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Analysis of influence of bitumen composition on the properties represented by empirical and viscosity test
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Transportation Research Procedia 00 (2019) 000–000
ScienceDirect
www.elsevier.com/locate/procedia
Available online at www.sciencedirect.com
Transportation Research Procedia 00 (2019) 000–000
ScienceDirect
www.elsevier.com/locate/procedia
13th International Scientific on40Sustainable, Modern and Safe Transport TransportationConference Research Procedia (2019) 34–41 (TRANSCOM 2019), High Tatras, Novy Smokovec – Grand Hotel Bellevue, www.elsevier.com/locate/procedia Slovak Republic, May 29-31, 2019 13th International Scientific Conference on Sustainable, Modern and Safe Transport Analysis of influence ofTatras, bitumen onHotel theBellevue, properties (TRANSCOM 2019), High Novy composition Smokovec – Grand Slovak May 29-31, 2019 represented byRepublic, empirical and viscosity test
Analysis of influence of bitumen composition Michal Holýa, *, Eva Remišováa on the properties represented and viscosity8215/1, testZilina, 010 26, Slovakia Department of Highway Engineering, Faculty by of Civilempirical Engineering,University of Zilina,Univerzitna a
Abstract
Michal Holýa, *, Eva Remišováa
Department of Highway Engineering, Faculty of Civil Engineering,University of Zilina,Univerzitna 8215/1, Zilina, 010 26, Slovakia
a
Bitumen are one of the products in oil processing. The properties of bitumen are influenced by the source of oil itself and by the technological process of oil processing. Most European refineries, of course, are processing for reasons of the resale of petroleum Abstract products, especially petroleum suitable for the recovery of light and middle fractions. Therefore, light petroleums are required, with low yields of heavy fractions which are highly economically and in dispositions efficient for processors on the petroleum Bitumen are one the products processing. The properties bitumen are influenced by the source of oil itself and by the market. From theofperspective of in theoilrafinery the content and the of ratio of asphaltenes and maltenes as essential components of technological process of oil processing. Most refineries,impact of course, are processing of the resale of petroleum bitumen become less important, however, thisEuropean can significantly on future propertiesfor of reasons the bituminous binder. The basic products, especiallyand petroleum suitable for dedicated the recovery of light the andbitumen middle fractions. light are required, tests as penetration softening point are to evaluate propertiesTherefore, and classify the petroleums bitumen. These tests are with low yields of heavy fractions which are highly economically and in dispositions efficient for processors on the petroleum currently insufficient and therefore new test methods and procedures for bitumen characterization are developed. The main theme market. From the perspective of thetorafinery contentproperties and the ratio of asphaltenes and maltenes as essential of of the performance-based approach bitumenthe binders’ assessment is the evaluation of properties fromcomponents the pavement bitumen become important, however, this can significantly on futureThe properties of the bituminous binder. properties The basic performance pointless of view as permanent deformation, fatigue andimpact frost cracking. evaluation of changes of bitumen tests asthe penetration and softening point are evaluate the bitumen properties and classify on theinvestigating bitumen. These tests are during production and paving process of dedicated the asphalttomixture is also important. The study is focused the viscouscurrently insufficient and therefore new test methods and procedures for bitumen characterization are developed. The main theme temperature behavior and fundamental properties represented by the penetration and the softening point of the samples of paving of the bitumen performance-based approach to bitumen binders’ is the of evaluation of properties from the pavement grade 50/70 and polymer modified bitumen PMBproperties 45/80-75.assessment The composition the bitumen was determined by the SARA performance of view as permanent fatigueout andhow frostthe cracking. The evaluation of changespoint, of bitumen properties analysis and point organic elemental analysis.deformation, The paper points “traditional” tests as softening penetration, and during theare production andthe paving process of asphalt mixture is also important. studychanges is focused investigating viscousviscosity affected by composition of the bitumen and how the composition of The bitumen theon basic properties the of bitumen. temperature behavior and fundamental properties represented by the penetration and the softening point of the samples of paving grade bitumen 50/70 and polymerbymodified © 2019 The Authors. Published Elsevierbitumen B.V. PMB 45/80-75. The composition of the bitumen was determined by the SARA analysis and under organicresponsibility elemental analysis. The papercommittee points outofhow tests as softening point, penetration, and Peer-review of the scientific the the 13th“traditional” International Scientific Conference on Sustainable, viscosityand are Safe affected by the composition of bitumen Modern Transport (TRANSCOM 2019). and how the composition of bitumen changes the basic properties of bitumen. © 2019 The Authors. Published by Elsevier B.V. © 2019 The Authors. Published by of Elsevier B.V. committee of the 13th International Scientific Conference on Sustainable, Peer-review under responsibility the scientific Peer-review responsibility of the scientific Modern and under Safe Transport (TRANSCOM 2019).committee of the 13th International Scientific Conference on Sustainable, Modern and Safe Transport (TRANSCOM 2019).
* Corresponding author. Tel.: +421-41-513-5930 E-mail address: [email protected] 2352-1465 © 2018 The Authors. Published by Elsevier B.V. Peer-review * Corresponding underauthor. responsibility Tel.: +421-41-513-5930 of the scientific committee of the 13th International Scientific Conference on Sustainable, Moder n and SafeE-mail Transport address: (TRANSCOM [email protected] 2019). 2352-1465 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 13th International Scientific Conference on Sustainable, Moder n and Safe Transport (TRANSCOM 2019). 2352-1465 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 13th International Scientific Conference on Sustainable, Modern and Safe Transport (TRANSCOM 2019). 10.1016/j.trpro.2019.07.007
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Keywords: bitumen, empirical test, composition of bitumen, dynamic viscosity
1. Introduction Bitumen 1, is a complex mixture of many chemical compounds with high molecular weight, typically between from 500 to 50 000. Because of this complexity, a complete analysis of the composition of bitumen would be almost impossible. However, it is possible to characterize the constituents by a wide variety of methods such as solubility in different solvents, by molecular weight or by broad chemical type. Chromatography, in conjunction with solvent extraction, is commonly used to separate the components of bitumen into following four broad chemical groups: • Asphaltenes: brown/black amorphous solids of high molecular weight, typically 1000 – 50 000. They are precipitated from bitumen by dissolving in a paraffinic solvent such as n-heptane. Asphaltenes generally comprise 5-25 % by weight of the bitumen. • Resins: dark brown solids or semi-solids, which are soluble in heptane. They are adhesive and very polar in nature. Molecular weights are typically 900-1300. Resins may comprise 5-50 % by weight of the bitumen. • Aromatics: generally dark brown viscous liquids. Molecular weight is typically 500-900. Usually present at 40-60 % by weight in the bitumen. • Saturates: solids or viscous liquids, light colored with molecular weights in the range 500-800. This fraction may be present from 1 to 25 % by weight in the bitumen. The resins, aromatics and saturates fractions are often known collectively as the “maltenes” fraction. These four general compound types are regarded as making up bitumen in the colloidal system in which the asphaltenes are present as “micelles” dispersed in the lower molecular weight maltenes. It is generally accepted that the asphaltene micelles are stabilized by a cover of compounds predominantly found in the resins fraction. The covered asphaltenes are dispersed in the “oily” medium of aromatics and saturates, as shown Fig. 1.
Fig. 1. The colloidal composition of bitumen. 1
The configuration of the bitumen internal structure 1, is largely determined by the chemical constitution of the molecular species present. Bitumen is a complex chemical mixture of molecules that are predominantly hydrocarbons with a small amount of structurally analogous heterocyclic species and functional groups containing sulphur, nitrogen and oxygen atoms. Bitumen also contains trace quantities of metals such as vanadium, nickel, iron, magnesium, and calcium, which occur in the form of inorganic salts and oxides or in porphyrin structures. Elementary analysis of bitumen manufactured from a variety of crude oils shows that most bitumens contain – carbon 82-88 %, hydrogen 811 %, sulphur 0-6 %, oxygen 0-1.5 %, nitrogen 0-1 %. When a harder bitumen is produced by increasing the temperature and/or the vacuum conditions inside the distillation column, it is the more volatile saturates and aromatics fractions which are removed the residue, thus concentrating the asphaltenes and resins. Therefore, a hard bitumen will have a higher asphaltenes content than a softer grade from the same crude oil. In the production of harder bitumen by air blowing, the concentration of saturates, being relatively inert to oxidation, remains largely unchanged. However, the reactivity of the aromatics and resins fractions to air and the resulting formation of asphaltenes from this reaction
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increases the concentration of the asphaltenes in the bitumen more so than by distillation alone. Thus a bitumen produced by air blowing will have a higher asphaltenes content than a bitumen produced by vacuum distillation from the same crude oil. At standard environment temperatures, bitumen is a very stable and inert material, especially when it is in large quantity. However, when exposed to the atmosphere in very thin films as in asphalt mixtures, it slowly hardens until eventually, it becomes brittle. The mechanism of this hardening is complex as would be excepted from the complex nature of bitumen. Also, the mechanism is difficult to study under real asphalt pavement service conditions due to the contamination from traffic such as droppings of lubricating oil and diesel fuels. The studies under controlled conditions in the laboratory have shown that oxidation is the main reaction occurring and this results in similar changes in the chemical composition which occur at high temperatures. At normal bitumen storage temperatures of 130 °C to 180 °C, bitumen is fairly stable and may be stored hot for quite long periods without significant changes occurring. This is due to the very restricted access of oxygen to bitumen inside a storage tank. However, if the bitumen is pumped to and from a storage tank and bitumen is allowed to return to the tank via a “splash-back” system through the vapour space above the bitumen in the tank, significant hardening can occur due to greater access of oxygen. During mixing, storage, transport, and laying of asphalt mixtures, a thin film of bitumen on the aggregate surface is exposed at high temperatures to atmospheric oxygen. Under the conditions, significant chemical changes can occur which result in significant physical changes. As in the production of bitumen by air blowing, the main chemical changes are the oxidation, condensation and polymerization. In consequence, the changes in group composition are substantial reductions in the aromatics fraction, together with increases in the resins and asphaltene contents. The saturates contents are usually little changed due to relatively low reactivity of the compounds of this fraction. These changes in the chemical composition result in an increase in the average size of molecules present (the molecular weight increases) and this, in turn, is accompanied by a hardening of the bitumen. Once asphalts are compacted, providing the mixture has sufficiently low air voids. An analysis of bitumen recovered from road trial sections has shown that several other changes occur in the chemical composition as a result of asphalt porosity, the bitumen will continue to harden and eventually become brittle and will crack under traffic or thermally-induced stresses or a combination of both. 2. Physical properties of bitumen The main physical properties 2, which are relevant to the performance of bitumen as a road binder are its rheological (elasticity, stiffness and flow) properties and its strength. The mechanical strength of bitumen is important at low temperatures when it becomes progressively harder and exceeding a certain temperature limit brittle. In this state, the fracture strength is 4 x 106 Pa, which is low compared to other engineering materials such as steel and concrete. The temperature at which the bitumen becomes brittle is caused by its rheological properties, the bitumen grading or hardness. The quality of bituminous binders used in the construction and maintenance of road surfaces is currently being assessed by empirical tests based on obtaining one value for specific boundary conditions that were designed around 100 years ago. The consistency at middle working temperatures (penetration), consistency at increase working temperatures (softening point) and consistency at lower temperatures (breaking point) are measured, regardless of the composition of the bitumen and the loads corresponding to the real load on the road. Research work on bituminous binders and asphalt mixtures were based on the assumption that empirical tests can characterize and classify the binder, however inaccurately describe the properties of bitumen as a viscoelastic material. The current state 7 of the asphalt roads has led to new ways and approaches being sought to better describe the properties of bitumen binders and mixtures. One such approach is "performance related” approach (Fig.2). The system evaluates bitumen binders mainly after thermal stability tests (short-term RTFOT and long-term PAV) by functional tests, determining the stiffness modules using the dynamic rheometer (DSR) and the deflection beam rheometer (BBR). Bitumen binders are tested not in the state when they leave the refinery, but in the state when they leave the asphalt mixing plant, or after a certain period of exposure on the road in service. The primary emphasis is given to the characterization of rheological behavior that is viscoelastic behavior as a function of temperature and loading rate.
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The behavior of bitumen is primarily given by a chemical composition that is influenced by the crude oil source and the processing method of bitumen. The main aim in the application of new, modern procedures, performance related characteristics is much better in
Fig. 2. Types of equipment and requirements for bituminous binders at different temperatures. 3
assessing, evaluating, or optimizing bituminous binders and then in finished designs, to use a description of behavior that best fits to real conditions, taking into account factors such as temperature changes, load changes or overall load dynamics road construction. Bitumen binder is considered a relatively complex material and the description of its properties is very demanding. The functional approach in general, to a great extent, places emphasis on rheology which is an important aspect with respect to the viscoelastic nature of bitumen binders. The basic variable in rheology that characterizes the flow behavior of the material is viscosity and one way of describing the properties of bitumen binders could be the use of viscosity. 3. Experimental program Within laboratory measurements, there were studied the properties of binders for the production of asphalt mixes which are commonly used in practice for asphalt pavement construction – paving grade bitumen 50/70 (9 samples from different producers 1 - 9) and polymer modified bitumen PMB 45/80-75 (5 samples from different producers 1 – 5). The determination of basic properties was performed using penetration test at 25 °C according to EN 1426 and softening point test according to EN 1427 (Fig. 3). a
b
c
d
Fig. 3. (a,b) Equipment for penetration test of bitumen, (c,d) Equipment for softening point test of bitumen.
The content of structurally similar compounds in bitumen 4, SARA analysis (determination of the percentage of saturated hydrocarbons, aromatics, resins and asphaltenes) was carried out using the combined extraction method and liquid chromatography. This requires special equipment and chemical agents (n-heptane, toluene, alumina 507C sorbent, silver nitrate modified silica gel) and the specialized laboratories. The apparatus for determining the asphaltenes content and group composition of maltenes is shown in Figure 4. The elementary analysis, determine C, H, N, S content, was performed by Elementar Vario Cube with TCD detection. The test was performed by means of
Michal Holý et al. / Transportation Research Procedia 40 (2019) 34–41 Holy Michal, Remisova Eva / Transportation Research Procedia 00 (2019) 000–000
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5
the controlled sample combustion process at a temperature of 800 to 1000 °C and subsequent analysis of the flue gases by the detector. These analyses were carried out at the Institute of Oil and Alternative Fuels VŠCHT in Prague.
Fig. 4. (a) Scheme of equipment for the determination of asphaltenes by extraction, (b) Scheme of equipment for determining the group composition of maltens.
The experimental measurements of dynamic viscosity of bitumen samples were realized by Brookfield viscometer – model DV-II+PRO with the cylindrical spindle. This rotating spindle viscometer covers a range of shear rates in the range of 1 to 104 s-1 and dynamic viscosity in the range of 10 -2 to 106 Pa·s (temperature from 40 °C to 200 °C). For obtaining representative results of bituminous binders the viscosity must always be measured at various test temperatures. Typical temperatures for the unmodified or polymer modified bitumen binders are in the range of 90 to 180 C. For the calculation we use the following equations: • shear rate, in s-1
•
•
𝑆𝑆𝑆𝑆 = 𝑅𝑅𝑅𝑅𝑅𝑅. 𝑆𝑆𝑆𝑆𝑆𝑆
(1)
𝑆𝑆𝑆𝑆 = 𝑇𝑇𝑇𝑇. 𝑆𝑆𝑆𝑆𝑆𝑆. 𝑆𝑆𝑆𝑆𝑆𝑆. 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇
(2)
shear stress, in N.cm2
viscosity, in mPa·s 𝑐𝑐𝑐𝑐 =
100 . 𝑆𝑆𝑆𝑆𝑆𝑆. 𝑇𝑇𝑇𝑇. 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑅𝑅𝑅𝑅𝑅𝑅
(3)
where TK is viscometer torque constant (for model RVDV-II+, TK = 1), RPM is current viscometer spindle speed, SMC is current spindle multiplier constant (for torque of model SC4-27, SMC=25), SRC is current spindle shear rate constant (for model SC4-27, SRC = 0.34), Torque is current viscometer torque (%) expressed as a number between 0 and 100. 4. Results and analyzing The values from measurements of softening point and penetration of tested bitumen binders are presented in Table 1. Despite the same grade of bitumen, we can observe a relatively high variability of results. In the case of paving grade bitumen, the range of softening points is from 48 °C to 53 °C and a range of penetration is from 54.3 to 76.7 x0.1mm. In the case of polymer modified bitumen, the range of softening points is from 75.4 °C to 80.75 °C and a range of penetration is from 54.6 to 74.3 x0.1mm. The results are within the prescribed limits (the only exception is sample 7, which is out of range of penetration) for penetration (from 50 to 70 x0.1mm for paving grade bitumen and from 45 to 80 x0.1mm for modified bitumen) and softening point (from 46 to 54 C for paving grade bitumen and ≥75 C for paving grade bitumen) which are defined in the specifications for bitumen.
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Table 1. The values from measurements of softening point and penetration of tested bitumen binders. Softening point in oC
Penetration in 0.1mm
50/70
PMB 45/80-75
50/70
PMB 45/80-75
1.
49.75
85.15
64,07
54.33
2.
49.75
80.75
63.70
54.60
3.
49.00
75.40
62.70
74.33
4.
48.00
78.40
61.00
60.53
5.
48.95
86.00
70.03
51.60
6.
51.00
-
54.33
-
7.
47.00
-
76.70
-
8.
48.00
-
62.53
-
Sample
9.
53.00
-
50.46
-
Mean value 𝑥𝑥̅ = ∑𝑛𝑛𝑖𝑖=1 𝑥𝑥𝑖𝑖
49.38
81.14
62.85
59.07
Variance 𝜎𝜎 = ∑𝑛𝑛𝑖𝑖=1(𝑥𝑥𝑖𝑖 − 𝑥𝑥̅ )2
2.86
16.06
52.79
66.64
Standard deviation 𝜎𝜎 = √𝜎𝜎 2
1.69
4.00
7.26
8.16
Variation coefficient 𝑣𝑣[%] = . 100
3.42
4.93
11.56
13.81
2
1
𝑛𝑛
1
𝑛𝑛
𝜎𝜎 𝑥𝑥̅
Calculated statistical parameters for dynamic viscosity measurement of tested bitumen binders (nine samples of paving grade bitumen 50/70 and five samples of polymer modified bitumen PMB 45/80-75) from different production are presented in Table 2. and Table 3. Despite the same grade of bitumen, we can observe a certain variability of results. In the case of paving grade bitumen, the standard deviation of softening point is ±1.69 °C and penetration is ±7.26 x0.1mm. In the case of polymer modified bitumen, the standard deviation of softening point is ±4 °C and penetration is ±8.16 x0.1mm. The results are within the prescribed limits (the only one exception is sample 7, which is out of range of penetration) defined in the specifications for bitumen. The viscosity results showed high variability in the results and confirmed the known facts. Modified bitumen have higher viscosity values with compare to paving grade bitumen. The viscosity with increasing temperature decreases. From the point of view of variability, we can state that with increasing temperature the variability decreases. Table 2. Calculated statistical parameters for dynamic viscosity measurement of paving grade bitumen. Viscosity of 50/70 in mPa·s at temperature in oC 120
130
135
140
150
160
165
170
180
185
190
Mean value
2032.5
748.4
513.8
399.6
254.4
165.8
129.5
105.4
71.3
58.6
49.3
Variance
266832.2 7928.7
1632.2
1518.2
696.7
196.4
80.4
57.9
36.4
19.9
19.2
Standard deviation
516.6
89.0
40.4
39.0
26.4
14.0
9.0
7.6
6.0
4.5
4.4
Variable coefficient, %
25.4
11.9
7.9
9.7
10.4
8.4
6.9
7.2
8.5
7.6
8.9
180
185
190 217.8
Table 3. Calculated statistical parameters for dynamic viscosity measurement of polymer modified bitumen. Viscosity of PMB 45/80-75 in mPa·s at temperature in oC 120
130
135
140
2320.2
1690.7
150
160
165
170
Mean value
10889.4
3514.6
1055.6
689.5
534.6
433.7
316.0
256.4
Variance
4296410.9
329636.3 169690.2 88579.4
34812.5
13665.9
5157.8
3906.9
2223.9
1460.5 1114.8
Standard deviation
2072.8
574.1
411.9
297.6
186.6
116.9
71.8
62.5
47.2
38.2
33.4
Variable coefficient, %
19.0
16.3
17.8
17.6
17.7
17.0
13.4
14.4
14.9
14.9
15.3
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The average values from the measurement of the group composition of bitumen respectively of the elemental composition are shown in Table 4. The table shows the average composition of paving grade bitumen 50/70 (9 tested samples 1 – 9) and polymer modified bitumen 45/80-75 (5 tested samples 1 – 5). Table 4. Average values of elemental and group composition of tested bitumen samples. Average content of components in samples in % Type of bitumen
Saturates
Aromatics
Resins
Asphaltenes
50/70
8.41
36.03
42.41
13.15
PMB 45/80-75
8.50
35.62
40.65
15.23
Type of bitumen
C
H
N
S
50/70
84.50
10.26
0.58
3.95
PMB 45/80-75
84.96
10.37
0.54
3.64
From the results of the chemical composition, it can be stated that at the biggest difference between the average values of the group composition of PMB and PG is in the Resins content (PG has a +1.76% higher content of resins with compared to PMB) and Asphaltenes content (PMBs have a +2.08 % higher content of asphaltenes with compared to PG). From the elemental composition point of view, we can say that both types of bituminous binders have relatively the same Nitrogen and Hydrogen contents and differences can be observed for Carbon (PMB has a +0.46% higher C content compared to PG) and Sulphur (PG has a +0.31% higher S content compared to PMB) content. The last step was to find out whether there is a relationship between elemental and / group composition of bitumen and empirical tests represented by penetration and softening point, dynamic viscosity and composition of bitumen respectively empirical tests and composition of bitumen. Viscosity dependencies were performed from measurements at each test temperature and evaluated depending on the composition of bitumen. Together, 126 dependencies for PG and 126 dependencies for PMB were determined and assessed. From the determined dependencies were chosen dependencies with the highest coefficient of determination, respectively, with a high tightness. The values from the investigated dependencies are shown in Table 5. and Table 6. The highest dependence between penetration and viscosity was found at a temperature 165°C for PG bitumen and temperature 160 °C for PMB (the values of R2 were a 0.80 for PG and 0.82 for PMB). Between the softening point and the viscosity we observed dependencies only in the case of PMB at a temperature 160 °C (R2 0.53), for PG the coefficient of determination was low. In the case of composition and viscosity, an interesting finding can be observed. While for PG bitumen we can see only one higher dependence (carbon content and viscosity where R2 0.8 at 185 °C), so for PMB we can find good correlation with group composition respectively elementary composition. The values of determination coefficient are 0.82 at temperature 130 °C (Saturates), 0.66 at 170 °C (Resins), 0.80 at 165 °C (Hydrogen content) and 0.74 at 120 °C (Nitrogen content). In case the of dependence between composition and empirical tests (Tab. 5) we can observe the following dependencies. For PG bitumen, we can see dependence between penetration and aromatics (R 2 0.55) and between penetration and carbon content (R2 0.67). The same case as for dependence of softening point and viscosity occurs for the dependence of the softening point and composition, where we found no more significant dependencies for PG bitumen. For PMB we can observe the dependence of the softening point (R 2 0.91) and penetration (R2 0.55) and hydrogen content. Table 5. Values of dependencies between the bitumen viscosity and the empirical tests and composition. Temperature in °C 120
130
135
140
Parameter/Component Coefficient of determination R
150
160
165
170
180
185
190
Bitumen binder
2
Carbon
0.04
0.21
0.66
0.58
0.48
0.74
0.48
0.58
0.43
0.80
0.56
PG
Penetration
0.00
0.55
0.51
0.75
0.69
0.54
0.77
0.77
0.71
0.51
0.35
PG
Saturates
0.62
0.82
0.74
0.66
0.65
0.71
0.59
0.65
0.80
0.76
0.77
PMB
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Michal Holý et al. / Transportation Research Procedia 40 (2019) 34–41 Holý Michal, Remišová Eva / Transportation Research Procedia 00 (2019) 000–000
Resins
0.62
0.04
0.30
0.24
0.58
0.03
0.63
0.66
0.65
0.63
41
0.48
PMB
Hydrogen
0.01
0.37
0.39
0.46
0.59
0.66
0.80
0.66
0.62
0.54
0.48
PMB
Nitrogen
0.74
0.03
0.00
0.00
0.03
0.02
0.00
0.00
0.04
0.01
0.01
PMB
Penetration
0.11
0.45
0.43
0.49
0.75
0.79
0.82
0.72
0.75
0.62
0.55
PMB
Softening p.
0.28
0.22
0.17
0.19
0.50
0.53
0.45
0.38
0.52
0.34
0.27
PMB
Table 6. Values of dependencies between the bitumen composition and the empirical tests. Parameter
Saturates
Aromatics
Resins
Asphaltenes
C
H
N
S
Bitumen binder
Penetration
0.12
0.55
0.24
0.14
0.67
0.15
0.01
0.04
PG
Softening p. 0.37
0.14
0.03
0.25
0.42
0.91
0.00
0.36
PMB
Penetration
0.28
0.01
0.40
0.19
0.55
0.15
0.10
PMB
0.34
5. Conclusions Quality assurance of bituminous binders is carried out by penetration test and softening point test of bitumen thus with using the empirical method based on obtaining one value for specific boundary conditions. These empirical tests, however, cannot adequately characterise the complicated, rheological behavior of bituminous binders, which is also proven by practice. Therefore, new ways of determination the properties of bitumen binders are tested, functional tests or combining of functional and empirical tests, bitumen composition tests. In the first step, empirical tests (softening point and penetration) were measured and statistically analysed. The dynamic viscosity was chosen to characterize the behavior of bitumen in a wide temperature range (120 to 190 oC). The chemical composition determination allows to measure and understand the various interactions among molecular species that contribute to the behaviour of bitumen. Therefore, the goal of a study was to determine the correlation between the chemical and physical properties of bitumen. Analysis of the group and elemental composition of tested bitumen binders have been performed. In the last step, the dependence between bitumen composition, bitumen viscosity and empirical tests was investigated. It has been shown that in terms of elemental composition the content of carbon and hydrogen affects the binder penetration and softening point. The same conclusions can be drawn from the analysis of the composition effect on bitumen viscosity. In the case of group composition, the influence was demonstrated at proportion of maltenes groups and viscosity. Good correlations were found for the bitumen viscosity and penetration. These results give an assumption for further research. Acknowledgments The authors are grateful for the financial support from the research project VEGA 1/0300/17 Research of performance related and rheological properties of bituminous binders. References J.C. Nicholls, 1998. Asphalt Surfacings – A guide to asphalt surfacings and treatments used for the surface course of road pavements. Transport research laboratory. ISBN 0-419-23110-2. [2] J. Read, D. Whiteoak, 2003. The Shell Bitumen Handbook, 4th edition. Thomas Telford, London. ISBN 0-7277-3220-X. [3] Superpave asphalt binder specification 2016. Avaible from: https://www.slideshare.net/hronaldo10/04superpave-binder-testing-highwayand-airport-engineering-dr-sherif-elbadawy. [4] Team of autors, 2017. Instructions for laboratory work of the Institute of Oil and Alternative Fuels, University of chemistry and technology Prague, Avaible from: http://utrap.vscht.cz/files/uzel/0014520/0004~~8zu8sCw_pVKhoChfIScxKb8osSS_KO_wWqDA4YXJqQqHdxWXJJaVKhgZmgIA.pdf?r edirected . [5] EN 1426, 2016. Bitumen and bituminous binders. Determination of needle penetration. [6] EN 1427, 2016. Bitumen and bituminous binders. Determination of the softening point. Ring and Ball method. [7] D. Ďurčanská, M. Decký, R. Libcinsky, J. Huzlik, 2013. Project SPENS - sustainable pavement for European new member states. In: Communications: scientific letters of the University of Zilina. Vol. 15, no. 2, s 49-55. ISSN 1335-4205. [1]
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13th International Scientific on40Sustainable, Modern and Safe Transport TransportationConference Research Procedia (2019) 34–41 (TRANSCOM 2019), High Tatras, Novy Smokovec – Grand Hotel Bellevue, www.elsevier.com/locate/procedia Slovak Republic, May 29-31, 2019 13th International Scientific Conference on Sustainable, Modern and Safe Transport Analysis of influence ofTatras, bitumen onHotel theBellevue, properties (TRANSCOM 2019), High Novy composition Smokovec – Grand Slovak May 29-31, 2019 represented byRepublic, empirical and viscosity test
Analysis of influence of bitumen composition Michal Holýa, *, Eva Remišováa on the properties represented and viscosity8215/1, testZilina, 010 26, Slovakia Department of Highway Engineering, Faculty by of Civilempirical Engineering,University of Zilina,Univerzitna a
Abstract
Michal Holýa, *, Eva Remišováa
Department of Highway Engineering, Faculty of Civil Engineering,University of Zilina,Univerzitna 8215/1, Zilina, 010 26, Slovakia
a
Bitumen are one of the products in oil processing. The properties of bitumen are influenced by the source of oil itself and by the technological process of oil processing. Most European refineries, of course, are processing for reasons of the resale of petroleum Abstract products, especially petroleum suitable for the recovery of light and middle fractions. Therefore, light petroleums are required, with low yields of heavy fractions which are highly economically and in dispositions efficient for processors on the petroleum Bitumen are one the products processing. The properties bitumen are influenced by the source of oil itself and by the market. From theofperspective of in theoilrafinery the content and the of ratio of asphaltenes and maltenes as essential components of technological process of oil processing. Most refineries,impact of course, are processing of the resale of petroleum bitumen become less important, however, thisEuropean can significantly on future propertiesfor of reasons the bituminous binder. The basic products, especiallyand petroleum suitable for dedicated the recovery of light the andbitumen middle fractions. light are required, tests as penetration softening point are to evaluate propertiesTherefore, and classify the petroleums bitumen. These tests are with low yields of heavy fractions which are highly economically and in dispositions efficient for processors on the petroleum currently insufficient and therefore new test methods and procedures for bitumen characterization are developed. The main theme market. From the perspective of thetorafinery contentproperties and the ratio of asphaltenes and maltenes as essential of of the performance-based approach bitumenthe binders’ assessment is the evaluation of properties fromcomponents the pavement bitumen become important, however, this can significantly on futureThe properties of the bituminous binder. properties The basic performance pointless of view as permanent deformation, fatigue andimpact frost cracking. evaluation of changes of bitumen tests asthe penetration and softening point are evaluate the bitumen properties and classify on theinvestigating bitumen. These tests are during production and paving process of dedicated the asphalttomixture is also important. The study is focused the viscouscurrently insufficient and therefore new test methods and procedures for bitumen characterization are developed. The main theme temperature behavior and fundamental properties represented by the penetration and the softening point of the samples of paving of the bitumen performance-based approach to bitumen binders’ is the of evaluation of properties from the pavement grade 50/70 and polymer modified bitumen PMBproperties 45/80-75.assessment The composition the bitumen was determined by the SARA performance of view as permanent fatigueout andhow frostthe cracking. The evaluation of changespoint, of bitumen properties analysis and point organic elemental analysis.deformation, The paper points “traditional” tests as softening penetration, and during theare production andthe paving process of asphalt mixture is also important. studychanges is focused investigating viscousviscosity affected by composition of the bitumen and how the composition of The bitumen theon basic properties the of bitumen. temperature behavior and fundamental properties represented by the penetration and the softening point of the samples of paving grade bitumen 50/70 and polymerbymodified © 2019 The Authors. Published Elsevierbitumen B.V. PMB 45/80-75. The composition of the bitumen was determined by the SARA analysis and under organicresponsibility elemental analysis. The papercommittee points outofhow tests as softening point, penetration, and Peer-review of the scientific the the 13th“traditional” International Scientific Conference on Sustainable, viscosityand are Safe affected by the composition of bitumen Modern Transport (TRANSCOM 2019). and how the composition of bitumen changes the basic properties of bitumen. © 2019 The Authors. Published by Elsevier B.V. © 2019 The Authors. Published by of Elsevier B.V. committee of the 13th International Scientific Conference on Sustainable, Peer-review under responsibility the scientific Peer-review responsibility of the scientific Modern and under Safe Transport (TRANSCOM 2019).committee of the 13th International Scientific Conference on Sustainable, Modern and Safe Transport (TRANSCOM 2019).
* Corresponding author. Tel.: +421-41-513-5930 E-mail address: [email protected] 2352-1465 © 2018 The Authors. Published by Elsevier B.V. Peer-review * Corresponding underauthor. responsibility Tel.: +421-41-513-5930 of the scientific committee of the 13th International Scientific Conference on Sustainable, Moder n and SafeE-mail Transport address: (TRANSCOM [email protected] 2019). 2352-1465 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 13th International Scientific Conference on Sustainable, Moder n and Safe Transport (TRANSCOM 2019). 2352-1465 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 13th International Scientific Conference on Sustainable, Modern and Safe Transport (TRANSCOM 2019). 10.1016/j.trpro.2019.07.007
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Michal Holý et al. / Transportation Research Procedia 40 (2019) 34–41 Holý Michal, Remišová Eva / Transportation Research Procedia 00 (2019) 000–000
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Keywords: bitumen, empirical test, composition of bitumen, dynamic viscosity
1. Introduction Bitumen 1, is a complex mixture of many chemical compounds with high molecular weight, typically between from 500 to 50 000. Because of this complexity, a complete analysis of the composition of bitumen would be almost impossible. However, it is possible to characterize the constituents by a wide variety of methods such as solubility in different solvents, by molecular weight or by broad chemical type. Chromatography, in conjunction with solvent extraction, is commonly used to separate the components of bitumen into following four broad chemical groups: • Asphaltenes: brown/black amorphous solids of high molecular weight, typically 1000 – 50 000. They are precipitated from bitumen by dissolving in a paraffinic solvent such as n-heptane. Asphaltenes generally comprise 5-25 % by weight of the bitumen. • Resins: dark brown solids or semi-solids, which are soluble in heptane. They are adhesive and very polar in nature. Molecular weights are typically 900-1300. Resins may comprise 5-50 % by weight of the bitumen. • Aromatics: generally dark brown viscous liquids. Molecular weight is typically 500-900. Usually present at 40-60 % by weight in the bitumen. • Saturates: solids or viscous liquids, light colored with molecular weights in the range 500-800. This fraction may be present from 1 to 25 % by weight in the bitumen. The resins, aromatics and saturates fractions are often known collectively as the “maltenes” fraction. These four general compound types are regarded as making up bitumen in the colloidal system in which the asphaltenes are present as “micelles” dispersed in the lower molecular weight maltenes. It is generally accepted that the asphaltene micelles are stabilized by a cover of compounds predominantly found in the resins fraction. The covered asphaltenes are dispersed in the “oily” medium of aromatics and saturates, as shown Fig. 1.
Fig. 1. The colloidal composition of bitumen. 1
The configuration of the bitumen internal structure 1, is largely determined by the chemical constitution of the molecular species present. Bitumen is a complex chemical mixture of molecules that are predominantly hydrocarbons with a small amount of structurally analogous heterocyclic species and functional groups containing sulphur, nitrogen and oxygen atoms. Bitumen also contains trace quantities of metals such as vanadium, nickel, iron, magnesium, and calcium, which occur in the form of inorganic salts and oxides or in porphyrin structures. Elementary analysis of bitumen manufactured from a variety of crude oils shows that most bitumens contain – carbon 82-88 %, hydrogen 811 %, sulphur 0-6 %, oxygen 0-1.5 %, nitrogen 0-1 %. When a harder bitumen is produced by increasing the temperature and/or the vacuum conditions inside the distillation column, it is the more volatile saturates and aromatics fractions which are removed the residue, thus concentrating the asphaltenes and resins. Therefore, a hard bitumen will have a higher asphaltenes content than a softer grade from the same crude oil. In the production of harder bitumen by air blowing, the concentration of saturates, being relatively inert to oxidation, remains largely unchanged. However, the reactivity of the aromatics and resins fractions to air and the resulting formation of asphaltenes from this reaction
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increases the concentration of the asphaltenes in the bitumen more so than by distillation alone. Thus a bitumen produced by air blowing will have a higher asphaltenes content than a bitumen produced by vacuum distillation from the same crude oil. At standard environment temperatures, bitumen is a very stable and inert material, especially when it is in large quantity. However, when exposed to the atmosphere in very thin films as in asphalt mixtures, it slowly hardens until eventually, it becomes brittle. The mechanism of this hardening is complex as would be excepted from the complex nature of bitumen. Also, the mechanism is difficult to study under real asphalt pavement service conditions due to the contamination from traffic such as droppings of lubricating oil and diesel fuels. The studies under controlled conditions in the laboratory have shown that oxidation is the main reaction occurring and this results in similar changes in the chemical composition which occur at high temperatures. At normal bitumen storage temperatures of 130 °C to 180 °C, bitumen is fairly stable and may be stored hot for quite long periods without significant changes occurring. This is due to the very restricted access of oxygen to bitumen inside a storage tank. However, if the bitumen is pumped to and from a storage tank and bitumen is allowed to return to the tank via a “splash-back” system through the vapour space above the bitumen in the tank, significant hardening can occur due to greater access of oxygen. During mixing, storage, transport, and laying of asphalt mixtures, a thin film of bitumen on the aggregate surface is exposed at high temperatures to atmospheric oxygen. Under the conditions, significant chemical changes can occur which result in significant physical changes. As in the production of bitumen by air blowing, the main chemical changes are the oxidation, condensation and polymerization. In consequence, the changes in group composition are substantial reductions in the aromatics fraction, together with increases in the resins and asphaltene contents. The saturates contents are usually little changed due to relatively low reactivity of the compounds of this fraction. These changes in the chemical composition result in an increase in the average size of molecules present (the molecular weight increases) and this, in turn, is accompanied by a hardening of the bitumen. Once asphalts are compacted, providing the mixture has sufficiently low air voids. An analysis of bitumen recovered from road trial sections has shown that several other changes occur in the chemical composition as a result of asphalt porosity, the bitumen will continue to harden and eventually become brittle and will crack under traffic or thermally-induced stresses or a combination of both. 2. Physical properties of bitumen The main physical properties 2, which are relevant to the performance of bitumen as a road binder are its rheological (elasticity, stiffness and flow) properties and its strength. The mechanical strength of bitumen is important at low temperatures when it becomes progressively harder and exceeding a certain temperature limit brittle. In this state, the fracture strength is 4 x 106 Pa, which is low compared to other engineering materials such as steel and concrete. The temperature at which the bitumen becomes brittle is caused by its rheological properties, the bitumen grading or hardness. The quality of bituminous binders used in the construction and maintenance of road surfaces is currently being assessed by empirical tests based on obtaining one value for specific boundary conditions that were designed around 100 years ago. The consistency at middle working temperatures (penetration), consistency at increase working temperatures (softening point) and consistency at lower temperatures (breaking point) are measured, regardless of the composition of the bitumen and the loads corresponding to the real load on the road. Research work on bituminous binders and asphalt mixtures were based on the assumption that empirical tests can characterize and classify the binder, however inaccurately describe the properties of bitumen as a viscoelastic material. The current state 7 of the asphalt roads has led to new ways and approaches being sought to better describe the properties of bitumen binders and mixtures. One such approach is "performance related” approach (Fig.2). The system evaluates bitumen binders mainly after thermal stability tests (short-term RTFOT and long-term PAV) by functional tests, determining the stiffness modules using the dynamic rheometer (DSR) and the deflection beam rheometer (BBR). Bitumen binders are tested not in the state when they leave the refinery, but in the state when they leave the asphalt mixing plant, or after a certain period of exposure on the road in service. The primary emphasis is given to the characterization of rheological behavior that is viscoelastic behavior as a function of temperature and loading rate.
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The behavior of bitumen is primarily given by a chemical composition that is influenced by the crude oil source and the processing method of bitumen. The main aim in the application of new, modern procedures, performance related characteristics is much better in
Fig. 2. Types of equipment and requirements for bituminous binders at different temperatures. 3
assessing, evaluating, or optimizing bituminous binders and then in finished designs, to use a description of behavior that best fits to real conditions, taking into account factors such as temperature changes, load changes or overall load dynamics road construction. Bitumen binder is considered a relatively complex material and the description of its properties is very demanding. The functional approach in general, to a great extent, places emphasis on rheology which is an important aspect with respect to the viscoelastic nature of bitumen binders. The basic variable in rheology that characterizes the flow behavior of the material is viscosity and one way of describing the properties of bitumen binders could be the use of viscosity. 3. Experimental program Within laboratory measurements, there were studied the properties of binders for the production of asphalt mixes which are commonly used in practice for asphalt pavement construction – paving grade bitumen 50/70 (9 samples from different producers 1 - 9) and polymer modified bitumen PMB 45/80-75 (5 samples from different producers 1 – 5). The determination of basic properties was performed using penetration test at 25 °C according to EN 1426 and softening point test according to EN 1427 (Fig. 3). a
b
c
d
Fig. 3. (a,b) Equipment for penetration test of bitumen, (c,d) Equipment for softening point test of bitumen.
The content of structurally similar compounds in bitumen 4, SARA analysis (determination of the percentage of saturated hydrocarbons, aromatics, resins and asphaltenes) was carried out using the combined extraction method and liquid chromatography. This requires special equipment and chemical agents (n-heptane, toluene, alumina 507C sorbent, silver nitrate modified silica gel) and the specialized laboratories. The apparatus for determining the asphaltenes content and group composition of maltenes is shown in Figure 4. The elementary analysis, determine C, H, N, S content, was performed by Elementar Vario Cube with TCD detection. The test was performed by means of
Michal Holý et al. / Transportation Research Procedia 40 (2019) 34–41 Holy Michal, Remisova Eva / Transportation Research Procedia 00 (2019) 000–000
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5
the controlled sample combustion process at a temperature of 800 to 1000 °C and subsequent analysis of the flue gases by the detector. These analyses were carried out at the Institute of Oil and Alternative Fuels VŠCHT in Prague.
Fig. 4. (a) Scheme of equipment for the determination of asphaltenes by extraction, (b) Scheme of equipment for determining the group composition of maltens.
The experimental measurements of dynamic viscosity of bitumen samples were realized by Brookfield viscometer – model DV-II+PRO with the cylindrical spindle. This rotating spindle viscometer covers a range of shear rates in the range of 1 to 104 s-1 and dynamic viscosity in the range of 10 -2 to 106 Pa·s (temperature from 40 °C to 200 °C). For obtaining representative results of bituminous binders the viscosity must always be measured at various test temperatures. Typical temperatures for the unmodified or polymer modified bitumen binders are in the range of 90 to 180 C. For the calculation we use the following equations: • shear rate, in s-1
•
•
𝑆𝑆𝑆𝑆 = 𝑅𝑅𝑅𝑅𝑅𝑅. 𝑆𝑆𝑆𝑆𝑆𝑆
(1)
𝑆𝑆𝑆𝑆 = 𝑇𝑇𝑇𝑇. 𝑆𝑆𝑆𝑆𝑆𝑆. 𝑆𝑆𝑆𝑆𝑆𝑆. 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇
(2)
shear stress, in N.cm2
viscosity, in mPa·s 𝑐𝑐𝑐𝑐 =
100 . 𝑆𝑆𝑆𝑆𝑆𝑆. 𝑇𝑇𝑇𝑇. 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑅𝑅𝑅𝑅𝑅𝑅
(3)
where TK is viscometer torque constant (for model RVDV-II+, TK = 1), RPM is current viscometer spindle speed, SMC is current spindle multiplier constant (for torque of model SC4-27, SMC=25), SRC is current spindle shear rate constant (for model SC4-27, SRC = 0.34), Torque is current viscometer torque (%) expressed as a number between 0 and 100. 4. Results and analyzing The values from measurements of softening point and penetration of tested bitumen binders are presented in Table 1. Despite the same grade of bitumen, we can observe a relatively high variability of results. In the case of paving grade bitumen, the range of softening points is from 48 °C to 53 °C and a range of penetration is from 54.3 to 76.7 x0.1mm. In the case of polymer modified bitumen, the range of softening points is from 75.4 °C to 80.75 °C and a range of penetration is from 54.6 to 74.3 x0.1mm. The results are within the prescribed limits (the only exception is sample 7, which is out of range of penetration) for penetration (from 50 to 70 x0.1mm for paving grade bitumen and from 45 to 80 x0.1mm for modified bitumen) and softening point (from 46 to 54 C for paving grade bitumen and ≥75 C for paving grade bitumen) which are defined in the specifications for bitumen.
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Table 1. The values from measurements of softening point and penetration of tested bitumen binders. Softening point in oC
Penetration in 0.1mm
50/70
PMB 45/80-75
50/70
PMB 45/80-75
1.
49.75
85.15
64,07
54.33
2.
49.75
80.75
63.70
54.60
3.
49.00
75.40
62.70
74.33
4.
48.00
78.40
61.00
60.53
5.
48.95
86.00
70.03
51.60
6.
51.00
-
54.33
-
7.
47.00
-
76.70
-
8.
48.00
-
62.53
-
Sample
9.
53.00
-
50.46
-
Mean value 𝑥𝑥̅ = ∑𝑛𝑛𝑖𝑖=1 𝑥𝑥𝑖𝑖
49.38
81.14
62.85
59.07
Variance 𝜎𝜎 = ∑𝑛𝑛𝑖𝑖=1(𝑥𝑥𝑖𝑖 − 𝑥𝑥̅ )2
2.86
16.06
52.79
66.64
Standard deviation 𝜎𝜎 = √𝜎𝜎 2
1.69
4.00
7.26
8.16
Variation coefficient 𝑣𝑣[%] = . 100
3.42
4.93
11.56
13.81
2
1
𝑛𝑛
1
𝑛𝑛
𝜎𝜎 𝑥𝑥̅
Calculated statistical parameters for dynamic viscosity measurement of tested bitumen binders (nine samples of paving grade bitumen 50/70 and five samples of polymer modified bitumen PMB 45/80-75) from different production are presented in Table 2. and Table 3. Despite the same grade of bitumen, we can observe a certain variability of results. In the case of paving grade bitumen, the standard deviation of softening point is ±1.69 °C and penetration is ±7.26 x0.1mm. In the case of polymer modified bitumen, the standard deviation of softening point is ±4 °C and penetration is ±8.16 x0.1mm. The results are within the prescribed limits (the only one exception is sample 7, which is out of range of penetration) defined in the specifications for bitumen. The viscosity results showed high variability in the results and confirmed the known facts. Modified bitumen have higher viscosity values with compare to paving grade bitumen. The viscosity with increasing temperature decreases. From the point of view of variability, we can state that with increasing temperature the variability decreases. Table 2. Calculated statistical parameters for dynamic viscosity measurement of paving grade bitumen. Viscosity of 50/70 in mPa·s at temperature in oC 120
130
135
140
150
160
165
170
180
185
190
Mean value
2032.5
748.4
513.8
399.6
254.4
165.8
129.5
105.4
71.3
58.6
49.3
Variance
266832.2 7928.7
1632.2
1518.2
696.7
196.4
80.4
57.9
36.4
19.9
19.2
Standard deviation
516.6
89.0
40.4
39.0
26.4
14.0
9.0
7.6
6.0
4.5
4.4
Variable coefficient, %
25.4
11.9
7.9
9.7
10.4
8.4
6.9
7.2
8.5
7.6
8.9
180
185
190 217.8
Table 3. Calculated statistical parameters for dynamic viscosity measurement of polymer modified bitumen. Viscosity of PMB 45/80-75 in mPa·s at temperature in oC 120
130
135
140
2320.2
1690.7
150
160
165
170
Mean value
10889.4
3514.6
1055.6
689.5
534.6
433.7
316.0
256.4
Variance
4296410.9
329636.3 169690.2 88579.4
34812.5
13665.9
5157.8
3906.9
2223.9
1460.5 1114.8
Standard deviation
2072.8
574.1
411.9
297.6
186.6
116.9
71.8
62.5
47.2
38.2
33.4
Variable coefficient, %
19.0
16.3
17.8
17.6
17.7
17.0
13.4
14.4
14.9
14.9
15.3
Michal Holý et al. / Transportation Research Procedia 40 (2019) 34–41 Holy Michal, Remisova Eva / Transportation Research Procedia 00 (2019) 000–000
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The average values from the measurement of the group composition of bitumen respectively of the elemental composition are shown in Table 4. The table shows the average composition of paving grade bitumen 50/70 (9 tested samples 1 – 9) and polymer modified bitumen 45/80-75 (5 tested samples 1 – 5). Table 4. Average values of elemental and group composition of tested bitumen samples. Average content of components in samples in % Type of bitumen
Saturates
Aromatics
Resins
Asphaltenes
50/70
8.41
36.03
42.41
13.15
PMB 45/80-75
8.50
35.62
40.65
15.23
Type of bitumen
C
H
N
S
50/70
84.50
10.26
0.58
3.95
PMB 45/80-75
84.96
10.37
0.54
3.64
From the results of the chemical composition, it can be stated that at the biggest difference between the average values of the group composition of PMB and PG is in the Resins content (PG has a +1.76% higher content of resins with compared to PMB) and Asphaltenes content (PMBs have a +2.08 % higher content of asphaltenes with compared to PG). From the elemental composition point of view, we can say that both types of bituminous binders have relatively the same Nitrogen and Hydrogen contents and differences can be observed for Carbon (PMB has a +0.46% higher C content compared to PG) and Sulphur (PG has a +0.31% higher S content compared to PMB) content. The last step was to find out whether there is a relationship between elemental and / group composition of bitumen and empirical tests represented by penetration and softening point, dynamic viscosity and composition of bitumen respectively empirical tests and composition of bitumen. Viscosity dependencies were performed from measurements at each test temperature and evaluated depending on the composition of bitumen. Together, 126 dependencies for PG and 126 dependencies for PMB were determined and assessed. From the determined dependencies were chosen dependencies with the highest coefficient of determination, respectively, with a high tightness. The values from the investigated dependencies are shown in Table 5. and Table 6. The highest dependence between penetration and viscosity was found at a temperature 165°C for PG bitumen and temperature 160 °C for PMB (the values of R2 were a 0.80 for PG and 0.82 for PMB). Between the softening point and the viscosity we observed dependencies only in the case of PMB at a temperature 160 °C (R2 0.53), for PG the coefficient of determination was low. In the case of composition and viscosity, an interesting finding can be observed. While for PG bitumen we can see only one higher dependence (carbon content and viscosity where R2 0.8 at 185 °C), so for PMB we can find good correlation with group composition respectively elementary composition. The values of determination coefficient are 0.82 at temperature 130 °C (Saturates), 0.66 at 170 °C (Resins), 0.80 at 165 °C (Hydrogen content) and 0.74 at 120 °C (Nitrogen content). In case the of dependence between composition and empirical tests (Tab. 5) we can observe the following dependencies. For PG bitumen, we can see dependence between penetration and aromatics (R 2 0.55) and between penetration and carbon content (R2 0.67). The same case as for dependence of softening point and viscosity occurs for the dependence of the softening point and composition, where we found no more significant dependencies for PG bitumen. For PMB we can observe the dependence of the softening point (R 2 0.91) and penetration (R2 0.55) and hydrogen content. Table 5. Values of dependencies between the bitumen viscosity and the empirical tests and composition. Temperature in °C 120
130
135
140
Parameter/Component Coefficient of determination R
150
160
165
170
180
185
190
Bitumen binder
2
Carbon
0.04
0.21
0.66
0.58
0.48
0.74
0.48
0.58
0.43
0.80
0.56
PG
Penetration
0.00
0.55
0.51
0.75
0.69
0.54
0.77
0.77
0.71
0.51
0.35
PG
Saturates
0.62
0.82
0.74
0.66
0.65
0.71
0.59
0.65
0.80
0.76
0.77
PMB
8
Michal Holý et al. / Transportation Research Procedia 40 (2019) 34–41 Holý Michal, Remišová Eva / Transportation Research Procedia 00 (2019) 000–000
Resins
0.62
0.04
0.30
0.24
0.58
0.03
0.63
0.66
0.65
0.63
41
0.48
PMB
Hydrogen
0.01
0.37
0.39
0.46
0.59
0.66
0.80
0.66
0.62
0.54
0.48
PMB
Nitrogen
0.74
0.03
0.00
0.00
0.03
0.02
0.00
0.00
0.04
0.01
0.01
PMB
Penetration
0.11
0.45
0.43
0.49
0.75
0.79
0.82
0.72
0.75
0.62
0.55
PMB
Softening p.
0.28
0.22
0.17
0.19
0.50
0.53
0.45
0.38
0.52
0.34
0.27
PMB
Table 6. Values of dependencies between the bitumen composition and the empirical tests. Parameter
Saturates
Aromatics
Resins
Asphaltenes
C
H
N
S
Bitumen binder
Penetration
0.12
0.55
0.24
0.14
0.67
0.15
0.01
0.04
PG
Softening p. 0.37
0.14
0.03
0.25
0.42
0.91
0.00
0.36
PMB
Penetration
0.28
0.01
0.40
0.19
0.55
0.15
0.10
PMB
0.34
5. Conclusions Quality assurance of bituminous binders is carried out by penetration test and softening point test of bitumen thus with using the empirical method based on obtaining one value for specific boundary conditions. These empirical tests, however, cannot adequately characterise the complicated, rheological behavior of bituminous binders, which is also proven by practice. Therefore, new ways of determination the properties of bitumen binders are tested, functional tests or combining of functional and empirical tests, bitumen composition tests. In the first step, empirical tests (softening point and penetration) were measured and statistically analysed. The dynamic viscosity was chosen to characterize the behavior of bitumen in a wide temperature range (120 to 190 oC). The chemical composition determination allows to measure and understand the various interactions among molecular species that contribute to the behaviour of bitumen. Therefore, the goal of a study was to determine the correlation between the chemical and physical properties of bitumen. Analysis of the group and elemental composition of tested bitumen binders have been performed. In the last step, the dependence between bitumen composition, bitumen viscosity and empirical tests was investigated. It has been shown that in terms of elemental composition the content of carbon and hydrogen affects the binder penetration and softening point. The same conclusions can be drawn from the analysis of the composition effect on bitumen viscosity. In the case of group composition, the influence was demonstrated at proportion of maltenes groups and viscosity. Good correlations were found for the bitumen viscosity and penetration. These results give an assumption for further research. Acknowledgments The authors are grateful for the financial support from the research project VEGA 1/0300/17 Research of performance related and rheological properties of bituminous binders. References J.C. Nicholls, 1998. Asphalt Surfacings – A guide to asphalt surfacings and treatments used for the surface course of road pavements. Transport research laboratory. ISBN 0-419-23110-2. [2] J. Read, D. Whiteoak, 2003. The Shell Bitumen Handbook, 4th edition. Thomas Telford, London. ISBN 0-7277-3220-X. [3] Superpave asphalt binder specification 2016. Avaible from: https://www.slideshare.net/hronaldo10/04superpave-binder-testing-highwayand-airport-engineering-dr-sherif-elbadawy. [4] Team of autors, 2017. Instructions for laboratory work of the Institute of Oil and Alternative Fuels, University of chemistry and technology Prague, Avaible from: http://utrap.vscht.cz/files/uzel/0014520/0004~~8zu8sCw_pVKhoChfIScxKb8osSS_KO_wWqDA4YXJqQqHdxWXJJaVKhgZmgIA.pdf?r edirected . [5] EN 1426, 2016. Bitumen and bituminous binders. Determination of needle penetration. [6] EN 1427, 2016. Bitumen and bituminous binders. Determination of the softening point. Ring and Ball method. [7] D. Ďurčanská, M. Decký, R. Libcinsky, J. Huzlik, 2013. Project SPENS - sustainable pavement for European new member states. In: Communications: scientific letters of the University of Zilina. Vol. 15, no. 2, s 49-55. ISSN 1335-4205. [1]