Resilient Modulus Tests Research Articles

Investigating the Effect of Gradation, Temperature and Loading Duration on the Resilient Modulus of Asphalt Concrete

This research was carried out to assess the effect of aggregate skeleton, temperature variation, and loading duration on the resilient modulus of asphalt concrete mixtures. Two different gradation methods, i.e., the conventional method of gradation and the Bailey method of gradation, were adopted to design the aggregate skeleton. The effect of these gradation methods, with temperature and loading duration, on the resilient modulus of asphalt concrete has not been previously investigated. The Modified Marshall Test was used to determine optimum binder content against 4% air voids, and then volumetric and strength parameters were calculated against optimum binder content. For performance tests, specimens were prepared at optimum binder content using a Superpave gyratory compactor. An indirect tensile strength test on both types of mixtures was conducted, and a 20% value of indirect tensile strength was kept for peak load, whereas 10% was kept for seating load for conducting resilient modulus tests. The tests were conducted at 100 and 300 ms duration loads under two different temperatures, i.e., 25 oC and 40 oC. The results declared that aggregate skeleton, temperature, and loading duration have a prominent effect on the resilient modulus of asphalt concrete mixtures. Bailey gradation mixtures disclosed higher resilient modulus values than conventional gradation mixtures. Higher values of resilient modulus were observed for both gradation mixtures at low temperatures and under small duration loads than at high temperatures and large duration loads. The results of the two-way factorial design also confirmed the above findings. Doi: 10.28991/CEJ-2022-08-02-07 Full Text: PDF

Effects of Iron Ore Tailing on Performance of Hot-Mix Asphalt

In Brazil, large quantities of iron ore tailings (IOT) are produced as a result of iron mining, which may affect the environment negatively. This work evaluated the use of IOT in hot mix asphalt type C (HMA-C). For this purpose, IOT was incorporated as a filler (at 1% in relation to the total mass of HMA-C). The hot asphalt mix with IOT (called HMA-IOT) was designed and compared with a control HMA-C. The behavior of the mixtures under monotonic (indirect tensile strength, ITS, and the Marshall stability test), under dynamic (fatigue and resilient modulus tests), and static (static creep test) loading conditions was evaluated. Also, the resistance to induced moisture damage (tensile strength ratio, TSR) was calculated. As a general conclusion, it was shown that the use of IOT in HMA improves its mechanical response without increasing mixing and compaction temperatures and using less effective asphalt binder content. This could provide a new form of environmentally safe disposal of IOTs.

Stabilisation of clayey and sandy soils with ladle furnace slag fines for road construction

This study investigated the use of ladle furnace slag fines (FLF) for soil stabilisation. It contributes to the current state-of-the-art by comparing the effects of FLF on engineering properties of clayey and sandy soils, evaluating the effects of different curing periods on mechanical performance of soil-FLF mixtures, and investigating the resilient behaviour of the stabilised tropical soils. The present experimental programme covers the characterisation of FLF and soils, compaction, unconfined compression, diametral compression, CBR, and resilient modulus tests of soil-FLF mixtures. FLF provided increases in mechanical properties of both soils in all tests. Some highlights are the improvements in the CBR index of the clayey soil from 8% to 44%, and the sandy soil from 7% to 140%, together with significant reductions in CBR swelling and improvements in the resilient behaviour. The benefits can be mainly attributed to improvements in cementitious reactions, cation exchange capability, and the filler effect provided by FLF.

Effect of Soft Clay on the Volumetric and Mechanical Properties of Hot Mix Asphalt

Abstract. To define the behaviour of asphalt mixture including various penetration grade bitumen has been a major subject of paving engineering. This search investigated the volumetric and mechanical properties of a hot-mix asphalt (HMA) mixture with the Superpave mix design. The mixture was added with powdered soft clay at five different percentages based on the bitumen weight (0%, 2%, 4%, 6%, and 8%). Performance tests were then conducted to determine the resilient modulus and volumetric properties of the mixture. Results show that bulk specific gravity increased after adding soft clay to the asphalt mixture. The amount of air and mineral aggregate voids also decreased with increasing SC contents. Furthermore, the addition of 4% SC improved mixture stiffness, as determined through indirect resilient modulus test under aging conditions. Therefore, soft clay can be added to asphalt mixtures to improve their volumetric and mechanical properties, such as strength and durability.

Key parameters controlling strength and resilient modulus of a stabilised dispersive soil

Dispersive clays are seen as problematic geomaterials due to their structural instability associated to the presence of high amounts of sodium adsorbed to the clay minerals. Thus, such soils are prone to deflocculate in the presence of water, having the potential to cause severe damage to man-made structures. Generally, the replacement of the weakly adhered sodium cations by calcium ions through the usage of lime is effective to cease the dispersivity potential. Yet, little is known concerning the resilient modulus response of lime stabilised dispersive soils for pavement applications. Present research intends to address this gap by conducting unconfined compressive strength tests and resilient modulus tests on a dispersive soil from the Paraguayan Chaco stabilised with hydrated lime. The results of both the strength and the stiffness tests could be successfully correlated to the adjusted porosity/lime index, resulting in power-type relationships, which is the major novelty of present research.

Stiffness assessment of cold recycled asphalt mixtures – Aspects related to filler type, stress state, viscoelasticity, and suction

Cold recycling is an advantageous technique, from economic and environmental perspectives, for asphalt pavement rehabilitation, interventions, and maintenance. Additional investigation is still needed for the widespread of the technique. Some of the issues evolve predicting the recycled material mechanical behavior and performance along its service life. Therefore, stiffness assessment (through triaxial resilient modulus and dynamic modulus tests) and suction tests were performed to better understand the cold recycled asphalt mixture (CRAM) behavior. This paper covered an investigation of the suction pressure phenomenon and its effects regarding the stiffness of emulsion-stabilized cold recycled asphalt mixtures, considering different fillers. A non-contact suction test method was proposed for CRAM compacted specimens in a way to enable total suction readings. Further theoretical analysis, key literature review, and discussions were presented. Some of the findings of the work are: (i) CRAM’s stiffness may present similar behavior of a granular material, with confining pressure dependence, and at the same time, presents a temperature/frequency dependence (as asphaltic materials); (ii) suction phenomenon may be responsible for part of the stiffness of CRAM; (iii) the filler type (even in small percentage) affects the mechanical behavior of CRAM.

Effect of glass fibers and waste engine oil on the properties of RAP asphalt concretes

ABSTRACT The increase in the cost of virgin materials and the environmental sustainability have contributed to increasing the incentive to use asphalt mixtures containing high percentages of recycled asphalt pavement (RAP). However, the use of high percentage of RAP into virgin asphalt mixture could negatively affect the performance of some properties of asphalt mixtures. Thus, using an appropriate additive to offset the negative effect of RAP could lead to an increase in the amount of RAP in asphalt mixtures. Therefore, this study aimed to evaluate the effect of using glass fiber (GF) with different contents (0.0%, 0.1%, 0.2%, and 0.3%) as an additive on the performance of asphalt mixtures containing RAP materials (60%, 70%, and 80%) and rejuvenated with waste engine oil (WEO) i.e., 6%, 9%, and 12%. The performance of RAP mixtures incorporating GF was evaluated using the indirect tensile strength test (ITS), resilient modulus test, and moisture susceptibility test. Hamburg wheel track testing was done to evaluate the rutting performance of the 70% RAP mixture. The results showed that the GF modification enhanced the ITS, rutting resistance, moisture susceptibility, and resilient modulus of rejuvenated mixtures. It was also found that the GF content of 0.2% was the optimum.

Characterization and Improvement of Natural and Blended un-bound Gravels From Khartoum State for Use as Base Course Material

This paper presents the outcome of a comprehensive testing program aimed at studying the strength, stiffness and deformation characteristics of three selected natural unbound materials in their natural state and when blendedwith Wadi sand or crushed stone with different size grades to satisfy base course specifcations. A graded crushed stone sample was prepared as reference material. The natural materials C1, M2 and F3 were obtained from openquarries to represent coarse, medium and fne gradations, respectively. The materials were also stabilized with cement. Only 1% cement by weight of dry material rendered the three unbound gravels to behave as rigid materials.The California Bearing Ratio (CBR), resilient modulus (MR) and permanent deformation (PD) tests were performed on the natural, blended and stabilized samples for determination of their strength, stiffness and deformationcharacteristics. Initial assessment of the improvement methods has shown that the strength (CBR) of the three materials, blended with Wadi sand, signifcantly improved to satisfy or nearly satisfy the GB3 requirement. Blending with crushed stoneimproved the gradation and caused large increase in strength (CBR) of the three materials. Cement stabilization of the three materials using 1% cement by weight of dry material rendered them to become hard material with CBRexceeding 100%. Further study of the stiffness and deformation characteristics of the studied materials has shown that blending with crushed rock gave better results in terms of increase in stiffness compared to Wadi sand when coarse gravel size material was added. It was enhanced by the improvement of gradation and interlocking caused by the shape of the coarse crushed stoneparticles. The crushed stone mix measured MR values exceeding 250 kPa indicating very stiff mix of superior quality when compared to the naturally occurring unbound materials and their corresponding blended products.Cement stabilization resulted in a very rigid material with MR values twice those for the pure crushed stone sample. The graded pure crushed stone sample showed very high resistance to permanent deformation when compared to the natural or blended materials. Blending a material with graded crushed stone gave lower PD values compared to blending the same material withWadi sand. This investigation has also shown that blending with sand and crushed rock could result in high increase in the strength of unbound material as demonstrated by CBR values, but would not necessarily result in comparable increase in rigidity or in resistance to permanent deformation

Influence of Gradation on the Mechanical Properties of Aged Hot-Mix Asphalts

When a hot-mix asphalt (HMA) ages, its mechanical properties, resistance, and durability change. Several studies have been conducted throughout the world to evaluate the effects of aging in HMAs. However, few studies have analyzed the influence of gradation. The main objective of this study was to evaluate the influence of gradation on the mechanical properties of aged HMA mixes. For such purposes, three HMA mixes with different gradations were manufactured (named HMA-10, HMA-19, and HMA-25), which were conditioned in STOA (short-term oven aging) and LTOA (long-term oven aging) by following the guidelines established by the AASHTO R30 specification. Marshall, Indirect Tensile Strength (ITS), resilient modulus, permanent deformation, fatigue (under controlled-stress condition), and Cantabro tests were performed. These tests were carried out to evaluate resistance under monotonic and cyclic load as well as the resistance to moisture damage and abrasion. The best performing mix in the test was HMA-19. There is no clear trend about the influence of gradation over the susceptibility of mixes for aging. This susceptibility changes depending on the test performed and the property measured. Furthermore, in resilient modulus tests, it is observed that the influence of gradation on aging susceptibility changes depending on the test temperature.

Evaluation of climate effect on resilient modulus of granular subgrade material

This study examines the effects of freeze-thaw actions and the concurrent seasonal fluctuations in water content, named as climate effect in this study, on the resilient modulus of subgrade materials to evaluate their mechanical behavior in cold regions. A series of suction-controlled resilient modulus tests on subgrade materials with variant freeze-thaw, wheel loads, and water contents conditions were conducted using a newly developed test apparatus. Test results were used to construct a simple model to estimate the climate effect on the resilient modulus by considering the synergistic effects between water content and freeze-thaw. Besides, this study calculated the fatigue life of eight local flexible pavement projects with variant subgrade layer moduli considering climate effect by combining the newly proposed model and long-term in-situ measured data. Results proved that climate-related degradation of the subgrade materials decreases the fatigue life of asphalt pavements in cold regions.

Investigation of Effect of Bakelite on Mechanical Properties of Hot Mix Asphalt Mixes - A Full Factorial Design Experiment

In Pakistan, mostly flexible pavements are constructed which have a higher susceptibility to rutting, moisture damage and stripping. Under current economic conditions, one such solution to overcome this is the addition of economical and locally available additives in the bitumen being produced by our refineries. This study investigates the effects of bakelite as an additive on various mechanical properties. Bakelite is a high-density plastic, cost-effective and locally available material. The modified Hot Mix Asphalt (HMA) specimens were prepared with (2%,4%,6%,8%,10%,12%) Bakelite by weight of optimum binder content found using Marshall Mix design. Performance tests, including Marshall Stability and flow. Retained stability and Resilient Modulus tests were performed to check the performance of modified mixes. The test results revealed that a modified mix containing 6% Bakelite by weight of optimum bitumen content provides the best resistance against moisture damage, rutting and enhancing the HMA mix's stability than the other modifier percentages. The Marshall stability and quotient values of the modified mix increased by almost 22% and 44% respectively. The results showed an increase of 3.5% in the tensile strength ratio indicating an increase in the capability of HMA to resist moisture-induced damage and strength retention. The resilient modulus test was then performed under different conditions, i.e., bakelite (0% & 6%), temperature (25˚C &40˚C) and load duration (100 ms & 300 ms) and analyzed by full factorial design experiment. The factorial analysis showed that Bakelite content is the most significant factor affecting the MR and, ultimately, the strength of the HMA mix. The Resilient modulus test results showed a 20% increase for the modified mix containing 6% Bakelite as compared to the conventional mix. Therefore, it is concluded that the addition of bakelite as an additive in hot mix asphalt mixes gives better results regarding pavement performance.

Application of electric arc furnace slag for stabilisation of different tropical soils

ABSTRACT Steelmaking wastes have been reused in civil construction to decrease environmental damages. This work evaluated the use of fines of oxidising electric arc furnace (EAF) steel slag (FEAF) as stabilising agents of two different soils Tests for geotechnical characterisation of soils and chemical, physical, and morphological characterisation of FEAF were carried out. Natural soils and soil-FEAF mixtures were subjected to standard Proctor compaction, unconfined compression strength (UCS), California Bearing Ratio (CBR), and resilient modulus (RM) tests. FEAF provided UCS increases up to 128%, maximum dry density increases up to 6% and optimal moisture content reductions up to 10%. The highest improvements were provided by 15% of FEAF (UCS increases from 7 to 56 days of A-7-5(19) and A-2-7(0) soils were 60% and 21%, respectively). Regardless of the curing period, CBR index of A-7-5(19) soil with 15% FEAF was 60–65% of CBR index of A-2-7(0) soil containing 15% FEAF. Similar reductions (27–29%) in CBR swelling were observed in both soils. Incorporation of 15% FEAF into A-7-5(19) and A-2-7(0) soils provided RM increases of 30% and 45%, respectively. Mechanical properties increases were attributed to filler effects and improvements in cementitious reactions FEAF improved soils’ performance, enabling their use in pavement design and earthworks.

Use of building demolition waste as lime treated base course in bituminous road

Building Demolished aggregate are the waste generated when the building is demolished due to disaster like earthquake, flood, tsunami etc. So the generated wastes are piled up to the dumping site or laid over the subgrade soil without treating it which only pollute the environment. In this paper it is studied that the waste aggregate generated after the building is demolished can be used as a base course layer for bituminous pavement. When the quick lime is mixed with the demolished building aggregate it regains its strength as natural aggregate. The CBR values, Resilient Modulus and Compression test result shows the balance mixed of lime, water and aggregate with filler gives the adequate result. So the demolished building aggregate can be use as Lime Treated Base Course (LTBC) for bituminous pavement by treating it with lime. As per IRC SP 89 mentioned compressive strength for cement treated base course should be 2.1 to 5.5 MPa in 7 days whereas the same result should be obtained by lime or fly-ash in 28 days. It is studied that when the excess amount of lime is used that is more than 8% in this study then it may increase the strength but also due to excess lime content shrinkage may occur which leads to crack or fatigue. Similarly resilient modulus calculated from the CBR values gives the satisfactory result. As per IRC 37 for base course resilient modulus can be taken as 300 MPa and 350 MPa.

Utilization of Waste Glass Powder and Glass Composite Fillers in Asphalt Pavements

Today, researchers around the globe are looking for suitable alternatives of conventional fillers which can form flexible pavements with satisfactory engineering performance in an environmental friendly and cost-effective manner. This study investigated the engineering, economical, and environmental viability of recycling waste glass powder (GP) and glass-hydrated lime (GL) composite as alternative fillers, in place of stone dust (SD). All fillers were characterized, and asphalt concrete mixes incorporating them at different proportions (4–8.5%) were designed using the Marshall mix design method. The engineering performance of asphalt mixes was analyzed using the static creep analysis, indirect tensile fatigue test, Cantabro test, modified Lottman test, resilient modulus test, mixing time analysis, and boiling water test. Additionally, the design of single km of two-lane flexible pavements utilizing aforesaid mixes was done as per the mechanistically empirical method suggested in IRC 37 guideline. Finally, the economic and environmental analysis was done by comparing their material cost and global warming potential (GWP). GL and GP mixes exhibited better resistance against rutting, fatigue, and low temperature cracking at lower optimum asphalt content than SD mixes. However, GP mixes also displayed poor moisture resistance and adhesion due to the high amount of silica in GP. GL mixes had satisfactory moisture resistance up to 7% filler content due to the fine nature and anti-stripping properties of hydrated lime. The pavement containing GL and GP fillers also reduced material cost and GWP up to 35% while consuming up to 74 tons of GP.

A Machine-Learning Approach for Extracting Modulus of Compacted Unbound Aggregate Base and Subgrade Materials Using Intelligent Compaction Technology

This study presents a rigorous approach for the extraction of the modulus of soil and unbound aggregate base materials for quality management using intelligent compaction (IC) technology. The proposed approach makes use of machine-learning methods in tandem with IC technology and modulus-based spot testing as a local calibration process to estimate the mechanical properties of compacted geomaterials. A calibrated three-dimensional finite element (FE) model that simulates the proof-mapping process of compacted geomaterials was used to develop a comprehensive database of responses of a wide range of single and two-layered geosystems. The database was then used to develop different inverse solvers using artificial neural networks for the estimation of the modulus from the characteristics of the roller and information about the geomaterials. Several instrumented test sites were used for the evaluation and validation of the inverse solvers. The proposed approach was found promising for the extraction of the modulus of compacted geomaterials using IC. The accuracy of the inverse solvers is enhanced if a local calibration process is incorporated as part of a quality management program that includes the use of in situ measurements using modulus-based test devices and laboratory resilient modulus testing. Moreover, compaction uniformity plays a key role in the retrieval of the modulus of geomaterials with certainty. The proposed approach fuses artificial intelligence with mechanistic solutions to position IC as a technology that is well suited for the quality management of compacted materials.

Correction to: Laboratory Study on the use of Reclaimed Asphalt Pavement and Copper Slag in Warm Mix Asphalt Pavements using Waste Engine Oil as a Rejuvenator

This study aims to evaluate the effect of waste engine oil (WEO) on warm asphalt mixes incorporated with waste materials. Copper slag (CS) and reclaimed asphalt pavement (RAP), both considered waste materials were used in asphalt mixes. Seven types of mixes were prepared with different proportions of copper slag (0–15%) and RAP (0–30%) at 5%, 7.5%, and 10% WEO dosages. Marshall stability test, indirect tensile test, resilient modulus, and flow number test was carried to check the performance of these mixes. Also, a cracking test was used for evaluating the fracture energy of asphalt mixtures. It was found that asphalt mixes incorporated with CS (15%) and RAP (30%) performed similar to control mixes up to 7.5% rejuvenator dosages. The incorporation of copper slag (5%) improved the Marshall stability and tensile strength due to more angularity (multi-faced) and frictional angle (53°) of CS, resulting in excellent stability and load capacity. The resilient modulus in Mix 6 (30%RAP-5% CS) was observed to be maximum (3310.3 MPa). The use of waste engine oil softened the aged RAP bitumen, which leads to a decrease in stability, resilient modulus, rutting resistance, and increase in fracture energy. The RAP incorporated mixes showed lesser fracture energy due to the presence of stiff RAP bitumen. However, with the addition of WEO, the fracture energy increased which indicates that the cracking resistance of these mixes improved due softening action of WEO. Marshall quotient, which represents stiffness, decreased with an increase in CS content at all rejuvenator dosages.

Anisotropic Resilient Modulus Model of Granular Materials Based on Particle Characteristics

Granular materials are widely used for bases or subbases in pavement structures. They typically exhibit strong anisotropic properties which relate to stress states and particle characteristics. The conventional design procedure for flexible pavements underestimates the anisotropy of resilient moduli. This study established an anisotropic resilient modulus model for granular materials that considered gradation and particle shape characteristics. Vertical and horizontal resilient moduli of certain granular materials were measured in self-developed triaxial tests to obtain corresponding model parameters and anisotropic coefficients. Gradation and particle shape models were established to quantify the granular material characteristics, and the parameters were regressed. Particle shapes were obtained via image processing, and the ratio ( η) of particle sphericity to roundness was chosen as a shape parameter. Results show that η increases with the decrease in particle size, and the average values of η for graded gravel and natural laterite are 0.54 and 0.63, respectively. The η distribution curves indicate that the proportion of relatively anisotropic particles, rather than extremely anisotropic particles, results in the differences in particle shape characteristics. The regression relationship between the anisotropic calculation parameters and the model parameters of vertical resilient modulus, gradation, and particle shape was established. Thus, the horizontal resilient modulus and the anisotropic coefficient can be predicted via conventional resilient modulus tests and gradation, and particle shape analysis. This study shows that the anisotropy of granular materials decreases with the increase in coarse particles and the uniformization of the particle size distribution, and it increases with the increase in anisotropic particles and the polarization of the η distribution.

Prediction of resilient modulus with consistency index for fine-grained soils

It is crucial to accurately predict the resilient modulus of subgrade soils. The modulus is influenced by a soil’s properties, as characterised by the soil’s moisture index values. Thus, it may be feasible to predict resilient modulus based on the soil index. Consistency index, as one of the common soil indices, incorporates plasticity index and moisture content. Therefore, this study aims to establish its relationship with resilient modulus. By collecting and analysing the previous testing results, it is found that resilient modulus was well correlated and increased with consistency index. Two prediction models, a consistency index model and a modified consistency index model, were also proposed to evaluate the resilient modulus of 15 soils with plasticity indices ranging from 6 to 52 at various moisture contents. Model parameters of the consistency index model were estimated from the plasticity index and exhibited excellent correlation. The modified consistency index model incorporated stress states to predict resilient modulus. The models were validated using selected testing results. Despite some limitations, it proves reasonable as a simple alternative means to determine the resilient modulus of fine-grained soils for foundation design, in place of complex resilient modulus testing.

Utilization of fly ash and glass powder as fillers in steel slag asphalt mixtures

In the developing countries, the management of industrial wastes such as fly ash, glass powder, and steel slag has become a severe problem. If the fly ash, glass powder, and steel slag can be utilized for road construction, this problem will be solved. The present study investigates the effects of fly ash (FA) and glass powder (GP) as filler (in lieu of stone dust) and coarse steel slag aggregate (in lieu of coarse natural stone aggregate), on the performance of asphalt mixes for road construction. Based on Marshall Mix design, the optimum amount of FA and GP is 60 % and 30 %, respectively, in place of stone dust. Control mix and steel slag mixes made with FA and GP are subjected to moisture sensitivity, resilient modulus, and wheel tracking tests. The inclusion of FA improves the moisture damage resistance of steel slag mixture, while the GP shows reduced moisture damage resistance due to silica content. Nevertheless, it satisfies the moisture criteria as per standards. Besides, both FA and GP improve the stiffness and show reduced rutting depth by 39.33 % and 22.3 %, respectively, in steel slag mixture. The FA exhibits better performances than the GP. Moreover, cost analysis reveals that asphalt mixes using FA, GP, and steel slag aggregate decrease the construction and life cycle costs compared to the control mix. As a whole, FA, GP, and steel slag aggregate can be used as alternative materials in asphalt mixes for road construction.

Using Artificial Intelligence to Estimate Nonlinear Resilient Modulus Parameters from Common Index Properties

The Mechanistic–Empirical Pavement Design Guide (MEPDG) considers a hierarchical approach to determine the input values necessary for most design parameters. Level 1 requires site-specific measurement of the material properties from laboratory testing, whereas other levels make use of equations developed from regression models to estimate the material properties. Resilient modulus is a mechanical property that characterizes the unbound and subgrade materials under loading that is essential for the mechanistic design of pavements. The MEPDG resilient modulus model makes use of a three-parameter constitutive model to characterize the nonlinear behavior of the geomaterials. As the resilient modulus tests are complex, expensive, and require lengthy preparation time, most state highway agencies are unlikely to implement them as routine daily applications. Therefore, it is imperative to make use of models to calculate these nonlinear parameters. Existing models to determine these parameters are frequently based on linear regression. With the development of machine learning techniques, it is feasible to develop simpler equations that can be used to estimate the nonlinear parameters more accurately. This study makes use of the Long-Term Pavement Performance database and machine learning techniques to improve the equations utilized to determine the nonlinear parameters crucial to estimate the resilient modulus of unbound base and subgrade materials.