increase in stiffness with time is visible for materials treated with hydraulic binders. This publication presents the change in stiffness modulus of Mineral-Cement-Emulsion mixtures by Simple Performance Test. For the analysis, two batches of specimens were used: the first was tested 28 days after compaction (period stated in Polish recommendations) and the second was tested 1.5 years after compaction. Analysis showed that after 1.5 years the stiffness modulus increased by about 10% in comparison to the 28 days after compaction. The change is minor but still significant. Unexpectedly, the level of the increase was unaffected by the combination of the binding agents (asphalt emulsion, cement).

Compaction and freeze-thaw degradation assessment of recycled aggregates from unseparated construction and demolition waste

Although previous studies attested to the feasibility of using recycled aggregates from unseparated construction and demolition waste (UCDW aggregates) in unbound layers of road pavements, the degradation caused by compaction and freezing action under simulative conditions has not been investigated yet. To investigate the effects of these two sources of degradation on resilient modulus (RM), three UCDW aggregates were collected from different plants in the Turin area and compared with a natural (NAT) aggregate. Partially-saturated specimens of UCDW aggregates at the optimal moisture content (wopt) and at wopt±2% were prepared at the gyratory shear compactor with 30 and 100 gyrations, and by subjecting specimens to 0, 4 and 8 two-day freeze–thaw cycles from −18 °C to +20 °C.Brittle and weak components of UCDW aggregates (crushed concrete, bricks) generate fine particles in the first part of the compaction process (in the first 30 gyrations). Freeze–thaw action led to a clear increase in the resilient modulus of UCDW specimens compacted at wopt and wopt+2%. A similar trend in RM was observed in the case of NAT aggregate in similar moisture conditions, while both UCDW and NAT exhibited a slight decrease for some samples prepared at wopt−2%. Under more severe but non–simulative testing conditions such as those currently used to select conventional granular materials, UCDW aggregate exhibits lower performances than NAT aggregate. Conversely, when evaluated in more simulative test conditions, the behaviour of UCDW aggregate is comparable to that of NAT one.

A Soil-Cement Formulation for Road Pavement Base and Sub Base Layers: a Case Study

The transport sector is a key element in societal development and economic growth, with road transport playing a dominant role. The minimisation of economic and environmental costs throughout the road structure lifecycle without compromising the performance is a major concern. As such, the use of local treated soils with cement can be a good alternative to base and sub base road pavement layers. The objective of this laboratory study was to formulate a soil-cement solution for applying as base and sub base layers in an experimental test section. The formulation was realised according two different methodologies: the Portuguese and the South African. Local clayey sand was used to the formulation process. Aiming to assess the soil-cement mechanical behaviour, unconfined compressive strength and indirect tensile strength tests on soil-cement specimens with different curing times (1, 7, 14, 21, 28, 60, 90, 120, 150 and 180 days) were realised. Strengths determined for both methodologies showed significant differences between them and also variations between the results obtained for the specimens presenting the same curing time. The strengths determined according to the South African standards are generally higher than the same characteristics measured according to the European standards. In addition, the results obtained by the South African standards show a better repeatability than those obtained according to the applied European standards. For the studied clayey sand, the obtained results suggest a minimum curing period of 28 days when about 90 and 70% of maximum unconfined compressive strength and indirect tensile strength, respectively, obtained according to the South African methodologies were achieved.

A new practical method for determining the LA abrasion value for aggregates

The Los Angeles (LA) abrasion method is commonly used for determining the abrasion characteristics and classification of the granular materials used in road and pavement construction. The abrasion resistance of materials can significantly affect the service life of road pavements when exposed to long-term dynamic traffic loads. The LA abrasion method suffers from several drawbacks including the time needed to perform the test, the operational noise and dust and the space required by the machine. The objective of this study was to investigate whether the modified compaction method can be a suitable alternative for determining the LA abrasion value. This study was proposed in consideration of the similarities in the treatment of materials by the LA abrasion method and the modified compaction method. It was considered that the laboratory-modified compaction method closely simulates the abrasion resistance of the unbound granular materials in the base course and sub-base layers of road pavements that experience repetitive dynamic loads. As indicated by the results of tests on nineteen different aggregate samples, a strong correlation exists between the Los Angeles Abrasion Values (LAVs) and the values obtained when implementing the modified compaction method, namely, the Compaction Abrasion Values (CAVs).

Sand equivalent as an evaluation of unbound mixtures suitability for road pavement layers.

In the article a review of sand equivalent evaluation methods of mineral mixtures for unbound road pavement layers was shown. Considering that there are various test methods and different evaluation criterions of these materials suitability, the need to develop unified sand equivalent method for aggregates and unbound mixtures in Poland was pointed. The objective method and limiting values of sand equivalent test were suggested. It was done based on laboratory examinations coupled with California bearing ratio tests.

Numerical modelling of flexible pavement incorporating cross-anisotropic material properties. Part I: Surface circular loading

Accurate numerical modelling of the behaviour of road pavement layers is an important requirement for the design and evaluation of road pavements. This modelling includes the prediction of pavement performance under the action of traffic loading and environmental factors. Depending on the complexity of the models, properties of pavement layers that may be considered are wide-ranging - from linear or nonlinear elastic to cross-anisotropic through to linear visco-elasto-plastic. Some properties, such as cross-anisotropic, are not only related to placement and compaction of the pavement layers, but are also inherent to the materials used. Other properties, such as linear visco-elasto-plastic, are specific to asphalt concrete and depend on the speed and magnitude of traffic loading, as well as the environment (temperature) in which the road is located. This paper presents basic theoretical derivation of numerical modelling of a flexible pavement considering cross-anisotropic material properties (with isotropic properties as a special case). The solutions derived in this paper are based on Hankel transformation of Navier's equations. The accuracy and validity of the solutions are verified through comparisons with a proprietary finite element method (FEM) package. For this purpose, a pavement structure composed of five main layers constituted by isotropic and cross-anisotropic (also known as transversely isotropic) material properties is analysed. In order to vary some of the layer properties with depth, the main layers were sub-layered, resulting in a 17-layer pavement system.