INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (IJCIET) International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6308 ISSN 0976 6308 (Print) ISSN 0976 6316(Online) Volume 4, Issue 2, March - April (2013), pp. 250-257 IAEME: www.iaeme.com/ijciet.asp Journal Impact Factor (2013): 5.3277 (Calculated by GISI) www.jifactor.com IJCIET IAEME RUTTING RESISTANCE OF FILLER MODIFIED BITUMINOUS CONCRETE SURFACES Dr. K.V.Krishna Reddy 1 Professor & Principal, Chilkur Balaji Institute of Technology, Hyderabad-75, AP, India ABSTRACT In the present study, an attempt is made to study the improvement in rut resistance of the conventional bituminous concrete by modification with fillers like fly ash, lime and crumb rubber. The study includes evaluation of the conventional and modified bituminous surface courses in the laboratory and with the Medium Scale Accelerated Pavement Rut Tester on a test track. The results found were encouraging with crumb rubber providing the maximum benefit. Key Words: Accelerated Pavement Testing, Rutting resistance, Filler modified bituminous concrete. 1. INTRODUCTION In recent years, highways have experienced an increase in the severity and extent of permanent deformation (rutting) in hot mix asphalt pavements. The increased rutting has been attributed to increase in axle loads and traffic volumes. Conventional flexible pavements have water bound macadam being used as the base course and granular material in the subbase, both of which are load distributing layers. They have good material properties and sufficient strength to transfer the loads coming from the top layers and need no replacement or additives except for strict quality control during construction, leaving the top surface course for modification for desired performance. In the present study, an attempt is made to evaluate the rutting resistance of the flexible pavements by improving the stiffness of the surface courses sufficiently to sustain the high stress states. The study includes evaluation of optimal quantities of fillers for bituminous concrete layer and conduct laboratory wheel tracking test along with field tests on the test track built for the purpose to evaluate the life benefit due surface modifications in various combinations using a Medium Scale Accelerated Pavement Rut Tester (Krishna Reddy.K.V, 2007) to evaluate the rutting resistance. 250
2. RESEARCH METHODOLOGY 2.1 Laboratory testing 80/100-penetration grade bitumen has been considered as basic material for the surface course. Aggregates with grade II specifications as per MORTH (Ministry of Road Transport and Highways) specification have been collected from local quarry. Basic material properties have been determined as per codal provisions. Laboratory tests, namely abrasion, attrition, impact value, shape and crushing value have been conducted on the aggregate and the properties of the same are reported in Table 1. Tests on bitumen, namely penetration, ductility, softening point, specific gravity and flash& fire point test have been conducted and the findings are as per Table 2. Table 1 Properties of aggregate used for surface course Property Value Property Value Specific gravity CA 2.79 FA 2.76 Abrasion value 24% Impact value 15% Attrition value 21% Crushing value 20% Shape test (EI+FI) Table 2 Properties of bitumen used for modification 13% Property Value Property Value Specific gravity 1.04 Ductility 100+ cm Penetration (in 0.1mm) 84.65 Flash point Fire point 270 0 C 315 0 C Softening point 47 0 C Viscosity 130 Sec Fly ash is procured from Ramagundam super thermal power plant, Hydrated lime of specific gravity 2.35 is procured locally. The filler is introduced as filler by replacing the finer fraction (<75micron) in the aggregate in terms of % by weight of aggregate. Crumb rubber obtained by grinding scrap pneumatic motor vehicle / truck tires is procured locally. Wet process of mixing crumb rubber was adopted, where in the crumb is added to the conventional bituminous binder by weight of bitumen before incorporating the same into the final mix. Crumb rubber is added to bitumen after heating the conventional 80/100-bitumen to a temperature of 163 0 C. Marshall Mix design using conventional materials was conducted on three samples each. The optimum bitumen content for conventional bituminous concrete mix is found to 4.3% for grade-ii aggregates. Further, optimum filler content in case of lime, fly ash and crumb rubber were evaluated by adding them at the optimum bitumen content obtained for the conventional bitumen The mix design values for conventional and modified mixes are as given in Table 3. 251
Table 3. Properties of conventional and modified bituminous mixes S. No Mix / Property Conventional mix Crumb modified mix Fly ash modified mix Lime modified mix 1 Optimum Bitumen / filler content 4.3% (Bitumen) 11.8% 2.30% 2.80% 2 MSV (Kg) 1300 2405 1505 2650 3 Air voids (%) 4 Flow value (mm) 5 Bulk density (g/cc) 3.875 3.425 4.5 4.05 2.375 3.750 3.38 3.5 2.520 2.470 2.43 2.446 2.2 Equipment used Laboratory wheel tracking test is used in the laboratory to evaluate the rutting resistance of the conventional and filler modified bituminous concrete samples. The medium scale accelerated pavement rut tester (MAPRT) is used to conduct field tests operating on a circular track. This equipment can be used to evaluate the performance of the pavements in terms of rut depth. The lab and field equipments used are as shown in the Fig. 1(a) and (b). Fig.1 (a) Laboratory wheel-tracking test Fig.1 (b) Medium scale accelerated rut tester 252
2.3 Test Track Layout and Design A test track of the flexible pavement was considered to study the performance and life benefit of stabilization in four combinations as depicted in the pavement lay out shown in Fig.2. The design of the test track was done to ensure that the stresses reach the subgrade. FPAVE program was used to determine the stresses reaching the subgrade. Since, the wheel considered distributes load over a circular area of radius 2.82cm, to ensure that the stresses reach the subgrade and facilitate the testing of subgrade and surface in combination, a pavement with 40mm thick bituminous concrete, 75mm of WBM base course and 100 mm of subbase course was prepared. This pavement system is similar to the full-scale pavements in terms of stresses reaching the subgrade under full-scale wheel loads. 1.2m 3.6m 1.2m Section 1 Section 2 Section 3 Arm of the accelerated testing facility 2m Section 4 Section 5 Section 6 2m Fly ash modified bituminous surface 1 & 3 2 4 & 6 5 Crumb modified bituminous surface Gravel subgrade Lime modified bituminous surface Subbase + Base Conventional Bituminous surface Fig.2 Test track Layout 3. DATA ANALYSIS The results obtained are plotted with number of wheel load repetitions on x -axis and rut depth on y-axis as shown in the Fig.3 for laboratory testing and Fig 4 for test track testing using medium scale pavement rut tester. 253
4000.00 graph Type Model predicted R-square 1 Conventional surface Y = 0.0129763 * X + 69.3329 0.999333 R u t de pth in 0.0 1m m 2000.00 2 Flyash modified surface Y = 0.0106765 * X + -28.1223 0.999591 3 Lime Modified Surface Y = 0.011543 * X + -57.2172 0.999831 4 Crumb Modified Surface Y = 0.00789102 * X + 24.6849 0.999647 1 2 3 4 0.00 0.00 50000.00 100000.00 150000.00 200000.00 250000.00 300000.00 No. of revolutions Fig 3. Figure showing rut life of the bituminous mixes in terms of wheel load repetitions in lab 3000.00 1 2 3 4 Rut depth in 0.01mm 2000.00 1000.00 Graph Type of pavment Equation R-sqr 1 Conventional surface log(y) = 0.396119 * log(x) + 3.16338 0.996853 2 Flyash modified surface log(y) = 0.468024 * log(x) + 2.27849 0.979371 3 Lime modified Surface log(y) = 0.516154 * log(x) + 1.65014 0.986836 4 Crumb modified surface log(y) = 0.588003 * log(x) + 0.725106 0.971563 0.00 0.00 40000.00 80000.00 120000.00 160000.00 200000.00 240000.00 No of repetitions Fig 4. Figure showing rut life of the bituminous mixes in terms of wheel load repetitions with MAPRT 4. RESULTS The plots are interpreted and the results are tabulated in the tables 4 and 5. Table 4 depicts the no of wheel load repetitions sustained by the conventional and filler modified bituminous concrete materials under the laboratory wheel tracking test on laboratory samples and under the medium scale accelerated pavement rut tester on the test track. Table 5 presents the rut life benefit of the filler modified bituminous concrete materials in comparison to the conventional bituminous concrete material. 254
Table 2 Rut Life of pavement in terms of repetitions of wheel load S. No Type of Bituminous Surface No of repetitions at a rut depth of 25.4mm Wheel tracking test Medium Scale Accelerated Pavement Rut Tester 1 Conventional 190000 132000 2 Flyash modified 225000 152027 3 Lime modified 240000 160000 4 Crumb modified 322000 208000 S. No Table 3 Rut Life benefit of pavements with fillers compared to Conventional pavement Type of Bituminous Surface Wheel tracking test Life Benefit Ratio Medium Scale Accelerated Pavement Rut Tester 1 Fly ash modified 18.42% 15.1% 2 Lime modified 26.30% 21.2% 3 Crumb modified 69.47% 57.5% 5. ACKNOWLEDGEMENT At the outset the author would thank the Head, CED and TE division, and other professors at NIT Warangal for their valuable guidance and encouragement during experimentation. 6. CONCLUSION 1) 11.8% crumb addition by weight of bitumen through wet process to 80/100 bitumen and grade II aggregates gave optimum mix design values for bituminous concrete with a Marshall Stability value or 2405kg and 3.42% Air voids. 2) 2.3% Flyash replacement by weight of aggregate has resulted in optimum mix design values for bituminous concrete with a Marshall Stability value of 1505kg and 4.5% Air voids 3) 2.8% Hydraulic lime replacement by weight of aggregate has resulted in optimum mix design values for bituminous concrete with a Marshall Stability value of 2650kg and 4.05% Air voids 4) Medium Scale Accelerated Pavement Rut Testing represent an ideal case for pavement testing unlike laboratory wheel tracking tests, where in the pavement moves under a standard wheel. The laboratory results are conservative than the field results by 50% and hence laboratory results does not depict the actual rut life when done on individual samples to evaluate the rut resistance. 255
5) The average rut life improvement of crumb modified bituminous surface is 57% compared to conventional bituminous concrete 6) The average rut life improvement of Lime modified bituminous surface is 21% compared to conventional bituminous concrete 7) The average rut life improvement of Crumb modified bituminous surface is 57% compared to conventional bituminous concrete REFERENCES 1. Aschenbrener, T., R. Terrel, and R. Zamora. (1994), Comparison of the Hamburg Wheel-Tracking Device and the Environmental Conditioning System to Pavements of known Stripping Performance Rep.No.CDOT-DTD-R-94-1, Colorado Department of Transportation, Denver, CO. 2. Aschenbrener, T. (1994), Comparison of Test Results from Laboratory and Field Compacted Samples - Final Report Rep. No. CDOT-DTD-R-94-3, Colorado Department of Transportation, Denver, CO 3. Aschenbrener, T. (1995), Evaluation of the Hamburg Wheel-Tracking Device to Predict Moisture Damage in Hot-Mix Asphalt TRR- 1492, TRB, Washington, DC, pp. 193-201. 4. Albritton, G.E., and Gatlin, G.R. (1996), Construction and Testing of crumb Rubber Modified Hot Mix Asphalt Pavement, Rep. No. FHWA/MS-DOT-RD-96-115, Washington D.C. 5. Carl W. Lubold, Jr. (2001), Are u in a Rut?, Pro. Moving forward, The Pennsylvania Local Road Program, Pennsylvania, Vol. 19, No.2, pp4-5. 6. Cockrell, C. F. and Leonard, J. W., (1970), Characterization and Utilization Studies of Limestone Modified Flyash, Coal Research Bureau, Vol. 60. 7. Collins, R. J., and Ciesielski, S. K. (1992), Highway Construction use of wastes and By-products Utilization of Waste Materials in Civil Engineering Construction, Published by ASCE, New York, pp.140-152 8. Durga Prasad, K. (2002), A study of lime and fly ash on the performance of bituminous concrete mix, Mtech thesis, NITW. 9. FPAVE, Software program for Analysis and Design of Flexible Pavements, Transportation Engineering Section, Civil Engineering Department, IIT, Kharagpur. 10. Izzo, R.P., and Tahmoressi, M. (1999), Use of the Hamburg Wheel Tracking Device for Evaluating Moisture Susceptibility of Hot-Mix Asphalt, TRR-1681, TRB, pp 76-85. 11. Jorgenson, L. (2003), Tires make the road - asphalt rubber pavement construction, Public Works Journal, Vol. 134, No. 1, pp 30-31. 12. MORT&H - 2001: Specifications for Roads and Bridge works, Ministry of Road Transportation and Highways. 13. Krishna Reddy,KV, 2007, Medium Scale Accelerated Pavement Rut Tester, Indian Highways, Indian Roads Congress, New Delhi, Vol 35, No.12, PP 23-30 14. Metcalf, J. B. (1996), Application of Full-Scale Accelerated Pavement Testing, NCHRP Synthesis of Highway Practice, Rep. No. 235, National Research Council, TRB, Washington D.C. 15. Quintus Von, H.L. (2001), Hot-Mix Asphalt Layer Thickness Design for Longer-Life Bituminous Pavements, Transportation Research Circular, No. 503. 256
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