Los Angeles Abrasion Test Research Articles

Experimental Investigation to Find the Strength of Ballast

Although ballast is only part of the substructure, it plays an important role in keeping the railway track in position. But less attention has been given to the substructure because the properties of the substructure are more varies and difficult to define than those of the superstructure. Research about ballast behaviours still needs to be developed. Objective of this research is to use Los Angeles Abrasion (LAA) and Aggregate Impact Value (AIV) test to analyse the strength of nature rock (NR), slag (S) and their different combination. Four different types of samples have been prepared for testing. LAA and AIVtest has been performed to assess the strength of the ballast. Finally, the result shows that the combination of slag and nature rock showed good results, even not really significantly. The result for 25%NR+75%S (LAA test) and 1NR+2S (AIV test) is 7,41% and 6,02%, respectively.

Comparative Evaluation of Railway Ballast Degradation

Ballast bed is one of the most important components of ballasted railway track system. Over a period of service, it undergoes axial deformation due to the accumulation of train cyclic loading. However, there has not been a universally accepted method of evaluating ballast degradation, hence, this study focused on comparing two most common methods namely; Marsal breakage ratio and fouling index (FI). The degraded ballast material was prepared using Los Angeles abrasion (LAA) method at an interval of 250 turns of the LAA test drum, from the fresh ballast to degraded ballast at 2000 turns of the LAA test drum. Series of sieve analysis were conducted and the changes in ballast gradations were evaluated. A strong correlation was observed between the results obtained using the two approaches with a coefficient of determination of 99.24%. Based on the results obtained from the ballast degradation analysis both Marsal’s breakage ratio and the fouling index can be used for the evaluation of ballast degradation. However, Marsal’s breakage index is recommended due to its ability to give the breakdown of the particle size variations. Keywords: Ballast degradation; fouling; Los Angeles Abrasion; gradations; breakage ratio

Influence of the Performance of Reclaimed Asphalt Pavement (RAP) Material on Bituminous Mix

The utilization of reclaimed asphalt pavement (RAP) material to prepare a durable bituminous concrete (BC) mixture, used for flexible pavement surface courses is a challenging task in this investigation. RAP material is one of the latest substitutes for virgin aggregate and virgin binder of the bituminous mix. Using RAP material in flexible pavements can improve the engineering properties of bituminous mix and is also beneficial for economic and environmental. To execute such study, virgin aggregate (VA) has been replaced by 0, 10, 20, 30, 40, 50, 60, 75, and 100% of RAP material, respectively, in the cited mix with 2% Ordinary Portland Cement (OPC) as mineral filler. To characterize the RAP material, several laboratory tests such as specific gravity test, water absorption test, shape test, impact test, Los-Angeles abrasion test and, advanced tests as X-RF, X-RD, and GPC test, etc. have been employed. However, to assess the durability and strength of RAP enriched BC mix, Marshall stability test, modified Marshall immersion test, indirect tensile strength (ITS) test and, Cantabro abrasion test has been conducted. Marshall stability test, modified Marshall immersion test, ITS test, and Cantabro abrasion test is explored that 50% RAP modified bituminous mix has the capability to best perform than the other studied mix in terms of durability and strength. Because the molecular bonding of carbonyl compound between aged and virgin binder is suspected in the mix improvement factor that leads to the longer span life of the RAP modified flexible pavement.

Analysis of influence of ballast shape on abrasion resistance using discrete element method

The ballast resistance performance—an important indicator of the performance and maintenance of railway ballast—is strongly dependent on the ballast shape, but this relationship is not yet fully understood. Despite many attempts to model the constitutive behavior of the ballast under cyclic loading using the discrete element method (DEM), few studies have obtained any conclusive results on the ballast breakage behavior. Therefore, in this study, a series of innovative techniques have been adopted to develop a crushable-ballast DEM model, and this model is further calibrated using the results of the Los Angeles abrasion (LAA) test. The results indicate both needle-shaped and flake-shaped ballast samples tend to break more easily than the normal-shaped samples. Thus, only the normal-shaped ballast samples are recommended for LAA test. Furthermore, by considering the ballast dynamic stability, a strict restriction on the proportion of needle-shaped ballast (≤10%) was recommended as the relevant technical standard.

Predicting Aggregate Degradation in Forest Roads in Northwest Oregon

In the Pacific Northwest, forest roads have the potential to cause significant environmental degradation, especially to water resources due to increased sediment production. The goal of this research is to improve the understanding of road degradation during hauling by improving our understanding of the aggregate degradation process. We correlate the wear rates to standard material property tests that may allow for improved prediction of the impacts from forest roads based on the selection of aggregate surfacing. Finally, we determine the changes in stress distribution between the subgrade and aggregate interface. High-, medium-, and low-quality aggregates were used from three quarries in western Oregon for this project. These aggregates are indicative of the range of materials used on forest roads in the region. Two material property tests, namely the Los Angeles (LA) abrasion and micro-Deval tests, were used to determine their ability to predict aggregate performance during hauling by relating values for aggregate wear to these aggregate properties. Eighteen nonwoven geotextile bags were created, measuring 60 cm (two-feet long) and 20 cm (eight inches) in diameter, with a pore size equivalent to a 0.149 mm (# 100) sieve. They were filled with a known quantity and particle size distribution of aggregate and embedded into a newly constructed forest road. Stress gages were installed in the road surface between the aggregate and subgrade levels to record the changes in stress at the subgrade level. Samples were subjected to three levels of traffic (500, 950, and 1500 passes) using a loaded dump-truck that had a steering axle and one tandem drive axle, weighing 25,038 kg or 55,200 lb. The results showed that less breakage occurred with the medium- and high-quality aggregates than the low-quality aggregate. There was a correlation between the material property test (either the micro-Deval or the LA abrasion test) and the fine index, indicating the predictability of these tests in terms of aggregate performance. Finally, the higher quality aggregate was able to better distribute the stresses from the wheel better than the lower quality aggregate and was able to reduce the stress reaching the subgrade. Although the results are limited to the three types of rock used in this study, they indicate the ability of the high-quality aggregate to lessen the environmental impacts from forest roads.

Degradation-induced evolution of particle roundness and its effect on the shear behaviour of railway ballast

Abstract Ballast degradation has a strong effect on railway track performance (including accumulative deformation, ballast resistance, and drainage). The main objective of this research is to determine the evolution of roundness during ballast degradation and investigate the mechanical properties of real ballast shape at different abrasion stages. To this end, the Los Angeles (LA) abrasion test is conducted on three groups of fresh ballast materials with different sizes (i.e., 25–30 mm, 40–50 mm, and 50–60 mm). Then, a homemade image-acquisition platform is used to extract ballast outlines from multiple projection directions. Next, the corner sharpness of the degraded ballast is quantified by particle roundness. The LA abrasion test shows that particle roundness gradually increases with increasing abrasion. Subsequently, biaxial shear tests are performed on ballasts with different roundness characteristics based on the discrete element method (DEM). The shear behaviours of degraded ballasts with different degrees of roundness are investigated through macroscopic (e.g., the shear strength and dilatancy response) to microscopic (e.g., the mean coordination number, the ratio of sliding contacts, and the mean particle contact moment) analyses. The results show that the shear strength slightly increases in the peak state, while a substantial reduction in shear strength is observed in the residual state with increasing roundness. Moreover, the microscopic analysis shows that greater roundness results in a smaller mean coordination number, as well as decreases in the ratio of sliding contacts and the mean particle contact moment.

An experimental investigation on the durability of railway ballast material by magnesium sulfate soundness

In this study, the durability of railway ballast material is investigated by magnesium sulfate soundness tests. Two types of ballast aggregates, which are produced from basaltic rocks and currently used as railway ballast in such high speed railway routes in Turkey, are investigated regarding their resistance against freezing–thawing (FT) and traffic loads. Firstly, the mineralogical and physico-mechanical properties of rocks are determined. Then the degradation of investigated ballast aggregates is determined by magnesium sulfate soundness and Los Angeles abrasion (LAA) tests. The natural FT effects are simulated by magnesium sulfate soundness tests up to 40 cycles, whereas the traffic loads are represented by LAA tests up to 3000 revolutions. The ballast fouling that leads to such problems are also investigated within the scope in the present study. The degree of ballast fouling is quantified as fouling index (FI) which is determined using the crushed particles generated after LAA tests. It is concluded from laboratory studies that rock properties considered are considerably influenced by simulated FT cycles. It is also achieved from the laboratory studies that magnesium sulfate soundness and Los Angeles abrasion tests are good indicators to clarify the fragmentation mechanism of the ballast aggregate in laboratory scale. In conclusion several empirical formulas are developed to predict LAA and FI for each rock type. The proposed empirical formulas could be utilized as a pre-design tool for new railway routes in design stage provided that the investigated ballast aggregates are considered.

Ballast degradation: Effect of particle size and shape using Los Angeles Abrasion test and image analysis

Ballast track is the most widely used track for the railway transport, and ballast bed plays a significant role to provide resistances during train operation. Generally, the ballast bed consists of crushed stones. To achieve the mitigation of ballast degradation, the first priority is to describe the degradation development and to study its effect factors.The influence of ballast morphology (particle size and shape) on ballast degradation is examined here using the Los Angeles Abrasion (LAA) test in combination with 3-D image analysis. LAA tests are used to obtain the deteriorated ballast. Then, based on the 3-D images, the changes of ballast particles after the tests were analysed. To quantify the ballast degradation (abrasion and breakage), the Abrasion Depth based on the analysis of 3-D images were proposed, while ballast breakage was estimated using the broken particles ratio.The results have shown that ballast degradation is directly related to the ballast morphology. The proposed image-based procedure can effectively be applied to assess ballast degradation. The results can be used for ballast material standardization, modelling of ballast degradation process and maintenance cycle prediction.

Gyratory abrasion with 2D image analysis test method for evaluation of mechanical degradation and changes in morphology and shear strength of compacted granular materials

Mechanical degradation of granular materials can significantly influence the performance and durability of pavement systems. The commonly used Los Angeles (LA) abrasion test does not test the entire gradation of the material, nor simulate the compaction and field loading conditions. A new Gyratory Abrasion and Image Analysis (GAIA) test method was developed in this study and compared with the LA abrasion test for five granular material types. Results show that the GAIA test can address shortcomings of the conventional test, provide insight into mechanical behavior of granular materials during compaction, and enable performance-based specifications for field compaction of granular materials.

Morphological Characterization of Railroad Ballast Degradation Trends in the Field and Laboratory

Field and laboratory degradation trends of railroad ballast are investigated in this paper by using an aggregate image analysis approach. In addition to gradation changes, in-service ballast materials undergo degradation of particle shape properties (i.e., angularity, flatness and elongation, and surface texture), which can be quantified through imaging techniques. In the field, five ballast types were installed in eight steel boxes at a test section in the western heavy axle load revenue service test megasite near Ogallala, Nebraska. In-service performance evaluations consisted of sampling, sieving, and imaging-based shape property analyses of the field-collected ballast materials to monitor degradation twice a year. In the laboratory, following the Los Angeles (LA) abrasion test procedure, a sample of granite ballast was tested at increasing numbers of LA abrasion drum turns to assess changes in gradations and study degradation levels. All of the LA abrasion–tested granite samples and approximately 3,000 particles from the different sizes of the field-monitored ballast materials were collected and scanned with the Enhanced University of Illinois Aggregate Image Analyzer. Imaging-based particle shape indexes were determined at different degradation levels from both the LA abrasion and the field projects. The magnitudes and rates of measured degradation and breakage, as well as the captured changes in morphological properties of particles, were quite different between the LA abrasion test and the field degradation from repeated traffic loading. A comprehensive study with improved ballast sampling and testing techniques is recommended to further investigate mechanisms of ballast degradation.

Principal Component Analysis for Physical Properties of Electric Arc Furnace Oxidizing Slag

In this study, the principal component analysis (PCA) was used to analyze and classify the electric arc furnace oxidizing slag based on physical properties. The results indicated that about 91.44 % information could be explained using the previous four PC. The Los Angeles abrasion test (LAAT) and loss of sodium sulfate soundness test (LSSST) mainly contributed to the first PC, meanwhile the saturated surface-dry specific gravity (SSDSG) contributed mainly to the second PC. The significant physical properties of EAF slag including LAAT, LSSST, and SSDSG could be identified according to PCA. According to the two dimension classification using PC1 and PC2, the 60 samples could be approximately classified into two groups. They could be also classified into two groups in three dimension classification.

Comparative Evaluation of Micro-Deval Abrasion Test with Other Toughness/Abrasion Resistance and Soundness Tests

This study presents the findings from a research investigation conducted to characterize the toughness/abrasion resistance and soundness of aggregates from 23 sources using the micro-Deval, Los Angeles (LA) abrasion, sodium sulfate soundness, and magnesium sulfate soundness tests. Correlations between the results of micro-Deval test and other tests were explored, and the NCHRP 4-19 study recommendation of maximum loss of 18% in micro-Deval test to characterize good versus poor aggregates was evaluated against the field performance of the aggregate. Also, the effect of aggregate gradation on the loss observed in micro-Deval and LA abrasion tests was studied. Based on the results from this study, the recommendations from the NCHRP 04-19 study appear to be valid for the aggregates evaluated. Also, a high degree of correlation was observed between the size of the aggregate evaluated and the micro-Deval loss, with smaller sized aggregates yielding larger loss. Good correlation was observed between results of sodium sulfate and magnesium sulfate soundness tests, however, no significant correlation was observed between the losses observed in micro-Deval test and either of the two sulfate soundness tests or the LA abrasion test.