Improvement of bitumen performance with epoxy resin

Fuel 88 (2009) 1324–1328

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Improvement of bitumen performance with epoxy resin Meltem Çubuk a, Metin Gürüa *, M. Kürsßat Çubuk b a b

Gazi University, Eng. and Arch. Fac., Chem. Eng. Depart. 06570, Maltepe-Ankara, Turkey Gazi University, Eng. and Arch. Fac., Civil Eng. Depart. 06570, Maltepe-Ankara, Turkey

a r t i c l e

i n f o

Article history: Received 8 April 2008 Received in revised form 16 December 2008 Accepted 17 December 2008 Available online 18 January 2009 Keywords: Modified bitumen Epoxy Rheology Adhesion Stability

a b s t r a c t This paper studies the modification of petroleum bitumen with epoxy resin. Different amounts of epoxy were doped into bitumen with 50/70 penetration grade and variations in viscosity as a function of temperature and additive concentration were determined. The effects of the epoxy additive were examined by rheometer, penetration, softening point, DSR (dynamic shear rheometer), DSC (differential scanning calorimeter), RTFOT (rolling thin film oven test), PAV (pressure aging vessel), BBR (bending beam rheometer) and surface tension tests. Adhesion and stability of bitumen aggregate mixtures prepared using original and modified bitumen were compared using Nicholson stripping and Marshall tests. The optimum dosage of the additive yielding the best rheological and performance properties was found to be 2% (w/ w). Appreciable decrease in the formation of rutting, bleeding, stripping and cracking of modified bitumen may be obtained through epoxy addition. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction Bitumen, obtained from petroleum refinery bottoms is a thermoplastic containing bituminous materials and finds widespread use in sealants, binders, waterproof coatings and paving materials and is preferred for its low cost, inherent cohesive nature, rheological properties and thermal resistance. Flexible paving used in the top layer of the roads is formed from bituminous binders and aggregates. This layer is exposed to a wide range of temperatures and great stresses due to seasonal change and heavy truck traffic. It tends to crack at low temperatures and its cohesive strength decreases at elevated temperatures. Problems related to deformations such as formation of rutting, cracking and stripping are becoming more severe as traffic loads increase. Performance and stability improvements of this top paving layer would improve the quality of roads and appreciable savings would result through decreased maintenance costs. Since it is the material properties of bituminous binders and the aggregates that determine the quality of the paving, improving this quality by various modifications of bitumen is widely attempted. Bitumen can be modified through doping with additives such as surfactants and polymers. Surfactants, both cationic and anionic are generally used as antistripping agents. Cationic surfactants are appropriate for electronegative materials such as silex, quartz and granite. Gürü had reported on the addition of manganese abietate, an anionic surfactant, to electropositive bitumen material

* Corresponding author. Tel.: +90 312 2317400/2555; fax: +90 312 2308434. E-mail address: [email protected] (M. Gürü). 0016-2361/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2008.12.024

mixture by 0.1% (w/w) to prevent stripping [1]. Use of domestic incinerator ash as an aggregate in asphalt concrete was evaluated by Garrick and Chan, who showed that a mix containing up to 32% (w/w) incinerator ash yielded acceptable parameters on the Marshall tests. This mix requires a higher than usual asphalt content and is prone to stripping [2]. Polymers are used as additives with the intent to improve the performance of binders. Polymers may be classified into four main groups: thermoplastics, rubbers, thermosetting plastics and block copolymers. Maleic anhydride was reported to significantly improve both the low temperature cracking resistance and the high temperature cohesive strength of bitumen. In the same study, styrene butadiene styrene copolymer was found to improve the low temperature behavior of bitumen, but not its high temperature cohesive strength and flux resistance [3]. Aged modified bitumen with styrene butadiene styrene also showed an improvement in rheological properties [4]. Two penetration grade bitumens can be modified by styrene butadiene styrene [5]. Very good stability results were obtained with a blend containing 1% of EVA copolymer [6]. Improvements were also observed with atactic polypropylene, ethylene–propylene copolymer and ethylene–propylene rubber [7]. Amorphous polyalphaolefin, cellulose fiber, polyolefin and styrene butadiene styrene were used as modifiers in asphalt mixtures [8]. Styrene butadiene styrene addition into the binder can delay aging. [9]. Promising results were obtained by doping bitumen with high density polyethylene [10]. Modification of bitumen with EVA recycled polymer may enhance its service properties by increasing its viscosity [11]. In a similar study, viscosity of base asphalt modified by styrene butadiene styrene and ethylene–vinyl acetate polymers was investigated and discussed [12].

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M. Çubuk et al. / Fuel 88 (2009) 1324–1328 Table 1 Chemical and physical properties of the bitumen with 50/70 penetration. Property Penetration, 25 °C, 100 g, 5 s, 0.1 mm Solubility in trichloroethylene (%) Softening point (°C) Flash point (°C) Viscosity, 135 °C (Pa s) Asphaltene (w/w)% Aromatics (w/w)% Saturated hydrocarbons (w/w)% Resin (w/w)%

Data 62 99.7 49.2 260+ 0.280 20.75 53.72 6.55 18.98

Table 2 Properties of epoxy resin. Status of physical

Liquid

Equivalent weight of epoxy (g/eq) Viscosity (cps/25 °C) Colour (Gardner) Flash point (°C) Hdrolyzable Chlorine (ppm) Density (25 °C)

184–190 12,000–15,000 1 max. 150 " 1000 " 1,16

Waste polymer and rubber material may also be used as modifying agents in bituminous materials. The modification of bitumen with four different types of waste polymers, namely EVA, EVA/ LDPE blend, crumb tire rubber and ABS has been investigated [13]. Rheological characteristics of ground tire rubber-modified bitumen were determined and compared with unmodified and polymer modified (SBS) bitumens [14]. In a similar study, flexible bituminous material was obtained through the modification of bitumen with tire rubber waste [15]. The purpose of the present study is to investigate the effects of epoxy addition on the rheology of modified bitumen through viscosity, penetration, softening point, DSR, DSC, RTFOT, PAV, BBR,

surface energy tests. Adhesion and stability properties of bitumen aggregate mixtures are studied with the Nicholson stripping test and the Marshall test and compared to those of unmodified bitumen. 2. Materials and methods 50/70 penetration grade bitumen widely used as pavement material was obtained from Aliag˘a Petroleum Refinery and used throughout the study. Properties of the bitumen used in all experiments are given in Table 1. Properties and chemical open formula of the BPA type epoxy resin used in all experiments as the modifying agent are given in Table 2 and Fig. 1. The experimental set-up consisted of an open reactor, oil bath with a thermostat and a mixer. Modified bitumen was obtained by placing it in an oil bath preheated to 150 °C in an oven. Epoxy was added to the hot bitumen at ratios varying between 1% (w/ w) and 6% (w/w) and mixed for 1 h. This sample was then maintained at 150 ± 2 °C in an oven for 1 h and at 20 ± 1 °C for 1 day. Effects of epoxy dosages on the viscosity of modified bitumen were measured according to the ASTM D 4402 standard at 19 ± 1 of shear rate by means of a Brookfield DV-III Rheometer. Transition glass temperature tests of bitumens were done with a Perkin–Elmer DSC. Experiments were carried out at the heating rate of 50 °C/min under the running of nitrogen gas. Conventional tests such as penetration (ASTM D 5), softening points (ASTM D 36) and rolling thin film oven tests (ASTM D 2872) were carried out on bitumens with and without epoxy by Krebs Elec. & MFG, Sur Berlin RKA2 and CS 325-A (James Cox.&Sons Inc.), respectively. Surface energies of samples were automatically determined using contact angle method by means of KRUSS DSA 100 apparatus. Pressure aging vessel tests was carried out using a Buttler PAV apparatus (AASHTO PP1). A Thermoelectric BBR (Canon Instrument Company) (AASHTO TP1) and a CVO 100 ADS DSR Rheometer

Fig. 1. Chemical open formula of BPA type epoxy resin.

4.0

Viscosity (Pa.s)

3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

0

1

2

3

4

5

Epoxy Resin (%) 90 °C 100 °C 110 °C

120 °C 130 °C 140 °C

150 °C 160 °C 170 °C

Fig. 2. Variation of bitumen viscosity as a function of epoxy concentration

6

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(Bohlin Instrument) (AASHTO TP5) apparatus were used for asphalt rod strength and dynamic shear stress tests. In order to determine the adhesion properties of asphalt-aggregate mixtures, the Nicholson stripping test was carried out on the non-compacted mixtures with and without epoxy. At the end of the test, the nonstripped aggregate surface related to total aggregate surface has been given as the data of resistance to stripping. Additionally, Marshall Stability test (ASTM D 1559) were applied on the compacted mixtures with and without epoxy. Behavior of modified bitumen and asphalt-aggregate systems with varying epoxy concentrations and temperatures were determined.

ever, at higher concentrations, a noticeable decrease, due to the domination of epoxy was observed. Above 110 °C, the effect of the additive on bitumen viscosity decreases with increasing temperature. On the other hand, viscosities of bitumen with and without epoxy decreased exponentially as a function of temperature, as can be seen in Fig. 3. This is the expected result of the Newtonian property of bitumen. The viscosity increase at environmental temperatures obtained through (2–3)%wt epoxy addition will prevent rutting arising from heavy truck traffic. Expected bitumen–polymer reactivity is to form the cross linking structure and leads to the increasing of bitumen viscosity. At higher temperatures, doping does not increase viscosity due to the poor cross linking bonds. Therefore, doping does not pose a problem at asphalt plant processing temperatures. The epoxy addition ratio (2%) which corresponds to the maximum viscosity below 110 °C, was chosen as a constant parameter for the experiments that followed. Styrene butadiene styrene doping was also used to increase the viscosity of modified bitumen. [16]. After the logarithmic viscosity change with temperature was plotted for each epoxy concentration, the change of lnl as a function of 1/T was drawn, as shown in Fig. 4. The forward activation

3. Results and discussions Viscosity was the first parameter to be investigated for bitumen as a function of additive concentration and temperature, due to its importance in processing, aging and service. Viscosity was measured with epoxy concentrations of 0–6% by weight. As is evident from Fig. 2, viscosity increased exponentially at below the 110 °C with increasing epoxy concentration up to 2% (w/w), due to the increased cohesion of bitumen at low epoxy concentrations. How-

4.5 4.0

Viscosity (Pa.s)

3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

90

100

110

120

130

140

150

160

170

Temperature ( °C) Pure bitumen 0% Epoxy resin 3%

Epoxy resin1%

Epoxy resin 2%

Epoxy resin 4% Epoxy resin 6%

Epoxy resin 5%

Fig. 3. Variation of bitumen viscosity as a function of temperature.

2.0 1.5 1.0

lnμ

0.5 0.0 2.26 -0.5

2.31

2.36

2.41

2.46

2.51

2.56

2.61

2.66

2.71

2.76

y = 7.2947x - 19.148 y = 7.9038x - 20.494

-1.0

y = 7.5482x - 19.401

-1.5

y = 7.54x - 19.443 y = 6.9998x - 18.25

-2.0

y = 6.7673x - 17.684

-2.5

y = 6.6081x - 17.321

-3.0

[1/T(K)]∗10

3

% 0 Epoksi

% 2 Epoksi

% 4 Epoksi

% 1 Epoksi

% 3 Epoksi

% 5 Epoksi

% 6 Epoksi

Fig. 4. Variation of bitumen lnl data as a function of 1/T for each concentration.

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M. Çubuk et al. / Fuel 88 (2009) 1324–1328

energy of viscosity change was determined from the slope of the logarithmic line for each concentration using the Arrhenius Eq. (1).

m ¼ AeEa=RT

ð1Þ

As can be seen from Table 3, activation energy (Ea) of bitumen decreases below 110 °C with increase in epoxy concentration up to 2% (w/w). It is known that crystallization and cross linking of modified bitumen increases, resulting in a hardened structure due to decreasing activation energy [7]. In order to investigate the effects of epoxy resin curing period on the variation of viscosity, viscosities of modified bitumen with

Table 3 Intersection and activation energy data of bitumen. Epoxy additive (%)

A (Pa s)

Ea (kJ mol1)

0 1 2 3 4 5 6

4,832  109 1,257  109 3,752  109 3,597  109 1,186  108 2,089  108 3,003  108

60,648 65,712 62,756 62,688 58,196 56,263 54,940

110°C 120°C

90°C 100°C

5.0

130°C 140°C

150°C 160°C

2% (w/w) and 3% (w/w) epoxy additive were measured as a function of time up to 28 days. As shown in Fig. 5, below 110 °C viscosity change of modified bitumen with 2% epoxy reaches the maximum value on the fourteenth day and then starts to decrease. This curve flattens at higher temperatures and the maximum is no longer present. Viscosity variation after the second day remains steadily above 140 °C. For the 3% epoxy mixtures, viscosity change of modified bitumen below 110 °C reaches the maximum value on the 21st day, and then starts to decrease. This shows that the curing period increases with increasing of epoxy concentration. Penetration and softening point tests were applied to the original and to the 2% epoxy modified bitumen. Modification decreased penetration from 62 to 54. Softening point increased from 49.2 °C to 52.2 °C. Transition glass temperature of modified bitumen with 2% epoxy increased from 22.50 °C to 13.85 °C. Decrease in penetration, increase in softening point and transition glass temperatures are thought to arise from a hardening in modified bitumen. In a similar study, polyolefin and EVA additives decreased the penetration and increased the softening point of bitumen [17,18]. Increasing of the softening point was reported to lead to a decrease in rutting [19]. In order to determine the effect of doping on stripping durability of asphalt-aggregate, surface energy of bitumen with and without epoxy were measured and 30.90 and 32.00 mN/m were observed. Percent stripping with and without epoxy were found to be (0–5)% and (50–55)% in the Nicholson stripping test. It is pos-

170°C

4.5

1300

Marshall Stability (kg)

Vscosity (Pa.s)

4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0

0

7

14

21

28

1200 1100 1000 900 800 2.5

3

3.5 Pure bitumen

Fig. 5. Variation of viscosity as a function of curing period for modified bitumen with 2% epoxy.

4

4.5

5

Bitumen %

Time (Day)

Epoxy Resin 2%

Fig. 6. Variation of Marshall Stability values as a function of bitumen percent.

Table 4 Superpave test results of original and modified bitumen. Bitumen

Status of Bitumen

Applied test

Result

Limits of specification

Pure bitumen

Original

Viscosity, 135 °C 20 rpm, 18,6 SR DSR (G*/sind) 10 rad/s, 64 °C DSR (G*/sind) 10 rad/s, 64 °C DSR (G*  sind) 10 rad/s, 25 °C BBR 60 sn, 12 °C Viscosity, 135 °C 20 rpm, 18.6 SR DSR (G*/sind) 10 rad/s, 64 °C DSR (G*/sind) 10 rad/s, 64 °C DSR (G*  sind) 10 rad/s, 25 °C BBR 60 s, 12 °C

0.280 Pa s

3 Pa s

0.99817 kPa

1 kPa (min.) 2.2 kPa (min.) 5000 kPa (max.) 300 MPa (max.) 0.300 (min.) 3 Pa s

RTFOT is executed PAV is executed

Modified bitumen with 2% epoxy resin addition

Original

RTFOT is executed PAV is executed

2.3915 kPa 4099 kPa S m

148 MPa 0.318 0.435 Pa s 1.2223 kPa 3.08655 kPa 3010 kPa

S m

218 MPa 0.388

1 kPa (min.) 2.2 kPa (min.) 5000 kPa (max.) 300 MPa (max.) 0.300 (min.)

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M. Çubuk et al. / Fuel 88 (2009) 1324–1328

Pouring values (1/100")

20

4. Conclusion

15

10

5

2.5

3

3.5

4

4.5

5

Bitumen %

Pure bitumen

Epoxy Resin 2%

Fig. 7. Variation of pouring values as a function of bitumen percent.

sible to conclude that doping increases the adhesion of the asphaltaggregate system and stripping is prevented through doping with 2% (w/w) epoxy resin. Strength of the asphalt concrete increases and water penetration is blocked. Gürü had also recommended manganese abietate as an antistripping agent [1]. Test results and requirement limits of RTFOT, PAV, DSR and BBR are given in Table 3. Test results of modified bitumen remained within the requirement limits. G*/sind values of bitumen have to be higher than 1 and 2.2 kPa to resist rutting. G*/sind values of bitumen given in Table 4 show that epoxy addition to bitumen decreases rutting. G*sind value as a fatigue cracking factor of aged bitumen was limited at a maximum 5000 kPa. It is seen that 2% (w/w) epoxy addition to bitumen offers the best outcome in decreasing fatigue cracking. Creep hardness in the BBR test was limited at a maximum of 300 MPa in the superpave requirement. Creep hardness values of bitumen with and without additive stayed in the required limits. M values which indicate creep hardness as a function of time were required to be higher than 0.300. Our results were consistently above this value. Superpave tests indicate a decrease in rutting in modified bitumen by 22%, and in modified aged bitumen by 29%. The decrease in fatigue cracking is 27%. The results for Marshall Stability and pouring of original and modified bitumen are presented in Figs. 6 and 7, respectively. Variation of Marshall Stability as a function of percent bitumen for original and modified bitumen with 2% (w/w) epoxy is presented in Fig. 6. Addition of 3% epoxy into the bitumen increased the stability from 1044 to 1199. Maximum Marshall Stability was found at 3% bitumen ratio and decreased with further increase in bitumen. Stability of the mixture depends on the internal friction and cohesion between aggregates and the binder. Addition of epoxy increases the stability by increasing cohesion and shear stress. Previous research had indicated that the stability of polymer modified bituminous sample was higher than the stability of the original bituminous sample [8,20]. As seen from Fig. 7, generally pouring values of epoxy modified bitumen are less than those of the original bitumen. Elastic to plastic behavior transition point is also elevated with the addition of epoxy. The minimum pouring value has been recorded at 3% bitumen and increased with increasing amount of bitumen. Therefore, preparation of superpave with 2% (w/w) epoxy addition will resist to the formation of rutting, collapse, fatigue cracking, thermal cracking and creep hardness under the heavy traffic.

Viscosity, softening point, transition glass temperature and stability increase and heat sensitivity, surface energy, penetration and stripping decrease when bitumen is modified with the addition of 2% epoxy. Therefore, modified bitumen can be recommended for use in hot climates, humid regions, in roads with heavy traffic loads, at road curves and at bus stations to prevent rutting, bleeding, cracking, stripping and aging. Low cost and lower operating and maintenance requirements offer additional advantages for superpave applications. Waste epoxy powder could be substituted for epoxy resin for further economy and environmental advantage. Acknowledgement This study was supported by DPT (the State Planning Organization of Turkey) under project number 2001K120590. The authors are grateful to the DPT for financial support and Gazi University for the provision of laboratory facilities. References [1] Gürü M. Improvement of adhesion of bitumen-aggregate coatings by additives. Cellulose Chem Technol 2004;38(1–2):129–40. [2] Garrick NW, Chan KL. Transportation Research Record 1993;1418-1430. [3] Nadkarni VM, Shenoy AV, Mathew J. Thermomechanical behavior of modified asphalts. Ind Eng Chem Pord Res Dev 1985;24:478–84. [4] Lu X, Isacsson U. Chemical and rheological evaluation of ageing properties of SBS polymer modified bitumens. Fuel 1998;77:961–72. [5] Airey GD. Rheological properties of styrene butadiene styrene polymer modified road bitumens. Fuel 2003;82(14):1709–19. [6] Gonzales O, Munoz ME, Santamaria A, Garcia-Morales M, Navarro FJ, Partal P. Rheology and stability of bitumen/EVA blends. European Polymer Journal 2004;40(10):2365–72. [7] Fawcett AH, McNally T. Blends of bitumen with various polyolefins. Polymer 2000;41(14):5315–26. [8] Tayfur S, Özen H, Aksoy A. Investigation of rutting performance of asphalt mixtures containing polymer modifiers. Construction and Building Materials 2007;21(2):328–37. [9] Valtorta D, Poulikakos LD, Partl MN, Mazza E. Rheological properties of polymer modified bitumen from long-term field tests. Fuel 2006;86(7– 8):938–48. [10] Perez-Lepe AP, Martinez-Boza FJ, Gallegos C, Gonzales O, Munoz ME, Santamaria A. Influence of the processing conditions on the rheological behaviour of polymer-modified bitumen. Fuel 2003;82(11):1339–48. [11] Garcia-Morales M, Partal P, Navarro FJ, Martinez-Boza F, Gallegos C, Gonzales N, et al. Viscous properties and microstructure of recycled eva modified bitumen. Fuel 2004;83(1):31–8. [12] Stastna J, Zanzotto L, Vacin OJ. Viscosity function in polymer-modified asphalts. Journal of Colloid and Interface Science 2003;259:200–7. [13] Garcia-Morales M, Partal P, Navarro FJ, Gallegos C. Effect of waste polymer addition on the rheology of modified bitumen. Fuel 2006;85(7–8):936–43. [14] Navarro FJ, Partal P, Martinez-Boza F, Valencia C, Gallegos C. Rheological characteristies of ground tire rubber-modified bitumens. Chemical Engineering Journal 2002;89:53–61. [15] Gürü M, Tekeli S, Çubuk M K, Çubuk M. Recycling of scrap vehicle tyre as elastic surface material. The First Jordanian International Conference of Materials Science and Engineering Jordan 2005; pp. 39–44. [16] Eribol S, Orhan F. Elostomerlerle modifiye edilmisß bitümlerin özellikleri. 4. Ulusal Asfalt Sempozyumu 2004; 80–93 [Ankara]. [17] Topal A, Sßengöz B, Metli M. Polyolefin katkılı bitümlü bag˘layıcıların kıvamı ve yumusßama noktasına etkileri. 4. Ulusal Asfalt Sempozyumu 2004; 70–79 [Ankara]. [18] Malkoç G, Güngör N, Dumanlılar N. Çesßitli katkı maddeleri ile modifiye edilen asfalt çimentolarının özelliklerindeki deg˘isßiklikler. 1. Ulusal Asfalt _ Sempozyumu 1996;77–89 [Istanbul]. [19] Asphalt Institute, Mix Desing Methods For Asphalt Concerete and Other Hot Mix Types, Asphalt Instutite Manuel Series No. 2 (MS-2) 1996 [Kentucky]. [20] Namlı R, Kulog˘lu N. Farklı tasarım yöntemlerine göre hazırlanmısß asfalt beton numunelerinin rijitlig˘i. Fırat Üniversitesi Fen ve Müh. Bil. Der. 2001;8(2):235– 241.