Resilient Modulus Tests Research Articles

Performance evaluation of polyamine anti-stripping additives

Polyamine anti-stripping additives in asphalt mixes are chemical chains that bond chemically with an acidic siliceous aggregate at one end and an asphalt binder at the other. They help to prevent the hydro-oxide of siliceous aggregates from reacting with water molecules, which can lead to a breakdown of the asphalt mix. The effect of two proprietary polyamine-based anti-strippers, Wetfix and Tackamin-200, on moisture susceptibility, the resilient modulus and rutting performance were evaluated at percentages from 3 to 6% with increments of 0·1%. Wet and dry indirect tensile strength, the indirect tensile resilient modulus and dynamic creep tests were used to assess the moisture susceptibility, structural response and rutting resistance of treated asphalt mixes. The results indicated that 0·5% was the optimum dosage for both additives with respect to all performed tests, with Wetfix being more efficient. Overall, it was found that the impact of the anti-stripping agents on moisture susceptibility was significant.

Evaluation of Hot-Mix Asphalt Containing Portland Cement Treated Blast Furnace Slag

AbstractIron production’s waste materials include significant quantities of blast furnace slag (BFS) which could potentially be used as a substitute for natural aggregates in hot mix asphalt (HMA) used in highway projects. Although many of properties of slag are interesting, its porosity and absorption rate would lead to greater consumption of asphalt. For this study, a Portland cement (PC) paste was used to reduce the porosity of a BFS. This PC treated BFS (called BFS-C) was then used in an HMA to replace the coarse fraction of a natural aggregate. Marshall, Indirect Tensile Strength (ITS), resilient modulus and Cantabro tests were then carried out on different HMA mixtures that included BFS-C. Using BFS-C, HMA’s resistance under monotonic loading, stiffness under cyclic loading, and resistance to moisture damage increased remarkably. In addition, the Cantabro abrasion resistance of BFS-C improved was better than that of the HMA mixture produced with untreated BFS.

Cyclic load triaxial test procedures for soils in transportation engineering

Unbound granular base course is built in pavement structures between subgrade and bound base course. Its main function is bearing capacity - load transfer from upper layers to subgrade. For its successful design, one of the required parameters is resilient modulus. Resilient modulus describes behaviour of unbounded materials at various load conditions, and is defined as the ratio of the applied cyclic stress to the elastic strain. It can be determined with cyclic triaxial test that gives good simulation of stresses and strains which are result of traffic loads. In this paper resilient modulus testing procedure will be described with the emphasis on European Standard (EN 13286-7). Furthermore, it will be given comparison of European standard with other test procedures.

Characterisation of crushed base for mechanistic-empirical pavement design guide

This paper describes a recently completed laboratory test programme to determine the standard properties of crushed base aggregates collected from 14 road projects throughout Wyoming. Eleven of 14 base aggregates were selected for resilient modulus testing performed in accordance with the Wyoming modified AASHTO T 307 procedure. Effects of moisture content, percent fines content, stresses, and gradation on base resilient modulus were assessed. Models were developed using statistical methods to estimate the resilient modulus of base materials. The NCHRP and Hicks and Monismith constitutive models were calibrated. A design chart of resilient modulus in terms of asphalt thicknesses was established to facilitate the iterative process involved in a pavement design. Finally, a design table of base properties for MEPDG Level-3 inputs was developed to facilitate the full implementation of the MEPDG. The proposed framework for developing these methods could be adopted nationally to facilitate the full implementation of MEPDG.

Investigation of accuracy of pavement mechanistic empirical prediction performance by incorporating Level 1 inputs

Abstract The recently developed AASHTOWare pavement mechanistic empirical (M-E) design requires advanced characterization of pavement materials. In particular, M-E Level 1 analysis requires materials input parameters to be obtained from the laboratory test results. In cooperation with the New Mexico Department of Transportation (NMDOT), six pavement sites were selected to compare M-E Level 1 predicted performances from laboratory tested data with the field performances. Pavement materials such as subgrade, base, asphalt concrete, binder, aggregate, etc., were collected from these pavements sites during construction. Laboratory dynamic modulus, fatigue endurance limit (FEL), dynamic shear rheometer, and resilient modulus tests were conducted on the collected materials. Using these parameters, pavement sections, as constructed, were modeled and analyzed in M-E at Levels 1, 2 and 3. The predicted distress quantities for international roughness index (IRI) and rutting were compared with the field collected data as well as among the three design levels. The analysis results demonstrated that M-E overpredicts IRI and rutting in the pavement compared to the field performance. It was also observed that Level 1 showed the lowest rutting, whereas the maximum rutting was found at Level 2. The dynamic modulus of AC layer was underpredicted at Levels 2 and 3 resulting in higher rutting and IRI.

Reversible moisture damage in asphalt mixture

A moisture damage has been one of the major concerns for HMA pavement by loss of adhesion between bitumen and aggregate surface or loss of the cohesion within asphalt binder due to action of water. Water is the one of major contributor towards the damage of asphalt pavement. The aim of this research is to evaluate the effects of Moisture Damage (MD) towards the performance of asphalt mixture under different conditions (dry, wet and dry back). For this research laboratory fabricated specimens were conditioned in accordance to ASTM D4867 to achieve desire saturation level up to 80% and then immersed in water for different soaking period to simulate flooding scenario. Indirect Tensile strength (ITS) and Resilient Modulus (RM) tests were performed on moisture conditioned specimens at regular interval (1,3 and 5 days). After 5 days testing specimens were stored at room temperature for another 5 days to dry and were tested again to determine the recoverability of moisture damage. The results from this study indicated that tensile strength and modulus gradually decreased with the increasing of conditioning period, and upon drying at certain period specimens recovered 82% and 76% of initial ITS and RM respectively. The results suggested that moisture damage in asphalt mixture tested is reversible.

Effect of different rejuvenating agents on the mechanical performance of recycled bituminous mixture

Reclaimed asphalt pavement (RAP) is a waste material generated from pavement milling activity. Rejuvenating agent is introduced to restore the properties of aging bitumen in RAP. Many studies have been investigated the performance of recycled mixture incorporating RAP with oil-based (OB) rejuvenating agent, but there is still limited research on water-based (WB) rejuvenating agent. Therefore, this study evaluated the performance of mixture incorporating RAP with OB and WB rejuvenating agents (RAP-OB and RAP-WB). OB and WB rejuvenating agents were added at recommended content of 0.70% and 52.13% by weight of bitumen, respectively. Indirect tensile strength, resilient modulus, dynamic creep and asphalt pavement analyzer (APA) tests were conducted to assess the resistance of the mixtures toward permanent deformation and fatigue cracking. It was found that the addition of OB rejuvenating agent enhanced the tensile strength, resilient and stiffness modulus by approximately 41%, 94% and 158%, respectively, relative to the control mixture. APA recorded that RAP-OB produced the lowest rut depth, followed by RAP-WB and control mixture. It indicates that RAP-OB produced the highest resistance to permanent deformation and fatigue cracking. Thus, the OB rejuvenating agent significantly improved the performance of the recycled mixture compared to the WB rejuvenating agent.

Fundamental characterisation of the anisotropic resilient behaviour of unbound granular materials

ABSTRACT The paper presents an in-depth investigation of the resilient behaviour of an unbound base material. It is based on the assumption that the material is non-linear and cross anisotropic. A testing programme that includes different incremental stress paths, principal stress ratios and confining pressures is proposed. The programme requires the use of a triaxial cell where both the vertical and horizontal stresses and deformations are either controlled or measured. The paper describes the analysis steps whereby only three material parameters, out of the five cross anisotropic parameters, can be obtained in the above conditions. Four specimens of a good quality base material were prepared in the laboratory and tested according to the above testing programme. The analyses of the tests show that: (1) The vertical modulus depends solely on the bulk stress, as expected for a good quality base material; (2) The vertical to horizontal Poisson’s ratio and the horizontal parameter are also nonlinear and function of the first two stress invariants; (3) The material parameter functions from the incremental loading tests are different from those of the resilient modulus test; (4) The characterization is sensitive to the type of loading.

Evaluation of the Mechanical Properties of Asphalt Mixture Modified with RPET

The major objective of this study is to evaluate the influence of Rynite Polyethylene terephthalate (RPET) particles on the mechanical properties of hot mix asphalt by conducting several tests such as; resilient modulus, dynamic creep and wheel tracking test. Various RPET contents namely; 3, 5 and 7% by weight of bitumen were added to asphalt mixture using wet method. From resilient modulus test, it was found that the stiffness of modified mixtures with RPET increased compared with unmodified asphalt mixture. The improvement of stiffness for intermediate and high temperatures was between 68 % for 3% of PET, while 3.88% for 7% PET respectively. The results of dynamic creep have shown a better improvement to rutting, the 3% of RPET showed the best resistance to permanent deformation compared to control sample. The results of wheel tracking test proved that the modification of asphalt mixture with RPET improved significantly the resist to permanent deformation (rutting). The addition of RPET has good performance in hot mix asphalt.

Evaluating properties of wood ash modified asphalt mixtures

Nowadays, sustainable development has gained more attention because humanity will face the problem of energy shortage in the near future. Biomass’ consumption has increased year by year as it is a renewable material. However, there will be a lot of ash residue after combustion biomass, which can cause pollution problems. This research investigates the potential use of wood ash as filler replacement in the asphalt mixture because wood ash has similar physical and chemical properties to traditional fillers. Wood ash used in this study consisted of 100% passing the 0.075 mm sieve and 25%, 50%, 75% and 100% conventional filler (by weight) were replaced by the wood ash. Marshall Stability & Flow, Resilient Modulus, Rutting performance and Fatigue performance tests were employed to determine the influence of wood ash as filler to the hot mix asphalt (HMA) mixture. The results showed that present wood ash in the asphalt mixture could improve fatigue performance, reduce permanent deformation, and increase the resilient modulus of the asphalt mixture. Therefore, wood ash can be used as the filler substitute material for asphalt mixture.

Establishing a resilient modulus test protocol for miniature cylindrical asphalt mix specimens

The resilient modulus is a very important parameter to be identified and used in pavement design. The indirect tensile test is the most common repeated load test to measure the resilient modulus of asphalt mixtures and the easiest method to test laboratory compacted specimens and field core specimens. The resilient moduli of asphalt mixtures are measured using the indirect tensile procedure (ASTM D4123). A metal loading strip with a concave surface with the radius of the test specimen is required to apply load to the specimen. Typically, specimens are either a nominal 100mm or 150mm in diameter with a minimum thickness over diameter ratio of 0.4. However, typical 100mm diameter core samples with 40mm to 50mm thickness taken from the site most often do not fulfil the minimum ratio of 0.4 after the samples are trimmed for testing. As such, a new procedure was developed to test specimens smaller than 100mm in diameter. This expected to be very useful and minimize the volume requirement from the field. This novel protocol for resilient modulus test using miniature specimens of 37.5mm and 56.3mm in diameter has great potential for practical relevance for the industry.

Investigation of the matric suction role on the curing mechanism of foamed asphalt stabilised mixtures

Moisture content is of great importance for foamed asphalt stabilised mixtures, since it influences mixing, compaction, curing process and the structural performance. The curing process, in which water evaporates, is responsible for the increase of the bearing capacity of foamed mixtures. Although different loading resistance mechanisms contribute simultaneously to the layer stiffness, the aim of this research is to evaluate the influence of matric suction in the stiffness of two foamed asphalt mixtures that have been used as base course materials in experimental test sections. Filter paper, X-ray microcomputed tomography and triaxial resilient modulus tests were conducted at four moisture conditions. The filter paper test indicated an increase in the matric suction when water evaporated from the specimen, which was validated by the reduction of the air voids measured with microcomputed tomography. From triaxial resilient modulus and matric suction results, it was observed that although other mechanisms might be dominating the loading resistance of foamed mixtures, the matric suction influences the stiffness of these materials.

Performance evaluation of fatigue resistance of asphalt mixtures modified by SBR/PP polymer blends and SBS

Abstract Using durable asphalt mixtures to increase the quality of pavement, improving the safety and comfort of drivers and reduce pavement damage and maintenance cost is inevitable. Major damage to asphalt pavement is fatigue, which happens due to everyday increase in traffic and the passing load. One way to improve the quality, strength and fatigue resistance of asphalt mixtures is to use high quality or modified, asphalt binder. This study aimed to use a polymer blend (a combination of two polymers) made of efficient and inexpensive polymers to modify the properties of asphalt binder and asphalt mixtures against fatigue. For this purpose, SBR and PP polymers with ratios of 70/30, 50/50 and 30/70, at 3, 4 and 5 wt% of asphalt binder were used, and the fatigue performance of asphalt mixtures containing these polymer blends was compared with that of asphalt mixtures containing 4% and 5% SBS polymer. Nanoclay CLOSITE 15A was used at 1.5 wt% of asphalt binder to increase the stability of polymers in asphalt binder. The results of bending beam fatigue, indirect tensile fatigue, indirect tensile strength, and resilient modulus tests performed on asphalt specimens showed that the use of polymer blends improves the fatigue performance of asphalt mixtures so that in samples containing 5% of polymer blends containing 50% and 70% SBR, fatigue life is increased by more than 50% compared to that of 5% SBS samples. Accordingly, it can be said that polymer blends can be used as an efficient and economical additive in asphalt mixtures.

Expansion Level of Steel Slag Aggregate Effects on Both Material Properties and Asphalt Mixture Performance

The influence of steel slag expansion level on the early stage performance of hot mix asphalt (HMA) is evaluated. Initially, samples of Linz-Donawitz type steel slag with different levels of expansion (6.71%, 3.16%, 1.33%) were submitted to physical, mechanical, and morphological characterization to assess the effects of expansion on individual material properties. Steel slag was then used as aggregate in HMA to verify the effects of its expansion characteristics on the volumetric and mechanical performance of the asphalt mixture. Four different asphalt mixtures were designed based on Marshall mix design, using asphalt cement (pen. grade 50/70), natural aggregate (granite), and steel slag (in three different levels of expansion). The mechanical characteristics of the asphalt mixture were evaluated based on results from Marshall stability, indirect tensile strength, and resilient modulus testing. A modified Pennsylvania testing method (PTM) was also performed on the studied asphalt mixtures to verify the potential of asphalt binder film to minimize the expansive reactions of steel slag. It was observed that the level of steel slag expansion changes some of the material’s individual properties, which can affect the volumetric parameters of the mix design. The use of steel slag as aggregate in HMA also improves the mechanical properties of non-aged asphalt mixtures. Moreover, the expansive characteristics of this material could be minimized when combined with other asphalt mixture components.

Effect of setting accelerator additive on short- and long-term properties of cold recycled mixture containing bitumen emulsion–cement composites

Cold recycled layers have low early stiffness and are prone to rutting at initial days of curing. In this research, it was tried to resolve these issues by concurrent use of cement and chloride-free sodium carbonate-based accelerator. The cement content was fixed to 2% by weight of dry reclaimed asphalt pavement. The accelerator contents varied from 0% to 15% of the cement weight at 5% intervals. Experimental study was conducted on recycled mixes and emulsion–cement pastes. The partial and full curing protocols have been used to simulate the short- and long-term field curing processes, respectively. Marshall stability, indirect tensile strength and resilient modulus tests were accomplished on recycled mixes after both curing protocols and indirect tensile fatigue test was performed after the full curing process. Micro-structural analysis including the X-ray diffraction and scanning electron microscopy were conducted on cured pastes. Furthermore, the hydration heat release was measured by isothermal calorimetric procedure. It was concluded that the existence of emulsion in cement paste to some extent hindered the cement–water reactions. The addition of accelerator evidently increased the rate of cement hydration at initial days of curing and compensated the retarding effects of emulsion. For partially cured specimens, the strength and stiffness of recycled mixes containing accelerator was higher than the conventional mixture. However, a significant decrease in stiffness occurred after finishing the curing process for accelerator containing mixes. The retardation in portlandite development and growth of calcium carbonate crystals were the main reasons for stiffness decrease in these mixes after the full curing process.

Comparing the Effect of Nanomaterial and Traditional Fillers on the Asphalt Mixture Properties

Several parameters affect asphalt mix performance against loading and environmental conditions. Minor changes in the filler amount or type can cause obvious changes in the asphalt mixture properties. Accordingly, in this research attempts have been made to optimally make asphalt mixture strong against loading and environmental conditions by changing the type, size and percentage of filler used in asphalt mixture. In this line, the effect of two types of cement and nano-silica fillers in two different percentages was investigated and compared as an alternative for part of the main filler in asphalt mixture samples made by two types of limestone and granite aggregate. Cement filler by 2% and 4% of the aggregate mass as the alternative for part of the main filler is added to stone materials before mixing with binder, but nano-silica filler by 2% and4 % of weight of the binder as the alternative for part of the main filler is added to binder and a modified and homogeneous binder is produced using a high speed mixer. In the following, considering the optimum binder content for each mixture, resilient modulus tests were conducted to determine the strength performance against loading and indirect tensile strength ratio was used to determine moisture sensitivity of asphalt mixtures. Results obtained from resilient modulus tests show that the use of nano-silica and cement has been capable of favorably improving the resilient modulus of samples containing these two types of fillers. The improvement of the resilient modulus of samples containing nano-silica is very significant. Additionally, the studies conducted based on the indirect tensile strength ratio show that both types of alternative fillers, especially cement has been capable of desirably improve the strength of asphalt mixtures against moisture damage.

The effect of laboratory compaction method on the resilient behaviour and fabric of aggregate base course materials

Aggregate base course (ABC) layer is a key structural component of most pavements. The compaction of ABC is a crucial procedure affecting its mechanical performance. There are two different methods commonly used in the lab to compact ABC specimens: impact and vibratory. Past studies have demonstrated that the compaction method can affect the resilient deformation behaviour of ABC. However, the reasons for these differences in terms of the constituent ABC particle properties and the resultant compacted aggregate fabric remains unclear. This study evaluates the influence of the laboratory compaction method on the resilient behaviour and fabric of two ABC materials with differing mineralogies. Resilient modulus tests performed on the specimens compacted with the two methods result in different behaviours. A series of subsequent laboratory tests were performed to explain the observed resilient behaviour by assessing changes in aggregate morphology and fabric. The study presented herein incorporates digital imaging analyses using a novel specimen preparation technique. The results demonstrate that impact compaction can degrade ABC materials that are susceptible to crushing. This, in turn, increases the resilient modulus of the ABC by increasing the number of contact points between particles. It is recommended that the compaction method used in the laboratory match the compaction processes in the field as best as possible to obtain the most representative resilient modulus test results.

Quantifying the effects of geogrid reinforcement in unbound granular base

This study presents an effort to quantify the effects of geogrid reinforcement in the unbound granular base through laboratory testing. Two laboratory tests, the large-scale cyclic shear test and the repeated load triaxial test, were employed. The test protocol of the cyclic shear test was developed by modifying that for the triaxial test. The cyclic shear test was performed by applying a series of cyclic shear stresses to the geogrid-aggregate interface under different normal stresses. Two different types of geogrids were used as reinforcement in unbound granular material. Resilient modulus (MR) from the repeated load triaxial test and a term named resilient interface shear modulus (Gi) from the cyclic shear test was used to characterize the effects of geogrid reinforcement in unbound granular base, respectively. The results of triaxial tests showed that the inclusion of geogrid had a negligible effect on the resilient modulus, indicating that the triaxial resilient modulus test may not be effective in evaluating the geogrid reinforcement in unbound granular materials. Compared to the triaxial resilient modulus test, the cyclic shear test showed great potential in identifying the effects of geogrid reinforcement, with an obvious improvement in the degree of interlocking between geogrids and aggregates.

Influence of Sisal Fiber on Resilient Modulus of Hot Mix Asphalt with Addition of Marble Dust

A material's resilient modulus is extremely a gauge of its modulus of elasticity (E). While the modulus of springiness is pressure isolated by stress for a step by step associated load, the resilient modulus is stress isolated by strain for immediately applied loads – like those practiced by pavements. This can be resolved in the laboratory by leading test according to system indicated AASHTO T30-99 (2003) and the resilient modulus estimated in the indirect tensile mode as indicated byASTMD 4123. Bituminous concrete comprises of a blend of totals aggregates evaluated from most extreme size, normally under25 mm, through fine filler that is littler than0.075 mm. Adequate bitumen is added to the blend with the goal that the compacted blend is successfully impermeable and will have satisfactory dissipative and elastic properties. Mineral filler characteristics and their effect on the permanent deformation characteristics (rutting) of bituminous mixes vary with the type and amount of filler added to the mix. About 3.8 million tons of sisal fibres are cultivated every year throughout the world. Roughly 3500 metric ton of marble powder produced every day amid the preparing of marble squares. The present paper portrays the outcomes from a progression of resilient modulus tests that were led in a lab situation utilizing a repeated load triaxial test setup. The impacts of optimum marble filler and sisal fibres and different binding and deviatoric stress of levels on the resilient modulus (MR) response of treated modified blend were contemplated. MR estimations of conventional and modified are 2416 and 2777 MPa, which enhancements the improvements with marble filler and sisal fibres .rutting and fatigue resistances investigated with immersion wheel tracking device, indirect tensile strength, and repeated load test. The examination demonstrates that 3.30mm rutting depth and 28.1 msa fatigue life for the modified blend.

Performance of Nano kaolin clay as modified binder in porous asphalt mixture

The performance of porous asphalt (PA) mixture incorporating Nano kaolin clay (NKC) was presented in this study. The study covers basic properties of PA including morphology characteristic, penetration and softening point test. In addition, cantabro loss and resilient modulus test with regards to the variations of mix design of the PA was also examined. The kaolin clay used in this study has gone through the grinding process to produce the NKC with the percentage replacement of bitumen used was 3%, 5%, 7% and 9%. The results show that the used of NKC improved the physical properties of PA by reducing the penetration value, meanwhile increasing the softening point value. This indicates that NKC enhanced the temperature susceptibility of PA. The experimental result also show that NKC modified binder improved the durability and resistance to rutting and cracking of PA. Furthermore, 5% NKC is also considered as the optimum NKC proportion. The utilization of NKC is able to improve the physical and mechanical properties of PA. Therefore, it can conclude that the performance of PA is also enhanced with utilization of NKC in the bitumen.