Multigrade bitumen verses conventional bitumen

Transcription

1 Journal of Scientific & Industrial JAIN Research et al: MULTIGRADE BITUMEN VERSES CONVENTIONAL BITUMEN 37 Vol. 67, April 8, pp Multigrade bitumen verses conventional bitumen M C Jain*, R S Negi, A Krishna and B R Tyagi IndianOil Corporation Limited (IOCL), Research and Development Centre, Sector 13, Faridabad 11 6 Received 9 May 7; revised 17 January 8; accepted 7 February 8 To evaluate field performance at hot and cold climatic regions, test tracks were laid using multigrade bitumen (MB) and conventional bitumen (CB) following cm thick premix carpet, mix seal surfacing, semi-dense bituminous concrete and dense bituminous concrete road specifications at hot climatic region of Jaisalmer (Rajasthan) in May 6 and cold climatic region of Drass, Kargil (J&K) in September 5. Laboratory test results indicate that MB (softer grade) behaves better than bitumen 8/1 at low temperatures and better/comparable with bitumen 6/7 at high temperatures. MB has been characterized for conventional, mechanical properties and Strategic Highway Research Programme (SHRP) protocol. Field trial indicates that performance of MB is superior to CB in both cold and hot climatic regions. Keywords: Bitumen, Field performance, Marshall Stability, Multigrade bitumen, Performance grading Introduction To combat with rutting in hot climatic region and cracking in cold climatic region, Shell International Petroleum Company Ltd developed multigrade bitumen 1 (MB). Shell Research Laboratory reported that by using MB, pavement life can be extended by %. MB is purely crude-based and performs better over a wider temperature range compared to conventional bitumen (CB). MB exhibits better rutting resistance (RR) at high temperature and better resistance toward the low temperature cracking in comparison to CB. In addition to this, MB are elastic enough to withstand fatigue at normal / intermittent temperatures. Thus, MB possesses characteristic advantages of both softer grade and harder grade bitumen. IndianOil developed and patented the technology for manufacture of MB 3 and manufactured million tonnes MB (softer grade) in one of its refinery for market seeding and field performance evaluation in hot and cold climatic regions. In present paper, a comparative study has been made between CB (8/1 and 6/7 grades) and MB (softer and harder grades), which has been characterized by conventional and Strategic Highway Research Programme (SHRP) test methods, and field trials conducted at Drass, Kargil (J&K) at low temperature *Author for correspondence jainmc@iocrd.co.in region and Jaisalmer (Rajasthan) at high temperature region. Materials and Methods CB 8/1 and 6/7 grades were collected from Mathura Refinery. MB-softer grade, was scaledup in one of its refinery by using patented technology of IndianOil R&D 3 whereas MB-harder grade () was prepared at IndianOil, R&D using self-designed MB- Pilot plant. Both MB are purely crude based and prepared from different refinery streams by optimizing experimental conditions using Biturox type reactor without adding any additive / chemical. At present, BIS specification for MB is under consideration whereas CB meet IS: Both CB and MB were RTFO-aged and PAV-aged following ASTM D-87-6 and ASTM D-651- methods 7, respectively. Bitumen under study, were subjected to super pave protocol (high and low temperature grading) for studying high temperature stiffness property using Paar Physica Dynamic Shear Rheometer (DSR), model MCR-3 supplied by M/s Anton Paar Physica Messtechnik, GmbH and low temperature rheological property using Cannon Bending Beam Rheometer (BBR), model no TE-BBR-F, supplied by M/s Cannon Instrument Company, USA and Instron Direct Tension Tester (DTT), model 555, supplied by M/s Instron Corporation, USA. Apparent viscosity

2 38 J SCI IND RES VOL 67 APRIL 8 measurements were taken using Thermo Haake Rotational Viscometer, model Roto Visco-1, supplied by M/s Thermo Haake, Germany at 135 C. Results and Discussion Penetration number of all conventional and nonconventional bitumen decreases after RTFO and PAV tests (Table 1). Reduction in penetration values from un-aged bitumen has been found for RTFO-aged bitumen (33-38%) and for PAV-aged bitumen (59-6 %). Softening points of both CB and MB have increased in RTFO-aged (9.-1.5%) and PAV-aged bitumen (6.-35.%). Elastic recovery of 5% for and 31% for has been found higher in comparison to that of CB (8/1 grade, 17%; 6/7 grade, %), indicating that MB are more flexible and less prone to pavement deformation than CB at lower temperature. FRAAS breaking point -19 for MB ( and -16 for has been found lower than that of CB (8/1, -1 and 6/7, -9), indicating that MB are more flexible and possess higher resistance towards fatigue and low temperature cracking than CB.Larger negative values of penetration index 9 of CB indicate greater temperature susceptibility, whereas MB shows positive value of penetration index indicating its lower temperature susceptibility. MBs are stiffer than CBs as viscosity of MB are higher than corresponding CB. To further characterize rutting behavior of bitumen, both CB and MB were subjected to Dynamic Shear Rheaometer (DSR) for determining (RR) G* / sinδ in un-aged and RTFO-aged bitumen and (fatigue resistance (FR)) G*. sinδ in PAV-aged bitumen following ASTM e1 / AASHTO TP-5 method 1. is the most resistant and CB (8/1) is least resistant to rutting (Fig. 1a). RR in un-aged bitumen can be expressed as follows: MGB(H) > 6/7 H MGB(S) >8/1. Sequence of RR of RTFO-aged bitumen has changed from un-aged bitumen ((Fig. 1b). RR of after RTFO test has increased from CB (6/7) because of predominant contribution of G* in comparison to phase angle perhaps due to chemistry of bitumen. RR behaviour of RTFO-aged bitumen in pavement, therefore, can be represented as follows: > > 6/7 > 8/1. The 5 kpa is maximum limit for FR, G*.sinδ, for qualifying performance grading (Fig. 1c). Therefore, Table 1 Physico-chemical properties of multigrade and conventional bitumen Bituminous products > CB(8/1) CB(6/7) PG Grading Original binder Penatration, 5 o C, 1g, 5s Softening Point, o C Fraass Breaking point, o C Penetration Index, PI K V at 135 o C, cst Ab.Vis. at 6 o C, P Elastic Rec. at 15 o C, % Rot. Vis. at 135 o C, Pa.s RTFO-aged binder Penatration at 5 o C, 1g, 5s Reduction in Penetration % Original Softening Point, o C Increase in Softening Point, % original Viscosity at 6 o C, Poise Rot. Vis. at 135 o C, Pa.s PAV-aged binder Penatration at 5 o C, 1g, 5s Softening Point, o C

3 JAIN et al: MULTIGRADE BITUMEN VERSES CONVENTIONAL BITUMEN 39 G * /Sin, kpa RUTTING BEHAVIOR OF BITUMEN RUTTING BEHAVIOR OF BITUMEN a) b) Original Bitumen 63. C 8/ C 6/ C 78. C G * /Sin, kpa 6 3 BITUMEN After RTFO Test 8/1 6.3 C 6/ C 67.6 C 78. C G * *Sin, MPa Temperature, C RUTTING BEHAVIOR OF BITUMEN c) Bitumen after PAV Test 8/ C 6/7 1.6 C C Temperature, C Temperature, C Fig. 1 Rutting behaviour of CB and MB: a) as such; b) after RTFO Test; c) after PAV Test temperature of bitumen, at which FR is 5 Kpa, can be utilized for assessing bitumen based on FR. In present study, FR for is highest and lowest for CB (6/7) and bitumen can be sequenced on the basis of FR as follows: MGB(S) > MGB(H) > 8/1 > 6/7. All PAV-aged bitumen were subjected to Bending Beam Rheometer (BBR) for determining low temperature rheological properties, Creep stiffness and m-value by following ASTM D method 11. Test temperature for 6 seconds, at which Creep stiffness value was found up to 3 MPa maximum and m-value.3 minimum, considered as a pass temperature for performance grading. Creep stiffness and m-values of PAV-aged bitumen has been plotted against temperature (Fig. ). Stiffness values and m-values of MB behave differently than CB because of change in chemistry (Fig. 3). grade is least stiff whereas CB( 6/7) is stiffest at low temperatures and stiffness order can be expressed as follows: MGB(S)< MGB(H) < 8/1 < 6/7. Direct tension failure strain was determined for PAVaged bitumen using Direct Tension Tester (DTT) as per ASTM: D 673- method 1. Test temperature at failure strain (minimum 1% at 1mm / min pull) considered as pass temperature for performance grading (Fig. ). PG grading was determined for all bitumen under study as per ASTM D: CB(8/1) qualifies PG 58- and CB(6/7) for PG 6- whereas and exhibits PG 6- and PG 76- (Fig. 5). For mechanical properties of bitumen, bituminous mixes were prepared by mixing CB and with aggregates having the gradation of bituminous concrete specification 13 at 163 C and compacted using Marshall Compactor as per ASTM test method 1. Specimens were prepared by adding bitumen (.5-6.5%) by weight of mixes. Marshall strength and flow of specimens were evaluated at 6 C using Marshall Tester as per ASTM test method 15. Mix prepared from shows highest Marshall Strength (bitumen content, 5.35%) followed by CB(6/7) (bitumen content, 5.3%) and lowest for

4 31 J SCI IND RES VOL 67 APRIL 8 m-value /1 6/ Temperature, o C Stiffness,MPa 5 8/1 6/ Temperature, a) b) Fig. PAV aged bitumen temperature change with: a) m-value b) creep stiffness, STIFFNESS, MP CB(8/1) CB(6/7) MB (S) MB (H) BITUMEN TYPE CB(8/1) CB(6/7) MB (S) MB (H) BITUMEN TYPE Stiffness m-value Temperature Failure strain% Temperature Fig.3 BBR Results of bitumen after PAV Test Fig. DTT Results of bitumen after PAV Test CB(8/1) (bitumen content, 5.3%) as per weight of mix (Fig. 6). was evaluated against CB(8/1) for performance on circular test track at Highways Research Station (HRS), Chennai for three different road specifications, cm thick premix carpet 16, semi dense bituminous concrete 17 and mix seal surfacing 18. The test was conducted by applying one-tonne load at ambient temperature under dry conditions till completion of 6, revolutions by test track wheel. Performance of was found better than corresponding CB (8/1) in visual performance, skid resistance and texture depth 19. Field Performance Requirements for MB for using in pavement construction is given in Table. Conventional laboratory tests and PG grading / SHRP tests have indicated that is better in low and high temperature properties from corresponding CB(8/1) and from CB(6/7). After getting encouraged results, IOCL conducted field trial of MB at hot and cold climatic regions in association with Central Road Research Institute, New Delhi and Border Road Organization. In field trial study, the test and reference sections, 1 m each, were laid at Jaisalmer, Rajasthan and Drass, Kargil, J&K using MB and CB(8/1) and CB(6/7) following commonly used four road resurfacing specifications, cm thick premix carpet, mix seal surfacing, bituminous concrete and semi dense bituminous concrete. Performance of test tracks was evaluated after the completion of one year at Drass in August, 6 and after six months at Jaisalmer in

5 JAIN et al: MULTIGRADE BITUMEN VERSES CONVENTIONAL BITUMEN 311 PG Grading, C CB(8/1) CB(6/7) HIGH TEMP GRADING. LOW TEMP GRADING Marshall Strength, Kg CB(8/1) BITUMEN,% CB(6/7) Fig.5 PG grading of bitumen Fig.6 Marshall strengthof bitumen-mix Table Requirements for multigrade bitumen for use in pavement construction & properties of Indian Oil developed multigrade bitumen Sl. No. Characteristics Multigrade bitumen Method of Ref/IS Indian Oil multigrade Developed bitumen MB5 MB i) Penetration at 5 C 1 g, s ii) Softening Point (R&B), C, Min iii) FRAASS Breaking Point, C, Max iv Flash point, (Cleveland >85 >75 open cup), C, Min. v) Ductility after TFOT at C, cm, Min vi) Penetration Index (PI)* >. >. Note vii) Penetration ratio, Min 5 Pen at C 5 1 Pen 5 C viii) Viscosity at 6 C, Poise, 5 16 (Pt II) Min ix) Viscosity at 135 C, cst, (Pt III) 789 Max x) Ageing Index, Max 3.5 Note Note: 1 penetration index (PI) may be calculated from the value of penetrations at two different temperatures (5 C & C) using following relationship: Penetration Index (PI) = 5A 1 + 5A where A = Log C Log C 5 C C Aging index can be calculated by dividing viscosity value at 6 C of residue from thin film oven test (see IS 938) by the viscosity value of neat bitumen at 6 C Ageing Index is measure of resistance to age hardening of bitumen and defined as a ratio of viscosity at 6 C for oxidized bitumen (TFOT) and neat bitumen.

6 31 J SCI IND RES VOL 67 APRIL 8 Table 3 Field performance data of multigrade bitumen and Conventional bitumen, after one year at Drass, Kargil (J&K) Test track Performance grading and % of marks CB 8/1 CB 6/7 DBC Satisfactory, 73.5% Good, 8.5% Good, 8.75% SDBC Satisfactory, 73.8% Satisfactory, 77.3% Good, 8.75% Mix seal Satisfactory, 75.5% Satisfactory, 7.% Satisfactory, 7.5% Premix carpet Satisfactory, 71.5% Satisfactory, 75.% Satisfactory, 73.5% Table Field performance data of multigrade bitumen and conventional bitumen after six months at Jaisalmer (Rajasthan) Test track Performance grading & % of marks CB 8/1 CB 6/7 DBC Good, 85% Very good, 9% Very good, 9% SDBC Good, 87% Good, 9% Very good, 9% Mix seal Good, 86% Good, 9% Very good, 9% Premix carpet Good, 89% Good, 9% Very good, 9% October, 6 based on bitumen, aggregate, surface texture, cracking, potholes, surface evenness, reveling and stripping. Field performance data indicates that MB has performed marginally superior than CB at both cold and hot locations (Tables 3 & ). Conclusions MB is superior to corresponding CB in terms of stiffness low temperature / fatigue cracking in flexibility. MB exhibits superior performance at high and low temperatures in terms of rutting resistance, stiffness, flexibility, low temperature and fatigue cracking. and grades qualify for PG 6-8 and PG 76- grading against corresponding CB(8/1) and CB(6/ 7) for PG 58- and PG 6- grading. Mechanical testing of mixes prepared from MB shows higher Marshall strength in comparison to mix prepared with CB. Circular test track performance study conducted at Highways Research Station (HRS), Chennai also indicated superior performance of MB against corresponding CB in three road specifications, cm thick premix carpet, semi dense bituminous concrete and Mix seal surfacing in visual performance, skid resistance and texture depth. Field trials studies of test tracks laid at Drass, Kargil and Jaisalmer for four road specifications indicate that MB shows marginally superior performance than CB at both hot and cold climatic regions. Acknowledgements Authors thank CRRI, New Delhi, for providing mechanical stability test results of mixes prepared from MB and CB. Authors also thank Director General, Border Road Organization, Commanding Officers of 93 RCC & 95 RCC and Dr Sunil Bose, CRRI, and their teams for laying and monitoring performance of the test tracks at Drass, Kargil (J K) and Jaisalmer (Rajasthan). References 1 John Read & David WhiteOak, The Shell Bitumen Handbook, 5th edn (Thomas Telford Publishing, London) July 3, Chapter 5.3, Koole R C, Valkering C P & Lancon D JL, Development of a multigrade bitumen to alleviate permanent deformation, in Proc Australian Asphalt Paving Conf, Sydney, 1991, Krishna A, Negi R S, Kala M P, Tyagi B R, Srivastava S P & Bhatnagar A K, A Process for the preparation of multigrade bitumen for enhanced pavement life, Indian Pat 19133(to Indian Oil Corporation Ltd, R&D Centre) 15 January Document: PCD 6 (336) P, Multigrade bitumen binders for use in pavement construction (Bureau of Indian Standards, New Delhi). 5 IS: , Specification for paving bitumen specification (Bureau of Indian Standards, New Delhi). 6 ASTM D87-, Standard test method for effect of heat and air on a moving film of asphalt (Rolling Thin-Film Oven Test),.3. 7 ASTM D651-5, Standard practice for accelerated aging of asphalt binder using a pressurized aging vessel (PAV),.3.

7 JAIN et al: MULTIGRADE BITUMEN VERSES CONVENTIONAL BITUMEN ASTM D , Standard specification for performance graded asphalt binder, Button J W, Epps J A, Little D N & Gallaway B M, Influence of Asphalt Temperature Susceptibility on Pavement Construction & Performance (Texas Transportation Institute, Texas) 1983, ASTM D7175-5e1, Standard test method for determining the rheological properties of asphalt binder using a Dynamic Shear Rheometer, ASTM D668-1, Standard test method for determining the flexural creep stiffness of asphalt binder using the Bending Beam Rheometer (BBR), ASTM D673-, Standard test method for determining the fracture properties of asphalt binder in direct tension (DT), Ministry of Road Transport and Highways, Specifications for Roads and Bridge works, MOST: Section 5, Clause 51 (BIS, New Delhi) ASTM D696-, Standard practice for preparation of bituminous specimens using Marshall apparatus, ASTM D697-5e1, Standard test method for Marshall Stability and flow of bituminous mixtures, Ministry of Road Transport and Highways, Specifications for roads and bridge works, MOST: Section 5, Clause 59 (BIS, New Delhi), Ministry of Road Transport and Highways, Specifications for roads and bridge works, MOST: Section 5, Clause 511 (BIS, New Delhi), Ministry of Road Transport and Highways, Specifications for roads and bridge works, MOST: Section 5, Clause 51 (BIS, New Delhi), Highway Research Station, Chennai, Report on evaluation of new bitumen, Project //99 (Indian Oil Corporation, R & D Wing, Faridabad). Pundhir N K S & Nanda P K, Development of bitumen emulsion based cold mix technology for construction of roads under different climatic conditions of India, J Sci Ind Res, 65 (6)