Recycling of Waste Materials in Asphalt Mix

Transcription

1 Recycling of Waste Materials in Asphalt Mix Yazan Issa a a Assistant Prof. Civil Engineering Department, Fahd Bin Sultan University, Tabuk 71454, Saudi Arabia. Tel: , P.O Box 15700, address: yissa@fbsu.edu.sa. Keywords: Pavement, crushed glass, bitumen, rubber, waste tires, and stability Abstract With the continuously increased consumption, a large amount of waste materials is generated in the world. Asphalt modification can be made at different stages of its usage, from binder production to asphalt pavement production. The main objective of this paper is to study the change in asphalt mixture properties after adding two types of waste materials separately (waste tires rubber and waste car windshields glass). In the first experiment percentage of bitumen is replaced with melted waste tire rubber, while a fraction of fine aggregate is replaced with waste crushed glass in the second trial. The results showed that properties of modified asphalt are improved in comparison with normal asphalt pavement. The suitable amount of added rubber or glass was found to be 10% by bitumen or aggregate weight. 1. INTRODUCTION The use of industrial additives in asphalt mixes will increase its cost. However, the use of alternative waste materials is less costly and eco-friendly, and is expected to enhance the asphalt properties [1]. Enhancing asphalt properties will increase asphalt resistance to several pavement distress [2]. Rubber and glass is widely used in our daily life, and with the continuously increased consumption, a large amount of waste from these materials is generated annually. The best way to deal with these wastes is to recycle and reuse them as raw materials or modifiers [3]. Recycling these wastes can save energy and decrease environmental waste [4]. Glass recycling can be made without changing its composition and properties [5]. Laboratory experiments showed that the strength and resistance to water damage of glass-asphalt pavement is higher than ordinary asphalt [6]. In their study, Sajed and Shafabakhsh indicated that asphalt containing 10 15% crushed glass in surface course mixtures has been observed to perform satisfactorily [7].

2 In Australia, a road section was constructed using crushed glass in pavement mixes in 2010 [8]. A research study found that using tire rubber in asphalt mixture could decrease tire noise by approximately 50% [9]. The study of Mashaan indicated that replacing 12% of bitumen weight by rubber will give higher asphalt stability [10]. Hicks and Epps concluded that asphalt rubber pavement could be more cost effective than conventional pavement [11]. This paper examines the performance of asphalt in which a percentage of bitumen or aggregate is replaced with waste rubber or glass. 2. EXPERIMENTAL WORK Conventional laboratory tests were conducted on bitumen and aggregate. Samples of tests results are shown in Table 1 below. Table (1): Conventional Properties of Bitumen and Aggregate Bitumen Aggregate Test Value Test Value Penetration (0.1mm) 78.1 Wear percentage (Los-Angeles) 21.3% Softening point (ºC) 52.3 Bulk Specific Gravity 3.00 Flashing point (ºC) 291 Apparent Specific Gravity 3.34 Specific gravity 1.02 Absorption 5.15% The conventional samples are prepared with 4.5%, 5%, and 5.5% bitumen percentage as shown in Table 2. Table (2): Original Samples Preparation for Different Bitumen Percentage Aggregate Size 4.75mm 9.5mm 12.5mm BITUMEN TOTAL Weight (gram) (4.5%) Weight (5%) Weight (5.5%)

3 Stability (KN) The crumb rubber from waste tires is melt in bitumen at 170 C and mixed with aggregate. On the other hand, waste car windscreen glass was crushed, and glass particles with diameter less than 4.75 mm were used in preparing the experiments. The mixture of aggregate and glass is heated to a temperature of 135 ºC before mixing with asphalt bitumen. All samples were compacted at temperature of 160 ± 5 ºC and subjected to 75 blows of compaction by Marshall Hammer on each side of specimen at temperature of 145 ºC. Nine samples are prepared by mixing the melted rubber with bitumen at 5%, 10% and 15% of bitumen weight. Similarly, other nine samples are prepared by replacing the same mentioned percentages of fine aggregates with crushed glass. 3. RESULTS AND DISUSSION The main objective of this paper was to examine the performance of asphalt in which a percentage of bitumen or aggregate is replaced with waste rubber or glass. The tests were conducted using the standard Marshall Apparatus. Stability of the prepared samples were recorded. Results are shown in Fig. 1, 2 and 3. Rubber Glass % 5% 10% 15% Used Percentage Fig. 1: Stability results at 4.5 bitumen percentage

4 Stability (KN) Stability (KN) 15 Rubber Glass % 5% Used Percentage 10% 15% Fig. 2: Stability results at 5% bitumen Rubber Glass % 5% 10% 15% Used Percentage Fig. 3: Stability results at 5.5% bitumen From above figures showed that stability of mixes varied clearly after adding rubber on opposite of glass addition. Comparing the results of stability for asphalt-glass mix with conventional mix showed that there is an improvement at 10% glass. Stability increased with rubber addition up to 10%, and decreases at higher percentages. At high percentage of bitumen (5% or more), average stability of asphalt without rubber is low compared to asphalt with 10% rubber. The results showed that the stability values increase with an increase in the bitumen content. The average values of Marshall Test stability with different added percentage were summarized in Table 3 below.

5 Table (3): Average Stability Test (KN) Results Used Percentage 0% 5% 10% 15% Rubber Glass From above table, average stability of asphalt without rubber is higher in comparison with the asphalt with 5%, and 20% rubber, but lower than 10%. It is also appeared that the average stability increased with glass addition until the maximum level (approximately 10% of glass) then it started to decrease. Table (4) Typical Marshall Design Stability Criteria Light Traffic Medium Traffic Heavy Traffic Mix Criteria (< 104 ESALs) ( ESALs) (> 106 ESALs) Min. Max. Min. Max. Min. Max. Compaction: number of blows on each end of the sample Stability (minimum) 2.27 KN 3.40 KN 6.80 KN (Asphalt Institute, 1997). The above standards table (Table 4) indicated that all test values consistence minimum stability of Marshal Test [12]. 4. CONCLUSION Stability was improved by adding rubber or glass to the asphalt pavement. The appropriate used percentage was 10%. The finding of this study agreed with other international studies. Concerning the cost, several studies showed the high cost of modified asphalt. But it is more accurate to consider the design life cost of pavement not the initial construction cost. In this research article, a number of asphalt samples were examined on laboratory tests. The conclusions are summarized as follows.

6 1- Waste tires rubber and crushed glass can be used in asphalt pavement with optimum replacement ratio of 10%. 2- The average stability for 10% modified mixture was higher than the control mixture. Therefore, a significant improvement occurred in the Marshall properties of asphalt mixtures using a waste rubber or crushed glass modifier. 3- All test values are consistent with the specifications limits. 4- The results of this study apply only to the type of rubber that was used, and to the specific gradation and type of glass that was used. Other resources of rubber or glass may produce different results. REFERENCES [1] Mashaan N, The effect of crumb rubber modifier to the properties and rheological behaviour of asphalt binder [M.S. thesis], University of Malaya, Kuala Lumpur, Malaysia. [2] Xiang Shu, Baoshan Huang, Recycling of waste tire rubber in asphalt and portland cement concrete: An overview Construction and Building Materials, ELSEVEIR. [3] Arnold, G, Werkmeister, S & Alabaster, D. The effect of adding recycled glass on the performance of base course aggregate, NZ Transport Agency Research Report 351, New Zealand [4] Jony, H, Al-Rubaie, M, & Jahad, I. The effect of using glass powder filler on hot asphalt concrete mixtures properties, Engineering & Technology Journal, Vol.29, No.1, pp [5] Gautam, S, Srivastava V & Agarwal V, Use of glass wastes as fine aggregate in Concrete, Journal of Academic and Industrial Research, Vol. 1(6) [6] Wu S, Yang W, and Xue Y Preparation and properties of glass asphalt concrete. Wuham, China: Key Laboratory for Silicate Materials Science and Engineering of Ministry of Education, Wuham University of Technology [7] Shafabakhsh G.H., Sajed Y. Investigation of dynamic behavior of hot mix asphalt containing waste materials; case study: Glass cullet. Case Studies in Construction Materials 1 (2014) Published by Elsevier Ltd. [8] Waverley Council recycled glass in roads Australian Government, Department of Sustainability, Environment, Water, Population and Communities. National Waste Policy: Case study [9] Zhu H, and Carlson D, A spray based crumb rubber technology in highway noise reduction application, Journal of Solid Waste Technology and Management, vol. 27, no. 1, pp [10] Nuha Mashaan, Asim H. Ali, Suhana Koting, and Mohamed Karim, Performance Evaluation of Crumb Rubber Modified Stone Mastic Asphalt Pavement in Malaysia Hindawi Publishing Corporation. Advances in Materials Science and Engineering. Article ID , 8 pages [11] Hicks G, Epps J Life cycle costs for asphalt-rubber paving materials. In: Proceeding, Asphalt Rubber The Pavement Material of 21st Century. Vilamoura, Portugal; November 14 17, 2000) [12] Asphalt Institute. Mix Design Methods for Asphalt, Manual Series No. 2 (MS-02). Asphalt Institute. Lexington, KY