Dec 12, 2014 - Recent Indian Road Congress standard (IRC: 37-2002) focus for use of harder grade bitumen for better performance. Therefore, an attempt is ...
Available online at www.sciencedirect.com
ScienceDirect Transportation Research Procedia 17 (2016) 349 – 358
11th Transportation Planning and Implementation Methodologies for Developing Countries, TPMDC 2014, 10-12 December 2014, Mumbai, India
Characterization of Bituminous Mixes Containing Harder Grade Bitumen Siksha Swaroopa Kara, Khusboo Arorab, ChandraKant Manib & Dr P K Jainc
* a Scientist, CSIR-Central Road Research Institute, New Delhi-110025 Project Fellow, CSIR-Central Road Research Institute, New Delhi-110025 c Chief Scientist, CSIR-Central Road Research Institute, New Delhi-110025 b
Abstract
IS:73-2013 specified four grades of bitumen such as VG-10, VG-20, VG-30 and VG-40. Indian refineries are producing only two grades of paving bitumen such as VG-10 and VG-30, which are not adequate for prevailing climate and traffic conditions of India. Recent Indian Road Congress standard (IRC: 37-2002) focus for use of harder grade bitumen for better performance. Therefore, an attempt is made to develop harder grade bitumen by an alternate method to meet the demand of the highway profession. This study deals with laboratory evaluation of binder for SHRP performance characteristics and study of analytical properties of the mixes prepared by new harder grade bitumen. Results of indirect tensile strength, indirect tensile strength ratio, static creep, rutting and resilient modulus are reported in this paper. Results indicate superior performance characteristics of new binder names as VG 50 grade which meets requirement of PG-76-22 as specified in SHRP performance based specification. It is also observed from test results of mixes that thinner layer of bituminous binder course may be serve the intended purpose if VG 50 grade bitumen is used.
© 2015 2016The TheAuthors.Published Authors. Published by Elsevier © by Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Selection and peer-review under responsibility of the Department of Civil Engineering, Indian Institute of Technology Bombay. Peer-review under responsibility of the Department of Civil Engineering, Indian Institute of Technology Bombay
* Corresponding author. Tel.: 9999411171. E-mail sikshaswaroopa2gmail.com
2352-1465 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Department of Civil Engineering, Indian Institute of Technology Bombay doi:10.1016/j.trpro.2016.11.123
350
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 Keywords:High Grade Bitumen, Complex Modulous and SHRP
1.
Introduction
India is currently at a critical juncture in the history of infrastructure developments since independence, as road construction and developmental activities are at the peak. Intensive and high value road construction programs/schemes, under the aegis of National Highways Authority of India, National Rural Roads Development Agency, Ministry of Road Transport and Highways, State Public Works Departments, Ministry of Urban Development and Ministry of Rural Development are currently under various stages of implementation. Flexible pavements with bituminous surfacings are the most preferred and commonly used construction in India, because of their lower construction cost and possibility of their up gradation through stage construction. Due to shortage of material, high performance mixes are needed for different projects. Bitumen is a complex material produced from crude oil; this complexity is due to the fact that bitumen comprises numerous hydrocarbon species (Guern et al 2010 and Speight 1999). It is composed of asphaltene micelles (solid asphaltene particles covered by a shell of resins) dispersed in a liquid phase, constituted of the remaining resins, along with aromatics and saturates (Lesueur et al 1996 and Lesueur et al. 2009). Temperature and chemical composition exert a very strong effect on the microstructure of bitumen and physical properties. The quality of bitumen to be used in India is required to conform to IS:73:2012. India consumes more than five million tons of paving bitumen in a year. Bitumen is used as binder for production of bituminous mixes for road construction. Harder grade bitumen is used in highly stressed areas such as intersections, roads near toll booths and truck parking lots. Due to its higher viscosity, stiffer bitumen mixes can be produced to improve resistance to shoving and other problems associated with higher temperature and heavy traffic loads. Therefore, attempts is made to develop harder grade bitumen by alternate method to meet the requirement of the Industry. A laboratory investigation was undertaken for paving grade bitumen from different sources to determine their quality and performance. The distress such as rutting can be predicted by analysis of the rheological characteristics and performance testing of bituminous binders (Roberts et al. 1996 and Soleymani et al.2004). Studies have already completed on development of harder grade bitumen and on its rheological properties to address performance parameters such as safety, workability, rutting, thermal cracking and fatigue cracking (Arora et al.2014). The objective of this study is evaluation of laboratory performance of the mixes prepared by newly developed harder bitumen and their implications on thickness of bituminous layers. 2. Experimental Study 2.1 Materials Harder grade bitumen was developed by blending softer grade bitumen(VG-10) and a specific vacuum residue (VR). VG-10 was used as feed stock in this study . Properties of VG-10 and VR are given in Table 1 and 2 respectively. The mineral aggregate was obtained from a local quarry and the results of the various tests conducted on the aggregates are reported in Table 3. Table 1: Properties of bitumen (VG 10) used in the present study
Properties Penetration, 0.1mm, (25°C, 100 g, 5s)
Test Method IS 1203
Value 81
Specified value (IS:73:2013) 80(Min.)
Softening point (Ring and Ball), °C
IS 1205
44
40(Min.)
Ductility at 25°C ,cm Specific gravity , g/cc at 25̊C
IS 1208 IS 1202
100+ 1.001
75(Min.) 0.99 (Min)
Viscosity at 60°C,Poise Viscosity at 135°C, cSt
IS 1206 IS 1206
1150 400
800-1200 250(Min.)
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 Table 2: Properties of VR
Properties
Test Method
Value
Penetration, (25°C, 100 g, 5s), 0.1 mm
IS 1203
10
Softening point (Ring and Ball), °C
IS 1205
62
G*/sinδ at 82°C,kPa
ASTM D 7175
2.19
Viscosity at 135°C, cSt
IS 1206
1350
Table 3. Properties of mineral aggregates
Properties
Test Method
Value
Aggregate Impact Value, %
IS 2386 (Part IV)
22
MoRTH ,2001 Specifications 30 max
Water Absorption Value, %
IS 2386 (Part III)
0.7
2 max
Specific Gravity
IS 2386 (Part II)
2.66
2.5-3.0
Combined (EI + FI) Index, %
IS 2386 (Part I)
26
30 max
Stripping, % Min retained coating
IS 6241
98
95
El: Elongation Index
FI: Flakiness Index
3. Methods 3.1 Preparation of harder grade bitumen VG 10 bitumen was heated to a temperature of 160°C in a glass beaker and VR heated to a temperature of 180°C was then added to the melted VG 10 bitumen. VG 10 and VR were blended together in the ratio of 52:48. Contents were then blended by high shear stirrer at specific rpm for 2 hrs at a temperature of 160°C till a homogenous blend was obtained. The properties of the available and new harder grade bitumen are given in Table 4 and Table 5 respectively. The new harder grade blend is designated as HGB(VG:30) in the present study and this binder is meeting tentative requirement of SHRP specifications for performance grade bitumen.
351
352
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358
Table 4 Properties of available harder grade bitumen
Properties Penetration, 0.1mm, (25°C, 100 g, 5s)
Test Method IS 1203
VG-30 47
VG-40 42
Softening point (Ring and Ball), °C
IS 1205
50.6
54
Viscosity at 60°C, Poise
IS 1206
3230
4325
Viscosity at 135°C, cSt
IS 1206
525
625
Fail Temp,°C Unaged(G*/sinδ=1.0kPa)
ASTM D 7175
70
73
Fail Temp,°C aged(RTFOT)(G*/sinδ=2.2kPa)
ASTM D 7175
72
74
Fail Temp,°C aged(RTFOT)(G*.sinδ=5000kPa)
ASTM D 7175
18
20
Bending Beam Rheometer Test, Temp ̊C
ASTM D 6648
-14
-13
Table 5: Properties of new harder grade bitumen(HGB)
Properties
Test Method
Value
Penetration, 0.1mm, (25°C, 100 g, 5s)
IS 1203
25
Limits Tentative 20-40
Softening point (Ring and Ball), °C
IS 1205
56
55 min
Viscosity at 60°C, Poise
IS 1206
5027
5000±1000
Viscosity at 135°C, cSt
IS 1206
645
750 cSt max
Fail Temp,°C Unaged(G*/sinδ=1.0kPa)* Fail Temp,°C aged(RTFOT)(G*/sinδ=2.2kPa)*
ASTM D 7175
76
76C min
ASTM D 7175
77
76C max
* SHRP PG-76-22 specification 3.2 Design of Mixture Grading of aggregate as per specification of Ministry of Road Transport and Highways Specification (MoRTHS, 2001) used for design of 50 mm thick dense bituminous macadam is given in Table 6. For the preparation of bituminous mixtures, aggregate was heated to 160 ºC in a pan for about 30minutes and requisite quantity of bitumen at 174̊ C was then added to heated aggregate. Then bitumen is added (at optimum bitumen content of 4.6% by weight of aggregates). The designed DBM mixes were prepared in a laboratory mixer. Samples were prepared using the
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 Marshall method (ASTM D 1559) by application of 75 blows on both faces. The properties of the designed DBM mixture are given in Table 7. Table 6: Gradation of DBM Mixes
Sieve Size mm
Cumulative % passing
Specified Grading
37.5
100
100
26.5
95
90-100
19
83
71-95
13.2
68
56-80
4.75
46
38-54
2.36
35
25-42
0.3
14
21-42
0.075
5
2-8
Table 7: Properties of Mix at optimum bitumen content
Properties
Method
DBM
Bulk Density, g/cm3
ASTMD2726
2.43
Air Voids, %
ASTMD3203
3.91
Bitumen Content, %
ASTMD 3203
4.6
Marshall Stability kN, 60ºC
ASTMD 1559
21.25
Marshall Flow, mm at 60ºC
ASTMD 1559
3.2
Marshall Quotient,kN/mm
Stability/Flow
6.64
Tensile Strength Ratio,%
ASTM D 1075
81.74
Stiffness Modulus MPa, 35ºC
ASTM D 4123
2868
3.3 Testing of mixes
3.3.1 Indirect tensile strength (ITS) test Indirect tensile strength test is useful to evaluate resistance of compacted bituminous mixture to cracking as well as sensitivity of mixture to moisture damage. To identify whether the coating of bitumen binder and aggregate is susceptible to moisture damage, Tensile Strength Ratio (TSR) is determined according to AASHTO T 283. TSR is the ratio of average indirect tensile strength of conditioned specimens to the indirect tensile strength of unconditioned specimens. The conditioned specimens (set of three specimens) were placed in a water bath maintained at 60°C for 24 hours and then placed in an environmental chamber maintained at 25°C for two hours. These conditioned specimens were tested for their tensile strength. The failure load was recorded and the indirect tensile strength ( St ) was calculated using following Equation (1) ݏ௧ ൌ
ʹܲ ሺͳሻ ߨ݀ݐ
353
354
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 Where, P is the load (kg), d is the diameter in cm of the specimen; t is the thickness of the specimen in cm. The Tensile Strength Ratio (TSR) of specimen was computed by considering Equation (2). ܵ௧ ൰ ͲͲͳ כሺʹሻ ܵ௧௨ Where TSR is tensile strength ratio ܵ௧ average indirect tensile strength of conditioned specimens and ܵ௧௨ is indirect tensile strength of unconditioned specimen ܴܶܵ ൌ ൬
3.3.2 Resistance to deformation The aspect of deformation at high temperature has been investigated by conducting rutting and creep tests. (a) Rut depth studies by wheel tracking test Rutting is an important parameter for evaluation of performance of a bituminous mixture. To check the rutting resistance of the DBM mixtures, tests were performed using a Wheel Tracking Device (WTD), which is a destructive test and involves direct contact between the loaded wheel and the rectangular test specimens. The test was conducted on prepared slab specimens of 300*300*50 mm at optimum binder content. The test was conducted as per BS: 5981998. The test applied 20,000 passes at 45 °C and resulting rut depth was measured. (b) Creep Test In the Dynamic creep test, an axial load is applied dynamically to the test specimen throughout the duration of the test. The Dynamic creep test was performed on Universal Testing Facility (UTM). The test was conducted as per NCHRP 9-19 (unconfined). During the test, a cyclic stress of 69 kPa was applied with a seating stress of 11 kPa and haversine pulse is applied with loading width of 0.1 s followed by a rest period of 0.9 s. A maximum of 10000 load cycles were applied and accumulated permanent strain was recorded. 3.3.3 Resilient modulus (MR) test Resilient Modulus (M R) is one of the most important mechanistic properties of bituminous mixtures. To check the effect of binder rheology on the resilient modulus values at different temperatures, the repeated loading indirect tensile test on compacted bituminous mixtures was performed as per ASTM D-4123. The test was conducted by applying the compressive load in the form of haversine wave at 25°, 35°, and 45°C for three DBM mixtures containing VG-30,VG 40 and Harder grade. The specimens were conditioned for 5 hr in the environmental chamber at the given temperature and then subjected to repeated loading pulse width of 100 ms, and pulse repetition period of 1000 ms. 4.
Results and Discussion
4.1 Properties of Harder Grade Bitumen Rheology, by definition, involves the study of the flow properties of time and temperature dependent visco-elastic materials, such as bitumen, that are stressed (usually under shear stress or extensional stress) through the application of force (Bernes 1989, Aiery et al 1997, Saley et al. 2007). In Table 7 storage modulus (G’) and the complex modulus (G*) are shown at 600C. HGB shows higher value of G*/sinδ compared to available harder grade binder. This indicates that the stiffness of the HGB is high compared to available VG 30 bitumen. As previously mentioned, G* is measure for overall resistance of the binder to flow, while G’ is an indicator how much binder can recover after having been loaded. Hence good rutting resistance is expected if both G* and G’ are large. From Table 8, it can be seen that harder grade bitumen has 3.3 and 6.4 times higher values of complex modulus and storage modulus respectively showing higher rutting resistance over the base binder.
355
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358
Table 8 G*, G*/sinδ and G’ value at 60 0C
Binder Type VG-10 VG-30 VG-40 HGB
G* (kPa) 2.24 4.96 5.14 7.61
G' (kPa) 0.14 0.33 0.49 0.89
4.2 Tensile Strength Ratio (TSR) Results of tensile strength and TSR of VG 30 and harder grade bitumen are given in Table 9 and plotted in Figure 1. Results indicate that tensile strength of harder grade bitumen is much higher than VG 30 bitumen. TSR values of VG 30 and Harder Grade Bitumen are 85 and 81.7% respectively. The tensile strength ratio values are found greater than 80 percent indicating acceptable resistance to moisture damage for bituminous mixtures and containing harder grade bitumen. Table 9 Results of Dry Tensile strength, Wet Tensile strength and TSR.
Binder content type
Average tensile strength of the conditioned sample(Mpa)
Average tensile strength of the dry sample(Mpa)
TSR(%)
VG-10 VG-30 HGB
0.783 0.809 0.860
0.652 0.948 1.052
83 84 82
Indirect Tensile Strength Ratio
86 85 84 83 82 81 80 VG-30
Harder grade
Bituminous Mixes Figure 1 Tensile strength Ratio of Bituminous Mixes
4.3 Dynamic Creep Test
356
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 The test was conducted with harder grade bitumen at different temperatures such as 350C and 450C and the results for the total permanent strain (%) are plotted in Fig.2. Significant creep deformation is lower at temperature 350C compared to higher temperature. Total permanent deformation at 350C and 450C are 0.28 and 0.41 respectively. Similarly deformation is lower for HGB compared to VG 30. Total permanent deformation after 3600 cycles are given in Table 10 for VG 30 and HGB. Table 10 Dynamic Creep results of harder grade bitumen and VG 30 at different temperature Binder content type HGB VG 30
Temperatures 350C 450C 0.28 0.41 0.37 0.52
0.45
Total permanent straion,%
0.4 0.35 0.3 0.25 Creep at 35C
0.2
Creep at 45C
0.15 0.1 0.05 0 0
1000
2000
3000
4000
No. of Cycles
Fig.2 Dynamic Creep results of harder grade bitumen at different temperature
4.4 Resilient Modulus Test (MR) Results of the test conducted by applying the compressive load in the form of haversine wave at 25°C, 35°C and 45 °C for VG 30 and new Harder Grade Bitumen are given in Table 11. At 350C, MR value for harder grade bitumen is nearly 2.9 times higher than the VG 30. Resilient modulus values of harder grade bitumen are found higher than the conventional VG 30 bitumen at the temperature range of 25°C to 45°C. Higher values of resilient modulus values indicate that they are resistance to rutting at high pavement temperature. These findings indicate that higher grade bitumen are substitute for better performance of bituminous base course and their thickness can also be reduced. Table 11 Resilient Modulus Values of different grade and HGB at different temperature
Temperature (0C) 25 35
VG 10 4210 811
VG 20 8046 1282
VG 30 9651 1789
VG 40 12847 2584
HGB 12900 3280
357
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 45
433
468
700
825
900
4.5 Rut Depth Studies The rut depths of different DBM mixtures are given in Table 12. It can be seen from the data given in Table 10 that rutting is high in case of VG 30 compared to Harder Grade Bitumen. Table-12 Rut Depth Results
Bitumen Type HGB VG-30 VG 10
Rutting(in mm) after 20,000 cycles 4.0 4.8 6.2
4.6 Effect of Harder Grade bitumen on thickness design IRC:37-2012 specify guidelines for design of flexible pavement layers. For a compacted soil of CBR 8 projected traffic of 150 msa and design life of 20 years, the computed thickness of pavement are 200 mm GSB, 250 mm WMM, 135 mm DBM and 50 mm BC. The values of εt and εc are given in Table 13:
Table 13 The values of εt and εc are as under:
Bitumen Grade
MR
εt
εc
VG 20 VG 30 VG 40 HGB
1400 1700 2300 3300
231 210 180 147
307 294 273 248
Thickness DBM(mm) 135 125 115 105
of
The thickness of DBM may be reduced upto 30 mm using VG 50(PG-76-22) bitumen based upon pavement analysis by IIT Pave. 5
Conclusion
The following conclusions are drawn from the study. i. Results indicate that harder grade bitumen can be prepared by blending VG 10 and vacuum residue. ii. Harder Garde Bitumen shows higher resistance to rutting at high temperature showing higher value of resilient modulous. At 350C, MR value for harder grade bitumen is nearly 2.9 times higher than the conventional VG 30. iii. Performance studies results indicate that higher grade bitumen is substitute for better performance of bituminous base course.
Acknowledgements The authors would like to thank Dr. S. Gangopadhyaya Director CSIR-Central Road Research Institute, NewDelhi for
358
Siksha Swaroopa Kar et al. / Transportation Research Procedia 17 (2016) 349 – 358 permission to publish this paper. References Airey, G.D. Rheological Characteristics of Polymer Modified and Aged Bitumens. PhD Thesis, the University of Nottingham, 1997. 2Barnes, H.A., Hutton, J.F. and Walters, K. An Introduction to Rheology, Volume 3. Netherland; Elsevier Science Publishers, B.V., 1989. KhusbooArora, Siksha Swaroopa Kar, Dr P K Jain “Effect of Vacuum Residue on Rheological Properties of Low Viscosity Bituminous Binders” IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE), Volume 11, Issue 2 Ver. I (Mar- Apr. 2014). Lesueur, D.; Gerard, J. F.; Claudy, P.; Letoffe, J. M.; Planche, J. P.;Martin, D. A structure-related model to describe asphalt linear viscoelasticity.J. Rheol. 1996, 40, 813. Lesueur, D. The colloidal structure of bitumen: Consequences on the rheology and on the mechanisms of bitumen modification. AdV. Colloid Interface Sci. 2009, 145, 42. M. Le Guern ,*, E. Chailleux , F. Farcas , S. Dreessen and I. Mabille “Physico-chemical analysis of five hard bitumens: Identification of chemical species and molecular organization before and after artificial aging” Fuel 89 (2010) 3330–3339 Roberts, F. L., P. S. Kandhal, D. Lee, and T. W. Kennedy. 1996. “Hot Mix Asphalt Materials, Mixture, Design, and Construction,” 2nd Edition, Napa Education Foundation, Lanham, Maryland (USA). Saleh, F.M. Effect of Rheology on the Bitumen Foam-ability and Mechanical Properties of Foam Bitumen Stabilised Mixes. International Journal of Pavement Engineering, Vol. 8 (2), pp. 99–110, 2007. Speight JG. The chemistry and technology of petroleum. 3rd ed. New York: Marcel Dekker; 1999. Soleymani, H. R., H. Zhai, and H. Bahia. 2004. “Role of Modified Binders in Rheology and Damage Resistance Behavior of Asphalt Mixtures,” Transportation Research Record: Journal of Transportation Research Board, No. 1875, TRB, National Research Council, Washington, D.C. (USA). 70-79.
