STUDY ON RUTDEPTH CHARACTERISTICS OF MODIFIED BITUMINOUS MIXES

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1 STUDY ON RUTDEPTH CHARACTERISTICS OF MODIFIED BITUMINOUS MIXES Miss Nandini 1 and K. Rajasekhar 2 1 Associate Professor, BITS College, Adoni, Kurnool (DT), AP, India 2 M.Tech, (PG Scholar, Highway Engineering), BITS College, Adoni, Kurnool (DT), AP, India Abstract Due to increase in traffic volume, pavement constructed with conventional bitumen is getting damaged before the expected life time, resulting in permanent deformation, low temperature cracking, load associated fatigue, wear, stripping andaging Permanent deformations, primarily in the form of ruts, are one of the basic asphalt pavement damages impairing its service properties. Vehicle wheel load acting on the pavement of a road may result in permanent deformation. Permanent deformations, primarily in the form of ruts in the form of imprints, tracks, corrugations, and shovings are one of the basic asphalt pavement damages impairing its service properties. Among these, ruts are most dangerous because they might cause vehicles to skid during precipitation. So as to increase the pavement performance there is a need to increase the quality of pavement using modifiers. Now a days modified bitumen are being used worldwide due to there improved performance. In the present study an attempt has been made to evaluate the permanent deformation characteristics of modified bitumen. Aggregates used in this study are from Peda Pendyal quarry. Crumb Rubber modified bitumen and Polymer Modified Bitumen are used in this study are obtained from Shell Bitumen company and Hindustan Colas Limited (HINCOL). Stability, flow value and Rutting resistance are taken as the evaluation parameters in this study. Using these evaluation parameters modified bitumen are evaluated and Compared with each other.it has been found that Polymer Modified Bituminous Mixes performed better than Crumb Rubber Modified Bituminous Mixes. I. INTRODUCTION The economic development of a place or country depends upon various resources available and related activities. In the process of proper utilization of resources, transportation emerges to be the vital activity. Good marketing, by providing a place and utility value to an item, depends upon good transportation system, while the road network of the area is the most flexible mode of transportation system. With a rapid population growth rate globally, the necessary means of earning the livelihood for increased population are also increased. This resulted more area of agriculture, new industries and new markets. To connect all these areas, an efficient network of various transportation systems is badly needed; particularly the highway system had been on demand for tremendous growth. In contrast, the vehicular traffic has undergone a spurt in increase necessitating the same. Due to increase in traffic volume, pavement constructed with conventional bitumen is getting damaged before the expected life time, resulting in permanent deformation, low temperature cracking, load associated fatigue, wear, stripping and aging. Under such circumstances the necessity has been arisen to upgrade the existing highway system to suit the changing trends. Permanent deformations, primarily in the form of ruts, are one of the basic asphalt pavement damages impairing its service properties. Vehicle wheel load acting on the pavement of a road may result in permanent deformation. Permanent deformations, primarily in the form of ruts in the form of imprints, tracks, corrugations, and shovings are one of the basic asphalt pavement damages impairing its service properties. Ruts are most dangerous because they might cause vehicles to skid during precipitation. Rut forming is connected with the process of accumulation of deformations of asphalt courses of the pavement resulting from frequent dynamic loads. What occurs then is pushing asphalt courses in wheel tracks. Application of appropriate asphalt mixtures and binder modification are effective methods for improving asphalt courses resistance. Since conventional binders failed to resist these damages, several researches have been done and the outcome was modified bitumen (Piotr Radziszewski, 27). IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 21

2 Coming to the scene of highway construction, particularly with reference to India, the total length of roads in India is 33 Lakhs kms and about 5% of this length is all weather roads with a large component made of flexible pavements. Almost all the flexible pavements constructed have used bitumen as pavement construction material. For a developing country like India pavements using bitumen are the most economical and best suited, since they permit phased construction. As the normal bitumens failed to resist damages, now a days modified bitumens are used for the construction of pavements. II. LITERATURE REVIEW In the previous chapter, a brief introduction has been given on necessity of modified bitumen s, types and Role of Modified bitumen s. Conventional bituminous materials have tended to perform satisfactorily in most highway pavement and airfield runway applications. However, in recent years, increased traffic levels, larger and heavier trucks, new axle designs and increased tire pressures, have added to the already severe demands of load and environment on the highway system. This increase in demand for transportation leading to the deterioration of pavements constructed with conventional bitumen in both ways i.e., Functionally and Structurally. To minimize the deterioration and, thereby, to increase the long-term durability of a flexible pavement, the bituminous layers should be improved with regard to performance-related properties, such as resistance to permanent deformation, low temperature cracking, load associated fatigue, wear, stripping and aging. One way of increasing the quality of a flexible material layer is the use of high quality bitumen. Furthermore, for certain applications, such as bridges, runways and surfaces with high traffic loading, special binders are urgently required. These examples suggest a potential area for bitumen modification. Bitumen modification offers one solution to overcome the deficiencies of bitumen and thereby improve the performance of asphalt mixtures. The performance of the modified bitumen depends upon the properties of the modifiers. While blending the modifier with bitumen Appropriate processing is chosen and controlled temperatures are maintained. Before the application of the modified bitumen for construction its performance should be thoroughly evaluated. Some of its evaluation parameters are its physical properties, stability, flow value, fatigue resistance, wearing, stripping property and ageing properties. In this present study parameters like physical properties, stability, flow value and fatigue resistance are taken as the evaluating criteria for the performance evaluation of the modified bituminous Concrete mixes like Crumb Shakir Shanthnavi and Bing Long (22) have evaluated the performance of CRMB as thin overlays and concluded that CRMB has advantages over unmodified binders in fatigue performance, deformation resistance, thermal cracking and moisture sensitivity, provided they are properly designed and constructed. They also opined that Mechanistic analysis is necessary and also that the laboratory fatigue and reflective cracking test results are to be considered in designing the thickness of the overlays. Takollou and Hicks (1988) have explained the concept of modification of bitumen with rubber. Based on the results of a laboratory study at Oregon State University and field performance of rubber modified asphalt mixes, they have reported that the rubber modified asphalt pavements have not failed in fatigue, more susceptible than conventional mixtures to problems in preparation and compaction and bitumen mix required reaches a certain minimum voids level for rubber modified mixes, which depends on rubber, rubber content and aggregates gradation. The difficulties expressed by them have been overcome in the course of time and Hot Mix using asphalt rubber was since developed in many ways. Palit, Sudhakar Reddy, Pandey (22) concluded that the crumb rubber modified mixes have higher resistance to permanent deformation when compared to straight run bitumen mixes. Palit, Sudhakar Reddy, Pandey (23), based on the laboratory development of CRMB using 8/ bitumen and 1% of waste tire crumbs, have reported that the CRMB has shown improved physical and rheological properties and the mix prepared using the said CRMB also exhibited improved properties. G. D. AIREY (24) has shown that, Laboratory simulative short and long-term ageing of the SBS, PMBs has shown differences in the rheological characteristics of the modified binders after ageing compared to those experienced for penetration grade bitumens. The high polymer content modified binders have shown some shift IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 211

3 towards more viscous behavior after ageing.gordon D. Airey (22), has shown that, the rheological properties of bitumens are improved by means of EVA polymer modification. Conventional penetration, softening point, ductility and high temperature viscosity tests have demonstrated the increased stiffness (hardness) and improved temperature susceptibility of the EVA PMBs. Fluorescent imaging, (Differential scanning calorimetry) DSC analysis and fundamental rheological testing have shown the considerable changes that can occur in the physical, chemical, morphological and rheological properties of different EVA PMBs as a function of polymer type, base bitumen type, polymer bitumen compatibility and polymer content. EVA polymer modification increases the temperature and frequency-dependent binder stiffness (complex modulus), binder elasticity (storage modulus) and elastic behavior (phase angle) with larger increases being experienced by the polymeric dominant PMBs III. STUDY METHODOLOGY In the previous chapter, a detailed overview regarding the various bitumen modifiers was discussed. Further specific Scope of the work, arrived at from the literature review, was also presented. Details regarding the proposed methodology for the present study are presented in this chapter. Present dissertation work was carried out in 5 stages as depicted in Figure 3.1 and the details are discussed below. Different Laboratory experiments are proposed to be conducted on all the pavement materials to find out the individual properties of the materials, as indicated below MORT & H (21) has specified two different aggregate gradations for Bituminous Concrete suitable for different thickness requirements. From that two grading s Grade I is chosen for the present study. It is proposed to conduct the Marshall s Mix design for Bituminous Concrete Grade I Specification, using selected Modified Bitumen. The outcome of this process will be used for further trials and also for comparative purposes at a later stage. Bitumen It is proposed to carryout Marshall s tests on bituminous concrete G I Specification. By the end of this stage, the Optimum Bitumen Content for each Modified Bituminous mix are obtained. Obtained Optimum Bitumen Contents are further going to be used in Stage V for the preparation of Wheel tracking sample. Marshall test results for different Modified Bitumens are obtained at this stage. Obtained results like Stability value, Density and Flow values are compared for modified bitumens. Bitumen with High Stability value and Density value are considered as better performing Bitumens. Wheel Tracking test samples will be prepared using Roller compactor using Modified Bituminous Concrete G I Mix, with the OBC obtained at Stage IV. These samples will be subjected to wheel tracking tests for a minimum of revolutions with calibrated wheel arrangement having contact pressure of 5.6 Kg/cm2. Rutting potentiality of modified bitumen mixes is compared with each other. The basic concepts of the Marshall Mix design method were originally developed by Bruce Marshall of the Mississippi Highway Department in U.S. Army Waterways Experiment station (WES) took the Marshall Stability Test and added a deformation measurement, using a flow meter. At first this test was recommended for adoption by the U.S. Army because: It was designed to stress the entire sample rather than just a portion of it. It facilitated rapid testing with minimal effort. It was compact, light and portable. It produced densities reasonably close to field densities. The Marshall test procedure has been standardized by the American Society for Testing and Materials. Procedures are given by ASTM D 1559 Resistance to plastic Floe of Bituminous Mixtures using Marshall Apparatus. AASHTO T245 Resistance to plastic Flow of Bituminous Mixtures using Marshall Apparatus agrees with ASTM D 1559 expect for provisions for mechanically operated hammer. AASHTO T245 suggests that instead of a hand operated hammer may be used provided it has been calibrated to give results comparable to the hand operated hammer. The marshal mix design method consists of 6 basic steps 1. Aggregate selection 2. Asphalt binder selection 3. Sample preparation IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 212

4 4. Stability determination using the Marshall stability and flow test 5. Density and void calculations 6. Optimum asphalt binder content selection Aggregate Evaluation A typical aggregate evaluation for use with Marshal mix design methods includes three basic steps. a) Determination aggregate physical properties: this consists of running various tests to determine properties such as: Toughness and abrasion Durability and soundness Cleanliness and deleterious materials Particle shape and surface texture b) Determination of other descriptive physical properties: if the aggregate is acceptable according to step 1, additional tests are run to fully characterize the aggregate. These tests determine: Gradation and size Specific gravity and absorption c) Blending calculations to achieve the mix design aggregate gradation: often, aggregates from more than one source or stockpile are used to obtain the final aggregate gradation used in a mix design. Trial blends of these different gradations are usually calculated until an acceptable final mix design gradation is achieved. Typical consideration for a trial blend include: All gradation specifications must be met. Typical specifications will require the percent retained by weight on particular sieve sizes to be within a certain band. The gradation should not be too close to the FHWA s.45 power maximum density curve. If it is, then the VMA is likely to be too low. Gradation should deviate from the FHWA s.45 power maximum density curve, especially on the 2.36 mm sieve. Sample Preparation The Marshall method, like other mix design methods, uses several trial aggregate asphalt binder blends each with a different asphalt binder content. Then, by evaluating each trail blend s performance, optimum asphalt binder content can be selected. In order for this concept to work, the trail blends must contain a range of asphalt contents both above and below the optimum asphalt content. Therefore, the first step in sample preparation is to estimate optimum asphalt content. Trail blend asphalt contents are then determined from this estimate. Sample asphalt binder contents: Based on the results of the optimum asphalt binder content estimate, samples are typically prepared at.5 percent weight of mix increments, with at least two samples above the estimated asphalt binder content and two below. Table 3.1: Typical Marshall Design Criteria Mix Criteria Compaction ( No of blows on each side) Stability (min.) Light traffic (<1 4 ESALs) Medium traffic ( EALs) Heavy traffic (> 1 6 EALs) N 3336 N 6672 N Flow (.25) Percent Air voids IV RESULTS General In the previous chapter, different stages involved in the proposed study methodology have been explained. Details regarding laboratory investigations made for all the materials in isolation as well as a mix along with the analysis have been presented in this chapter. Laboratory Investigations for Basic Material Properties It becomes imperative to test individual material properties before they are being used for preparing the Bituminous Concrete mix. All the individual materials viz: Aggregate, Bitumen and Plastic modified mixes were subjected to number of specified tests as per the relevant codes of practice. Aggregate Gradation The gradation of Aggregates, as per MORT & H specifications, used for BC G I mix is presented in Table 4. 1 IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 213

5 <.75 % Passing through sieves Table 4.1 Aggregate gradation for Bituminous Concrete G I as per MORT & Hspecifications S.N o Gradatio n I.S Sieves in mm Cumulativ e % by weight of Total aggregate passing Midpoin Aggregate grading curve for Bituminous Concrete G I mix has been shown in Figure 4.1. t gradatio n of passing % Midpoint gradation of cumulativ e retention <.75 4 % Total Figure 4.1 Gradation curve for Bituminous Concrete G I as per MORT & H In the present study aggregate gradation is taken according to MORT & H specification for Bituminous Concrete with slight changes in it which is shown in Table 4.2. Gradation curve for the altered gradation is shown in Figure 4.2 Table 4.2 Altered Aggregate gradation Sl.N o Gradation as per MORT & H specifications Sieve Size % Passing Sieve Size, mm Sieve Size Altered Gradation % Passin g % Retaine d <.7 >/ Total IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 214

6 Volume of Voids, % Density, gm/cc >/75 % Passing through Sieves Marshal Stability, Kgs Marshal Stability Vs % Binder Content % 4.5% 5.5% 6.5% Binder Content, % Sieve Size, mm Figure 4.4 Bitumen content Vs Marshall s stability CRMB 6 Figure 4.2. Altered Aggregate Gradation Curve Aggregate grading curve as per MORT & H specification and grading curve for altered aggregate grading has been shown in Fig Density Vs Binder Content, % 3.5% 4.5% 5.5% 6.5% Binder Content, % Figure 4.5 Bitumen content Vs G b CRMB 6 Figure 4.3 Gradation Curve for actual gradation as per MORT & H and Altered gradation for Bituminous Concrete G I Mix. Mix Design details for Bituminous Concrete G I for Crumb Rubber Modified Bitumen 6 grade from Shell company has been shown in Table 4.6. Table 4.6: BC Gr.I Mix Design details for CRMB 6 from Shell Bitumen Company Figure 4.4, 4.5, and 4.6 depict the variation of various mix properties with different bitumen quantities for CRMB 6 are presented Volume of Voids Vs % Binder Content 3.5% 4.5% 5.5% 6.5% Binder Content, % IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 215

7 Rut Depth (.1 mm) Rut Depth, (.1 mm) Deformation.1 mm Figure 4.6 Bitumen content Vs V v CRMB 6 Mix Design details for Bituminous Concrete G I for Polymer Modified Bitumen 7 grade from Shell company has been shown in Table 4.7. I. Rut Depth Model Rut depths observed on different types of the samples are presented in the shape of graphs along with its trend lines and with the equation of the each curve separately represented below y = 34.44x R² =.684 and the same is shown in the Figure 4.31.the equation of both the above curves are as fallows. BC G I Modified Mix for CRMB 6 (Shell Company): Y=2.71 X R= Square Value=.682 Where Y= Number of repetitions X = Vertical deformation y = 26.71x R² =.82 Number of Repetitions Figure 4.7: Rut depth for CRMB 6 Shell with trend line. Number of repetitions 35 y = 2.71x R² = y = 2.71x R² =.682 Figure4.9: Rut depth for PMB Shell with trend line. The trend of rut depth is taken as linear equation, taking most of its traveling path in to consideration and the same is shown in the Figure the equation of both the above curves are as fallows. BC G I Modified Mix for CRMB 6 (Shell Company): Y=26.71X R= Square Value=.82 Where Y= Number of repetitions X = Vertical deformation Number of repetitions Figure4.8: Rut depth for CRMB 6 with trend line. The trend of rut depth is taken as linear equation, taking most of its traveling path in to consideration IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 216

8 Revolutions Rut Depth (.1 m) y = 1.55x R² =.81 The trend of rut depth is taken as linear equation, taking most of its traveling path in to consideration and the same is shown in the Figure 4.34.the equation of both the above curves are as fallows. BC G I Modified Mix for CRMB 6 (Shell Company): Y=31.8 X R= Square Value=.967 Where Y= Number of repetitions X = Vertical deformation V. CONCLUSION Number of Repetitions Figure 4.1 Rut Depth for BC G I mix for SBS 4 Modified bitumen with trend line. The trend of rut depth is taken as linear equation, taking most of its traveling path in to consideration and the same is shown in the Figure the equation of both the above curves are as fallows. BC G I Modified Mix for CRMB 6 (Shell Company): Y=1.55 X R= Square Value=.81 Where Y= Number of repetitions X = Vertical deformation y = 31.8x R² =.967 Series1 Linear (Series1) Figure4.11: Rut depth for EVA 7 with trend line. Optimum Binder Content for Bituminous Concrete for Crumb Rubber and Polymer Modified mixes were found to be 4.8% and 5.1% respectively. The stability of Polymer Modified Mixes from Shell Company (2496 Kgs) when compared with other modified bitumens showed higher stability value which shows its better performance. When the density values of all the modified bitumens are compared PMB 7 has higher density value. Rutting potentiality of the SBS 4 modified mix was quite low when compared with the other modified Bituminous Concrete mix which shows better performance of SBS 4. When Coefficient of determination (R2) is compared for all the modified bituminous mixes EVA 7 has R2 value of.967 which shows the better correlation between deformation and repetitions. Generally range of R2 value lies between.8-1 for better correlating parameters.when parameters like Strength, density and rutting resistance are compared for all the modified bituminous mixes used in this study Polymer modified bitumens indicated better performance than Crumb Rubber Modified Bitumen. REFERENCES [ 1 ] Piotr Radziszewski (27), Modified asphalt mixtures resistance to permanent deformations, Journal of civil engineering and management, Vol XIII, No 4, ,Poland. [ 2 ] S. K. Palit; K. Sudhakar Reddy; and B. B. Pandey, (24), Laboratory Evaluation of rumb Rubber Modified Asphalt Mixes, IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 217

9 Journal of materials in civil engineering asce / january/february 24 / 45. [ 3 ] Bahia, H. U., and Davies, R. (1994), Effect of crumb rubber modifiers on performance related properties of asphalt binders. J. Assoc. Asphalt Paving Technol., St. Louis, 63, [ 4 ] G. D. Airey; T. M. Singleton; and A. C. Collop, (22), Properties of Polymer Modified Bitumen after Rubber-Bitumen Interaction, 344 / Journal of materials in civil engineering / july/august. [ 5 ] Airey, G. D. 1997, Rheological characteristics of polymer modified and aged bitumens. PhD thesis, Univ. of Nottingham, Nottingham,U.K. [ 6 ] Airey, G. D., and Brown, S. F. (1998), Rheological performance of aged polymer modified bitumens. J. Assoc. Asphalt Paving Technol.,67, 66. [ 7 ] American Association of State Highway and Transportation Officials AASHTO,a. (1994), Standard method of test for determining therheological properties of asphalt inders Dynamic Shear Rheometer~DSR AASHTO TP5, Washington, D.C. [ 8 ] X. Lu and U. lsacsson,(1997), Rheological characterization of styrene-butadiene- styrene copolymer modified bitumens, Construction and Building Materials, Vol. 11, No. 1, pp , 1997 [ 9 ] Gordon D. Airey(22), Rheological evaluation of ethylene vinyl acetate polymer modified bitumens Construction and Building Materials 16 (22) [ 1 ] Abdelaziz MAHREZ and Mohamed Rehan KARIM (23), Rheological evaluation of ageing properties of rubber Crumb Modified bitumen, Journal of the Eastern Asia Society for Transportation Studies, Vol.5, October. [ 11 ] Isacsson, U. and Lu, X. (1999), Characterization of bitumens modified with SEBS, EVA and EBA polymers, Journal of Materials Science 34, [ 12 ] Lu, X. and Isacsson, U. (1998) Chemical and rheological evaluation of ageing properties of SBS polymer modified bitumens. Elsevier Science Ltd, Fuel Vol. 77 Number 9/1, [ 13 ] Gordon D. Airey (23), Rheological properties of styrene butadiene styrene polymer a. modified road bitumens, / Fuel 82 (23) [ 14 ] Collins JH, Bouldin MG, Gelles R, Berker (1991)A. Improved performance of paving asphalts by polymer modification, J Assoc Asphalt Paving Technologists;6: [ 15 ] Perviz Ahmedzade *, Mehmet Yilmaz, (27), Effect of polyester resin additive on the properties of asphalt bindersand mixtures, Construction and Building Materials 22 (28) IJIRT INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 218