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The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures
Materials Today: Proceedings xxx (xxxx) xxx
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures Estabraq N. Ezzat a,⇑, Alaa H. Abed b a b
Highways and Transportation Engineering Department, Al-Mustansiriyah University, Baghdad, Iraq Civil Engineering Department, Al-Nahrain University, Baghdad, Iraq
a r t i c l e
i n f o
Article history: Received 9 July 2019 Received in revised form 30 August 2019 Accepted 29 September 2019 Available online xxxx Keywords: Moisture damage PVC Hybrid polymers Tensile Strength Ratio SBS
a b s t r a c t Moisture damage can be defined as the loss of strength of asphaltic mixtures that resulted from the presence of water. The main objectives of this research is to investigate the influence of using hybrid elastomer and plastomer polymers modifiers, aggregate gradations and mineral fillers on moisture resistance of asphalt concrete mixture. In this study, 1% and 3% of plastomer Polyvinyl Chloride (PVC) were added for both pure asphalt binder and asphalt modified with 3% of elastomer Styrene Butadiene Styrene (SBS) to form hybrid polymers. Two types of mineral fillers were used: portland cement and limestone dust with two types of aggregate gradations: fine and coarse. A Humboldt Machine was used to measure the maximum load which makes the specimens completely fractures and then to estimate the Tensile Strength Ratio (TSR). The results of the study depict that the hybrid polymers improve the tensile strength ratio. This give an indication that hybrid polymers have great effect on improving the performance of modified asphalt binder. Also, results show that hybrid polymers improve the properties of flexible pavement against moisture damage and as a result increasing the durability and the service life of the pavements. According to that, it is concluded that modifying asphalt with hybrid polymers is more preferable to be used as anti-striping. Furthermore, it is deduced that fine gradation mixtures is more resistance than coarse mixtures to moisture damage. It is also recommended to use portland cement instead of limestone dust as mineral filler material in HMA. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
1. Introduction Factors of environment like air, degree of temperature, and water have a great influence on the stiffness of asphalt pavement [1]. Distresses that may occur in asphalt concrete pavement decrease the service life of pavement. When water penetrates the pavement, it will cause the reduction in the strength of the pavement [2]. Kanitpong et al. [3], studied the influence of aggregates gradation and properties on the moisture damage mechanism. They found that fine gradation mixture has higher resistance to moisture susceptibility than coarse gradation mixture. Abed and Qassim [4] studied the influence of using SBS polymer and aggregates gradation on moisture damage of the pavement, the results showed that when using the SBS modifier, TSR increased by 6.1 ⇑ Corresponding author. E-mail addresses: [email protected] (E.N. Ezzat), alaa. [email protected] (A.H. Abed).
percent for coarse gradation and 4.5 percent for fine gradation at modified asphalt content with limestone dust filler. Hamedi [5] demonstrated the effect of using PVC on the characteristics of mixtures, he was found that all of the mixtures prepared by adding PVC have less moisture sensitivity as compared with control mixtures. Also, it is deduced that adding PVC to the mixtures makes the aggregate to become hydrophobic and as a result increases asphalt mixtures resistance to moisture damage. Obaid [6] investigated the influence of using different percentage of SBS to reduce moisture damage effect and enhance resistance. The results demonstrated that adding 3% of SBS increased TSR to 84.21% which provides enhancement by 15% as compared with 73.23% for reference mix. This percentage of SBS gave the highest percentile tensile strength ratio as compared with other percentages; therefore, it can be concluded that 3% of SBS is considered the optimum value with passable results. Aburkaba and Muniandy [7] stated that fillers provide dual purposes when added to the asphalt mixtures. Firstly, they fill the voids between coarser
https://doi.org/10.1016/j.matpr.2019.09.176 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
2
E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx
aggregates particles and then strengthen the asphalt mixture of the pavement. Secondly, mixing mineral fillers with asphalt form high consistency asphalt binder which cements coarser aggregate particles with each other’s. Aljassar et al. [8] used limestone and Ordinary Portland Cement (OPC) as mineral filler. They concluded that using OPC provides higher percentage of retained strength. 2. Objectives The main objectives of this research is to study the effect of aggregate gradations, types of mineral fillers and hybrid elastomer and plastomer polymers modifiers on moisture resistance of asphaltic concrete mixtures.
Fig. 1. Gradation blends with Iraqi and superpave requirements.
3. Materials properties All of the materials used in this work are currently used in road construction in Iraq and locally available. They include asphalt cement, aggregates and mineral fillers in addition to additives. 3.1. Asphalt binder The asphalt cement was brought from Al-Daurah refinery in Baghdad. It was with penetration grade of (40–50). Table 1 depicts the physical properties of asphalt cement. 3.2. Aggregates Two aggregates blends with 12.5 mm nominal maximum size are selected to design aggregate structure: a coarse blend and a fine blend. Fig. 1 demonstrates the specification limits of the used gradations.
Fig. 2. SEM image for polyvinyl chloride.
temperatures, while butadiene contributes to give the flexibility for asphalt at low temperatures.
3.3. Mineral filler Mineral filler is usually used to enhance the properties of the mixture and fill the voids. Two types of mineral fillers were used: limestone dust with specific gravity of 2.74 and it was brought from the lime factory in governorate of Karbala and portland cement is from factory of Kubbesa which obtained from the local market. 3.4. Additives Two types of polymers were used in this study, the first plastomer polymer is polyvinyl chloride (PVC) which was purchased from the local markets and produced by SABIC Company. Fig. 2 shows SEM of PVC which is found that its particles size is in the range of 0.08–0.22 mm, while Table 2 depicts the typical property of PVC. The second elastomer polymer is (SBS) (Styrene Butadiene Styrene). The chemical chain of SBS is made up of three parts: styrene provides durability and performance for asphalt at high
4. Preparation of hybrid elastomer and plastomer modified asphalt The process of preparation the hybrid modified asphalt is conducted in two stages. The first stage, Included mixing pure asphalt with 3% Styrene Butadiene Styrene (SBS) together by mixer device at 2220 rpm, for 3.5–4.0 h, while keeping the temperature at 180 °C to ensure compatibility and homogeneity. At the second stage, mixing of the modified asphalt with PVC to form hybrid modified asphalt mixtures is performed. The hybrid mixture was mixed by mixer device at 2220 rpm. Also, the rotation was maintained for two hours, while keeping the temperature at 165 °C. It is important to mention that 1% and 3% of PVC was added to asphalt modified by 3% of SBS by the weight of asphalt binder. (SEM) (Scanning Electron Microscopy) was used to depict how PVC and SBS particles spread in the asphalt binder as shown in Fig. 3. It is obvious from Fig. 3 that there is no agglomeration of polymers’ grains, this means that the added polymers have spread
Table 1 Asphalt cement properties according to Iraqi specifications and ASTM requirements. Tests
Penetration test RV., Pas. sec Ductility, cm Flash Point, °C Softening Point, °C
Test condition
100 g, 5 s, 25 °C, 0.1 mm 135 °C 165 °C 5 cm/min, 25 °C . . .. . .. . . 4 ± 1 °C/min
ASTM Designations
D-5. D-4402 D-113 D-92 D-36
Penetration grade 40–50 Tests results
SCRB specifications
45 0.60 0.144 120 289 49
40–50 . . .... . .. >100 Min.232 . . .. . .. . ..
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
3
E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx Table 2 Typical properties of PVC. Apparent bulk density Kg/m3
Densityg/cm3
Passing through mesh 200
Tensile strength N/mm2
K-value
Color
570
1.38
Max 4%
2.6
67
White powder
6. Results and discussion 6.1. Effect of aggregate gradations
Fig. 3. SEM image for PVC and SBS modified asphalt binder.
well in the asphalt and the mixing process has achieved the required homogeneity. Fig. 4 shows the temperature–viscosity relationship which is certified by superpave and used to determine mixing and compaction temperature for HMA.
5. Moisture sensitivity test The moisture sensitivity test was accomplished according to AASHTO T283-14 [9]. To assess the moisture damage in asphaltic concrete, samples are compacted in Marshall Machine with dimensions of 100 mm – diameter, and 63.5 ± 2.5 mm – height and approximately 7.0 ± 0.5 percent air voids ASTM D 1559 [10]. Samples are split into two groups; each group consists of three samples. One group of three samples is considered unconditioned, while the other group of the three samples is considered conditioned group. For unconditioned dry group, the samples were placed in water path for (2 h ± 10 min) at (25 ± 0.5 °C). At the end of the required time, the samples were tested to obtain ITS. For conditioned group, the samples were immersed in water at 60 °C for (24 ± 1 h) period, and then they were placed in water path for (2 h ± 10 min) at (25 ± 0.5 °C) to test finally at 25 °C after the end of the required time. All of six samples ‘‘three unconditioned and three conditioned” are tested by using the machine illustrated in Fig. 5 at a rate of 50.8 mm/min. till maximum load is obtained and the sample is completely destroyed after that the load is recorded. ITS is estimated by using the equations below:
ITS ¼ 2000
P
ð1Þ
ptD
where: P is the maximum load, N; t is the thickness of specimen, mm; D is the diameter of specimen, mm; and ITS is the Indirect Tensile Strength, kPa. After that, TSR is calculated as follows:
TSR ¼
ITSCond: ITSUncond:
100
ð2Þ
where: ITSCond. is the average tensile strength of the conditioned group, kPa; ITSUncond. is the average tensile strength of the unconditioned group, kPa; and TSR is the Tensile Strength Ratio, percent. TSR should be greater than 80 percent [11].
Aggregates gradation is an essential part of the asphalt mixture performance. Gradation of aggregate influence in all of the important characteristics of asphalt concert mixture, like: stability, stiffness, resistance to moisture damage and resistance to rutting under environmental and traffic loads. Therefore, aggregate gradation is represented as a very essential parameter in the mixture design process [12]. From Fig. 6 it is observed that tensile strength ratio (TSR) for fine gradation is more than coarse gradation mixtures by 1.22% when using Portland cement as mineral filler but TSR for fine gradation is more than coarse gradation mixtures by 2.53% when using limestone dust as mineral filler as shown in Fig. 7. Based on the above results, it can be concluded that fine gradation mixtures is more resistance to moisture susceptibility than coarse gradation mixtures. This comes up because of the little amount of air voids since there is a good interlock between fine particles which will provide a tight structure and hence make the mixture is more resistance to stripping than the coarse gradation mixture. These results confirm with results which were achieved by Abo-Qudais and Al-Shweily [13]. They deduced that mixtures following the upper limits of aggregates gradation revealed more resistance to moisture susceptibility. 6.2. Effect of hybrid elastomer and plastomer polymer modifier To control the failure that results from moisture, the antistripping additives could be recommended to use. These antistripping may include conventional polymers which play a great role in enhancing the rheological properties of asphalt binder like viscosity, softening point and ductility. This enhancement in asphalt binder characteristics will reflect on the adhesion between asphalt binder and aggregates and later on the resistance of asphaltic concrete mixtures to moisture [14]. From Fig. 8 and for fine gradation mixtures, the results demonstrate that modifying asphalt with 3% SBS can increase TSR by 4.82%, while modifying asphalt with 1% and 3% PVC increases TSR by 2.41% and 8.4% respectively. For hybrid elastomer and plastomer polymers, it is obvious that modifying asphalt with 1% PVC plus 3%SBS enhances mixtures to moisture susceptibility by 12.05%, whereas modifying asphalt with 3% PVC plus 3% SBS increases TSR to 97% which provides enhancement by 16.87% as compared with pure asphaltic mixtures. But for coarse gradation mixtures, it is also found from Fig. 8 that modifying asphalt with 3% SBS improves TSR by 4.9%, while modifying asphalt with 1% and 3% PVC will increase TSR by 2.4% and 8.5% respectively. Furthermore, for hybrid elastomer and plastomer polymers, it is observed that modifying asphalt with 1%PVC plus 3%SBS improves mixtures to moisture susceptibility by 11%, while adding 3%PVCplus 3%SBS can enhance mixtures to moisture by 15.85% as compared with control asphaltic mixtures. From Fig. 9 and for fine gradation mixtures, the results indicate that modifying asphalt with 3%SBS led to increase TSR by 3.7%, while adding 1% and 3% PVC can increase TSR by 1.2% and 6.17%respectively. Also, it is found that mixing a hybrid of 1%PVC plus 3% SBS led to increase TSR by 11.11%, whereas mixing 3%PVC plus 3% SBS increases TSR to 93% which provides enhancement to moisture susceptibility by 14.8% as compared with standard asphalt mix.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
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E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx
Fig. 4. Temperature–viscosity relationship.
Also, from Fig. 9, it can be seen that adding 3%SBS increases TSR by 5.06%, while adding 1% and 3% PVC can increase TSR by 1.3% and 7.6% respectively. Moreover, it is found that for a hybrid of 1% PVC plus 3%SBS the TSR enhances by 11.4%, whereas adding 3% PVC plus 3% SBS led to increase in TSR percentages by 15.19% as compared with references mixtures, coarse gradation with limestone dust filler. The increasing in the percentage of TSR that occurred by using 3%SBS can be attributed to the fact that when mixing SBS with bitumen, it absorbs the oil parts from the bitumen and swells up to nine times as its initial volume and install a strong physical net-
work between the asphalt binder and the polymer. This installation will lead to increase the complex modulus and adhesion between the aggregates and the asphalt binder in hot mix asphalt. As a result, increase resistance to moisture damage [15]. Also, From Figs. 8 and 9, it can be seen that the percentage of TSR is increased as the percentage of PVC is increased from 1% to 3%, this can be attributed to the fact that PVC tends to reduce air voids percentage in the mixture; therefore water become unable to penetrate and stripping the asphalt binder from aggregate. Consequently, the pavement having better resistance to moisture damage [16]. Moreover, PVC and SBS have good hydrophobic properties, which is also
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx
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Fig. 5. Moisture sensitivity samples preparation and test.
Fig. 6. Effect of aggregate gradation on moisture susceptibility using portland cement filler. Fig. 10. Effect type of filler on ITS.
Fig. 7. Effect of aggregate gradation on moisture susceptibility using limestone dust filler.
a key factor for the pavement having better resistance to moisture damage. Since hybrid elastomer and plastomer polymers are used therefore, properties of the composites are strongly related to the properties of its constituents. So, the best resistance to moisture damage is provided when using hybrid elastomer and plastomer polymers which can be attributed to the properties of SBS and PVC.
Portland cement. As a result, the TSR for mixtures with limestone dust is lower than the mixtures with Portland cement. It is found from Fig. 11 that Portland cement increases TSR by 2.5% for fine gradation mixtures while it increase TSR by 3.8% for coarse gradation mixtures as shown in Fig. 12. Therefore, it is concluded that using Portland cement as mineral filler in HMA is more preferable to provide mixtures higher resistance to moisture susceptibility than limestone dust this is due to the fact that cement mixtures have high internal friction and interlock between particles of aggregate which give the mixtures good resistance against the
6.3. Effect type of filler It is obvious from Fig. 10, that (ITS) for conditioned mixtures with limestone dust has lower resistance than mixtures with
Fig. 11. Effect type of filler on TSR for fine gradation.
Fig. 8. Effect of hybrid elastomer and plastomer polymer modifiers for fine and coarse gradation mixtures with portland cement.
Fig. 9. Effect of hybrid elastomer and plastomer polymer modifiers for fine and coarse gradation mixture with limestone dust.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
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E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx
Transportation Engineering Department and Al-Nahrain University through Civil Engineering Department. References
Fig. 12. Effect type of filler on TSR for coarse gradation.
applied loads. Therefore, the values of ITS by using cement as mineral filler were higher than using limestone powder [17]. This is confirmed with in the obtained results. 7. Conclusions The main conclusions drawn from laboratory tests results are shown as follow: 1. Fine gradation mixtures are less susceptible to moisture damage as compared with coarse gradation mixtures. 2. Modifying asphalt with hybrid polymers are more preferable to be used as anti-striping materials to reduce the effect of moisture damage in flexible pavement since modifying asphalt with 3%PVC plus 3%SBS increases TSR to 97% and 95% for fine and coarse gradation mixtures respectively, while modifying asphalt with 1%PVC plus 3%SBS increases TSR to 93% and 91% for fine and coarse gradation mixtures respectively. 3. Portland cement increases TSR by 2.5% for fine gradation mixtures while it increases TSR by 3.8% for coarse gradation mixtures. 4. Using Portland cement as mineral filler in HMA is more preferable to provide mixtures higher resistance to moisture susceptibility than limestone dust filler.
Acknowledgments The authors would like to acknowledge the partial support provided by Mustansiriyah University through Highway and
[1] A.E.A.E.-M. Behiry, Laboratory evaluation of resistance to moisture damage in asphalt mixtures, Ain Shams Eng. J. 4 (3) (2013) 351–363. [2] I.L. Al-Qadi, I.M. Abauwad, H. Dhasmana, A.R. Coenen, Effects of Various Asphalt Binder Additives/Modifiers on Moisture-susceptible Asphaltic Mixtures, Illinois Center for Transportation, 2014. [3] K. Kanitpong, N. Charoentham, S. Likitlersuang, Investigation on the effects of gradation and aggregate type to moisture damage of warm mix asphalt modified with Sasobit, Int. J. Pavement Eng. 13 (5) (2012) 451–458. [4] A.H. Abed, Z.I. Qassim, Impact of gradation and modifier on moisture susceptibility of Iraqi hot-mix asphalt, The 2nd International Conference of Buildings, Construction and Environmental Engineering, 2015. [5] G.H. Hamedi, Effects of polymeric coating the aggregate surface on reducing moisture sensitivity of asphalt mixtures, Int. J. Civil Eng. 16 (9) (2018) 1097– 1107. [6] H.A. Obaid, The effect of styrene-butadiene-styrene on moisture damage resistance of asphalt mixtures, J. Univ. Babylon 23 (2) (2015) 263–270. [7] E. Aburkaba, R. Muniandy, An overview of the use of mineral fillers in asphalt pavements, Aust. J. Basic Appl. Sci. 10 (9) (2016) 279–292. [8] A.H. Aljassar, S. Metwali, M.A. Ali, Effect of filler types on Marshall stability and retained strength of asphalt concrete, Int. J. Pavement Eng. 5 (1) (2004) 47–51. [9] AASHTO, Standard Specifications for Transportation Materials and Methods of Sampling and Testing, Part 3 Provisional Standards, 35th ed., American Association of State Highway and Transportation Officials, 2015. [10] ASTM Standards,‘‘ Roads and paving materials,” Annual Book of the American Society for Testing and Materials Standards, section 4, Vol. 04-03, 2009. [11] AASHTO, Standard Specifications for Transportation Materials and Methods of Sampling and Testing, 5th ed., American Association of State Highway and Transportation Officials, Washington, D.C., USA, 2007. [12] E. Sangsefidi, H. Ziari, M. Sangsefidi, The effect of aggregate gradation limits consideration on performance properties and mixture design parameters of hot mix asphalt, KSCE J. Civil Eng. 20 (1) (2016) 385–392. [13] S. Abo-Qudais, H. Al-Shweily, Effect of aggregate properties on asphalt mixtures stripping and creep behavior, Constr. Build. Mater. 21 (9) (2007) 1886–1898. [14] H. Özen, Rutting evaluation of hydrated lime and SBS modified asphalt mixtures for laboratory and field compacted samples, Constr. Build. Mater. 25 (2) (2011) 756–765. [15] G.D. Airey, Rheological properties of styrene butadiene styrene polymer modified road bitumens, Fuel 82 (14) (2003) 1709–1719. [16] U.T. Ghani, Waqas, Performance evaluation of waste PVC modified bitumen, Int. J. Adv. Struct. Geotech. Eng. 04 (04) (2015). [17] N.K. Rashwan, Evaluation of aggregate and mineral filler types on characteristics of hot mix asphalt, Int. J. Civil Eng. Technol. (IJCIET) 6 (6) (2015) 213–222.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures Estabraq N. Ezzat a,⇑, Alaa H. Abed b a b
Highways and Transportation Engineering Department, Al-Mustansiriyah University, Baghdad, Iraq Civil Engineering Department, Al-Nahrain University, Baghdad, Iraq
a r t i c l e
i n f o
Article history: Received 9 July 2019 Received in revised form 30 August 2019 Accepted 29 September 2019 Available online xxxx Keywords: Moisture damage PVC Hybrid polymers Tensile Strength Ratio SBS
a b s t r a c t Moisture damage can be defined as the loss of strength of asphaltic mixtures that resulted from the presence of water. The main objectives of this research is to investigate the influence of using hybrid elastomer and plastomer polymers modifiers, aggregate gradations and mineral fillers on moisture resistance of asphalt concrete mixture. In this study, 1% and 3% of plastomer Polyvinyl Chloride (PVC) were added for both pure asphalt binder and asphalt modified with 3% of elastomer Styrene Butadiene Styrene (SBS) to form hybrid polymers. Two types of mineral fillers were used: portland cement and limestone dust with two types of aggregate gradations: fine and coarse. A Humboldt Machine was used to measure the maximum load which makes the specimens completely fractures and then to estimate the Tensile Strength Ratio (TSR). The results of the study depict that the hybrid polymers improve the tensile strength ratio. This give an indication that hybrid polymers have great effect on improving the performance of modified asphalt binder. Also, results show that hybrid polymers improve the properties of flexible pavement against moisture damage and as a result increasing the durability and the service life of the pavements. According to that, it is concluded that modifying asphalt with hybrid polymers is more preferable to be used as anti-striping. Furthermore, it is deduced that fine gradation mixtures is more resistance than coarse mixtures to moisture damage. It is also recommended to use portland cement instead of limestone dust as mineral filler material in HMA. Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
1. Introduction Factors of environment like air, degree of temperature, and water have a great influence on the stiffness of asphalt pavement [1]. Distresses that may occur in asphalt concrete pavement decrease the service life of pavement. When water penetrates the pavement, it will cause the reduction in the strength of the pavement [2]. Kanitpong et al. [3], studied the influence of aggregates gradation and properties on the moisture damage mechanism. They found that fine gradation mixture has higher resistance to moisture susceptibility than coarse gradation mixture. Abed and Qassim [4] studied the influence of using SBS polymer and aggregates gradation on moisture damage of the pavement, the results showed that when using the SBS modifier, TSR increased by 6.1 ⇑ Corresponding author. E-mail addresses: [email protected] (E.N. Ezzat), alaa. [email protected] (A.H. Abed).
percent for coarse gradation and 4.5 percent for fine gradation at modified asphalt content with limestone dust filler. Hamedi [5] demonstrated the effect of using PVC on the characteristics of mixtures, he was found that all of the mixtures prepared by adding PVC have less moisture sensitivity as compared with control mixtures. Also, it is deduced that adding PVC to the mixtures makes the aggregate to become hydrophobic and as a result increases asphalt mixtures resistance to moisture damage. Obaid [6] investigated the influence of using different percentage of SBS to reduce moisture damage effect and enhance resistance. The results demonstrated that adding 3% of SBS increased TSR to 84.21% which provides enhancement by 15% as compared with 73.23% for reference mix. This percentage of SBS gave the highest percentile tensile strength ratio as compared with other percentages; therefore, it can be concluded that 3% of SBS is considered the optimum value with passable results. Aburkaba and Muniandy [7] stated that fillers provide dual purposes when added to the asphalt mixtures. Firstly, they fill the voids between coarser
https://doi.org/10.1016/j.matpr.2019.09.176 2214-7853/Ó 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Materials Engineering & Science.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
2
E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx
aggregates particles and then strengthen the asphalt mixture of the pavement. Secondly, mixing mineral fillers with asphalt form high consistency asphalt binder which cements coarser aggregate particles with each other’s. Aljassar et al. [8] used limestone and Ordinary Portland Cement (OPC) as mineral filler. They concluded that using OPC provides higher percentage of retained strength. 2. Objectives The main objectives of this research is to study the effect of aggregate gradations, types of mineral fillers and hybrid elastomer and plastomer polymers modifiers on moisture resistance of asphaltic concrete mixtures.
Fig. 1. Gradation blends with Iraqi and superpave requirements.
3. Materials properties All of the materials used in this work are currently used in road construction in Iraq and locally available. They include asphalt cement, aggregates and mineral fillers in addition to additives. 3.1. Asphalt binder The asphalt cement was brought from Al-Daurah refinery in Baghdad. It was with penetration grade of (40–50). Table 1 depicts the physical properties of asphalt cement. 3.2. Aggregates Two aggregates blends with 12.5 mm nominal maximum size are selected to design aggregate structure: a coarse blend and a fine blend. Fig. 1 demonstrates the specification limits of the used gradations.
Fig. 2. SEM image for polyvinyl chloride.
temperatures, while butadiene contributes to give the flexibility for asphalt at low temperatures.
3.3. Mineral filler Mineral filler is usually used to enhance the properties of the mixture and fill the voids. Two types of mineral fillers were used: limestone dust with specific gravity of 2.74 and it was brought from the lime factory in governorate of Karbala and portland cement is from factory of Kubbesa which obtained from the local market. 3.4. Additives Two types of polymers were used in this study, the first plastomer polymer is polyvinyl chloride (PVC) which was purchased from the local markets and produced by SABIC Company. Fig. 2 shows SEM of PVC which is found that its particles size is in the range of 0.08–0.22 mm, while Table 2 depicts the typical property of PVC. The second elastomer polymer is (SBS) (Styrene Butadiene Styrene). The chemical chain of SBS is made up of three parts: styrene provides durability and performance for asphalt at high
4. Preparation of hybrid elastomer and plastomer modified asphalt The process of preparation the hybrid modified asphalt is conducted in two stages. The first stage, Included mixing pure asphalt with 3% Styrene Butadiene Styrene (SBS) together by mixer device at 2220 rpm, for 3.5–4.0 h, while keeping the temperature at 180 °C to ensure compatibility and homogeneity. At the second stage, mixing of the modified asphalt with PVC to form hybrid modified asphalt mixtures is performed. The hybrid mixture was mixed by mixer device at 2220 rpm. Also, the rotation was maintained for two hours, while keeping the temperature at 165 °C. It is important to mention that 1% and 3% of PVC was added to asphalt modified by 3% of SBS by the weight of asphalt binder. (SEM) (Scanning Electron Microscopy) was used to depict how PVC and SBS particles spread in the asphalt binder as shown in Fig. 3. It is obvious from Fig. 3 that there is no agglomeration of polymers’ grains, this means that the added polymers have spread
Table 1 Asphalt cement properties according to Iraqi specifications and ASTM requirements. Tests
Penetration test RV., Pas. sec Ductility, cm Flash Point, °C Softening Point, °C
Test condition
100 g, 5 s, 25 °C, 0.1 mm 135 °C 165 °C 5 cm/min, 25 °C . . .. . .. . . 4 ± 1 °C/min
ASTM Designations
D-5. D-4402 D-113 D-92 D-36
Penetration grade 40–50 Tests results
SCRB specifications
45 0.60 0.144 120 289 49
40–50 . . .... . .. >100 Min.232 . . .. . .. . ..
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
3
E.N. Ezzat, A.H. Abed / Materials Today: Proceedings xxx (xxxx) xxx Table 2 Typical properties of PVC. Apparent bulk density Kg/m3
Densityg/cm3
Passing through mesh 200
Tensile strength N/mm2
K-value
Color
570
1.38
Max 4%
2.6
67
White powder
6. Results and discussion 6.1. Effect of aggregate gradations
Fig. 3. SEM image for PVC and SBS modified asphalt binder.
well in the asphalt and the mixing process has achieved the required homogeneity. Fig. 4 shows the temperature–viscosity relationship which is certified by superpave and used to determine mixing and compaction temperature for HMA.
5. Moisture sensitivity test The moisture sensitivity test was accomplished according to AASHTO T283-14 [9]. To assess the moisture damage in asphaltic concrete, samples are compacted in Marshall Machine with dimensions of 100 mm – diameter, and 63.5 ± 2.5 mm – height and approximately 7.0 ± 0.5 percent air voids ASTM D 1559 [10]. Samples are split into two groups; each group consists of three samples. One group of three samples is considered unconditioned, while the other group of the three samples is considered conditioned group. For unconditioned dry group, the samples were placed in water path for (2 h ± 10 min) at (25 ± 0.5 °C). At the end of the required time, the samples were tested to obtain ITS. For conditioned group, the samples were immersed in water at 60 °C for (24 ± 1 h) period, and then they were placed in water path for (2 h ± 10 min) at (25 ± 0.5 °C) to test finally at 25 °C after the end of the required time. All of six samples ‘‘three unconditioned and three conditioned” are tested by using the machine illustrated in Fig. 5 at a rate of 50.8 mm/min. till maximum load is obtained and the sample is completely destroyed after that the load is recorded. ITS is estimated by using the equations below:
ITS ¼ 2000
P
ð1Þ
ptD
where: P is the maximum load, N; t is the thickness of specimen, mm; D is the diameter of specimen, mm; and ITS is the Indirect Tensile Strength, kPa. After that, TSR is calculated as follows:
TSR ¼
ITSCond: ITSUncond:
100
ð2Þ
where: ITSCond. is the average tensile strength of the conditioned group, kPa; ITSUncond. is the average tensile strength of the unconditioned group, kPa; and TSR is the Tensile Strength Ratio, percent. TSR should be greater than 80 percent [11].
Aggregates gradation is an essential part of the asphalt mixture performance. Gradation of aggregate influence in all of the important characteristics of asphalt concert mixture, like: stability, stiffness, resistance to moisture damage and resistance to rutting under environmental and traffic loads. Therefore, aggregate gradation is represented as a very essential parameter in the mixture design process [12]. From Fig. 6 it is observed that tensile strength ratio (TSR) for fine gradation is more than coarse gradation mixtures by 1.22% when using Portland cement as mineral filler but TSR for fine gradation is more than coarse gradation mixtures by 2.53% when using limestone dust as mineral filler as shown in Fig. 7. Based on the above results, it can be concluded that fine gradation mixtures is more resistance to moisture susceptibility than coarse gradation mixtures. This comes up because of the little amount of air voids since there is a good interlock between fine particles which will provide a tight structure and hence make the mixture is more resistance to stripping than the coarse gradation mixture. These results confirm with results which were achieved by Abo-Qudais and Al-Shweily [13]. They deduced that mixtures following the upper limits of aggregates gradation revealed more resistance to moisture susceptibility. 6.2. Effect of hybrid elastomer and plastomer polymer modifier To control the failure that results from moisture, the antistripping additives could be recommended to use. These antistripping may include conventional polymers which play a great role in enhancing the rheological properties of asphalt binder like viscosity, softening point and ductility. This enhancement in asphalt binder characteristics will reflect on the adhesion between asphalt binder and aggregates and later on the resistance of asphaltic concrete mixtures to moisture [14]. From Fig. 8 and for fine gradation mixtures, the results demonstrate that modifying asphalt with 3% SBS can increase TSR by 4.82%, while modifying asphalt with 1% and 3% PVC increases TSR by 2.41% and 8.4% respectively. For hybrid elastomer and plastomer polymers, it is obvious that modifying asphalt with 1% PVC plus 3%SBS enhances mixtures to moisture susceptibility by 12.05%, whereas modifying asphalt with 3% PVC plus 3% SBS increases TSR to 97% which provides enhancement by 16.87% as compared with pure asphaltic mixtures. But for coarse gradation mixtures, it is also found from Fig. 8 that modifying asphalt with 3% SBS improves TSR by 4.9%, while modifying asphalt with 1% and 3% PVC will increase TSR by 2.4% and 8.5% respectively. Furthermore, for hybrid elastomer and plastomer polymers, it is observed that modifying asphalt with 1%PVC plus 3%SBS improves mixtures to moisture susceptibility by 11%, while adding 3%PVCplus 3%SBS can enhance mixtures to moisture by 15.85% as compared with control asphaltic mixtures. From Fig. 9 and for fine gradation mixtures, the results indicate that modifying asphalt with 3%SBS led to increase TSR by 3.7%, while adding 1% and 3% PVC can increase TSR by 1.2% and 6.17%respectively. Also, it is found that mixing a hybrid of 1%PVC plus 3% SBS led to increase TSR by 11.11%, whereas mixing 3%PVC plus 3% SBS increases TSR to 93% which provides enhancement to moisture susceptibility by 14.8% as compared with standard asphalt mix.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
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Fig. 4. Temperature–viscosity relationship.
Also, from Fig. 9, it can be seen that adding 3%SBS increases TSR by 5.06%, while adding 1% and 3% PVC can increase TSR by 1.3% and 7.6% respectively. Moreover, it is found that for a hybrid of 1% PVC plus 3%SBS the TSR enhances by 11.4%, whereas adding 3% PVC plus 3% SBS led to increase in TSR percentages by 15.19% as compared with references mixtures, coarse gradation with limestone dust filler. The increasing in the percentage of TSR that occurred by using 3%SBS can be attributed to the fact that when mixing SBS with bitumen, it absorbs the oil parts from the bitumen and swells up to nine times as its initial volume and install a strong physical net-
work between the asphalt binder and the polymer. This installation will lead to increase the complex modulus and adhesion between the aggregates and the asphalt binder in hot mix asphalt. As a result, increase resistance to moisture damage [15]. Also, From Figs. 8 and 9, it can be seen that the percentage of TSR is increased as the percentage of PVC is increased from 1% to 3%, this can be attributed to the fact that PVC tends to reduce air voids percentage in the mixture; therefore water become unable to penetrate and stripping the asphalt binder from aggregate. Consequently, the pavement having better resistance to moisture damage [16]. Moreover, PVC and SBS have good hydrophobic properties, which is also
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
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Fig. 5. Moisture sensitivity samples preparation and test.
Fig. 6. Effect of aggregate gradation on moisture susceptibility using portland cement filler. Fig. 10. Effect type of filler on ITS.
Fig. 7. Effect of aggregate gradation on moisture susceptibility using limestone dust filler.
a key factor for the pavement having better resistance to moisture damage. Since hybrid elastomer and plastomer polymers are used therefore, properties of the composites are strongly related to the properties of its constituents. So, the best resistance to moisture damage is provided when using hybrid elastomer and plastomer polymers which can be attributed to the properties of SBS and PVC.
Portland cement. As a result, the TSR for mixtures with limestone dust is lower than the mixtures with Portland cement. It is found from Fig. 11 that Portland cement increases TSR by 2.5% for fine gradation mixtures while it increase TSR by 3.8% for coarse gradation mixtures as shown in Fig. 12. Therefore, it is concluded that using Portland cement as mineral filler in HMA is more preferable to provide mixtures higher resistance to moisture susceptibility than limestone dust this is due to the fact that cement mixtures have high internal friction and interlock between particles of aggregate which give the mixtures good resistance against the
6.3. Effect type of filler It is obvious from Fig. 10, that (ITS) for conditioned mixtures with limestone dust has lower resistance than mixtures with
Fig. 11. Effect type of filler on TSR for fine gradation.
Fig. 8. Effect of hybrid elastomer and plastomer polymer modifiers for fine and coarse gradation mixtures with portland cement.
Fig. 9. Effect of hybrid elastomer and plastomer polymer modifiers for fine and coarse gradation mixture with limestone dust.
Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176
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Transportation Engineering Department and Al-Nahrain University through Civil Engineering Department. References
Fig. 12. Effect type of filler on TSR for coarse gradation.
applied loads. Therefore, the values of ITS by using cement as mineral filler were higher than using limestone powder [17]. This is confirmed with in the obtained results. 7. Conclusions The main conclusions drawn from laboratory tests results are shown as follow: 1. Fine gradation mixtures are less susceptible to moisture damage as compared with coarse gradation mixtures. 2. Modifying asphalt with hybrid polymers are more preferable to be used as anti-striping materials to reduce the effect of moisture damage in flexible pavement since modifying asphalt with 3%PVC plus 3%SBS increases TSR to 97% and 95% for fine and coarse gradation mixtures respectively, while modifying asphalt with 1%PVC plus 3%SBS increases TSR to 93% and 91% for fine and coarse gradation mixtures respectively. 3. Portland cement increases TSR by 2.5% for fine gradation mixtures while it increases TSR by 3.8% for coarse gradation mixtures. 4. Using Portland cement as mineral filler in HMA is more preferable to provide mixtures higher resistance to moisture susceptibility than limestone dust filler.
Acknowledgments The authors would like to acknowledge the partial support provided by Mustansiriyah University through Highway and
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Please cite this article as: E. N. Ezzat and A. H. Abed, The influence of using hybrid polymers, aggregate gradation and fillers on moisture sensitivity of asphaltic mixtures, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.176