Four-point Beam Bending Test Research Articles

Enhancing Flexural Behavior of Reinforced Concrete Beams Strengthened with Basalt Fiber-Reinforced Polymer Sheets Using Carbon Nanotube-Modified Epoxy.

The external bonding (EB) of fiber-reinforced polymer (FRP) is a usual flexural reinforcement method. When using the technique, premature debonding failure still remains a factor of concern. The effect of incorporating multi-wall carbon nanotubes (MWCNTs) in epoxy resin on the flexural behavior of reinforced concrete (RC) beams strengthened with basalt fiber-reinforced polymer (BFRP) sheets was investigated through four-point bending beam tests. Experimental results indicated that the flexural behavior was significantly improved by the MWCNT-modified epoxy. The BFRP sheets bonded by the MWCNT-modified epoxy more effectively mitigated the debonding failure of BFRP sheets and constrained crack development as well as enhanced the ductility and flexural stiffness of strengthened beams. When the beam was reinforced with two-layer BFRP sheets, the yielding load, ultimate load, ultimate deflection, post-yielded flexural stiffness, energy absorption capacity and deflection ductility of beams strengthened using MWCNT-modified epoxy increased by 7.4%, 8.3%, 18.2%, 22.6%, 29.1% and 14.3%, respectively, in comparison to the beam strengthened using pure epoxy. It could be seen in scanning electron microscopy (SEM) images that the MWCNTs could penetrate into concrete and their pull-out and crack bridging consumed more energy, which remarkably enhanced the flexural behavior of the strengthened beams. Finally, an analytical model was proposed for calculating characteristic loads and characteristic deflections of RC beams strengthened with FRP sheets, which indicated a reasonably good correlation with the experimental results.

Analysis of viscoelastic behaviour in asphalt pavement through four-point beam bending tests

This study, conducted in accordance with ASTM T321-14 standards, offers crucial insights into the behaviour of asphalt materials subjected to cyclic loading. For proper maintenance and pavement design, it is essential to understand the material response under different loading conditions. This study focuses on the four-point beam bending test to investigate the viscoelastic behaviour of asphalt pavement. The four-point beam bending test is a useful method for determining the material's ability to withstand cyclic loading and deformation, which the material experiences during field traffic conditions. The experimental setup involves subjecting asphalt samples to cyclic loading using a four-point bending apparatus. The imposed load causes the specimen to experience bending strains, representing the actual loading conditions that pavements endure. The data gathered during testing include stress, strain, and deformation properties under various loading conditions. The stress-strain response demonstrates the material's resilience to fatigue, with a gradual decrease in stiffness beyond 10,300 cycles. Fatigue failure criteria include a 50% reduction in initial stiffness for strain-controlled fatigue tests and cracking in stress-controlled tests. The dynamic modulus in a compressive-type, repeated load test follows a three-phase pattern, highlighting the impact of temperature and binder characterization methods on sample performance. The results provide information about the material's resilience to rutting and fatigue cracking, the most significant distresses indicated in asphalt pavements. The findings from this study contribute to an in-depth understanding of the viscoelastic behaviour of asphalt pavement and can aid in the development of improved design guidelines and maintenance strategies characterizing the material response to cyclic loading. Engineers and researchers can make better decisions on the durability and performance of asphalt pavements, resulting in more cost-effective and sustainable road infrastructure.

Assessment of potential resistance to moisture damage and fatigue cracks of asphalt mixture modified with ground granulated blast furnace slag

Abstract Fatigue and moisture damage have been recognized as the most prevalent problems on asphalt roads, necessitating large annual expenditures for road maintenance. Much industrial waste is added to bitumen paving to enhance its conventional quality while decreasing the negative impacts on the natural environment and increasing resistance to pavement distress. This research uses ground granulated blast furnace slag (GGBFS) to substitute conventional filler (Portland cement [PC]) in hot mix asphalt (HMA). To determine how the GGBFS affects the HMA's susceptibility to moisture and fatigue cracks, Marshall characteristics, tensile strength ratio (TSR), and index of retained strength (IRS) of the asphalt concrete were evaluated. HMA was prepared with different rates of GGBFS (0, 25, 50, 75, and 100%) instead of PC. The data support the usage of 50% GGBFS in asphalt pavements as a partial replacement of PC, which enhanced Marshal stability by 34.4%, reduced flow value by about 12.9%, and increased TSR and IRS by 11.1 and 14.54%, respectively. The fatigue resistance of the modified asphalt mix at the optimum rate was evaluated with the four-point bending beam test; the fatigue life (Nf) increased by 33.8% relative to the reference mixture. The results obtained from this research hold scientific value for researchers and method designers aiming to enhance the resistance of hot asphalt mixtures to moisture and cracking. Using waste materials as an alternative to PC contributes to cost reduction while mitigating the environmental damages associated with cement manufacturing. To summarize, this research highlights the significance of exploring sustainable options in the construction industry, emphasizing the importance of reducing costs, and minimizing environmental impacts.

Simplified methodology for fatigue analysis of reinforced asphalt systems

Fatigue analysis has an important role in evaluating the durability and performance of asphalt pavements, especially when novel or alternative materials are used. Numerous laboratory studies have investigated fatigue performance with the aim of estimating field behavior as accurately as feasible. Therefore, there are currently many different test methods and data analysis approaches that can be used. One of the most common laboratory test methods is the four-point bending beam (4PBB) test, which results are usually analyzed using the so-called traditional (where 50% reduction in initial stiffness is considered as failure criterion) or the energy ratio (ER) approach. However, outcomes from previous studies have shown that these approaches may not be appropriate and reliable if geogrids are used as a reinforcement. As a possible solution, this study proposes a new simplified flex point (SFP) approach that considers the flex point of the strain amplitude curve, measured during 4PBB fatigue tests, to calculate the number of cycles to failure. These three approaches were applied to four double-layered asphalt sets: one unreinforced and three reinforced with geogrids of different strength (50 x 50, 100 x 100 and 100 x 200 kN/m). The impact of reinforcement on the fatigue life was evaluated by comparing the critical strain values (ε6) of reinforced and unreinforced sets through the fatigue resistance improvement factor. The research findings showed that the use of geogrids improves fatigue life when the SFP and ER approaches are applied and that the traditional approach might not always be appropriate for assessing the fatigue resistance of reinforced asphalt mixtures.

Investigation of different parameters affecting the crack width and kb coefficient of GFRP-RC beams

Crack width control is one of the criteria affecting the design of glass fiber-reinforced polymer (GFRP)-reinforced concrete (RC) structural components. The provisions available in the CSA S806-12 standard and ACI 440.1R-15 guideline for controlling the crack width of GFRP RC elements account for the bond between the GFRP reinforcement and surrounding concrete through the bond-dependent coefficient (kb). In those design standards and guidelines, each GFRP bar surface profile is assigned a kb value obtained from four-point bending beam tests. This study aims to experimentally investigate the parameters that affect the crack width and kb coefficient of GFRP reinforcing bars, enrich the literature with more kb results for ribbed and sand-coated GFRP bars, determine whether kb is a fixed value that is solely dependent on the bar surface profile (as assumed by the above standard and guideline), recalibrate the kb coefficient considering the experimental results of this study and available experimental data in the literature, and provide the FRP engineering community with an equation that is capable of anticipating kb values based on different configurational and material parameters. To achieve the objectives of this study, 16 large-scale RC beams were tested under a four-point bending test setup. The studied parameters included the clear concrete cover, bar spacing, bar diameter, concrete compressive strength, bar surface profile, and confinement provided by transverse reinforcement. The experimental results of this study were combined with the available database to recalibrate the kb values and propose a kb equation. The results showed that the kb coefficient varies when changing the reinforcement configuration of the beam.

Evaluation of Rutting, Fatigue, and Moisture Resistance of Low-Energy Asphalt Mixtures Modified by Crumb Rubber

Low-energy asphalt (LEA) mixture, as an alternative to hot mix asphalt (HMA) due to its lower mixing temperature, has advantages such as reducing energy consumption and environmental pollutants. LEA has poor performance characteristics due to the presence of water in its manufacturing process and low mixing temperature. All the studies about LEA have been focused only on investigating the performance of this asphalt mixture, and the effect of additives in its modification is one of the research gaps in this field. Therefore, the use of crumb rubber (CR) and determining its optimal percentage in modifying the performance characteristics of LEA is considered an innovation of this research. In this research, the performance characteristics of LEA modified by 10%, 15%, and 20% CR were evaluated. In order to examine the rutting behavior, moisture sensitivity and fatigue resistance, dynamic creep, indirect tensile strength (ITS), and four-point bending beam tests were applied, respectively. The results of creep curves and flow numbers (FNs) indicated that modifying LEA by 15% increased the rutting resistance by 1.92 and 2.3 times, respectively, compared to the HMA specimen at the stress level of 207 and 310 kPa. Moreover, the evaluation of the creep strain slope revealed that modifying LEA significantly reduced stress sensitivity. ITS test showed an increase in tensile strength ratio by 22% in the specimen with 10% CR compared to the unmodified specimen. In the evaluation of fatigue resistance, while LEA containing 10% CR had almost similar results to the HMA specimen, other specimens represented a shorter fatigue life, so that with the increase in CR percentage, the fatigue life decreased. Determination of fatigue life by energy ratio and Rowe and Bouldin criteria showed similar results. Finally, by determining the plateau value (PV) in the ratio of the dissipated energy change method, the lowest PV was assigned to the 10% CR-modified LEA and HMA specimens, respectively.

A methodology for post-processing the four-point beam bending data and computing stiffness modulus using harmonic analysis

The computation of modulus of bituminous mixes from a beam bending test conforming to an undamaged yet steady state is not straightforward. The most widely used practice of choosing the 50th or 100th cycle, for modulus computation, does not ensure that the material response has reached a steady state, crossing the initial transient stage of drastic modulus reduction. In the current study, it is analytically shown that the material retardation time governs the attainment of a steady state response. The study proposes a methodology for post-processing the four-point beam bending test data so as to identify the cycles that could result in a sensible computation of material modulus. The experimental investigations involve four-point beam bending (4-PB) tests carried out on four bituminous mixes, prepared using an unmodified and three modified binders. The 4-PB tests are carried out at 20 oC, 10 Hz frequency at strain levels of 200, 400, 600 and 800 micro-strains. The harmonics of the input/output waveform has been used to identify the cycles that can be used for the computation of a material modulus, and the modulus is computed from the Lissajous plots (stress–strain plots) of the cycles prior to damage initiation. Based on harmonic analysis, the current study specifies a range of modulus for each mix at various strain levels, and the values are further compared with the modulus computed using the conventional post-processing procedure. It is observed that the conventional procedure of using the stiffness modulus at 100th cycle results in higher values of modulus than the ones computed using the proposed post-processing method, as a consequence of the transient response of the material before attaining a steady state.

Development and Analysis of High-Modulus Asphalt Concrete Predictive Model

The main purpose of this paper is to present the development of a new predictive model intended for the calculation of stiffness modulus |E*| determined by a four-point bending beam test (4PBB or 4PB-PR). The model developed, called model A, was based on the Witczak model, which was developed for the dynamic-modulus (DM) method. Most of the asphalt mixtures used to develop the model were high-modulus asphalt concrete (HMAC). The most commonly used methods for determining the stiffness modulus |E*| of asphalt mixtures were also discussed. The paper presents the results of the study for 10 asphalt mixtures but 8 of them were used to develop the predictive model. In addition, the results of complex shear modulus G* tests on neat and modified bituminous binders carried out in a dynamic shear rheometer (DSR), necessary for the development of a predictive model, are presented. The tests carried out in the dynamic shear rheometer had significant measurement uncertainties. The results of the volumetric parameters of the asphalt mixtures are also reported. The developed model A has maximum absolute errors e = 1930 MPa (p = 95%) and maximum relative errors re = 50% (p = 95%). The distribution of the absolute errors of the model, after discarding outliers, has a normal distribution as in the development of other models of this type, which was confirmed by appropriate statistical tests. On the basis of the tests and calculations carried out, it was concluded that, in order to increase the precision of the predictive models, it is advisable to reduce the measurement uncertainty of the bitumen complex shear modulus G*. For the developed model A, the limiting values of the stiffness modulus |E*| are also shown, within which the determined stiffness modulus should fall.

Cracking Behavior and Deflections in Recycled-Aggregate Beams Reinforced with Waste Fibers Subjected to Long-Term Constant Loading.

This report presents the results of long-term tests on concrete beams reinforced with steel cord. In this study, natural aggregate was wholly replaced with waste sand or with wastes from the production of ceramic products and ceramic hollow bricks. The amounts of individual fractions used were determined in accordance with guidelines for reference concrete. A total of eight mixtures were tested; these differed in terms of the type of waste aggregate used. Elements with various fiber-reinforcement ratios were made for each mixture. Steel fibers and waste fibers were used in amounts of 0.0%, 0.5%, and 1.0%. Compressive strength and modulus of elasticity were determined experimentally for each mixture. The main test was a four-point beam bending test. Beams with dimensions of 100 mm × 200 mm × 2900 mm were tested on a stand, which was specially prepared so that three beams could be tested simultaneously. Fiber-reinforcement ratios were 0.5% and 1.0%. Long-term studies were conducted for 1000 days. During the testing period, beam deflections and cracks were measured. The obtained results were compared with values calculated using several methods, considering the influence of dispersed reinforcement. The results enabled the best methods for calculating individual values for mixtures with different types of waste materials to be determined.

Real-time monitoring of strain and modulus of asphalt pavement using built-in strain sensor cluster

Pavement health monitoring is helpful to understand the structural state of interlayer and make reasonable maintenance decisions. This study aims to propose a real-time strain and modulus monitoring method using built-in strain sensor cluster. First, the four-point bending beam test was conducted to demonstrate the possible poor deformation compatibility between a single built-in strain sensor with asphalt mixture under different temperature. Then, the potential mapping relationship between the output of the built-in strain sensor and the real strain of the matrix material was explored by mechanical derivation. Subsequently, the real-time strain and modulus monitoring method based on built-in strain sensor cluster was discussed and proposed. Finally, a three-dimensional finite element model was developed to validate the applicability of the proposed method to the dynamic response monitoring of elastic and viscoelastic pavement systems. The results indicate that the difference in modulus between the built-in strain sensor and the asphalt mixture causes the sensor output to deviate from the true value. The modulus ratio and strain ratio between the built-in strain sensor and the asphalt mixture satisfy the mapping relationship. The monitoring method based on the built-in strain sensor cluster can overcome the strain measurement errors caused by the poor deformation compatibility and also enables real-time monitoring of pavement modulus. In general, this work provides a new framework for real-time evaluation of strain and modulus in pavement health monitoring.

Evaluation of the Effect of WCO/SBS-Modified RAB and RAP and Stiffness Recovery Procedure on Fatigue Performance of HMA

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures is an expedient and cost-effective solution against rutting failure, but its performance against fatigue and thermal cracking is unsatisfactory and causes the pavement to deteriorate sooner than expected. Rejuvenators can improve RAP performance under various operating conditions through stiffness recovery and binder healing. In this paper, waste cooking oil (WCO) and styrene butadiene styrene (SBS) polymer were used to evaluate the rheological behavior of reclaimed asphalt binder (RAB). The modified RAB has been evaluated using chemical composition, linear amplitude sweeping (LAS), and bending beam rheometer (BBR) tests. The results of the LAS test showed that the fatigue life of RAB containing WCO was about 6 to 9 times longer than the control RAB specimen at the strain level of 2.5% and 5%. The results of the BBR test also indicated the good performance of the WCO. Thus, the WCO used in this study was expected to enhance the fatigue performance and thermal cracking of RAB. To evaluate the behavior of RAP containing RAB and additives on the fatigue response before and after self-healing, four-point bending beam test (4PBB) was employed. The results showed that besides improved fatigue life of hot-mix asphalt (HMA) produced with RAP- and RAB-containing additives, it had a longer fatigue life after self-healing. The specimen containing WCO had a better performance than the specimen to other samples.

Evaluating fatigue and crack resistance of asphalt mixture containing zinc tailing aggregates

Roads as one of the most important components of the transportation system involve a large quantity of construction aggregate. Limitation in natural-aggregates sources makes it necessary to use alternative materials as a substitute to natural-aggregates. To achieve this goal, the by-products tailings of zinc soil separation and concentration process named zinc tailings were used as an aggregate in asphalt mixture. In this research study, the fatigue, low-temperature, and moisture susceptibility performance of fabricated asphalt mixtures using limestone, siliceous and tailing aggregates were investigated. For this purpose, the four-point bending beam (4PB),semi-circular bending (SCB), and indirect tensile strength (ITS)tests were employed. Findings from 4PB tests indicate that asphalt mixture containing zinc tailings as aggregates have longer fatigue life than the mixture fabricated with limestone aggregates at the strain level of 600 microstrain. However, caution needs to be exercised at higher strain levels. Based on SCB test results, the fracture energy values for mixture with tailing aggregates were almost constant at temperatures of − 6, − 10, and − 12 °C while the results show fracture energy reduction for other mixtures at a lower temperature. Moreover, the cracking resistance index (CRI) indicates that the tailing aggregates fabricated mixture has acceptable low-temperature performance. Finally, the TSR values show that mixture containing zinc tailing aggregates are more resistant to moisture damage compared with siliceous fabricated mixture.

Recycled plastics as synthetic coarse and fine asphalt aggregate

ABSTRACT This study investigates the performance of asphalt concrete containing recycled plastics as synthetic aggregates in the dry mixing process. Two types of recycled plastics were used, namely, acrylonitrile butadiene styrene (RABS) and Polyethylene Terephthalate (RPET), based on the high-temperature properties of the plastics that make them suitable to be treated as synthetic aggregates (i.e. do not melt during the asphalt mixing phase). The proportions of recycled plastics were chosen at 0.5%, 1%, 2% and 4% of the mix mass. The laboratory testing programme includes the evaluation of compactability properties, moisture resistance, cracking resistance via IDEAL-CT test, fatigue resistance via four-point bending beam test and rutting resistance via Hamburg wheel tracking (wet) test. It was found that the inclusion of recycled plastics did affect the compactability of the mixes depending on their relative size and shape. On the other hand, the inclusion of recycled plastics did not significantly vary the moisture resistance of asphalt mixes. The cracking and rutting behaviour of asphalt mixes that incorporated recycled plastics were also modified and some benefits were observed depending on the plastic content and size.

A three-dimensional deformable spheropolyhedral-based discrete element method for simulation of the whole fracture process

A deformable spheropolyhedral-based discrete element method (DS-DEM) is proposed for predicting the evolution of fracture by coupling the finite element method (FEM) with the spheropolyhedral-based discrete element method (DEM). Under the framework of the proposed method, each rock mass is discretized into finite elements, and zero thickness joint elements are inserted along the boundary of finite element elements. The fictitious crack model and the Mohr-Coulomb failure criterion are employed to determine the failure state and failure mode of joint elements. The contact interaction between discrete particles and fracture surfaces is captured by the spheropolyhedral-based DEM. The method is verified by particle stacking test, three-point bending beam test, Brazilian disc tensile strength test, crack propagation in a single notched beam test, four-point bending beam test, and sphere impact test. The results of numerical simulations indicate that the proposed method is adaptable in simulating the whole fracture process of quasi-brittle materials including the initiation and propagation of cracks, as well as the collision and deformation of fragments.

Numerical Analysis of Microcracks of Fly Ash/Slag Concrete with Cobble as Coarse Aggregate

In order to improve mechanical properties of fly ash/slag concrete with large size cobble as coarse aggregate, this paper analyzes the effect of different factors on the concrete through the flexural strength test. The Monte Carlo simulation is used in the finite element solver of ANSYS to conduct the four-point bending beam test. Three-dimensional and two-dimensional finite element models are established to discuss how the gradation of large size cobbles affects the performance of the concrete by comparing macromechanical experiments. Results show that the gradation of large size cobbles is the main factor affecting the performance of the concrete. Slag generates the least effect on the concrete with cobble as coarse aggregate. When the mixing amount of slag and fly ash is 10%, the concrete presents the best flexural performance. Through the numerical loading test of the two-dimensional model for fly ash/slag concrete with cobble as coarse aggregate, it can be concluded that the change of the concrete follows the law of macromechanical properties.

Fatigue performance enhancement and high-temperature performance evaluation of asphalt treated base mixture

For hot climate areas with heavy traffic loads, the use of Asphalt Treated Base (ATB) requires higher fatigue and rutting resistance performance. To enhance the fatigue resistance performance of ATB mixture and evaluate the high-temperature performance, this study selected different kinds of binders, binder contents, and modifiers to explore the influencing factors of ATB mixture fatigue behavior using the four-point bending beam test. The results show that the fatigue life of ATB mixture is increased with lower penetration grade, larger aggregate sizes, or higher asphalt-aggregate ratio. High modulus ATB mixture has better fatigue and rutting resistance performance.

Impact of Styrene-Butadiene-Styrene (SBS) content on asphalt Binder’s fatigue resistance at various aging levels using Viscoelastic Continuum Damage and fracture mechanics

The use Styrene-Butadiene-Styrene (SBS) modification of asphalt cement is considered as one of the effective ways to improve pavement performance. The increase in stiffness and the improved elastic response of the asphalt cement provide pavements with better rutting and fatigue resistance. On the other hand, cracking resistance in asphalt cement has proven to be a difficult property to evaluate. Several methods have been proposed, and one such method is the high strain Linear Amplitude Sweep (LAS) test using the dynamic shear rheometer, which has shown a good ability to evaluate cracking resistance in asphalt cement. The aim of this research is to examine the ability of different binder characterization techniques to distinguish the level of polymer modification in asphalt cements, as well as their ability to characterize fatigue resistance at different aging levels. Testing with the LAS has shown that the cycles to failure calculated using the Viscoelastic Continuum Damage Model correlate well with the concentration of SBS. The LAS can also be analyzed using fracture mechanics (Pure LAS) and this approach has also shown some correlation with SBS concentrations. The Pure LAS analysis has been shown to improve upon the characterization of different levels of laboratory aging. Finally, fatigue resistance of asphalt concrete specimens prepared with different levels of the SBS modification was studied using Four-Point Bending Beam test. A strong correlation was found between the results of asphalt cement LAS tests and fatigue testing of asphalt concrete mixtures. Both forms of analysis indicate that the LAS approach may provide good feedback when evaluating the role that SBS plays in improving the cracking resistance of asphalt cement. These are important developments for the characterization of cracking resistance in the asphalt binder which can lead to improved material selection for pavements.

Ethylene Propylene Diene Monomer (EPDM) Effect on Asphalt Performance

The asphalt industry is increasingly developing with greater focus on sustainability. This study focuses on the benefits of a binder modification of stone mastic asphalt (SMA) by adding a rubber—ethylene propylene diene monomer (EPDM)—into a class 320 bitumen. This study observes the advantages that occur for the rutting and fatigue performance of the samples. The binder modification was made by incorporating 0, 2, 4 and 6% binder weight into each sample. The tests performed on the samples were the wheel-tracking test and the four-point beam bending test. The results revealed varied outcomes, with the four-point beam bending test showing the 6% sample having the highest initial stiffness and modulus of elasticity but the lowest cycle to failure. Therefore, the best performer was determined as the 4% sample, which performed consistently throughout, having the highest cumulative dissipated energy and second-highest initial flexural stiffness, modulus of elasticity and cycle to failure results. There was a clear indication of the best performer for the wheel-tracking test, with the 4% sample having the lowest rut depth, although there were signs of further improvement to be achieved within the 4–6% range. In addition, drain-off tests were conducted on the mixtures, and the addition of EPDM significantly reduced the SMA drain-off values. Overall, the best improvements through binder modification for an SMA mix with EPDM concerning fatigue and rutting resistance came from a 4% incorporation.

Evaluating the Effect of Plastomer Modified Asphalt Mixture on High/Low Temperature Performance

Asphalt pavement’s surfaces deteriorate over time due to combined effect of traffic and surrounding environment. Fatigue and rutting are the major distresses which cause failures in flexible pavements. Different temperature control computer operated equipment’s are being used worldwide to predict the performance of asphalt mixtures at approximately same condition to those in-service pavements. Similarly, different types of polymers such as elastomer and thermoplastic have been used all over the world in Hot Mix Asphalt (HMA) for the improvement of asphalt mixtures. But little attention has been taken to evaluate the effect of plastomer on hot mix asphalt performance. Moreover, the initial cost of elastomer is higher than other types of polymers such as plastomer. The aim of this research study is to check the effect of various plastomers on high/low temperature performance of asphalt mixture. Four performance tests like Cooper wheel tracker, dynamic modulus, uniaxial repeated load and four-point bending beam test are used to evaluate the effect of different type of plastomers such as polyethylene terephthalate, high density and low density polyethylene with limestone aggregate quarry and 60/70 pen grade asphalt binder. This research study concludes that plastomer increases flexibility and hardness of asphalt mixtures and improves the rut resistance, dynamic modulus and fatigue life of asphalt mixtures. Plastomer modification shows significant benefits as compared to neat binder for high/low temperature performance. Moreover, it can be concluded that plastomer provides an efficient and economical blend of asphalt mixture.

Effect of CENEX polymer on the performance of bituminous concrete and dense bituminous macadam of pavement

This paper focuses on the effect of centrifuged latex (CENEX) polymer on the performance of bituminous concrete (BC) and dense bituminous macadam (DBM) of pavement. In this study, VG30 binder is modified with CENEX polymer at different percentages such as 0%, 2%, 4%, 6% and 8% by the weight of the binder. Using storage stability test it is found that optimum content of CENEX polymer is 6%. Mixes using CENEX modified binder require slightly lesser optimum binder content (OBC) than the plain mixes. Retained marshal stability (RMS) test, tensile strength ratio (TSR) test, resilient modulus ratio (RMR) test, boiling water test (BWT), four-point bending beam test (FPBT) and wheel tracking test (WTT) are conducted on these mixes. The results show that the incorporation of CENEX polymer improves the moisture damage resistance, fatigue life and rut resistance. Furthermore, life-cycle cost analysis reveals that CENEX modified mixes are more economical compared to plain mixes over long-run, even though the initial cost of modified and unmodified mixes are almost the same. As a whole, better performance is obtained by using CENEX modified mixes resulting in higher pavement service life.