Road Aggregates Research Articles

Magnitude and determinants of road traffic accidents in North Gondar Zone; Amhara Region, Ethiopia

Background Road traffic accidents are a severe health concern in Ethiopia. This study aims to examine the primary contributing variables of road traffic accidents in Ethiopia, North Gondar Zone, under 24 administrative wereda’s. Methods This study utilized secondary data collected from both the werda-level and North Gondar central-level offices within the study areas. The sector police typically submit reports to the zonal-level offices annually. Information regarding crashes, fatalities, and injuries during the study period was extracted from these police reports. The research focused on analyzing the frequency and severity of traffic accidents attributed to various factors of drivers, vehicles, road conditions, pedestrians, and environmental influences. Results In a sample of 603 aggregate road traffic accidents, the data reveals that the majority of damage results are attributed to young drivers, accounting for 58% of the cases, with junior grade level drivers contributing 29.4%. Driving without a license was a significant factor, representing 87%, while accidents involving recruited driver stood at 63.2%. Vehicles with small to articulated trucks contributing to 39%. Mechanical failures were prevalent, with an unknown diagnosis rate of 48.3%. Vehicles in service for 2-5 years accounted for 29.4%. Road surface conditions were 46%, while rural roads saw a higher percentage at 51.2%. Weather conditions played a role also influential, as dry asphalt and gravel roads under main access ownership were linked to of accident, with 91.2% occurring during visible daylight hours between 8:00-12:00 and 15:00-17:00. The victims were predominantly farmers at 49.6%, followed by students at 23%. Conclusions To reduce road traffic accidents in the study area, it is essential to manage causative factors such as driver and road users, vehicles, roads, pedestrians, and environmental behaviors. The study suggests the development of a successful, up-to-date traffic accident database system regionally within respective offices.

Enhanced Imaging Analysis of Aggregates for Road and Railway Applications

The South African pavement community has shown a keen interest in the use of imaging techniques to characterize the morphological characteristics of aggregates used in road and railway construction. This interest arises from the need to overcome the limitations of the traditional methods currently employed to quantify the shapes of these materials. Recent advancements and the use of enhanced aggregate imaging techniques for quantifying the shapes of crushed stone and ferro slag materials from 10 sources across the country are presented in this paper. A wide range of railway track ballast and road aggregates were selected from various quarries and sources across different provinces for this study. As part of this research, an improved protocol was developed to standardize imaging acquisition and ensure the repeatability of shape property measurements, thereby providing meaningful results and facilitating data analysis. The imaging analysis conducted in this study, which involved close to 2000 aggregate particles, revealed valuable insights into the angularity, surface texture, and flat and elongated ratio properties of coarse aggregates. Preliminary specification limits for these shape properties have been established. This contribution represents an initial step toward supporting the South African road and railway industry in adopting advanced techniques for the selection of aggregate materials.

Sustainable utilization of incineration bottom ash in pavement construction: Environmental impacts and life cycle assessment

The global drive towards sustainable development has prompted a notable shift in civil engineering practices towards utilizing secondary materials, such as incineration bottom ash (IBA). The literature review underscores the relevance of waste incineration and the crucial need for effective IBA management strategies. Existing studies, however, reveal a dearth of studies within the life cycle assessment (LCA) framework focusing on understanding IBA characteristics and field conditions. The study addresses this gap by proposing an LCA to assess the environmental implications of substituting natural aggregates with IBA in pavement layers. A comparative LCA was carried out, where different scenarios of reuse of IBA (as produced, treated, or with restrictions) were assessed against a baseline scenario that represents the conventional use of aggregates in roads and landfilling of IBA. The ReCiPe technique, incorporating a hierarchist perspective, was employed to assess impacts across different problem-oriented categories. Additionally, this study also explores the impact of data variability on LCA outcomes, considering changes in landfill height, pavement infiltration rate, time duration, and IBA transportation distance. The analysis indicates that incorporating IBA in road layers can significantly reduce impacts on non-toxic categories like global warming by over 35 %. However, the leaching properties of untreated IBA contribute to a more than 28 % increase in human carcinogenic toxicity, rendering it environmentally unsuitable for road layer reuse. The comparative study illustrated that reusing treated IBA is the most sustainable approach, remaining effective up to a distance of d + 15 km. In cases where treatment is not feasible, utilizing IBA with restrictions is recommended up to a distance of d + 5 km (d represents the transportation distance for natural materials). This research fills a critical gap in the literature by providing a framework to assess IBA reuse in road construction, thereby advancing the discourse on sustainable materials management in the construction industry.

Feasibility Study of Brick Aggregate as a Partial Replacement of Natural Stones in Dry Lean Concrete Mix

This study aims to use two types of brick aggregates as partial replacements for natural stone and checks their feasibility as road aggregates in dry lean concrete (DLC) mixes. Laboratory studies were performed by partially replacing natural stones with both types of brick aggregates, and the optimum contents were evaluated. The paper describes a detailed analysis of DLC mixes with several percentages of bricks including a number of laboratory tests such as the moisture density, strength parameters, ultrasonic pulse velocity, and resistance to acid attack. For the replacement of stone with brick aggregate, the prime focus was paid to the usage of cement content and the aggregate to cement (A/C) ratio. An A/C ratio of 10:1 is found to be suitable for 100% replacement of natural stone aggregate (NSA) with first-class brick aggregate (FCBA), whereas an A/C ratio of 11:1 may be suitable for the use of 100% overburnt brick aggregate (OBBA). However, high contents of the A/C ratio can also be used if NSA is partially replaced by OBBA or FCBA. The strength parameters of DLC mixes such as flexural strength or split tensile strength showed a reduction of about 20%–22% when replaced by 50% OBBA and FCBA, while the compressive strength was within the limit (i.e., 7 MPa after 7 days of curing). Finally, the cost analysis showed that the production cost of DLC mixes can be reduced by about 15.6%–16.2% and 29%–32%, if the stone aggregates are partially (50% by volume) or fully replaced by FCBA and OBBA, respectively. Thus, the paper indicates that not only the scarcity of stone aggregates can be minimized but the cost can also be reduced by partially or fully replacing NSA with FCBA and OBBA.

Polymorphic transformations of dicalcium silicates in steel slags used in the production of road aggregates

Polymorphic transformations of dicalcium silicates in steel slags used in the production of road aggregates

Utilizing pond ash as fine aggregates in sustainable green concrete pavement – A case study

According to a recent estimate, more than 75 major accidents related to coal ash ponds have been reported between 2010 and 2020 which have resulted not only in loss of life and property, but also in extensive pollution of land, water, and air around the accident sites. In order to promote mass consumption in lieu of disposal, this study was aimed at utilizing the unused coal ash as fine aggregates in concrete pavements. In this regard, a pilot study was undertaken at NTPC Mouda wherein M25 grade pavement quality concrete (PQC) was used for casting a 500 m stretch of road inside the power plant premises. The mix design was prepared at VNIT Nagpur utilizing coarse and fine pond ash from NTPC Mouda as fine aggregates. OPC 43 grade of cement along with locally procured crushed stone aggregates were used. A compatible hyper-plasticizer was also used to maintain the workability and rheology of the concrete. The concrete was laid manually and was observed to attain its final setting within 600 min. The segment was cured for 28-days and finally, cores were extracted to evaluate the in-situ compressive strength of PQC and ascertain its durability. A 28-day compressive strength of 29.3 MPa along with reduced chloride ion permeability and abrasion loss indicate that the suggested approach of utilizing pond ash as fine aggregates in concrete roads is a sustainable alternative to conventionally used mix designs. Hence, the said approach will be a “greener” approach towards PQC construction reducing the dependency on natural river sand. Owing to the abundance of coal ash available in ash dykes, it is also expected that the suggested approach will prove cost-effective in terms of unit cost of concrete production.

Investigation of Shear Strength of Subbase-Subgrade Interface with Geosynthetics Reinforcement Utilizing A Large-Scale Direct Shear Test

Geosynthetics are being used to strengthen road pavement. Geosynthetic inclusions improve pavement carrying capacity, maintenance costs, highway service life, reflective cracks, and undesirable large lateral and vertical deformations. The primary purpose of this research is to determine the effectiveness of geosynthetics (geogrids and geotextiles) in stabilizing the subgrade and reinforcing the base course layers in unpaved test sections. Determine the mechanical interaction of subgrade soils (clay and sand) and aggregate road base layers (subbase) with and without reinforcement. Compute the shear strength parameters (cohesion, friction angle, and interface coefficient factor). Therefore, Large-scale direct shear experiments in the laboratory were performed on subbase-subgrade materials with and without geosynthetics, under the applying normal of stresses (25, 50, 75, and 100) kPa, indicating the quantity overburden the pressure in paving. The present research uses a large-scale direct shear apparatus with an up square box (200 mm×200 mm×100 mm) and a bottom rectangular box (200 mm×250 mm×100 mm). A direct shear test was implemented by manufacturing this equipment. The results obtained from experiments showed that biaxial geogrid G1 has the best behavior for both (subbase-clay) and (subbase-sand) and has an interface shear coefficient factor more significant than unity and equal to 1.05 and 1.02, respectively.

Review of Visualization Technique and Its Application of Road Aggregates Based on Morphological Features

The sustainable performance of asphalt pavement depends on the quality and mix design of road aggregates. Identifying aggregate morphology and size is a prerequisite step for material design and numerical modeling of asphalt mixtures. The paper aims to review the morphometric measurement, characteristic parameters and visualization technique of road aggregates. Types, calculation methods and advantages of aggregate morphological characteristics are highlighted. The applications of aggregate morphological features on the volumetric design, compaction processes, mechanical properties and size effect of asphalt mixtures are summarized. Although digital image processing technology has been studied for years, aggregates in the complex accumulation are still difficult to measure accurately. In the current research, the morphological parameters of aggregates remain diverse without a standard protocol. Compared to theoretical models, numerical models have more difficulties establishing irregular morphology features in the simulated specimens but provide a volume parameter closer to the real value. The future investigation of road performance under dynamic loading should account for the microscopic evolution of shape, orientation and distribution of aggregates over time.

Study on the Performance of Steel Slag and Its Asphalt Mixture with Oxalic Acid and Water Erosion.

The reuse of steel slag, a large-scale solid waste from steel production, has good social and environmental benefits. The application of a steel slag asphalt mixture is mainly hindered by its volume expansion in water. The expansion of steel slag can be inhibited by oxalic acid. The expansion rate and adhesion of steel slag were investigated, and the immersion stability of steel slag and its asphalt mixture was evaluated by water erosion. By means of XRD, XRF, TG, SEM, etc., the influence mechanism of oxalic acid and water erosion on the properties of steel slag and its asphalt mixture was discussed. The results show that oxalic acid can not only inhibit the expansion of steel slag but also improve its crush resistance, with a reduction in the expansion rate of steel slag by 53%. Oxalic acid is able to leach alkaline metal elements, reducing its adhesion with asphalt. After 10 days of water erosion, the rutting stability and bending crack resistance of the treated steel slag mixture decreased by 37% and 43.2%, respectively. Calcium oxalate is generated on the surface of treated steel slag, which improves the surface compactness, effectively inhibits the expansion of steel slag caused by water erosion, and improves the performance of steel slag and its asphalt mixture. Water erosion can accelerate the hydration and shedding of calcium-containing substances on the surface of steel slag, reduce the adhesion of steel slag, and lead to degradation in the performance of steel slag and its asphalt mixture. Oxalic acid is able to effectively inhibit the expansion of steel slag, and the treated steel slag can be used as recycled aggregate in asphalt mixture, effectively solving the problems of road aggregate deficiency and environmental pollution caused by steel slag.

On the use of weathered rocks in road pavements: An experimental study on Tazekka schists

In Morocco, the management of materials in the road sector is framed by a panoply of technical and normative standards including the Moroccan guide of road earthworks dating from 2002. This document was inspired by its French counterpart and dictates the rules for soil reuse in embankments constituting an important part of the pavement structures. In fact, this document made the use of friable rocks (R category) complicated and leaves to the geotechnical engineer the definition of the necessary precautions. This ambiguity often discourages the administrative services from considering these materials as a reusable deposit and consequently they resort to more stable soils or rocks. This work illustrates the results of an experimental campaign carried out at the level of the Taza Province on several schistose massifs. The conclusions indicate the possibility of reusing these materials by adapting them through secondary treatment. In addition, the laboratory tests carried out on 250 samples from 35 different sites indicate the possibility of using these schists as road aggregates for low traffic roads constituting 70% of the provincial network of Taza. In addition, the treatment of this rock via hydraulic binders constitutes a promising and viable solution allowing its reuse in backfill and roadway subgrades. Indeed, the findings have shown that reduced proportions can significantly improve the behavior of schists and reduce their sensitivity to erosive factors.

Utilizing lowly-reactive coal gasification fly ash (CGFA) to stabilize aggregate bases

This study explored the feasibility of utilizing lowly-reactive coal gasification fly ash (CGFA) for stabilizing road aggregate bases. Three types of aggregate stabilizers including the ordinary Portland cement (OPC)-CGFA, hydrated lime (CH)-CGFA and alkali-activated CH-CGFA were evaluated based on the performances of compacted base specimens. It was found that the OPC-CGFA stabilized bases showed better mechanical and durability properties while the CH-CGFA samples had low water stability and freeze-thaw durability due to the dissolution of unreacted CH. However, the reaction degree of CGFA associated with the performances of CH-CGFA stabilization could be considerably enhanced by the alkali-activation. The sustainability and economic feasibility analyses showed the use of CGFA could significantly reduce the CO2 emissions and costs, highlighting the synergy between the recycling of CGFA and the construction of sustainable road bases. A framework of selecting CGFA-based stabilizers for road bases was proposed considering the performance ratings of the material properties.

Experimental Study on Characterization of Bituminous Mixes Containing Recycled Asphalt Pavement Materials for the Construction of Surface Course in Flexible Pavements.

Abstract: In India majority of the road network has a bituminous top surface made of naturally accessible road materials and bitumen. This process has resulted in a faster depletion of road aggregates as well as an increase in gas emissions into the atmosphere, resulting in pollution. The most promising approach for achieving sustainability in road building will be to use low emission bitumen, re-use aggregates obtained from milling, and material reclaimed from the old distressed pavement to create or rehabilitate new roads. In this regard, the current study seeks to evaluate and compare the physical and engineering features of bituminous mixes including RAP material in various percentages for the construction of the surface course in flexible pavements through thorough laboratory investigations. According to the results of laboratory experimental tests, a bituminous mix containing recycled asphaltic pavement (RAP) material exhibits better Marshall Properties, performance properties, and volumetric properties, and meets all of the requirements of the bituminous concrete (BC) layer as per standard specifications. According to the findings of the study, it is possible to create an acceptable grade bituminous mix with a high RAP component that meets the needed volumetric characteristics and performance parameters for the construction of flexible pavements under current traffic and environmental circumstances. Keywords: RAP, Sustainable roads, Volumetric properties, Marshall Properties, ITS.

Assessment of Geotechnical Properties of Laki Limestone for Coarse Aggregate, Nooriabad, Jamshoro Sindh, Pakistan

Present study is aimed at assessment of geotechnical properties of Laki limestone as coarse aggregate which is being quarried in Nooriabad area, Sindh, Pakistan. Coarse aggregate samples (n=20) of limestone were collected for the evaluation of physico-mechanical properties of the aggregate. Petrographic analysis revealed that the aggregate comprises of hard, compact, massive, crystalline and fossiliferous limestone. It is devoid of any reactive silica (chert, chalcedony) and other harmful constituents like clays or organic matter. Average values of specific gravity, absorption,bulk density, void content and combined index (EI + FI) of collected samples are 2.5, 2.1%, 1.54 g/cc, 38.55% and 13.04% respectively. The values of specific gravity (2.3-2.9), absorption (0-8%), bulk density (1.28 g/cc-1.92 g/cc) and void content (30%-45%) are varying within the range of normal weight aggregate as per American concrete institute (ACI)specifications. On the other hand, absorption values of aggregate samples are slightly higher (2.1%) than the reference range (2%) but meet other requirements. Mechanical properties including aggregate impact value (8.58%), aggregate crushing value (26.66%), Loss Angeles abrasion value (24.77%), sodium sulfate soundness (4.72%), water soluble sulfate (0.006%) and water soluble chloride (0.005%) are found to be within corresponding guidelines set by ASTM. On the other hand, average carbonate content is found to be 89.64% indicating that Laki limestone is of slightly low purity. Except absorption, all physical and mechanical properties lie within specified ranges. It is concluded that Laki limestone is suitable for use as road aggregate and concrete mix design.

Stabilization of the Gravels Material for Road Sub-Base: Flexible Pavement

Abstract: In many parts of India, high-quality aggregates that match the standards are becoming increasingly scarce and expensive. High-quality aggregates are required in both the base and sub-base course according to traditional flexible pavement requirements. In many circumstances, locally available aggregates do not fit the standards, and the aggregates that do must be transported over vast distances. This act greatly raises the cost of their construction, as well as their ongoing maintenance and restoration. Thus, in a big country like India, using locally available marginal materials in flexible pavement building is one of the viable solutions to high pavement construction costs and a lack of quality aggregates sources. A broad definition of a marginal aggregate is "any aggregate that does not fully conform to the specifications used in a country for normal road aggregates but can be successfully used in special conditions, made possible by climatic characteristics or recent advances in road techniques, or after being subjected to special treatment." So, if the usage of local resources can be permitted through appropriate material or structural design modifications, construction can be hastened and significant monetary savings can be realised. The study's major goal is to add cement and bitumen emulsion to locally accessible gravel soil/marginal aggregate (Moorum) to improve its qualities. An attempt has been made to use cement for increasing the strength of the gravel and emulsion for increasing the water resisting capacity. The whole work involves increasing strength of gravel soil (Moorum) and expressed in terms of CBR and UCS value.

The effect of metamorphism on the aggregate properties of gabbroic rocks

Granitic rocks are durable materials sought after for the production of road and railroad aggregates. Granitic bedrock commonly, however, includes gabbroic components, which may enhance or decrease the aggregate performance. This study evaluates the variation in resistance to fragmentation (Los Angeles value, LA) and wear/abrasion (micro-Deval value, MDE) for the fraction 10/14 mm of gabbro in different metamorphic states. Samples were collected along a 150-km profile where metamorphic conditions grade from epidote–amphibolite to high-pressure granulite-facies, and the degree of metamorphic recrystallization varies with the amount of hydrous fluid. Rocks with no or incipient metamorphic recrystallization preserving their primary igneous fabric and interlocking texture meet the criteria for both asphalt base course and track ballast in railroad, with LA and MDE values below 25% and 14%, respectively. Mafic granulite and fine-grained amphibolite have LA values below 25% and can be used in unbound layers. Mafic granulites crystallize at high temperatures but commonly preserve a relict igneous texture due to limited hydration. Coarse-grained amphibolite and migmatitic amphibolite have the poorest performance. They recrystallized at hydrous conditions, leading to complete recrystallization, grain coarsening, and loss of interlocking igneous texture. This study shows that both temperature and infiltration of hydrous fluids significantly affect the technical properties. Even at high metamorphic temperatures, gabbroic rocks may yield aggregates of high technical performance. At hydrous conditions, however, recrystallization results in rock aggregates suitable for unbound layers only. The variation in metamorphic grade and hydration is easily assessed by the geologist in the field and by using standard petrographic microscopy.

Prediction of Aggregate Impact Values and Aggregate Crushing Values Using Light Compaction Test

Abstract Crushing test and Impact test are very important to estimate strength and toughness characteristics of the road aggregate. Extensive experimental procedures and different sets of equipment are required for these types of aggregate testing. Therefore, the objective of the study is to investigate whether the light compaction test can be a suitable alternative for both these tests. For this experimental procedure, 60 aggregate samples were collected from different rock quarries spread along North-eastern states of India. The specifications of the aggregate samples are kept similar for all of these three test procedures. The result indicates a strong correlation of Light compaction values (LCV) with Aggregate crushing values (ACV) and Aggregate Impact Values (AIV). The R2 values for the relationship was found to be more than 0.9 for both these relationships. It indicates that the LCV can be used to closely predict the ACV and AIV. The root mean square error (RMSE) values estimated based on the actual and predicted values were also found to be low which further concrete the claim that light compaction test can be a suitable alternative for crushing test and impact test of the aggregates.

Self-healing of asphalt mixture: the impact of the minerals forming the aggregates in the efficiency of the heating by microwaves.

The current concern for the environment and the need to reduce greenhouse gas emissions have led to new technologies related to microwave energy. One of these technologies is the self-healing of asphalt mixtures, which consists of repairing pavements through microwave application on the surface, avoiding premature road failure. Asphalt mixtures for roads are made up of more than 90% by weight of aggregates of different compositions and origins, in addition to a bituminous binder and sometimes additives. From other studies, it is known that the physical behaviour of aggregates is a function of their composition, that is, of their minerals and their proportions. Microwave heating of aggregates has proven to be an effective technique, but there are gaps in understanding how microwaves interact with aggregates and the reasons for their differential heating.This research has studied 18 minerals that are commonly part of the rocks used as road aggregates. The objective is to identify the minerals that present the best heating rates to relate them to the differential heating of aggregates for roads. The results obtained are promising, facilitating the understanding of microwave heating of minerals. Regarding chemical composition, elements such as MgO, MnO, TiO, Al2O3, Fe2O3, and CaO (in silicate minerals) favour the heating of minerals and other elements such as SiO2 and K2O Na2O, and CaO (in carbonate minerals) retard the heating. Regarding the physical properties, density and habit of the minerals do not influence the heating, but other properties, such as the diaphaneity and the size of the crystals, influence the heating with microwaves.

Geotechnical evaluation of the quality and durability of argillites from Abakaliki Metropolis (Southeastern Nigeria) as road aggregates

Geotechnical evaluation of the quality and durability of argillites from Abakaliki Metropolis (Southeastern Nigeria) as road aggregates

Physico-mechanical characterization of schists in Tazzeka complex [Taza Province, Eastern Morocco

This paper presents the first results of a physicomechanical reconnaissance campaign on the schist of the Tazekka primary massif in northeast Morocco. The main objective of this work is to assimilate the mechanical behavior of those schists, propose characteristic correlations via more accessible tests and assess the technical and economic opportunities for the exploitation of this deposit. For this purpose, a total of 29 sites were selected according to a multi-criteria study. Thus, 203 sampled specimens were subjected to several characterization trials, namely the Los Angeles test, Micro Deval test, Uniaxial compression test, Fragmentability test, Degradability test and Ultrasonic wave velocity test. On the first hand, the results highlight the potential of these rocks as road aggregates according to European standards specifically for low traffic roads constituting 70% of the local network. On the second hand, The large amount of collected data allowed the proposal of representative correlations between the different mechanical tests relating to the compression and shearing ultrasonic waves velocities. Finally, this experimental study constitutes a first orientation work in favor of state services to update their technical approaches, which generally prohibit the reuse of the evolving rocks.

Experimental Analysis of Polymer Coated Aggregate in Comparison To Ordinary Road Material

Worldwide the broad usage of plastic has resulted in the massive production of plastic pollution, which is incinerated, put in landfills and oceans. The technique of coating road aggregate with plastic has a good potential to deal with this global issue. The unique physical, mechanical and thermal properties polymer offers effective binding, less moisture retention, less susceptibility to void formation. This research will ultimately reflect plastic waste management and road enhancement. The main purpose of this experimental study is to predict and highlight the effect of varying plastic composition coating on aggregate and select the best performing sample. For this study, samples of polymer-coated aggregates of different ratios are created, further tested for their enhancement in properties. To create polymer-coated aggregate, we have used recycled aggregates, Grade 70 bitumen, and polyethylene bags from waste. To coat the aggregates used dry-mix process.The effectiveness of the coating with varying plastic compositions was measured using seven different tests. It was hypothesized that incorporating plastic would enhance the properties of aggregate and increase the durability and workability of road materials. The tests results supported the hypothesis. Standard ranges were used to perform a comparative study between polymer-coated aggregate and conventional aggregate. Nearly all test's plastic composition >8% and less than 15% have shown good results, but the optimum value for all tests is achieved by sample with 12% plastic coating. Although this study supports that plastic incorporation is a better idea to enhance the longevity of roads, more research is required to explore the underlying mechanism of plastic coating and its long-term outcomes.