Flakiness Index Research Articles

Evaluation of Physical Properties of Aggregates: A Case Study on Aggregate Sources around Kathmandu Valley

Aggregates play a crucial role in construction works, and this research aims to characterize aggregates from different sources in the Kathmandu Valley, considering factors such as particle size, shape, water absorption, and toughness, resistance to abrasion, crushing value, and impact value. The study investigated identifying and testing aggregates from the sources around and within Kathmandu Valley. A preliminary survey identified nine quarries around Kathmandu Valley based on accessibility to the valley and the highest producers (regarding materials volume). Coarse aggregate samples were collected from Dukuchap (Lalitpur), kaldhunga (Kavre), Bogati Panauti (Kavre), Aagra Khola (Makwanpur) and Melamchi (Sindhupal Chowk. Fine aggregates were collected from Melamchi (Sindhupal Chowk), Belkhu (Dhading), and Sankhu (Kathmandu). Evaluation of physical properties of aggregates included fineness modulus test, water absorption test, crushing value test, Impact value test, silt content test, Flakiness and Elongation test, and abrasion resistance test. Upon meticulous evaluation of the collected samples, it was observed that Fineness Modulus, specific gravity, water absorption, materials finer than 75μm and silt content of the sources were found in between the respective range of (1.97 to3.49), (2.53 to2.62), (1.05 to1.96) % and (1.74 to 5)% and (1.21 to 11.04) respectively. Similarly, specific gravity, water absorption, flakiness index, abrasion value, impact value, and crushing value of coarse aggregates were found in the range of (2.65-2.72), (0.36-1.07)%,(15.03-18.41)%,(15.94-41.52)%,(15.23-34.31)% and(13.55-28.68)% respectively.

Characterization of heat-processed artificial lightweight aggregates from polyethylene terephthalate plastic waste

Plastic waste is an undeniable source of pollution that threatens the existence of the earth’s flora and fauna. The bulk of plastic waste generated globally does not go through the proper methods of disposal but is carelessly discarded into the aquatic or terrestrial environment. Current recycling efforts are largely inadequate and disposal in landfills is still fraught with environmental and land use challenges. The proper disposal of plastic waste, as well as mitigating the environmental, social, and health impacts of extracting natural aggregates can be achieved by incorporating plastic waste as aggregates in the construction industry. This paper presents a characterization of aggregates manufactured from polyethylene terephthalate plastic waste using thermal/mechanical methods. From the cost analysis, 24,341.67 Ugx (6.09 USD) was spent to produce 1 kg of PET aggregates. Morphological, intrinsic and mechanical characteristics of the produced aggregates were established using standard procedures and equipment. The results of morphological characterization indicate an irregular shaped aggregate with smooth surface, a dense graded aggregate with a fineness modulus of 4.25, flakiness index of 26%, elongation index of 16% and particle index of 13. Intrinsic characterization yielded particle density of 1330 kg/m3, bulk density of coarse aggregates of 715 kg/m3 and water absorption of 0.445%. Mechanical characteristics of aggregates were evaluated, with compressive strength of 50Mpa, Aggregate Crushing Value of 37%, Ten Percent Fines Value of 71KN, Aggregate Impact Value of 24% and Aggregate Abrasion Value of 20%. The characteristics of PET aggregates confirm their suitability for application in structural lightweight concrete and rigid pavement. The produced PET aggregates can be considered in mix design as a total or partial replacement of natural aggregates in concrete.

Recycled concrete aggregate and cinder gravel as base course construction materials

In this research, the potential use of recycled concrete aggregate (RCA) and CG as a base course construction material was investigated. A laboratory test involving the mechanical stabilization of RCA and CG was conducted to examine their physical properties. Eight samples of RCA blended with CG in varying proportions from 0% to 100 % with 10 % variation were studied. The laboratory test results indicate that 100 % CG yields specific gravity (SG), aggregate crushing value (ACV), aggregate impact value (AIV), Los Angeles abrasion (LAA), flakiness index (FI), elongation index (EI), plasticity index (PI), water absorption, soundness, and California bearing ratio (CBR) values of 2,54 %, 38,37 %, 20,10 %, 33,17 %, 5,59 %, 12,09 %, 0,90 %, 3,52 %, 10,60 %, and 38,08 %, respectively. The results for 100% RCA show SG, ACV, AIV, LAA, FI, EI, PI, water absorption, soundness, and CBR values of 2,70 %, 9,56 %, 5,30 %, 9,20 %, 15,30 %, 15,84 %, NP, 0,23 %, 1,49 %, and 105,87 %, respectively. These results also fail to meet the gradation requirements based on ERA standard specifications. Therefore, mechanical stabilization was adopted to improve the physical properties of the samples. Blending 60 % RCA with 40 % CG resulted in SG, ACV, AIV, LAA, FI, EI, PI, water absorption, soundness, and CBR values of 2,65 %, 19,46 %, 10,70 %, 10,88 %, 16,15 %, 22,01 %, NP, 0,26 %, 2,09 %, and 101,98 %, respectively. At this proportion, the gradation aligns with the required ERA standard specifications for GB2 and GB3 materials. Therefore, CG up to 40 % by weight with 60 % RCA is viable for road base course construction, especially when readily available or nearby.

Investigation of the Possible Correlations between Specific Characteristics of Crushed Stone Aggregates

This study rigorously investigates the interdependencies among a suite of crushed stone aggregate characteristics to enhance material selection for infrastructure projects. Utilizing data from Colas Északkő Ltd. (andesite quarries), the authors explore the relationships between mechanical and geometrical properties, particularly focusing on the interplay between the flakiness index, shape index, Los Angeles abrasion, Micro-Deval wear, and methylene blue assessments. The presented analysis reveals an unexpectedly robust correlation between FI and SI, proposing a novel paradigm for evaluating grain shape. Notably, the relationship between Los Angeles abrasion and micro-Deval wear values, typically considered disparate, is re-examined, unveiling potential predictive capabilities for environmental wear, especially as indicated by magnesium sulfate soundness testing. Additionally, the current study delineates a significant correlation between methylene blue values and micro-Deval wear performance, highlighting the intrinsic mineralogical influences on aggregate durability. The implications of findings are twofold: they suggest a streamlined approach for aggregate quality assurance and offer strategic insights into the refinement of material selection processes, thereby promising to enhance the durability and service life of transportation infrastructure.

Characterization and Environmental Evaluation of Recycled Aggregates from Construction and Demolition Waste in Belgrade City Area (Serbia).

Sustainable consumption of construction materials is an important segment of sustainable development goals towards reducing climate change. Since the consumption of natural aggregates raises environmental concerns, there is an increasing demand for use of recycled aggregates (RAs), as it enhances social and environmental benefits and creates a market opportunity. This paper presents the practice of using recycled construction and demolition waste (CDW) in the Belgrade city area (Serbia) as a resource. Two groups of CDW from Vinča landfill site near Belgrade are analyzed: raw material before, and RAs after, construction of a recycling facility on site. Comprehensive characterization is performed (including particle size distribution, density, water and organic pollutants content, various mechanical resistances, flakiness index, etc.) and compilation of samples analyzed and compared to show a holistic overview. The test outputs in both groups show acceptable values and meet required standards, indicating that recycled CDW generated in the Belgrade area can be used as a substitute to natural aggregates. In addition to that, the environmental and economic benefits from this use as a substitute are analyzed and discussed, proving the substantial income from sold Ras and the landscaping benefits, as well as ecological and economic benefits from energy savings.

A novel algorithm to model concrete based on geometrical properties of aggregate and its application

In this paper, a novel algorithm is developed to generate the geometrical model of coarse aggregate based on its physical properties. The size, elongation index, and flakiness index are considered while developing the algorithm. The developed geometrical model of aggregate is further used for generating the finite element (FE) meso-model of concrete. Three distinct phases are considered in the FE model, i.e., aggregate, mortar, and interfacial transition zone. Further, numerical simulation has been performed under different loading conditions (i.e., quasi-static and high-strain loading rate). Additional considerations are discussed to develop a suitable FE model for a 3D split Hopkinson pressure bar specimen. The finite element (FE) simulation results are compared with available literature to verify the developed meso-model. It is verified that the mortar and ITZ fail during the quasi-static loading, whereas the structural effect (lateral inertia confinement) plays a significant role in the high-strain loading rate.

Properties of pervious concrete made with different types of waste aggregate-A literature review

Pervious concrete, also known as porous concrete, contains interconnected pores that allow water from various sources to pass through. This type of concrete is generally used for pavement construction to protect the environment. Pervious concrete contains only coarse aggregate and sometime very small amount of fine aggregate. Many researches were conducted to develop an efficient type of pervious concrete with different types and combination of aggregates. In many studies, along with natural stone aggregate, other types of waste materials were also tried to use as a coarse aggregate in the mix design of pervious concrete. Some of waste materials showed very promising characteristics which can be effectively used in the mix design of pervious concrete with double environmental benefits. This review article provides an overview of some of the earlier investigations on pervious concrete made from waste and industrial by-product materials. The relationships between crushing strength, porosity and water permeability of the pervious concrete with different types of aggregate are presented in this paper. Steel slag, recycled aggregate, and palm oil clicker were among the waste materials utilized as aggregate in pervious concrete, showed comparable performance; even in some instances, better performance was achieved than pervious concrete made with conventional natural aggregate. The shape of waste aggregate, described by the elongation and flakiness indices, greatly affects the strength properties and water infiltration rate of pervious concrete. If these indices are high, the strength properties of the pervious concrete are significantly reduced, but the water permeability is significantly increased.

The Effect of Untreated Dura-Palm Kernel Shells as Coarse Aggregate in Lightweight Pervious Concrete for Flood Mitigation

This research aimed at ascertaining the performance of raw dura species of Palm Kernel Shells (PKS) in comparison to a different species of PKS (tenera) as a replacement for known aggregates for pervious lightweight concrete. Using limestones as the known aggregates, control pervious concrete was batched, and relevant tests were conducted. Major tests conducted on the composites concerned compressive, tensile, and flexural strength, as well as permeability, densities, and absorption. Logistic constraints on transporting the dura-PKS limited the quantity needed to ascertain the variety of replacements of the dura-PKS. With a 25% replacement known to be the most suitable ratio for related investigations, we adopted that ratio and compared to the extreme ratio of 100% dura-PKS. The tests revealed that a 100% replacement of known aggregates by the dura-PKS resulted in high porosity and permeability, although the resistances to compression, tension, and flexural loads read low for the same mixture. Instead, pervious concrete 25% of dura-PKS replacement yielded optimum water permeability rate and flexural and compressive stresses. However, the flakiness index recorded for the dura-PKS was almost half that of the tenera species and was not reflected in the mechanical properties as the results gave relatively lower strengths. The results in the case of the dura species do not differ significantly compared to the tenera-PKS in terms of strength and permeability.

Çankırı’da Bazı Kireçtaşı Agrega Kaynaklarının Betonda Kullanılabilirliğinin Araştırılması

In this study, the usability of limestone extracted from two different aggregate quarries located in Çankırı province as concrete aggregate was investigated. For this purpose, aggregate samples were taken from the two quarries and on the samples taken, sieve analysis, specific gravity, water absorption, bulk density, very fine material content, flakiness index, methylene blue, disintegration strength, abrasion resistance, freeze-thaw, alkali-silica reactivity, acid soluble sulfate and total sulfur tests were carried out. As a result, the results of the tests performed on aggregates obtained from the limestone quarries around Çapar village (Şabanözü, Çankırı), Seydiköy (Eldivan, Çankırı) and Doğu district (Korgun) were compared with the limit values given in the standards and the usability of these limestone as concrete aggregates was determined. According the tests performed on the aggregates it can be clearly seen that, that all properties of these aggregates are suitable according to the EN standards.

E-waste infused bituminous mix for flexible pavements

This is a research and development project which involves experimental study of e-waste infused bituminous mix for flexible pavements. Non– hazardous and inert components of e-waste (Printed Circuit Boards) are used for this purpose. This is an effective and sustainable use of e-waste thereby reducing its effect on the environment. The project involves preparation of e-waste infused modified bitumen for the normal mix design used in India i.e. Dense Bituminous Macadam and its properties are analyzed. The aggregates collected are to be tested for the following properties: Specific gravity, Impact value, Flakiness index, Waster absorption. The modified bitumen is to be prepared by adding 2 % and 5% e-waste. The following tests are to be carried out for bitumen: Penetration Test, Specific Gravity Determination, Softening point Test, and Marshall Stability Value. The results of 2% and 5% e-waste infused bitumen are compared with the normal bitumen and the maximum dosage of e-waste to be added is to be determined.

Evaluation of the Suitability of Mukdadiya Formation Rocks for Using in Concrete / Northern Hemrin Anticline

The aim of this work is to evaluate the suitability of gravely sediments of the Mukdadiya formation (Lower Pliocene) in the northern Hemrin anticline on Tikrit – Kirkuk road / north-eastern of Iraq for concrete uses , and compared with the standard specifications (Iraqi, American and British) samples have been collected from four different stations by two samples for each station for the purpose of conducting various geotechnical tests including physical tests , strength and durability as well as chemical tests) Results of geotechnical evaluation for physical tests show that the grain size distribution of the 1st and 2nd stations suitable for uses to concrete for classes (40) class except 3rd. and 4th station , according to[1] , the results of Flakiness Index and elongation Index shows that the samples of four stations did not exceed the permitted border According to the British Standard and suitable to be provided by the requirements for the use of concrete . 
 The strength tests also showed the results of (AIV) shows it's don’t exceed than 9.95%) for all sample in the study area , and for compressive strength that taken from point load test shows that all stations classified the aggregate strength (very strong - extremely strong) according to[3] . 
 Durability geotechnical tests (Loss Angeles) results shows the percentage of weight loss for the four samples are not exceed the defined value 35% , so it is suitable for use for concrete and sub-base coarse aggregate and soundness test results shows suitability of all samples to use in concrete works .
 The chemical analysis shows suitability according to the standards .
 Overall, the study showing suitability for all tests with the requirements of the aggregate that are used in concrete except simple deviation in the grain grading in the third and fourth station .

Analyze the Geotechnical Properties of Aggregate in Al-Mahzam area and Evaluation of its Suitability for Using in road purposes

This research studies the geotechnical properties of the Quaternary deposits aggregate in Al-Mahzam area in Tikrit city/Salahadin governorate. Samples are collected from three sites on the western bank of Tigris River for studying the physical, mineralogical, chemical, strength and durability properties and evaluating its suitability for sub base in road works. The results for the physical tests through the grain size distribution test show that the aggregate is well graded and suitable to use in road works as sub base for class A. Specific gravity and density tests were carried on according to ASTM, D854,C127 Liquid limit value are (5.10, 2.2 and 4) % and the samples are non-plastic while the value of the elongation and flakiness index according to ISS, 45/1989 are (21.65, 16.04 and 15.85)% and (26.11, 28.65 and 36.00)% respectively.
 Mineral composition test of gravel particles revealed that carbonate gravel forming the high percentage of the mineral composition, chert and quartz, sandstone, igneous and metamorphic rocks respectively. Strength test for aggregate Impact Value were carried out according to ISS,47/1970 and B.S.812-112,1990 are (7.06,9.79 and 8.8)% which is classified to exceptionally strong which is specified that shall not exceed 30% for using in road works, and compression strength value which is derived from point load test are (197, 189.3 and 182.4) MPa. according to Hawkins classification is very strong. The durability test results represented by the loss angles test are (26.72, 26.18 and 29.55)% which is suitable for sub base road work, and the average of the soundness test results were ranges (0.62-3.54)% for coarse and fine aggregates which is within the specification and suitable to use the aggregate in roadwork as the sub base. For the chemical tests the values of organic matter, pH value, TDS and sulfate salts (gypsum %) are within the specification and suitable for using in sub base course for road

Influence of Basalt Aggregate Crushing Technology on Its Geometrical Properties-Preliminary Studies.

The use of mineral aggregates is related to the increasing demand in construction, railway and road infrastructures. However, mineral aggregates can appear to be of variable quality, directly affecting their suitability for respective earthwork applications. Since the production of mineral aggregates should ensure the standardized, high-quality requirements of the final product, rock-crushing mechanisms should be investigated in a detailed manner. In this context, the aim of the present study is to evaluate and analyze the geometric parameters of basalt aggregates as a result of several rock comminution processes. Basalt aggregates from two deposits in Poland were used in the study. The samples are differentiated regarding both lithological variances, mineral composition as well as the host rock's tuff content. The rock comminution processes were conducted using two types of crushers, namely the laboratory-scale jaw and cone crushers. The feed for crushing was designed based on the original geometric grain composition and the separated feed in the form of flaky and non-flaky particles. The crushability test results demonstrated that the interparticle compression in the jaw crusher resulted in finer products compared to the one in the cone crusher. It was also observed that the flakiness and shape indexes decreased after crushing, both in the feed with the original geometric composition of the grains and those with flaky and non-flaky particles. Nevertheless, a higher flakiness index was obtained after the crushing of non-flaky particles and a lower one after the crushing of flaky particles. The flakiness index for grains below 16 mm after the crushing process was less than 10%, which indicates a more favorable result compared to the original feed. In addition, it was shown that flaky and non-cubical particles were accumulated in the finest (below 8 mm) and coarsest (above 20 mm) fractions in jaw and cone crushing processes, receiving flakiness and shape indexes ranging up to 80-100%. Finally, it was also observed that the lithological variances of the feed material have a significant impact on the particle size distribution of the product. More profoundly, basalt aggregates with a higher tuff content and weathering degree have a higher degree of crushing. The present study, in this context, provides accurate and satisfying information on understanding the crushing mechanisms of two important crushing equipment as well as their rock-crusher interactions.

A study on the applicability of scoria gravel an alternative base course material through blending with marble waste aggregate

This study aims to evaluate the applicability of Scoria gravel as an alternative base course material in flexible pavements through blending with marble waste aggregate (MWA) by modifying the physical and mechanical engineering properties of scoria. Non-Probabilistic sampling techniques and experimental methods were used. To achieve the objectives of the study, the laboratory tests were passed in three steps. First, the Engineering properties of materials were independently tested; the result proves the marginality of scoria gravel. Second, scoria gravel was mechanically stabilized by 20% percentages by weight increments of MWA. The obtained engineering properties test results at 20:80 Scoria to MWA mix ratios are 2.56%, 21.38%, 18.59%, 19.27%, 17.45%, 13.77%, Non-Plastic, 1.21%, and 73.4%, for Specific Gravity, Aggregate Crushing Value, Aggregate Impact Value, Loss Angeles Abrasion, Flakiness Index, Elongation Index, Atterberg's limit, Water Absorption, and California Bearing Ratio (CBR) respectively. These test results fulfilled the ERA standard specification for GB2 and GB3 base course materials. However, the CBR test results showed a failure to meet the standard spécification. Thus, 20:80 Scoria to MWA percentage by weight ratio was selected as a control mixture. So, Crushed Stone Aggregate was added at 5% percentage by weight to improve the CBR of scoria gravel. Therefore, the CBR value of 82.13% attained the ERA standard Specification limit for base course materials at 15:60:25 percentages by weight ratio of scoria gravel, MWA, and CSA respectively. Finally, Based on this study it was recommended to use scoria gravel as an alternative base course construction material, when it was found abundantly near construction vicinity.

Performance of Artificial Compared to Natural Coarse Aggregates as Road Pavement Materials

Aggregates are the main material for road pavement made of natural stone. The availability of this natural stone will decrease because the stone is a non-renewable resource. The use of artificial aggregates can be an alternative to natural aggregates. The promotion of the use of waste as an artificial aggregates is starting to develop, especially with fly ash. Aggregates road materials must be tested to determine their characteristics by methods according to applicable standards. In this study, it can be seen that the aggregates of all quarries can be used as pavement materials, but the aggregates of the KB quarry show a poor flakiness index value. The test results of geopolymer-made aggregates made from fly ash showed that the abrasion and absorption values were not good. However, in general, it has good characteristics as road materials, so further research is needed to obtain geopolymer-made aggregates that meet the abrasion and absorption requirements for use as road materials.

INVESTIGATING CAUSES OF FLEXIBLE PAVEMENT FAILURE: A CASE STUDY OF THE BAKO TO NEKEMTE ROAD, OROMIA, ETHIOPIA

Most of the roads constructed in Ethiopia fail prematurely before serving the design life due to various causes arising from many factors. One of the roads that failed before reaching its design lifetime is the Bako to Nekemte Trunk Road. This road was constructed and opened to traffic in 2013. The design pavement life was estimated at 20 years. However; pavement failures have manifested since 2014 after it was opened for traffic. The main objective of this research was to investigate the cause for the failure of flexible pavement on the Bako to Nekemte road segment. To achieve this objective, the study was followed by the experimental research type and purposive sampling method. Also, field observation and pavement condition survey methods for data collection were used. The asphalt, base course, subgrade, and sub-base layer material sampled from the road segment are the material used for this study. Different pavement failures such as rutting, pothole, alligator cracking, raveling, edge cracking, depression, and corrugation were observed along the road section. For estimations of pavement condition index, the road was divided into five different sections based on distress densities, which were measured during the pavement condition survey. From those five sections, four sections were selected for the determination of the Pavement Condition Index (PCI). Using systematic random sampling 159 sample units were evaluated for Pavement Condition Rating (PCR) and the result shows 1.89% excellent, 8.18% very good, 20.13% good, 31.45% fair, 18.87 % poor, 18.24% very poor, and 1.26% failed. Based on PCI value, samples of pavement layer were taken from failed surface condition (1), poor surface condition (2), and none distressed area (1) for comparison purposes. Different quality tests like Atterberg limit, wash gradation, soil classification, compaction test, California Bearing Ratio (CBR), Los Angeles Abrasion (LAA), Flakiness Index ( FI), Aggregate Crushing Value (ACV), Ten percent fines value (TFV), bitumen content, and gradation of asphalt were carried out. The results of these tests were compared with ERA specifications to identify the probable cause of pavement failure. The study found that the cause for failure of flexible pavement in the case of Bako to Nekemte was: insufficient and absence of side drainage structure, traffic loading, poor gradation of base course and sub-base material, and poor quality of subgrade soil. The study also recommended that the road urgently needed routine maintenance as a treatment option to reduce further deterioration and extend its service time.

Characterization of Coarse Recycled Aggregates Produced from Concretes with Different Strength Levels

With the acceleration of Urban Renewal Program, particularly in large cities of Turkey, the problem of finding land-fills and eliminating construction waste with the least environmental pollution necessitates its value-added recycling. However, the presence of adhered weak mortar layer, comprising 20-70% of recycled concrete aggregate (RCA), limits the use of RCA or lowers its inclusion level in concrete mixtures. Within the scope of this study, limestone- and basalt-bearing RCA obtained from 6 different concrete mixtures with three different water/cement ratios (0.45, 0.60, 0.70) were prepared and their water absorption, specific gravity, dense and loose unit weight, flatness indices, Los Angeles degradation values were determined. The results showed that, increasing w/c ratio of the parent concrete increased water absorption of the resultant RCA. However, the specific gravity, unit weight, abrasion resistance and flakiness index of RCA were decreased by increasing w/c ratio of the parent concrete.

Engineering properties of basalt aggregates in terms of use in granular layers of flexible pavements

In this study, it is aimed to increase the level of knowledge about the physical and mechanical properties of basalt aggregates which is produced as crushed-stone in quarries. For this purpose, an experimental study was carried out on aggregates and test results were compared with the current specifications in force. As a result of the initial tests, it was determined that the impact resistance, abrasion resistance and freeze-thaw durability of basalt aggregate were quite good. However, the water absorption and flakiness index of basalt aggregate was observed partially high. Based on the test results, it is observed that the findings obtained by single-graded and static test methods that are widely used for granular materials, do not provide sufficient information about the performance of materials. It would be appropriate to support routine laboratory test results with dynamic triaxial test findings. Elastic stiffness of the basalt aggregates under repetitive loading conditions has been investigated by the dynamic triaxial test method. Statistically significant results were obtained by placing the resilient modulus findings into the K-θ model. Recommended resilient modulus Mr(s) values obtained for basalt aggregates by the new K-θ formula are given in a table. Mr(s) could be used as a stiffness parameter in pavement design in conditions where basalt aggregate is used as conventional crushed-stone.

Evaluation of the Impact of Fines on the Performance of Sub-Base Materials

The study aims to evaluate the change in the behavior of sub-base materials being used in road pavements through blending fines of different types in different amounts. Fines are added in aggregate samples as part of gradations proposed by the American Association for State and Highway Transportation Official (AASHTO). Composite samples conforming to AASHTO gradations B and C were prepared by mixing coarse aggregates in varying proportions, ranging from 0 to 15%. Laboratory tests—including aggregate quality tests (abrasion test, flakiness index and elongation Index), physical tests (particle size analysis and specific gravity), and strength test (modified Proctor, California bearing ratio, and permeability test)—were performed on the control as well as the modified samples. It was observed that the material with 0% fines yielded the highest CBR values (greater than 98%) and coefficient of permeability of 4.4 × 10−4 cm/s. However, with the increasing of the fines up to 15%, a substantial reduction in CBR value up to 10% and coefficient of permeability to 1.62 × 10−7 cm/s was noticed. Based on these results, the modulus of rigidity (MR) and the corresponding structural numbers were determined for each layer. Conclusively, the required thickness of the base course was increased from 11 cm for the samples with 0% fines to 24 cm (118%) for the samples with the addition of 15% fines according to the AASHTO Design method.

Discrete element modelling of hot mix asphalt complex modulus using realistic aggregate shapes

To assess the mechanical response under traffic of asphalt mixtures, a typical practice is to perform a complex modulus test. In this work, the complex modulus test is reproduced numerically for an asphalt mixture by 3D simulations carried out with the LMGC90 code. A viscoelastic contact law is used to handle the interaction between particles with irregular shapes. The numerical aggregates were generated using the particle size distribution (PSD), the flakiness index (FI), and statistic data of actual aggregates, without using complex imaging techniques. Experimental and numerical testing campaigns were conducted for the complex modulus test on trapezoidal samples in a two-point bending (2PB) configuration. The numerical model was able to reproduce the mechanical performances obtained during the experimental tests, regarding the viscoelastic properties of the material. The influence on the mechanical performances of particle shape considering irregular aggregate was analysed.