Road Pavement Layers Research Articles

Calculation of the Number of Roller Passes When Strengthening Roads Using Recycled Asphalt Granulate

Statement of the problem. Work during the repair, overhaul and reconstruction of highways involves the destruction of old asphalt concrete pavement using the cold milling method. The resulting discrete material is used to strengthen roadsides, and if it is regenerated, it is used to construct base layers and lower layers of covering. The compaction of layers of road pavement is carried out with rollers, the efficiency of which depends on the properties of the resulting material, the power parameters of the rollers, and the technology of work, determined by the number of passes of the roller along one track. Analysis of the work showed that there are no substantiated recommendations for determining the number of roller passes taking into account the properties of the material being compacted. Establishing such dependencies makes it possible to clarify the composition of the compaction machine link when installing structural layers of road pavements while ensuring the required quality of work. Results. Analytical dependencies are presented for calculating the deformation modulus and rigidity of a layer of processed asphalt granulate under load, taking into account the thickness of the layer and the size of the fractions. The stresses under the rollers were determined for different types of rollers and their operating modes, taking into account the technical characteristics. The results of a study to determine the number of roller passes when installing a layer of recycled asphalt granulate are presented, taking into account the size of the fractions and the characteristics of the rollers used. Conclusions. It has been established that both the deformation modulus and the rigidity of the compacted layer can be taken as a criterion when choosing the parameters of the rollers and determining the number of passes of the roller along one track. Based on the results obtained, we can conclude that for a given value of the deformation modulus and the stiffness coefficient of the compacted layer of asphalt granulate, it is possible to determine the number of passes, the type of roller and its operating mode to ensure the required characteristics of the layer.

Studying the Structure of the Road Pavement and Specifying the Repair Method

Studying the structural condition of road pavement is essential for making effective decisions about the type of maintenance or rehabilitation that will be carried out on a pavement section. Reliable quantitative assessment of the volume of necessary repairs will ensure the performance characteristics and durability throughout the entire service life at minimal cost. This article presents detailed results from Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) studies. In addition, an analysis of these results and recommendations for strengthening the road pavement for the Sh-176 “Sighnaghi-Saint Nino Monastery” road to develop rehabilitation and maintenance scenarios. FWD results combined with road pavement layer thickness and traffic load information to determine residual service life and necessary treatment type. Thus, using the nonlinear theory of layered halfspace elasticity, pavement structure analyzed in the same way as other civil engineering structures.

ТЕХНІКО-ЕКОНОМІЧНЕ ОБҐРУНТУВАННЯ ДОЦІЛЬНОСТІ ЗАСТОСУВАННЯ АСФАЛЬТОБЕТОННИХ ШАРІВ ІЗ ЗОЛОЮ ВИНЕСЕННЯ

Introduction. The road construction industry is currently one of the strategic industries of Ukraine, and the issue of quality and availability of basic building materials for road construction is particularly topical, which is directly related to its high material intensity. The known reserves of high-quality raw materials that could be used as asphalt concrete components are constantly decreasing, so it is necessary to look for alternative sources of raw materials for construction materials and explore the possibility of their use. In this regard, the most efficient use of local raw materials is the use of industrial waste, which can be one of the solutions to the problem of shortage of raw materials of inorganic origin. Problem statement. In road construction, when repairing or arranging road pavement layers, in particular asphalt mixtures, the need for carbonate mineral fillers, which are scarce in some regions, is constantly growing. Industrial by-products can be an alternative. One of these materials is fly ash from thermal power plants, which can be used instead of mineral fillers in asphalt mixtures. Objective. To perform a feasibility study of the use of asphalt concrete layers with fly ash. Materials and Methods. Analysis of information sources and the materials market of Ukraine and calculation of the technical and economic efficiency of fly ash application in asphalt mixtures.

CORN-COB ASH AS PARTIAL REPLACEMENT OF CEMENT FOR STABILIZATION OF LATERITE SOIL

Properties of underlying soils and borrowed soil samples are some of the key factors that determine the performance rate of roads. Most of the underlying soils possess some characteristics that make them unsuitable for use. There are available agricultural waste products in most rural settlements which can be used to treat unsuitable soils. This research examined the use of corn cob ash (CCA) as an admixture to cement on some selected geotechnical properties of laterite soil. The choice of the A-7-5 class of laterite soil is due to its general rating as poor material for subgrade and other layers of road pavement by the classification system of the American Association of State Highway and Transportation Officials (AASHTO). Cement was gradually added to the soil sample in steps of 2% from 0% to 10% by weight of the soil sample and its effect on the plasticity of the sample was examined. The addition of cement performed optimally on the soil’s plasticity at 4% which was used to form different mixtures of cement and CCA having a total sum not exceeding 4%. The additives were added to the soil sample which was subjected to laboratory tests such as compaction, California bearing ratio (CBR) and unconfined compressive strength (UCS) compacted with the efforts of 596kN/m2 and 1192kN/m2. The combination of 2% cement and 2% CCA on the soil sample improved the plasticity index and UCS properties of the soil to its optimal level while 3-1 and 4-0 cement-CCA performed optimally for CBR and compaction respectively. Thus, it was concluded that CCA performed optimally with cement at a ratio varying between 4:0 to 3:1 total percentage not exceeding 4% of the weight of the soil sample.

Фиброцементогрунт в устройстве дорожных одежд лесовозных автомобильных дорог

The most important factor in increasing the efficiency of the development of forest tracts is the development and improvement of the transport and operational condition of the network of logging roads. Inert road construction materials, such as sand, crushed stone, crushed stone-sand mixture or gravel-sand mixture, are traditionally used for the construction of pavements for logging roads. However, in the areas with a shortage of these materials, the cost of road construction increases significantly. An alternative technology that can significantly reduce or completely eliminate the use of inert road construction materials is the stabilization of local soils for the construction of pavement structural layers. The soil stabilization technology consists in mixing them with binders and compacting them at the optimal moisture content of the mixture. In doing so, the resulting material acquires the desired strength and frost resistance. The most effective and common binder for soil stabilization is Portland cement. However, along with high strength properties and frost resistance, cement soils, due to their crystalline structure, have low crack resistance, which worsens transport and operational performance and shortens the service life of road pavements. One of the rational solutions for increasing the security of soil stabilization for the construction of road pavements is the installation of fiber cement soil layers. The object of this research is fiber cement soil for the construction of structural layers of road pavements for logging roads. The aim is to improve the physical and mechanical properties and frost resistance of soils stabilized with Portland cement with the addition of the material based on basalt fiber. Laboratory tests of compressive and tensile strength during splitting, as well as frost resistance of fiber cement soils of various compositions were carried out in accordance with GOST R 70452–2022. According to the data obtained, fiber cement soil has higher strength and frost resistance compared to cement soil. The fibers distributed throughout the cement-soil matrix effectively perceive external loads, providing high physical and mechanical indicators, and therefore crack and frost resistance of the material. The use of fiber cement soil for the construction of pavements for logging roads will increase the durability and reliability of their operation, as well as reduce the costs of construction and operation of road transport infrastructure of forest tracts.

Проблемы эффективного применения технологии холодного ресайклинга дорожных одежд

The technology of Cold-in-Place recycling is an alternative to the traditional methods of highway reconditioning. The research problems are the issues of effective application of this technology due to the imperfection of the regulatory standards. An important aspect of the effectiveness of cold recycling is obtaining homogeneous and durable structural layers of road pavement. Physical and mechanical properties of dispersed materials correlate with the particle size distribution. Asphalt granulat with minimum content of dusty fractions has a great influence on the aggregate composition in organomineral mixtures. The requirements of the current normative documents for cold regeneration do not take this fact into account. It causes composing of mixtures with suboptimal composition, and, consequently, a decrease in the efficiency of the applied technology. The results of the conducted researches of organomineral mixtures allow ones’ to optimize their grain composition, and to increase physical and mechanical properties of highways’ basecourses.

Marshall Performance Analysis Of Eggshells And Cement As Filler In Asphalt Concrete Mixtures (AC - WC)

Roads are transportation infrastructure whose needs in Indonesia continue to increase, along with the increasing number of vehicles. Road construction is a construction that receives traffic loads, therefore it is expected that a road pavement layer must have a strong pavement construction and be able to receive loads from traffic users. AC-WC (Black-top Concrete - Wearing Course) asphalt layer is a road pavement construction consisting of asphalt composition, coarse aggregate, fine aggregate and filler. Fillers in asphalt mixtures function to increase the binding power of AC-WC asphalt, so as to improve mixture stability and fillers can fill the voids between aggregate particles, filler commonly used is stone ash. This research will be conducted with the addition of broiler eggshell filler and porland cement in the Asphalt Concrete wearing Course (AC-WC) mixture. The research was conducted with an experimental method conducted in the Civil Engineering laboratory of Abdurrab University. The specification used in this study is Public Road Revision 2 Year 2018, The optimum asphalt content (KAO) used was 6.5%. Based on the results of the study, the largest marshall stability and melting value is found in the 100% cement filler variation, which is 1772.7 Kg and the value of flow value (melting) 3.77 mm while the largest marshall quotient (MQ) value is found in the 25% eggshell filler variation, 75% cement, which is 529.2 Kg/mm.

DURABILITY OF ASPHALT CONCRETE MIXTURE (AC-WC) USING CRUMB RUBBER WASTE AS AN ADDITIONAL MATERIAL AND PALM FRUIT ASH AS FILLER

The mixture of road pavement layers that is commonly used in Indonesia is a mixture of Asphalt Concrete (AC-WC). Addition of wastecrumb rubber (crumb rubber) in asphalt concrete mixture is a solution for highway planning and reducing waste pollutioncrumb rubber (crumb rubber) produced from a rubber tire factory. The purpose of this research is to determine the maximum percentage addition crumb rubber (crumb rubber) in the AC-WC mixture withfiller palm fruit bunch ash and to determine the residual strength index (RSI) value of the mixture which has a durability value that meets the requirements of General Specifications for Highways 2018 Revision 2. This study uses bitumen content with the percentage of mixed wastecrumb rubber used in the determination of OAC of 0%, 3%, and 6% by weight of asphalt andfiller palm fruit bunch ash 4% by weight of one AC-WC sample. The results of this study indicate testing marshall on variations crumb rubber 0% (without crumb rubber) as a normal mixture and 3% has met the specifications while the 6% variation does not. Maximum test results on the combination crumb rubber 3% resulted in the highest stability value of 1,028.85 kg at 0.5 hour immersion. The results of the durability test showed that the RSI value with a variation of 0% and 3% only fulfilled the 3 hour immersion time.

Pemanfaatan Batu Sungai Mappak Kabupaten Tana Toraja Dalam Campuran Laston Lapisan Antara

This research aims to find out how the aggregate characteristics of the Mappak River in Tana Toraja Regency can be used as a pavement material for asphalt mixtures. The method used is the conventional marshall method to obtain the properties of the mixture and marshall immersion to obtain residual marshall stability from the optimum asphalt content mixture. The results of the study indicated that the aggregate characteristics of the Mappak River stone in Tana Toraja Regency with an aggregate wear value of 21.6% met the specifications as a road pavement layer material for Mixed Laston Intermediate Layers with Optimum Asphalt Content of 6.20%, with the mixed properties of Laston Intermediate Layers, namely Density, Stability, flow, VIM, VMA, VFB and Marshall Quentient have met the Specifications of Bina Marga 2018. Through Marshall Immersion testing the Laston Intermediate Layers mixture with Optimum Asphalt Content of 6.20% obtained Remaining Marshall Stability of 95.07%, which means that it meets the Specifications Bina Marga 2018, namely at least 90%..

Structural forming of soil composites using as a pavement subgrade strengthening

The article substantiates the possibility of obtaining composite materials with improved functional properties to strengthen the subgrade, containing technogenic soil stabilized by an additive based on a gelling polymer. The introduction of technogenic soils into composites will not only reduce the consumption of expensive materials, but also solve a complex of acute environmental problems. Composite materials can be used in the construction of structural layers of road pavements, foundations of buildings and structures, sites for various purposes, for the prevention and elimination of defects in the foundations of engineering structures during their construction, reconstruction and repair, including in permafrost areas. Stabilized technogenic soils are more durable, frost-resistant and waterproof, which makes them applicable for creating impervious curtains in hydraulic structures and sealing storage facilities for hazardous substances. The cryogenic effect on a composite material allows one to vary its properties within a wide range and modify its macroporous structure. Studying the process of structure formation of the resulting organic-inorganic materials, consisting of macromolecules of high-molecular substances and inorganic inclusions that have undergone cryogenic treatment, will make it possible to specifically regulate their performance characteristics. The best values of strength characteristics were obtained for samples with a stabilizing additive concentration of 100 g/l. The resulting composite materials are hydrophobic, frost-resistant, characterized by a compressive strength of 2.3–6.5 MPa and a thermal conductivity of 0.19–0.20 W/(m·K). Data from differential scanning calorimetry and thermogravimetry and IR spectroscopy revealed that the binding of mineral particles by a stabilizing additive occurs due to the formation of organomineral complexes with the participation of clay minerals and the restructuring of hydration shells. SEM data indicate that crystallinity zones formed due to hydrogen bonds of hydroxyl groups of neighboring polymer chains can participate in the formation of the composite structure. An increase in the number of cryogenic treatment cycles promotes additional structuring and strengthening of the polymer phase due to the formation of additional nodes of the supramolecular network, ordering of crystallinity zones and the appearance of compacted areas in the structure. Computed X-ray tomography revealed an increase in the density of the composite upon drying, which helps to increase its strength characteristics. The structure of the sample is characterized by heterogeneity of the pore space, which is characterized by the presence of both fine-porous and large-porous regions, which determines its thermophysical properties.

The investigation of the frost resistance of the aggregate-sand mixes

Problem. Recently there is a steady trend to the increase of the intensity of traffic and of the loads from the wheels of the rolling stock on the whole structure of the road pavement, therefore during the building of the road pavement layers the most important thing is a rational choice of the materials for the base layers and for the top layers which will provide the performance of the entire structure during the designed service life under the working conditions which are getting worse all the time. Nowadays the most widespread material for the road base layers is aggregate mix strengthened by cement. One of the ways of the base layers materials improving is the increase of their frost resistance. One of the ways to solve this problem can be the different additive and fibers usage as a reinforcing component of the aggregate mix. But until today the influence of the internal factors such as size of mineral grains, granulometric composition and binder content on the indexes of frost resistance is still not investigated.
 Goal. The aim of the research is the investigation of the maximum grain size and content and also mineral binder concentration influence on the indexes of frost resistance of the aggregate mixes strengthened by cement. Methodology. To achieve this goal in the laboratory of the Department of Highway Building and Maintenance named after O. Birulia the samples of sand, fine-grained, medium-grained and coarse-grained aggregate mixes with cement content from 2 to 10 % were prepared. Results. For the frost resistance indexes determination of the aggregate mixes of different compositions strengthened by cement according to the maximum grain size the cement concentration influence on the grade strength indexes was found. The research results have shown that: with the increase of cement content the compressive strength indexes in the fine, medium and coarse-grained mixes are increasing; the increase of the maximum grain size of the same cement concentration shows that compressive strength and tensile strength indexes are increasing. The repeated freezing and thawing is one of the main aggressive factors of the external environment influence which reduces strength and durability of the materials, therefore the influence of this factor on the compressive strength and tensile strength was evaluated. In Ukraine according to the current standard the frost resistance of the aggregate mixes is evaluated only in terms of compressive strength index of samples which were subjected to certain number of freeze-thaw cycles. It is determined that the aggregate mixes with the same cement content with larger mineral grains in its composition have higher indexes of the frost resistance coefficient. Also it was found that the influence of the freeze-thaw cycles is more informatively shown at the samples testing according to the split tensile test. Conclusions: 1. The increase of the binder content in the composition of strengthened aggregate mixes leads to the decrease of the freeze-thaw cycles influence on the compressive strength and splitting strength for all studied compositions of aggregate mixes. 2. The aggregate mixes strengthened by the same cement amount with the larger size of mineral grains in its composition have higher values of frost resistance coefficients in comparison with strengthened aggregate mixes with smaller maximum size of mineral grains in its composition. 3. The influence of the freeze-thaw cycles is showed more informatively by the split tensile scheme.

Evaluasi Nilai Stabilitas Pada Aspal AC-WC Dengan Metode SNI 06-2489-1991

Asphalt concrete is a combination of aggregate, asphalt, with or without additives. To obtain high stability in asphalt concrete, it is necessary to have an aggregate that is well graded, dense, and has small voids between aggregate grains. Asphalt concrete performance testing can be done through the Marshall test. The Marshall Test Tool is used to determine the characteristics of a road pavement layer. One of the Marshall test kits that is still widely used in laboratories is the analog Marshall test kit. This study used an experimental method in the laboratory of the Jombang Regency Public Works Office with core test objects (KOR) made of a mixture of wear-resistant steel (AC-WC) with a thickness of 4 cm each. In this test, 4 core specimens were used in accordance with the 2010 General Highways Specifications (revision 3). With the composition of the constituent materials consisting of Aggregate 0-5 mm (42.2%), Aggregate 5 - 10 mm (33%), Aggregate 10 - 15 mm (16.9%), Filler Cement (1.9%), Asphalt Content (6%) those who get the value of 91.3% (stability) is the final residual stability value, before obtaining this value there are several values listed, namely; value 2,292gr/cm3 (Bj Mix), 5.274% (effective asphalt content), 0.772% (absorption of asphalt), 4.71% (VIM), VMA 16.80% (VIM), 71.97% (VFB ), 1178kg (initial marshall stability) , 3.55mm (flow), 332kg/mm (Marshall quetient).

Assessment of Mechanical Characteristics of Crushed Rock Substituted with Tyre Crumb for the Application of Road Base or Subbase Layers of Road Pavement

Assessment of Mechanical Characteristics of Crushed Rock Substituted with Tyre Crumb for the Application of Road Base or Subbase Layers of Road Pavement

Modelling the Environmental and Economic Life Cycle Performance of Maximizing Asphalt Recycling on Road Pavement Surfaces in Europe

The road pavement industry, worldwide, has often shown reluctance in quickly implementing innovative practices; however, in the case of raw material consumption, a cultural change is necessary and, in this sense, sustainability assessment could play a major role. Along these lines, this research study aims to provide evidence to all the involved stakeholders (material producers, pavement contractors, and road authorities) of how life cycle-based techniques can be crucial in evaluating whether the adoption of asphalt mixtures with high contents of reclaimed asphalt (RA) for wearing courses is actually a sustainable practice for major European roads. An evaluation framework composed of a life cycle assessment, to calculate the carbon footprint of both pavement materials and pavement activities, and a life cycle cost assessment, performed to determine the overall economic burden of the related road pavement surface courses and maintenance strategies over a sixty-year analysis period, is presented and applied to selected case studies. These were developed together with three major European national road authorities and include scenarios involving the construction of road surfaces with asphalt mixtures containing up to 90% RA. Results have shown that whenever high-content RA mixes do not under-perform against conventional mixtures, up to 50% CO2eq savings can be registered and up to 60% economic cost reductions can be reported. The durability of road pavement layers remains a key parameter for any road pavement sustainability assessment exercises; therefore, in order to adapt the obtained results to other contexts, researchers should always consider conducting a sensitivity analysis of the reference service life and/or road authorities should somehow request road pavement durability as a pre-requisite within procurement practices.

PENGARUH MATERIAL LOKAL KEDIRI TERHADAP TINGKAT DURABILITAS LAPIS STRUKTUR JALAN

<p><em>Air conditioning or asphalt concrete is formed from coarse aggregate, fine aggregate, and asphalt. An aggregate is a collection of grains of crushed stone, gravel, sand, and other minerals in the form of both natural and artificial products. Coarse aggregate is sieve holder No. 8 (2.36 mm) retained aggregate while fine aggregate is sieve No. 8 (2.36 mm) passed aggregate. The problems that often occur in road pavement layers are poor durability and surfaces that are easy to wear out. This study aimed to find the maximum marshall value in the form of 60/70 penetration asphalt mixture stability. This study used an experimental method with a laston AC-BC test, the test was carried out with abrasion, gradation, specific gravity, and Marshal testing tests using marshal test equipment, following SNI 06-2489-1991, or AASHTO T245-90, or ASTM D1559-76. Using aggregates from the Kedak area, stability results of 3046, 4896, 3754 were obtained, which met the standards of the Bina Marga specifications standards. So that the aggregate from the Kedak area can be used as an alternative constituent material in road planning in the Kediri area because it is more efficient and has good durability.</em></p>

The feasibility of using copper slag in asphalt mixtures for base and surface layers based on laboratory results

This study aims to assess the feasibility of using copper slag (CS) in asphalt mixtures in both the surface and base layers of road pavements. For this purpose, two sets of asphalt mixtures with different CS content (15 and 30%) and fraction sizes (0/8 and 0/16 mm) were prepared. The optimal binder content of each mixture was determined using the Marshall mix design method. Their laboratory performances were investigated and compared with the properties of reference asphalt mixtures, i.e. mixtures consisting exclusively of virgin materials. Test results showed that adding CS to the mixture for the surface layer improved stiffness and rutting resistance and had almost no negative impacts on the remaining properties apart from cracking resistance. Further, the addition of CS to the base-layer mixture improved cracking resistance, but negatively affected stiffness, rutting and fatigue resistance. In both cases, adding CS did not influence the strength, water sensitivity or freeze–thaw resistance. From a leaching perspective, the results showed that leachates gathered from the asphalt mixtures designed for the surface layer did not contain heavy metals. Overall, it can be concluded that CS has a potential to be used as an appropriate aggregate substitute for virgin aggregates in asphalt mixtures for both surface and base layers.

ОГЛЯД МЕТОДІВ ПІДБИРАННЯ СКЛАДУ АСФАЛЬТОБЕТОННИХ СУМІШЕЙ

Introduction. Asphalt mixtures are the most widely used road construction material for the arrangement of the top layers of road pavement. Asphalt mixtures are also used to arrange airfield runways, bridges deck surfacing, streets, pedestrian and cycle paths, etc. There is a large number of asphalt mixtures types that differ by grading, the largest nominal aggregate size, crushed stone content, crushed and uncrushed sand content, quality of components, and viscosity of the bitumen binder. Problem statement. The national method for asphalt mixture design is very similar to the Marshall method and the Superpave method in terms of determining the optimal bitumen binder content by the bulk properties of asphalt concrete. The only difference is that, according to the Marshall and Superpave methods, the optimal bitumen content is the one with an air pore content of 4.0 %. However, in accordance with the national method, the design air pore content varies depending on the type of asphalt mixture. A significant innovation of the Superpave method is the determination of asphalt performance indicators, such as rutting resistance, crack resistance, and resistance of the material to fatigue cracking. Apparently, these methods should also be implemented in Ukraine over time. Purpose. Analysis of the methods for asphalt mixtures design. Materials and methods. Analysis of literature sources on various methods of asphalt mixtures design. Results. The analysis of literary sources on different methods of asphalt mixtures design was carried out. Conclusions. The use of different methods of asphalt mixtures compaction can lead to the production of asphalt concrete with different volumetric properties, which will affect both the optimal bitumen content and the performance of asphalt concrete, thus further research should be aimed at defining the effect of the compaction method on the volumetric properties of asphalt concrete and their relationship with the production compaction of asphalt mixtures.

АЛГОРИТМ ВИБОРУ БІТУМУ ПІД ЧАС ПРОЄКТУВАННЯ КОНСТРУКЦІЇ ДОРОЖНЬОГО ОДЯГУ

Introduction. Asphalt concrete is the most common material for arranging road pavement layers. The significant advantages of asphalt concrete include high performance characteristics, relatively high technical indicators, suitability for regeneration, etc. At the same time, asphalt concrete also has disadvantages, one of which is the significant dependence of strength and deformation characteristics on ambient temperature. Problem statement. Currently, there are no clear criteria for the selection of bitumen in Ukraine that would take into account the conditions of asphalt concrete in the design of pavement structure, but the first steps are already being taken in this direction. The purpose of this work was to practically determine the required properties of bitumen in accordance with the previously proposed algorithms. Objective. Practical determination of the required properties of bitumen in accordance with the previously proposed algorithms. Materials and methods. Analysis of the algorithm for determining the required properties of bitumen, climatic conditions of asphalt concrete and calculation of the required bitumen grade when designing a pavement structure. Results. Suggestions for improving the algorithm for selecting bitumen when designing a pavement structure are provided. An analysis of the climatic conditions of asphalt concrete operation and the calculation of the required bitumen grade according to performance indicators when designing a pavement structure for a conditional road section were performed. A system for selecting bitumen by penetration classification based on established performance indicators is proposed. Conclusions. The proposed algorithm for determining the required bitumen grade when designing a pavement structure can be used to determine the bitumen grade both by performance and penetration classification.

Soil Improvement Using Blends of Coal Ash and Plantain Peel Ash as Road Pavement Layer Materials

The management of waste and its environmental impact remains an issue. Thus, various strategies are being explored to mitigate this problem. For this research case, the ash of plantain peel and coal was harnessed to enhance soil for usage in designing road pavements. The form of the soil, as regards its plasticity and grain assortment, positions it as a sandy lean clay material. Geotechnical parameters of the natural soil were established before being treated with coal ash (CA) and plantain peel ash (PPA), and subjected to tests for the Atterberg limits, California bearing ratio (CBR) and compaction, as well as investigations pertaining to its crystallinity and morphology. These assessments showed that strength parameters of soil increased on adding CA and PPA. However, the inclusion of these admixtures should be conducted until optimal strength is achieved as seen in 9% CA + 6% PPA. The use of soil stabilised with CA and PPA is suitable for general fillings and embankments. These findings revealed that integrating CA and PPA together would have the potential of stabilising soil as pavement layer material while also eliminating the pollution that emerges from the improper disposal of coal and plantain peels from the environment.

Stress dependent behaviour of unbound layers of unselected construction and demolition waste aggregates by lightweight deflectometer tests

The use of construction and demolition waste (CDW) aggregates in unbound road pavement layers is increasing. However, the lack of data on performance in the field has spurred this investigation into their in-situ properties. A lightweight deflectometer (LWD) is a fast and simulative testing device for estimating the elastic modulus of unbound pavement layers. A field test pit was built to run LWD measurements on an unbound subbase layer containing CDW aggregates compacted at different energy levels. To assess their stress-strain non-linear behaviour, several LWD drops were performed on the same location by varying (i) the loading mass, (ii) the drop height, and (iii) the plate diameter. A stress-hardening behaviour of in-situ CDW aggregates was observed, consistent with the stress dependent evolution of resilient modulus of granular material commonly recorded in laboratory tests. The LWD modulus was found to be dependent on the level of compaction energy but also sensitive to the mechanical response of the layer below. The outcomes at this test pit suggest it would be wise to consider the rational evaluation of the in-field stress dependent behaviour of unbound CDW granular materials at both the design stage and when devising quality acceptance procedures. Nonetheless, to have a comprehensive interpretation of LWD results a greater uniformity of material properties and a stronger control of construction procedures will be desired, especially when heterogenous materials such as CDW aggregates are investigated.