Using ash waste as a modifier for asphalt binders

Khalid Ghuzlan, Ghazi Al-Khateeb & Abdullah Abu Damrah

Journal of Material Cycles and Waste Management Official Journal of the Japan Society of Material Cycles and Waste Management (JSMCWM) and the Korea Society of Waste Management (KSWM)

ISSN 1438-4957 Volume 15 Number 4

J Mater Cycles Waste Manag (2013) 15:522-529 DOI 10.1007/s10163-013-0135-8

1 23 Your article is protected by copyright and all rights are held exclusively by Springer Japan. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”.

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J Mater Cycles Waste Manag (2013) 15:522–529 DOI 10.1007/s10163-013-0135-8

REVIEW

Using oil shale ash waste as a modifier for asphalt binders

Khalid Ghuzlan • Ghazi Al-Khateeb • Abdullah Abu Damrah

Received: 19 September 2012 / Accepted: 12 March 2013 / Published online: 16 May 2013 Ó Springer Japan 2013

Abstract: Oil shale rocks represent one of the most Introduction available sources of energy. Jordan land contains about 50 billion tons of oil shale, which makes Jordan the third in Energy is the soul of the new civilization. Oil is the main the world of the reserve of this material. Oil shale ash is a energy source in the recent era. Annual oil consumption is byproduct of the oil shale process and very high and expected to increase every year due to world considered a waste material and may cause hazards for population growth and due to the high rate of development human health. In this study, the effect of oil shale ash on in the entire world. Thus, it is expected that the oil will run asphalt binder rheological properties at higher temperatures out within the next few decades. Searching for other was investigated. Five oil shale ash to asphalt (OSA/A) sources of energy becomes essential; the best sources of percentages by volume (0, 5, 10, 15, and 20 %) were used. energy would be the sustainable sources such as the solar The complex shear modulus (G*) and phase angle (d)of and wind energy. However, there are still many challenges asphalt binders were investigated using the Superpave facing these sources of energy. Dynamic Shear Rheometer and the rotational Oil shale rocks represent one of the most available (RV). It was found that increasing the OSA/A percentage sources of energy in the world. The world reserve of this increased the G* value and the RV of asphalt binders, and material exceeds hundreds of billions of tons of oil shale improved the Superpave rutting parameter, but did not rocks, which may be used to produce energy. Jordan’s affect significantly the phase angle. Thus, adding oil shale reserve of oil shale rock exceeds 50 billion tons [1], and ash (the waste material) to asphalt binder enhanced with the dramatic increase of oil prices, Jordan started its rheological properties and performance at high looking into manufacturing oil shale ash to produce oil. temperatures. Crude is produced form heating the (found in the oil shale rock) where gases and char are Keywords Oil shale ash Waste Property of recycled formed also. The oil shale manufacturing process that is products Rheology Recycling Asphalt binder used to produce oil has an environmental impact which includes , water discharge and ash. Sedimentation can be used to treat the wastewater dis- charge in addition to some other methods. Dust removers, and sulfur dioxide absorber may be used to reduce the air pollution. Oil shale ash is a byproduct of the oil shale manufacturing process. This ash is a waste material and K. Ghuzlan (&) G. Al-Khateeb A. A. Damrah may cause a hazard for human health. Therefore, it is Department of Civil , Jordan University of Science essential to utilize this byproduct material. and Technology, P.O. Box 3030, Irbid 22110, Jordan e-mail: [email protected] Oil shale ash have been used for mine backfilling, agricultural use, and production. Ground disposal is G. Al-Khateeb e-mail: [email protected] a waste method that has some negative environmental URL: http://www.just.edu.jo/~ggalkhateeb impacts. Spent shale may contain leachable salts and an 123 Author's personal copy

J Mater Cycles Waste Manag (2013) 15:522–529 523 organic pyrolytic product which has always erosion noticed by the addition of oil shale as up to 10 % by vol- potential especially if surface disposal is used [2]. Alkali ume of the asphalt binder. hydrothermal activation was used to convert oil shale ash Al-Khateeb and Al-Akhras [10] studied the effect of into zeolite, which was used to remove cadmium and lead cement additive on some properties of asphalt binder using from wastewater [3]. In addition, the hydrated oil shale ash Superpave testing methods. The cement was added to the has a potential to be used in wastewater treatment as fil- asphalt binder at 5, 10, 15, 20, 25 and 30 % by volume of tration material [4]. asphalt binder. Oil shale was found to be effective in the production of The properties of modified asphalt binder were investi- Portland cement. Furthermore, a standard for using burnt gated. Superpave rotational viscosity (RV) and the shale in the rapid hardening of asphalt cement was devel- dynamic shear rheometer (DSR) tests for the modified oped in Estonia [5]. Smadi and Haddad [6] replaced binders were conducted. cement with oil shale ash in the Portland cement . It was found in their study that the addition of Portland The optimum compressive strength was obtained at 10 % cement to asphalt binders increased the RV of asphalt by weight. Furthermore, it was found that replacement of binders at 135 °C at different rotational speeds. The opti- cement with oil shale ash up to 30 % would not reduce its mum percentage of cement to asphalt was found to be 15 compressive strength. percent. This percentage provided a balanced increase in the value of the DSR G*/sin d rutting parameter and the RV of asphalt binders. The increase in cement to asphalt Oil shale ash waste as a modifier for asphalt binder percentage increased the stiffness of asphalt binders rep- resented by the complex shear modulus (G*) value and also Additives may be defined as any material that is added to improved the value of the rutting parameter (G*/sin d)at the binder to modify its properties. Desirable asphalt binder used temperatures. properties include resistance to fatigue cracking, rutting, Tuncan et al. [11] studied the properties of asphalt and thermal cracking. Furthermore, adding some materials binders and mixture after using rubber and to the binder may reduce the required structural thickness plastic concentrations as additives. Furthermore, they of the pavement section. replaced the filler in the asphalt concrete mixtures with fly Asphalt modifiers may be divided as fillers, fibers, ash and rubber powder. It was found that, specimen’s , polymers (elastomeric and plastomeric), and strength and Marshall Stability increased with adding antistripping agents, and crumb rubber [7]. plastic, on the other hand, adding rubber decreased the Khedaywi and Abu-Orabi [8] added the following strength. This study showed that fly ash could be used as materials to asphalt binder: oil shale ash, rubber ash, husk filler in the asphalt concrete mixtures. ash and polyethylene. Each material was added (separately) Yi-qiu et al. [12] studied the properties of the asphalt to the asphalt binder at 0, 5, 10, 15, and 20 % of ashes by mastics with mineral filler at low and high temperatures. volume of binder. The effect of adding these materials to Different filler/asphalt ratios by weight were used. The the asphalt binder was investigated. Specific gravity, soft- rheological behavior of the mastic was found to be non- ening point, penetration and ductility tests were performed linear and can be fitted as an exponential function. The for the modified asphalt binders. It was found that by balanced mastic properties at low and high temperatures increasing the percentage of these additives, the penetra- were achieved at filler/asphalt ratios ranging from 0.9 to tion and ductility of the modified asphalt binder decreased. 1.4. On the other hand, increasing the amount of ashes resulted Adding oil shale ash to asphalt binder may represent a in an increase in the specific gravity, but increasing the good way to utilize it. This may represent a modification amount of polyethylene in the asphalt binder decreased the that may improve the performance of the asphalt binder specific gravity. Additionally, increasing the amount of and the asphalt mixture in the future. Many researchers additives in the binder increased the softening point of the used different additives to modify asphalt binders. Oil shale modified asphalt binder. ash was one of these additives. The investigation included Al-Masaeid et al. [9] evaluated the influence of adding traditional tests such as ductility, penetration, and softening oil shale ash to binder on the asphalt concrete mixtures point. However, no previous studies used the Superpave properties under normal as well as freezing and thawing tests to investigate the effect of adding oil shale ash on conditions. Oil shale ash percentages, varied from 0 to asphalt binder’s rheological properties. 20 % by volume of asphalt binder. The results of their In this study, the rheological properties of the modified study indicated that the behavior of the asphalt concrete binder (with oil shale ash) were investigated using the mixes under dry and freeze–thaw conditions were Superpave tests namely using the DSR and the RV. Dif- improved by adding oil shale ash. The improvement was ferent oil shale ash to asphalt binder percentages (OSA/A) 123 Author's personal copy

524 J Mater Cycles Waste Manag (2013) 15:522–529 by volume were used. In addition, different testing parameters were used such as loading frequency and tem- perature. The performance of asphalt binder modified with the waste material (oil shale ash) was studied through using the DSR and the RV. This study did spotlight using the oil shale ash in highway construction (waste it) without scarifying the field performance of the pavement.

Materials and preparation of samples

An asphalt binder having a penetration grade of 60/70 obtained from the Jordan Refinery (JPR) was used in this study. The equivalent Performance Grade (PG) for this asphalt binder according to the Superpave asphalt binder classification system is PG 64-10. The oil shale ash Fig. 1 DSR test samples was obtained from the El-Lajjun deposit at the western part to remove it from the silicone mold and put it between the of central Jordan. The oil shale ash is the outcome of direct plate and the spindle of the DSR. burning of the oil shale rock conducted by the Natural Resources Authority in Jordan. It is composed of several components including mainly: CaO, SiO2, and Al2O3. The RV test results and analysis oil shale ash was sieved using sieve No. 200 (75 lm). The specific gravity of oil shale ash was determined according The Brookfield viscometer is used to conduct the RV test to ASTM C128 standard test method [13] and found to be (Fig. 2). Fresh binder and the OSA/A mastics with per- 2.699. centages of 5, 10, 15, 20, and 25 % by volume of asphalt The oil shale ash-asphalt binder mastics were prepared binder were tested. In the RV test a spindle (with specific with the following oil shale ash to asphalt binder (OSA/A) diameter) rotates through the sample at 20 rpm. During the percentages: 5, 10, 15, 20, and 25 % by volume of asphalt test, spindle rotation inside the sample is faced with resis- binder. A mechanical mixer was used to prepare the mastics at tance due to the viscosity of the asphalt binder; to keep the a mixing temperature range between 145 and 152 °Cthatwas Superpave standard rotational speed (20 rpm), a torque is found using the temperature–viscosity relationship of the applied to the spindle. From the required torque, rotational American Society for Testing and Materials (ASTM). speed, and the other device parameters, the shear strain and The rotational viscometer (RV) is used to evaluate the the RV can be obtained using the following equations: binder in its fresh state (i.e., in the tank at the asphalt T plant). The RV test was used to simulate the workability of s ¼ ; ð1Þ 2pR2L asphalt binder at high temperatures. The purpose of con- s ducting this test is to ensure that the asphalt binder is fluid 2-R2R2 c ¼ ÀÁc s ; ð2Þ enough for pumping and mixing. In addition, temperature 2 2 2 x Rc Rs ranges for selecting Hot Mix asphalt (HMA) mixing and s compaction temperatures are established using the rota- g ¼ ; ð3Þ c tional viscometer. The AASHTO T316 standard test method was used to where L = the effective spindle length (m); Rc = container prepare the RV test samples [14]. To prepare test samples, radius (m); Rs = spindle radius (m); w = rotational speed enough fresh and OSA/A mastic (approximately 30 g) is (radians/s); x = radial location where shear rate is being heated for enough period of time. Then the material is calculated (m); g = dynamic viscosity (Pa.s); s = shear poured into the RV container to reach an adequate level stress (N/m2); c = shear rate (s-1); and T = torque (N.m). below the top of the container. Superpave requires a maximum viscosity limit The samples of the DSR test were prepared in accor- of 3 Pa.s = 3,000 centi-Poise (cP) when tested at 135 °C dance with the AASHTO T315 standard test method [15]. [16, 17]. Asphalt binder should be workable through being The fresh asphalt binder (or OSA/A mastic) was heated for sufficiently fluid for pumping during delivery and in plant enough period of time. Then it was poured into the silicone operations; this can be achieved by ensuring the maximum mold (25.0 mm in diameter) to get the required DSR test limit for viscosity (3,000 cP). A higher stiffness (viscosity sample (Fig. 1). Then the sample is cooled down to be able value) for the asphalt binder is normally required in the 123 Author's personal copy

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DSR test results and analysis

Asphalt binder is considered a viscoelastic material. Vis- coelastic behavior means asphalt binder behaves like both a viscous material (such as liquid or water), and an elastic material (such as rubber). Asphalt binder is not completely viscous and not completely elastic; it is a combination of both materials depending on both temperature and time of loading. The effect of time can be compensated by tem- perature (superposition concept of asphalt binder). Asphalt binder behavior at a short time and at high temperature is equivalent to the behavior at a low temperature and longer Fig. 2 RV concept times. Superpave system in order to reduce the permanent defor- At high temperatures or under sustained (or slow mov- mation (rutting) that occurs in HMA pavements; yet ing) trucks, asphalt binder behaves like viscous liquids. according to the Superpave criteria, the maximum value for This explains how rutting or permanent deformation the RV at 135 °Cis3Pa.s= 3,000 cP to avoid cracking in develops in HMA. On the other hand, at low temperatures HMA pavements. The RV values of the modified binder or under rapid moving trucks, asphalt binder behaves as an obtained at each OSA/A percentage and at each test tem- elastic solid. Even though this elastic behavior occurs at perature are shown in Table 1. Results summarized in low temperatures; asphalt binder at these temperatures may Table 1 make it clear that as the OSA/A percentage become brittle and breaks under excessive repeated loading increased, the viscosity also increased. Viscosity at a 25 % causing the low-temperature cracking. At medium to high OSA/A percentage increased about 260 % of the value for service temperatures, asphalt binders have viscoelastic the fresh binder. Consequently, the maximum viscosity limit behavior. of 3 Pa s is achieved at all OSA/A percentages. It is clear Asphalt binder behaves simultaneously as viscous from the results shown in Table 1 that the RV results could material and elastic material. The relationship between be optimized to provide the best HMA construction and these two modes of behavior controls the resistance of performance outcome. The RV at 15 % OSA/A percentage fatigue cracking and rutting. Stiff and elastic material is was almost double the value at 0 % (fresh binder). The good for rutting resistance, while flexible and elastic relationship between the RV and the OSA/A percentage at a material is good to resist fatigue cracking. The balance rotational speed of 20 rpm is shown in Fig. 3. The data was between these parameters controls the desired pavement best fitted with the exponential function that produced a high performance. Thus, the viscous and elastic behavior of the coefficient of simple determination (r2)of0.98. material needs to be characterized. Past asphalt binder tests do not have the ability to do so. Therefore, the DSR is used Table 1 Rotational viscosity at 135 °C to measure the viscous and elastic properties of asphalt binder. The DSR measure the viscoelastic properties of a Oil shale ash content (%) 0 5 10 15 20 25 thin asphalt binder sample placed between an oscillating Average viscosity at 135 °C 448 578 753 888 1,415 1,663 (cP) spindle and fixed plate. The DSR measures the complex shear modulus (G*), and phase angle (d) of the asphalt binder. By measuring 2000 these two parameters the entire viscoelastic behavior of the asphalt binder is captured. The complex shear modulus 1600 (G*) is defined as the percentage of the maximum shear 1200 stress to the maximum shear strain. Phase angle (d)is defined as the time lag between the applied shear stress and 800 y = 439.68e 0.0538x the response (shear strain). The following equations are 2 400 R = 0.9844 used to calculate the complex shear modulus (G*), and phase angle (d): Rotational Viscosty,c 0 0 5 10 15 20 25 30 2T smax ¼ 3 ; ð4Þ OSA/A Percentage pr hr c ¼ ; ð5Þ Fig. 3 Rotational viscosity at 135 °C and 20 rpm versus OSA/A max h percentage 123 Author's personal copy

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s jjG ¼ max ; ð6Þ test was conducted at test temperatures of 58, 64, 70, and cmax 76 °C(a6° increment was used similar to that used in the and d ¼ 360ðtÞðf Þ; ð7Þ Superpave asphalt binder classification system) using a loading frequency of 10 rad/s (1.59 Hz). High temperature T where smaxis maximum applied shear stress, the maxi- properties of the OSA/A mastics were obtained; the testing r mum applied torque, radius of binder specimen (either matrix is shown in Table 2. 12.5 or 4 mm), cmax the maximum resulting shear strain, h The complex shear modulus (G*) values and the phase h the deflection (rotation) angle, the specimen height angle (d) values were obtained for all the OSA/A per- G (either 1 or 2 mm), j *j complex shear modulus and d is centages at the four test temperatures. Table 3 shows the the phase angle (degrees). total complex shear modulus values of the modified binder The DSR test is conducted according to the procedures obtained at each OSA/A percentage and at each test described in the AASHTO T315 standard test method [15]. temperature. In the DSR test the asphalt binder is placed between an A plot of the OSA/A percentages versus the G* values oscillating spindle from the top and a fixed plate at the was obtained for all temperatures as shown in Fig. 4. The bottom. For one cycle, the spindle oscillates from a point increase in the OSA/A percentage resulted in a significant like A then moves to a point like B, then oscillates back to exponential increase in the G* value as shown in this point A, and finally oscillates to the other side to point C figure. The exponential function was found to be the best-fit and so forth for all cycles. function that represented these results. The models for the During the test a force (shear stress, s) is applied to the G* value as a function of the OSA/A percentage are asphalt sample, then the resulting shear strain (c) is mea- summarized in Table 4 for all test temperatures. sured. The time lag between the shear stress and the In this figure, it is also obvious that the difference in G* resulting shear strain is also measured (phase angle). values between the different temperatures was higher at Finally, the complex shear modulus value (jG*j) is calcu- higher OSA/A percentages than that at lower OSA/A lated using Eq. 6. percentages. For a perfect elastic material, there will be no time Phase angle (d) values were obtained for all the OSA/A lag between the force and the response, i.e., the phase percentages at the four test temperatures. Table 5 shows angle, d = 0. This means the entire deformation is the phase angle values of the modified binder obtained at recoverable. On the other hand, for perfectly viscous each OSA/A percentage and at each test temperature. material the time lag between the force and the response is very large and phase angle, d = 90°. The deformation in the material is completely not recoverable. However, Table 2 DSR testing matrix under real pavement temperature (under traffic service) the asphalt binder behaves as viscoelastic material, i.e., Variable Number Value it shows both elastic and viscous behavior at the same OSA/A percentage 6 0, 5, 10, 15, 20, and 25 time. The phase angle will vary between 0 and 90°.The Temperature (°C) 4 58, 64, 70, and 76 complex shear modulus (G*) represents the total resis- Frequency in rad/s (Hz) 1 10 (1.59) tance of the material to deformation when repeatedly Replicates 3 3 Samples sheared. It consists of two parts, the elastic and the Total 6 9 4 9 1 9 3 = 72 viscous parts. The elastic part indicates that the asphalt binder behaves like an elastic solid and returns to its original shape after a load is removed (recoverable deformation); the viscous part (deformation due to Table 3 Average complex shear modulus (G*) values loading is not-recoverable, i.e., permanent deformation), OSA/asphalt percentage G* value (Pa) indicates that the asphalt binder behaves like a viscous liquid and cannot return to its original shape after a load Temperature (°C) is removed. The phase angle, d represents the relative 58 64 70 76 amount of recoverable and permanent deformation. Thus, the DSR, by measuring G*valueandd,isableto 0 4,089 1,859 866 434 determine the total complex shear modulus as well as its 5 4,699 2,333 1,097 570 elastic and viscous components. 10 6,166 2,921 1,492 729 In this study, fresh asphalt binder and OSA/A mastics 15 7,669 3,637 1,701 885 percentages of 5, 10, 15, 20, and 25 % by volume of 20 8,576 4,257 2,114 1,105 asphalt binder were tested using the DSR test. The DSR 25 12,038 5,578 2,825 1,506

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Fig. 4 G* values versus OSA/A ratio at different temperatures Fig. 5 Phase angle versus OSA/A ratio at different temperatures

Table 4 Models for the jG*j and OSA/A relationship at each Table 6 Average jG*j/sin d values temperature OSA/asphalt percentage jG*j/sin d (Pa) Temperature (°C) Exponential model r2 Temperature (°C) 58 jG*j = 3.9672e4.24 (OSA/A) 0.99 64 jG*j = 1.8762e4.30 (OSA/A) 1.00 58 64 70 76 4.58 (OSA/A) 70 jG*j = 0.8802e 0.99 0 4,187 1,885 874 437 4.80 (OSA/A) 76 jG*j = 0.43992e 1.00 5 4,819 2,370 1,107 573 10 6,294 2,957 1,502 731 15 7,824 3,682 1,713 888 Table 5 Average phase angle (d) values 20 8,732 4,304 2,128 1,109 25 12,262 5,641 2,843 1,511 OSA/asphalt percentage Phase angle d (°) Temperature (°C) 58 64 70 76 value for RTFO-aged asphalt binders at the high perfor- mance grade temperature. 0 77.6 80.5 82.7 84.0 The rutting parameter (|G*|/sin d) values were obtained 5 77.2 79.9 82.2 83.9 for all the OSA/A percentages at the four test temperatures. 10 78.4 81.0 83.2 85.0 Table 6 shows the rutting parameter (|G*|/sin d) values of 15 78.6 81.1 83.3 85.0 the modified binder obtained at each OSA/A percentage 20 79.2 81.5 83.6 85.2 and at each test temperature. 25 79.0 81.5 83.6 85.1 The relationship between |G*|/sin d versus the OSA/A percentages were plotted as shown in Fig. 6. The best fit The OSA/A percentage versus the phase angle (d) for this relation is the exponential function that produces relationship was illustrated in Fig. 5. The effect of the a high coefficient of determination (r2) as shown in increase in the OSA/A percentage on the phase angle (d) Table 7. was not significant according to this figure. That is to say, The dashed horizontal line shown in Fig. 6 represents that the addition of the oil shale ash material did not change the criterion of the Superpave rutting parameter (|G*|/sin the elastic behavior of the asphalt binder. d = 1.0 kPa minimum). The curves of 58 and 64 °C pas- Rutting in HMA pavements is defined as the accu- sed the Superpave lower limit of the G*/sin d value at all mulation of non-recoverable (permanent) deformation. In OSA/A percentages including the 0.0 percentage. On the the Superpave system rutting was addressed through using other hand, the 76 °C curve failed to meet the minimum what is called a rutting parameter. The rutting parameter requirement of the G*/sin d value at all OSA/A percentages is defined as G*/sin d (sometimes called the high tem- except the 25 % OSA/A percentage. However, the 70 °C perature stiffness). The Superpave criteria established a curve passed the criterion of the jG*j/sin d value at OSA/A lower limit of 1.0 kPa for the G*/sin d value for fresh percentages of 15 % and higher. In Fig. 6, the difference in (unaged) asphalt binders and 2.2 kPa for the G*/sin d |G*|/sin d values between the different temperatures was

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7. The addition of oil shale ash to asphalt binders increased the RV of asphalt binders at a temperature of 135 °C and rotational speed of 20 rpm. 8. Adding oil shale ash to asphalt binder is a way to utilize this waste material in the construction of asphalt pavements and at the same time improves the rheological properties of asphalt binder and, hence, the performance of asphalt pavements. 9. Further research is needed to study the behavior of asphalt binders modified with oil shale ash waste material although Jordan’s climate is not severe in the low-temperature range. In addition, it is recom- mended to further study the effect of adding oil shale Fig. 6 G*/sin d values versus OSA/A ratio at different temperatures ash to binder on the fatigue (cracking) properties through using aged materials. 10. In this study, oil shale ash is used as an additive to the Table 7 Models for the jG*j/sin d and OSA/A percentage at each test temperature binder, however, it can be used as filler in the Hot Mix Asphalt (HMA) and the effect of using it as filler Temperature (°C) Exponential model r2 in the HMA is recommended for further study. 58 jG*j/sin d = 4.065e4.214 (OSA/A) 0.98 11. Further research is recommended to ensure that 64 jG*j/sin d = 1.904e4.280 (OSA/A) 1.00 recycled products/materials contain no toxic sub- 70 jG*j/sin d = 0.8878e4.567 (OSA/A) 0.99 stances so that the use of recycled materials does not 76 jG*j/sin d = 0.4423e4.791 (OSA/A) 1.00 cause environmental pollution and human health risks. higher at higher OSA/A percentages than that at lower OSA/A percentages. References

1. Bsieso MS (2003) Jordan’s experience in oil shale studies Conclusions and practical applications employing different technologies. In: Oil shale, vol 20, 3rd edn. Estonian Academy Publishers, Estonia, pp 360–370 (SPECIAL ISSN 0208-189X) Based on the analysis and results of this study, the fol- 2. Routson R, Wildung R, Bean R (1979) A review of the envi- lowing conclusions and applications were drawn: ronmental impact of ground disposal of oil shale wastes. J Envi- ron Qual 8(1):14–19 1. The increase of the OSA/A percentage resulted in an 3. Shawabkeh R, Al-Harahsheh A, Hami M, Khlaifat, A (2004) increase in the complex shear modulus (G*) value of Conversion of oil shale ash into zeolite for cadmium and lead the asphalt binder (asphalt binder stiffness). removal from wastewater. 83(7–8):981–985 ¨ 2. The difference in G* values between the different 4. Kaasik A, Vohla C, Mo˜tlep R, Mander U, Kirsima¨e K (2008) Hydrated calcareous oil-shaleash as potential filter media for temperatures was higher at higher OSA/A percent- phosphorus removal in constructed wetlands. Water Resour ages than that at lower OSA/A percentages. 42(5):1315–1323 3. The effect of the increase of the OSA/A percentage 5. Hanni R (1996) Energy and valuable material by-product from on the phase angle (d) and the elastic behavior of the firing Estonian oilshale. Waste Manag 16(1–3):97–99 6. Smadi M, Haddad R (2003) The use of oil shale ash in Portland asphalt binder was insignificant. cement concrete. Cement Concr Compos 25(1):43–50 4. The increase in the OSA/A percentage improved the 7. Bahia H, Hanson D, Zeng M, Zhai H, Khatri M, Anderson R Superpave rutting parameter (jG*j/sin d) at all (2001) Characterization of Modified Asphalt Binders in Super- temperatures. pave Mix Design, National, NCHRP Report 459, Washington, D.C. 5. The increase in OSA/A percentage improved the 8. Khedaywi TS, Abu-Orabi ST (1989) Effect of oil shale ash, Superpave high temperature performance grade (the rubber ash, husk ash, and polyethylene on properties of asphalt high temperature at which the asphalt binder passed cement. J Petroleum 8(2):193–206 the Superpave criteria for jG*j/sin d). 9. Al-Masaeid H, Khedaywi T, Smadi M (1989) Properties of 6. The difference in G* /sin d values between the asphalt-oil shale ash bituminous mixtures under normal and j j freeze-thaw conditions. J Transp Res Board (TRB), Transporta- different temperatures was higher at higher OSA/A tion Research Record No. 1228, National Research Council, percentages than that at lower OSA/A percentages. Washington, D.C., USA, pp 54–62

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10. Al-Khateeb GG, Al-Akhras NM (2011) Properties of Portland AASHTO T316. Standard Method of Test for Viscosity Deter- cement-modified asphalt binder using Superpave tests. Constr mination of Asphalt Binder Using Rotational Viscometer Build Mater J (CBMJ) 25:926–932 15. American Association of State Highway and Transportation 11. Tuncan M, Tuncan A, Cetin A (2003) The use of waste materials Officials (AASHTO) (2008) AASHTO Standard Test Methods. in asphalt concrete mixtures. Waste Manag Res 21(2):83–92 AASHTO T315 Standard Method of Test for Determining the 12. Yi-qiu T, Li Z-H, Zhang X-Y, Dong Z-J (2010) Research on Rheological Properties of Asphalt Binder Using a Dynamic Shear high- and low-temperature properties of asphalt-mineral filler Rheometer (DSR) mastic. J Mater Civil Eng 22(8) (Technical Notes, posted ahead 16. (2001) The Asphalt Institute (AI) Superpave Mix Design Series of print) No. 1 (SP-1), Superpave Mix Design, Asphalt Institute Research 13. American Society for Testing and Materials (ASTM) (2007) Center, Lexington, Kentucky (KY), USA ASTM Standard Test Methods. ASTM C128. Relative Density 17. (2001) The Asphalt Institute (AI) Superpave Mix Design Series (Specific Gravity), and Absorption of Fine Aggregate No. 2 (SP-2), Superpave Mix Design, Asphalt Institiute Research 14. American Association of State Highway and Transportation Center, Lexington, Kentucky (KY), USA Officials (AASHTO) (2006) AASHTO Standard Test Methods,

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