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8PERFORMANCE EVALUATION OF THE MIXTURE OF CRUMB RUBBER AND BITUMEN DERIVED FROM PETROLEUM SLUDGE
RASULOV ELNUR1 MAMMADOVA RANA1
Azerbaijan State Oil and Industry University, Azadlig Avenue 20, Baku AZ1010, Azerbaijan
Abstract: Bitumen is known as a widely used material in road infrastructure and construction. The production of bitumen from petroleum sludge and its amalgam with modifiers deems promising when considering the environmental and economic aspect of application areas. Crumb rubber is a modifier which also plays a vital role in solving the waste disposal problems arise as a result of tyre dumping. This study presents the effect of crumb rubber on the thermomechanical properties of the bitumen matrix. Overall, the crumb rubber a modifier is considered effective to improve the viscosity and softening point. A linear increase is observed in these parameters so that the softening point is 48.5 °Cfor neat binder and 71 °Cfor the bitumen with 20% modifier content. As regards the ductility and penetration value, the figure decrease to 45 cm and 31*10-1mm for the maximum rubber content (20% weight), respectively.
Key words: bitumen, crumb rubber, petroleum sludge, modifier, thermomechanicalproperties
Xulasa:Bitum yol infrastrukturu vd tikintisinda geni§ istifada olunan bir materialdir. Neft §lamindan bitumun va onun modifikatorlarla qari§igi tatbiq sahdldrinin ekoloji va iqtisadi aspektlari ndzdrd alindiqda perspektivli hesab edilir. Qirinti rezin, takarlarin atilmasi naticasinda yaranan tullantilarin utilizasiyasi problemlarinin hallinda da muhum rol oynayan bir materialdir. Bu tadqiqat qirinti rezinin bitum matrisinin termomexaniki xususiyyatlarina tasirini taqdim edir. Umumilikda, modifikator kimi istifada olunan rezin qirinti ozluluk va kovraklik temperaturunu yax§ila§dirmaq ugun effektiv hesab olunur. Bu parametrlarda xatti artim mu§ahida olmu§dur ki, kovraklik temperaturu tamiz bitum ugun 48,5 °C va tarkibinda 20% rezin olan bitum ugun isa 71 °C-dir. Dartilma qabiliyyati (duktivlik) vapenetrasiya dayarina galdikda, maksimum rezin tarkibi (20% kutla) ugun raqam muvafiq olaraq 45 sm va 31 * 10-1 mm-a qadar azalir.
Agar sozlar: bitum, rezin qirintilari, neft §lami, modifikator, termomexaniki xassalar
Introduction
Bitumen is black and high-viscosity liquid material comprising of organic compounds and mainly derived in petroleum refining. Due to its adhesive and cohesive characteristics, bitumen finds a variety of applications ranging from road pavement to roofing and waterproof materials. The main components of bitumen are polyaromatic hydrocarbons such as asphaltenes and maltenes. As for the bitumen production, the conventional path is to obtain heavy bottoms of vacuum distillation units in oil refineries. Furthermore, the petroleum wastes, especially waste sludge appear promising to be an alternative way for bitumen formulation. Waste oil sludge is a multicomponent formation that is mainly composed of organic, aqueous and mineral substances such as waste oil, sand, waste water, metal oxides and etc. Oil refining processes produce a considerable amount of waste during processing of crude oil and oil products, storage, transportation and thus, sludge tend to accumulate in storage tanks, desalters and elsewhere. The principal composition of the petroleum based waste sludge makes it possible to formulate bitumen and composites with several additives [1].
While being widely used in road pavements, bitumen may still have some drawbacks that call for the incorporation of modifiers to binders in order to augment the material's properties. One of the reinforcing agents is crumb rubber which is mostly utilized in bitumen modification and has been the subject of numerous investigations. Crumb rubber is considered to be a blend of synthetic and natural
rubber plus additional components like antioxidants, carbon black, fillers, and extender types of oils. which are combined to form crumb rubber and then incorporated into asphalt binder [2].
In this paper, bitumen obtained from petroleum sludge was investigated and the effect of reinforced crumb rubber was assessed via employing various techniques used for the characterization of materials. The quantity of addition for modifier is also examined during the investigation. It should be noted that the optimal amount is preferable to increase the binder properties, while there are some studies point out that more than 10 percent reinforcement would lead to formulation of much viscous binder which is not suitable for field mixing operations [3]. Overall, the results derived from the experiment seem to be in agreement with previous studies.
Experimental section
Material Preparation
Bitumen shows variance in properties when combining with different reinforcing agents such as polymers, graphene and etc. In this paper, the bitumen which was obtained petroleum sludge found in crude oil storage. The desired material was produced by creating the distillation set up in laboratory scale and the resulting bitumen was subj ected to various tests for the sake of characterization. Initially, the properties of the pristine bitumen was assessed via relevant techniques then the crumb rubber added bitumen was examined. The mixture of bitumen and crumb rubber was prepared by means of mechanical stirring in a batch mixer. Initially, the bitumen material was heated up to 160 °C until it has melted and poured to the batch mixer and then crumb rubber was slowly added to carry out blending. The sample mixture was processed for around 1 hour at 160 °C and then poured into a small canister and left for cooling. One point to mention that the rubber concentration fall between 0 and 20%.
Ductility test
Ductility test of the pure and modified bitumen is carried out by means of ASTM D113 (American Standard Testing Method) technique and the overall results are shown in the result section. The apparatus employed by this method includes briquette mould, water bath, brass plate, testing machine and thermometers [4]. First of all, the brass plate surface is coated with a thin layer of glycerin and dextrin mixture to prevent the sticking of material to the brass plate. After that the briquette mould used for holding the bitumen material is placed onto the brass plate and then the melted sample is poured onto the plate at room temperature. The sample is allowed to stabilize at room temperature for 30 min and then put into water bath for 30 min to reach the specified temperature of 25 °C for the experimentation. Finally, the mould with sample is removed from the water bath and its surface is flattened with the help of hot spatula for accurate measurement. At the end, the mould assembly is placed in the testing (pulling) device, and it is turned on to pull the material from one end at a fixed speed of 50 millimetres per minute. The distance at which the bitumen samples are stretched and reach the breaking point is known as the ductility value. It is expressed in centimetres and represents the average of two samples with exactly the same composition. The obtained consequences can be found in the results section.
Viscosity test
The flow behaviour of materials is characterized by kinematic viscosity. As regards this paper, the kinematic viscosity of the bitumen itself and with a modifier was examined using the widely accepted method called ASTM D2170. The equipment need to conduct such experiment consist of thermometer, viscometer, stirrer and paraffin bath [5]. Overall, the kinematic viscosity of the bitumen sample is found by multiplying the efflux time that is the time required for a volume of bitumen to flow through the capillary of a calibrated viscometer by the calibration factor of the viscometer. The test temperature is 135 C at which the paraffin bath is maintained and the viscometer is heated up. The heated bitumen is gently poured into the viscometer up to the marked filling line. The viscometer is then placed in the bath. After heating the viscometer, the bitumen sample is allowed to move and the time is measured for the calculation of kinematic viscosity.
Penetration test
Penetration value of bitumen indicates how the material responds to variation in temperature. This parameter was determined using ASTM D5 standard test method. The apparatus involved in the experiment includes penetration apparatus, penetration needle, sample container, thermometer, water bath and timer [6]. Initially, the bitumen sample is heated and the melted sample is poured into a container in which it is allowed to cool at room temperature. In this case, attention should be paid in order to avoid the formation of bubbles during pouring and thus, the surface is heated by passing a flame over the sample within the container. The needle used for experiment is cleaned with a suitable solvent, in this case toluene, and placed into the equipment. The test is carried out at constant temperature of 25 °C and thus the samples are placed into the water bath at 25 °C for 2 hours and then placed on the penetrometer. Overall, a mass of 100 g ± 0.1 g is applied on the sample for 5 seconds and the distance measured as a result of the needle movement is penetration in tenths of a millimetres.
Softening point test
One of the widely used and oldest tests applied to bitumen for determination of characteristics of the material at increased service temperatures is called softening point test. Generally, softening point indicates the point at which the bitumen sample becomes soften via the application of heat. The softening point test of the prepared samples is carried out with respect to ASTM 36, which covers the measurement of the required parameter of the bitumen samples between 30 and 157 °C using the well-known ring-and-ball method. The equipment required for such experiment include two brass rings, two steel balls, pouring plate, water bath, thermometer, ring holder and assembly and ballcentering guides for centering steel balls on to the samples [7]. The apparatus sections are assembled orderly in accordance with the relevant standard and samples are prepared and placed with the ring and then placed inside the water bath. The starting temperature for the experiment is taken as 5 °C and this was achieved by placing the water bath in ice water. After the steel balls were placed on the samples within the brass rings, the heat was being given to the water bath at a constant rate of 5 °C per minute. Once the steel balls touched the metal plates by moving thorough the bitumen sample, the thermometer indicators were recorded and then averaged to calculate the softening point.
Result and Discussion
In general, various tests were carried out for the characterization of thermomechanical properties of crumb-rubber modified bitumen samples. The trend obtained for different concentrations is shown in the table below.
Table 1. Results of various test performed on bituminous samples.
Bitumen Property
Quantity of Rubber (%
0 5 10 15 20
114 108 88 65 45
375 465 740 1285 1970
53 47 43 36 31
48.5 51.3 57.6 60.5 71
Ductility (@25 °C, 50 mm/min, cm) Viscosity (cP)
Penetration (@25 °C, 0.1 mm) Softening Point (°C)
Overall, the addition of crumb rubber shows an enhancement of performance in bitumen matrix. It can be seen in the Table 1 that the penetration values decreased as the crumb rubber content increased up to 20%. This trend can be justified because of the viscosity increase by modifier addition. The same figure applies to ductility which shows elastic properties of the bitumen sample and it decreased from 114 cm for the neat binder to 45 cm for the reinforced bitumen with 20% crumb rubber. However, viscosity and softening point increased by the integration of crumb rubber. The softening point is 48.5 °C for pure binder and it experienced a linear increase up to 71 °C for 20% modified bitumen. The main reason for such increment is related to the increasing viscosity which leads to the fact that viscous bitumen tends to soften at higher temperatures. This paper, also
confirmed by other studies, shows that the crumb rubber as a modifier increases viscosity of the binder which leads to better permanent deformation resistance.
The evaluation of the properties seem to be in good agreement with similar studies with minor differences in results. This can be associated with the derivation of materials used in the experiment so that the bitumen was obtained from the petroleum sludge in lab scale and some properties may have deviation than that of industrial product. However, the obtained results appear to become satisfactory, and this may lead to the reconsideration of sludge based bituminous materials for the adoption in road pavement in which some modifying moieties such as crumb rubber. The characterization of such reinforced materials shows good results and thus paves the way for large scale usage in real life examples.
Conclusion
Overall, the obtained results seem satisfactory and aligned with other studies. The obtained amalgam displayed enhanced properties, and this may be due to good dispersion of modifier particles within the matrix. The integration of crumb rubber strengthens the binder regarding the thermomechanical properties of bitumen. For example, the viscosity values of the neat bitumen are lower than that of the modified bitumen and the figure tends to increase as the concentration of the reinforcing agent increases. Ductility test of the material was performed in order to measure elastic properties. As can be seen, the ductility expressed in centimetres display a substantial decrease with increasing crumb rubber content. These properties also define the quality characteristics of the bitumen especially when the material is used in hot weather and high-load conditions. In addition, a decrease is experienced in penetration value which is considered a measure of hardness and consistency of the bitumen as the content of modifying agent increases. As regards the softening point, the figure showed an improvement which is typical for bituminous materials with better quality. In fact, the water bath was used in the experiment instead of glycerine and ethylene glycol and it is typical for the determination of softening points up to 80 °C. Moreover, the crumb rubber modified bitumen samples display enhanced properties and it is deduced that these materials can be adopted in road pavement applications.
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