Pollution Reduction and Reuse of Sludge Waste in Asphalt Paving Mixtures

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1 Pollution Reduction and Reuse of Sludge Waste in Asphalt Paving Mixtures ZIAD GHAZAWI*, TAISIR KHEDAYWI**AND ALAA GOUNEEM Department of Civil Engineering, Jordan University of Science and Technology, P.O.Box Irbid, Jordan. * alghzawi@gmail.com ** khedaywi@just.edu.jo Abstract Sludge waste is produced in large amount as result of wastewater treatment in Jordan, which establishes an environmental problem. This research is to investigate the probability of consuming these products in asphalt paving mixtures. The main objective of this research is to evaluate the effect of sludge reuse on the properties of asphalt concrete mixtures. To conduct this research, sludge was used as part of aggregate as a percent weight of mineral filler with five contents (.%, 25.%, 5.%, 75.%, and 1. %), then the filler used to establish Marshall specimens which in turn were used in Marshall properties tests. It has been found that stability, flow, and air voids increase then decrease with increasing amount of sludge waste in the mix, while loss of stability and voids in mineral aggregate decrease with increasing percentage of sludge in the mix. Also, stiffness decreases then increases with the increasing amount of sludge. Keywords: Asphalt mixtures; sludge; stability; environmental problem. 1. Introduction Due to the problem of decreasing water in many countries of world, the demand for new source of water is increasing. The wastewater treatment is one of these new sources and there are a huge number of wastewater treatment plants in many countries of the world. Jordan as any poor water countries have many wastewater treatment plants, and that wastewater treatment plant are produce large quantities of sludge waste which produce due to primary and secondary treatment processes of wastewater that can be considered as an environmental problem. There is no efficient and specified way to handle the sludge but in-some time it is used as fertilizer for soil. For these reasons the idea of using dry sludge in asphalt mixture has been as a part of aggregate is born. Some previous studies indicate that using different waste material will increase asphalt mixture resistance to permanent deformation, fatigue cracking, and with cheaper cost than that for ordinary asphalt mixture. Other indicated that using of different resources will improve the performance of mixture with higher Marshall stability, greater tensile strength, larger stiffness modulus and higher resistance to freeze and thaw damage in comparison with mixture without waste materials, [1], [2], []. The main objective of this research is to study the effect of sludge on properties of asphalt paving mixture. 2. Literature Review 2.1 Methods of sludge disposal 1. Landfill disposal from a management and materials handling perspective, land filling is perhaps the simplest solution. From an economic standpoint, land filling presently compares favorably with other options. Nevertheless, as landfill space becomes more limited and tipping fees (waste-dumping costs) increase. From an environmental standpoint, land filling prevents the release of any sludge borne pollutants or pathogens by concentrating the sludge into a single location. If the landfill is properly constructed and maintained, environmental risks are minimal. However, Organic wastes undergo anaerobic decomposition in landfills, producing methane gas that could be released to the atmosphere. Methane is a greenhouse gas that has been implicated in global warming. Other gasses released from landfills can cause unpleasant odors. The large quantities of nutrients that sludge adds to a landfill pose a risk to the local environment. Should a failure of the landfill liner or leachate collection system occur, these nutrients could contaminate local groundwater and surface water. Land filling sludge also takes up valuable landfill space and forfeits the potential benefits of the organic matter and plant nutrients in the sludge, [4]. 2. Ocean disposal: the sludge is disposal in ocean in many countries. But this is can make problem for aquatic life in ocean, [5] 2.2 Solidification and Stabilization of waste in Asphalt Mixtures The performance of asphalt mixtures depends on physical and chemical properties of aggregate and asphalt. However many new materials have been used to enhance the performance of the asphalt mixtures, and in other hand to stabilize this materials especially ISBN:

2 if it is waste material in pavement. Khedaywi and Abu-orabi,[6] have investigated the effect of oil shale ash, rubber ash, husk ash and polyethylene on properties of asphalt. They indicated that penetration, ductility, and softening point were directly proportional with the the added amount of additives in the binder, but specific gravity of binder is directly proportional with the added amount of ash and inversely proportional with the added amount of polyethylene. [6] Al-Massaid,Khedaywi and Samadi,[1] studied thehe properties of asphalt-oil shale ash bituminous mixtures under normal and freeze-thaw conditions.they indicated ed that the substitution of ash up to 1% by volume of asphalt binder will improve the performance of mixtures under both conditions, such ash inclusion resulted in paving mixtures with higher Marshall stability, greater tensile strength, larger stiffness modulus and higher resistance to freeze and thaw damage in comparison with mixtures without ash.. Material Used In this research three materials were used, asphalt cement (6-7), limestone aggregates, and dried sludge..1 Asphalt cement Asphalt cement (6-7) penetration was used in this research, which was obtained from Petroleum Refinery Company, Zarqa, Jordan. Table 1 shows the asphalt cement properties and ASTM standard designations that were used for each test of asphalt cement. Table 1 Properties of asphalt cement used Properties ASTM test designation Test result grading aggregate.table 2 shows the properties of this aggregate and Table presents the aggregate gradation. TABLE 2 Properties of Aggregate used Type of aggreg ate ASTM test designati on Bulk specific gravity Apparen t specific gravity TABLE Aggregate gradation, Medium Traffic, wearing layer Water absorption (%) Coarse C Fine C Minera l filler C Sieve Size % Passing 1" 1 4 " " " 56 8 % In Betwee n # # # # # # Pan 5 6 Weight in Between Penetration (.1mm) at 25 C, 1gm,and 5sec Softening point (C) D5 64 D 6 5 Ductility(cm) D Flash point (C) D Dry Sludge The dry sludge was collected from Wadi Hassan wastewater treatment plant, where the sludge was pumped to lagoons in the plant and leave for a suitable time to being dry. Figure 1 shows Wadi Hassan treatment drying bed(d) dry sludge and Figure 2 presents the fine sludge after it extract from loss Anglos machine, and sieve #2 Fire point (C) D Solubility D 244 1%.2 Limestone aggregate The crushed limestone aggregate was used in this research which was obtained from Al-Hussen Quarries-north of Jordan. The Ministry of Public Works and Housing Work standards was used in ISBN:

3 Table 4. Percent of sludge and limestone filler in each mix Mix Number Sludge % Limestone % Mix1 1 Mix Mix 5 5 Mix Mix Test Result, Analysis and Discussion Figure1. Wadi Hassan treatment drying bed sludge. 5.1 Effect of sludge content on Marshall Stability Figure presents the relationship between Marshall stability and sludge content in mixtures. The results indicate that stability increases then decreases with increasing amount of sludge in the mix. Mix with 5% sludge has the maximum stability. Stability(Kg) Mixes Vs.stability Mean Std.Dev. Poly. (Mean) Figure 2. Fine sludge after it extract from loss Anglos machine, and sieve #2. 4. Laboratory Work To study the effect of sludge on properties of asphalt mixtures, five levels of sludge were added to the aggregate instead of mineral filler limestone (aggregate passing sieve # 2) at (.%, 25%, 5%, 75%, and 1%) by weight of filler. Asphalt concrete specimens were prepared using the above percentages of sludge. All of these specimens were tested for stability, loss of stability, flow, air voids, voids in mineral aggregate (VMA), and stiffness. To evaluate the optimum asphalt content, Marshall mix design procedure was used, three specimen were prepared for each asphalt, four asphalt content were considered in this research (4%, 5%, 6%, 7%) by total weight of mixture.the optimum asphalt content that should be used to have the best results was evaluated using Marshall Method of design according to the standard of American institute MS-2, [7]. Table 4 presents the percent of sludge and limestone filler in each mix Mix1(%) Mix2(25%) Mix(5% Mix4(75%) Mix5(1%) %Sludge by weight of Filler Figure. Effect of sludge waste content on stability 5.2 Effect of sludge content on loss of stability Figure 4 shows the relationship between sludge content with loss of stability. The results indicate that the addition of sludge decreases the loss of stability. Mix with 1 % of sludge has the best results of loss of stability. The results indicates that all the Mix within specifications, which is 25 maximum and the addition of sludge, was decrease the loss of stability ISBN:

4 Mix vs. Loss of Stability Mix vs. Air Void Loss of Stability% I Air Void% Mix1(%) Mix2(25%) Mix(5%) Mix4(75%) Mix5(1%) Mix1(%) Mix2(25%) Mix(5%) Mix4(75%) Mix5(1%) Figure 4 Effect of sludge waste content on loss of stability 5. Effect of sludge content on flow Figure 5 show the relationship between sludge content with flow. The result indicates that flow increases then decreases with increasing amount of sludge in the mix. Flow for all mixes is within the specifications limits. Mix with 1% sludge has the lowest flow because the addition of sludge will decrease the movement of asphalt mixture. Figure 6 Effect of sludge waste content on air voids 5.5 Effect of sludge content on voids in mineral aggregate (VMA) Figure 7 show the relationships between the sludge content with void in mineral aggregate (VMA). Voids in mineral aggregate decreases with increasing sludge conent in the mixtures. The result indicates that VMA for all Mix are within the specifications limits. Mix with 1 % slughe have the lowest void in mineral aggregate. Flow(.25mm) Mixes Vs.Flow Mean Std.Dev. Poly. (Mean) Mix1(%) Mix2(25%) Mix(5%) Mix4(75%) Mix5(1%) %Sludge by weight of Filler Figure 5 Effect of sludge waste content on flow 5.4 Effect of sludge content on air voids Figure 6 show the relationships between the sludge content with air voids.the result indicates that air voids increases then decreases with increasing amount of sludge in the mix. Air voids for all mixes are within the specifications limits. Mix with % sludge has the lowest air voids because addition of sludge will increase air voids in asphalt mixture. IFFigure 7 Effect of sludge content on voids in mineral aggregate (VMA) 5.6 Effect of sludge content on Marshall Stiffness Figure 8 shows the relationship between sludge content with Marshall Stiffness.The result indicates that Marshall stiffness decreases then increases with increasing sludge content in the mixtures. Stiffness for all mixes are within the specification limits. Mix with 1% slughe has the higher Marshall stiffness. ISBN:

5 7 Mix vs. Marshall Stifness [7] The Asphalt Institute. Mix Design Methods for Asphalt Concrete and other Hot-Mix Types. The Asphalt Institute, Manual Series No.2 (MS-2), U.S.A 6 Mrshall stiffness(kg/mm) Mix1(%) Mix2(25%) Mix(5%) Mix4(75%) Mix5(1%) Figure 8. Effect of sludge content on stiffness 6. Conclusions The following conclusions can be drawn from this investigation: 1. Sludge waste effect the properties of asphalt paving mixtures. 2. The Marshall stability, flow, and air voids of the studied mixtures were found to increase and then decrease upon increasing the sludge in the mixtures. 2. Loss of stability and voids in mineral aggregate increase with increasing the sludge content in the mixtures.. Stiffness decreases then increases with increasing sludge in the mixture. 6. References [1] Al-Massaied, H., Khedaywi, T., and Smadi, M Properties of Asphalt Oil Shale Ash Bituminous Mixtures Under Normal and Freeze Thaw Conditions. Transportation Research Record 1228, TRB, National Research Council, Washington D.C., U.S.A, [2] Khedaywi, T., Tamimi, A., Al-Masaeid, H. and Khamaiseh, k Laboratory Investigation on Properties of Asphalt Rubber Concrete Mixtures. Transportation Research Record No. 1417, Transportation Research Board, National Research Council, Washington D.C., U.S.A., [] Khedaywi,T., Taqieddin,S. and Abu-Eishah, S Effect of Phosphate Slimes on Properties and Performance of Asphalt-Cement and Asphalt Concrete Mixes. Dirasat Journal, Natural and Engineering Sciences, The University of Jordan, Amman-Jordan, 2: [4] Davis, B. (21) Sewage Sludge Disposal Enters EU Spotlight WRc plc. News articles/5111pdf. [5] European Union. (1999). Landfill derective (99/1 /EEC. European Union. [6] Khedaywi, T. S. and Abu-Orabi, S. (1999). Effect of Oil Shale Ash, Rubber Ash, Husk Ash and Polyethylene of asphalt Cement. Journal of Petroleum researchs, 8: ISBN: