Use of asphalt plant residue in hot mix asphalt

Transcription

1 Int. J. Global Warming, Vol. 6, Nos. 2/3, Use of asphalt plant residue in hot mix asphalt Murat Karacasu* Department of Civil Engineering, Eskisehir Osmangazi University. Batimeselik Campus, Eskisehir, Turkey Fax: *Corresponding author Fatih Hattatoğlu Department of Civil Engineering, Erzurum Ataturk University, Erzurum, Turkey Sinan Hınıslıoğlu Department of Civil Engineering, Zirve University, Kızılhisar Campus, Gaziantep, Turkey Yetis Sazi Murat Department of Civil Engineering, Pamukkale University, Denizli, Turkey Abstract: Environmental solid wastes increase more and more as a result of the industrial waste production day by day. Management of the solid wastes is the thrust area for researchers. In this study, the effects of asphalt plant residue (APR) on the properties of hot mix asphalt (HMA)s are investigated. APR was added into the asphalt concrete in 25, 50 and 100% by weight of the filler. In order to determine optimum bitumen content, Marshall Design procedure was applied. Optimum bitumen content (OBC) values were obtained less than control specimen (CS). APR specimens have shown little increase in Marshall stability and little decrease in flow except for APR-50 in comparison to the CS. All APR specimens have higher MQ than that of the control mixture. Although there are no meaningful differences between CS and APR specimens, APR can be used as a filler aggregate in asphalt mixtures. Use of APR will enable recycling of an environmental waste as well as providing some benefits in asphalt concrete performance. Thus, resources will be used more effectively all over the world as part of sustainability. Keywords: asphalt; environment; plant; residue; sustainability. Copyright 2014 Inderscience Enterprises Ltd.

2 128 M. Karacasu et al. Reference to this paper should be made as follows: Karacasu, M., Hattatoğlu, F., Hınıslıoğlu, S. and Murat, Y.S. (2014) Use of asphalt plant residue in hot mix asphalt, Int. J. Global Warming, Vol. 6, Nos. 2/3, pp Biographical notes: Murat Karacasu graduated from the Eskisehir Osmangazi University in 1994 and had his MSc from the same university. He received his PhD degree from Istanbul Technical University in He is currently working as an Assistant Professor at Eskisehir Osmangazi University, Turkey. His research interests are public transportation, transportation modelling, asphalt concrete, waste management and fuzzy logic. He has more than 20 research papers published in conference proceedings, research reports and journals. Fatih Hattatoglu received his BSc in Civil Engineering from Ataturk University, Erzurum, Turkey. In 2009, he obtained his PhD from Ataturk University about asphalt concrete. He is currently working as an Assistant Professor at Ataturk University, Erzurum, Turkey. He conducted few researches, thesis and projects about transportation engineering. Sinan Hınıslıoğlu graduated from and had his MSc degree at Dokuz Eylül University in 1988 and 1991, respectively. He received his PhD from Istanbul Technical University in He has research experience at Texas University, Austin, USA in 2002 and has worked as a Research Fellow at Belfast University, UK in His research interests are highway design and controlling, statistical methods, use of waste materials, Taguchi method, traffic accident analysis and highway management systems. He conducted many researches, thesis and projects. He has many papers published in journals. He is working as the Dean of Engineering Faculty at Zirve University, Turkey. Yetis Sazi Murat received his BSc in Civil Engineering from Dokuz Eylul University, Izmir, Turkey. In 2001, he obtained his PhD from Istanbul Technical University. He was a Postdoctoral Fellow at Virginia Polytechnic Institute and State University in USA in He conducted many researches, thesis and projects about transportation and traffic engineering. He is currently working at Pamukkale University, Denizli, Turkey. The paper is a revised and expanded version of a paper entitled Effect of asphalt plant residue on the properties of hot mix asphalt presented at the International Conference on Recycling and Reuse 2012 (R&R, 2012), Istanbul, Turkey, 4 6 June Introduction Conventional HMA is a composite material, whose major components are the aggregates (sand and coarse aggregates), the filler and the bitumen. Sometimes additives are incorporated to improve the performance of the HMA. The aggregate materials used in road construction are generally supplied from quarries which are close to the road course under construction. However, the quantity of good quality aggregate has been decreasing day by day. Bitumen is obtained by distillation of crude oil. Bitumen sourced from oil is a highly expensive material. Also, the total quantity of energy consumed in HMA sector is

3 Use of asphalt plant residue in hot mix asphalt 129 about 136*10 6 MWh/year. On the other hand, the average world crude oil production was millions of barrels per day in average (US EIA, 2009). This means that the whole industry of HMA consumes 0.28% of the world s crude oil production. Therefore, the minimisation of energy requirements for manufacturing HMA and the associated lowering of asphalt plant emissions have become important issues (Peinado et al., 2011; EAPA, 2007). On the other hand, there is an environmental deposition problem of the wastes resulting from industrial production. Deposition sites for those wastes are getting limited increasingly. In the course of events, it has become compulsory for researches to use those wastes in asphalt concrete. There are still many studies for increasing the performance of asphalt concrete. It has become an aim for researchers to provide better performance values using waste materials with less substance in the mixture. There have been deep changes in the way we live and work. Among these changes, conservation and recycling of such waste materials have become some of the major issues to manage the resource. Many authorities and researchers are going to seek to privilege the re-use of wastes in an environmentally and economically sustainable way. Hence, it is accomplished both to economise the materials and to prevent environmental contamination (Aubert et al., 2006; Xue et al., 2009) The waste materials can broadly be categorised as follows: a industrial wastes such as cellulose wastes, wood lignins, bottom ash and fly ash b municipal/domestic wastes such as incinerator residue, scrap rubber, waste glass and roofing shingles c mining wastes such as coal mine refuse (Kandhal, 1992). Waste materials are used instead of aggregate and bitumen. Akbulut and Karasahin used waste marble particles in the asphalt concrete mixtures as aggregate (Akbulut and Gurer, 2007; Karaşahin and Terzi, 2007). Çubuk et al. (2009) used epoxy resin to modify bitumen. Use of such wastes and examples for modifying the bitumen can be increased (Gandhi, 2008; Al-Khateeb and Al-Akhras, 2011). Huang et al. (2007) emphasise that the waste materials should be used in road construction by technical and financial aspect and that would prevent environmental contamination and provide clearance of the deposition sites. Their re-use for civil engineering in the developed countries, which are now facing a challenge to save natural resources for future generations while bringing industrial activities into a more stable long-term balance between environmental preservation and costs, has been widely accepted (Siddique, 2006; Katz and Kovler, 2004). The main advantages of the re-use of industrial by-products are in the preservation of natural resources, a substantial reduction in the landfill load, the protection of the environment and the positive economic effects (Motz and Geiseler, 2001; Jullien et al., 2006; Vahcic et al., 2008). Recycling of waste materials in highway construction should be encouraged. However, it is necessary to address the engineering, environmental and economic concerns mentioned in this paper before any large scale use of these materials. The use of these materials should be well based. HMA containing a waste material should perform at least better than conventional HMA. It should also be environmentally safe both for the first construction and future recyclability (Kandhal, 1992). Asphalt plant residue (APR) was used as the waste material for this study as seen in Figure 1.

4 130 M. Karacasu et al. Figure 1 APR materials in storage fields (see online version for colours) APRs are produced from filter systems and baghouses in asphalt plants which are sited close by, at a quarry site from which the aggregate was sourced. There are two types of plant as drum mix and batch plants. They differ in their asphalt concrete production operations. In drum mix plants presized cold aggregates are fed into a drum, in accordance with preselected mix design proportions. The aggregates are dried and mixed with bitumen, which is introduced at the end of the drum (coating zone), in a continuous process. In batch plants, unsorted aggregates are introduced into a dryer and subsequently screened into different sized fractions, stored in hot bins and fed by a batch weight, into a separate pugmill mixer where the hot aggregates are mixed with bitumen. Fabric filters or baghouses have been chosen in an increasing number of industrial processes for controlling atmospheric emissions (Silva et al., 1999; Gabites et al., 2008). HMA APRs are dust particles that are captured from the exhaust gases of asphalt mixing plants. Secondary collection equipment called baghouses is commonly used to capture these very fine sized materials. Roughly 40 to 50% of all hot mix asphalt plants are equipped with baghouse collection systems. Baghouses consist of several rows or compartments of fabric filters that collect the dust during the operation of a hot mix asphalt plant. Hot mix plants that do not have baghouse collection systems are equipped with wet scrubbers to control air emissions (FHWA, 2008). During asphalt concrete production, the aggregates are heated and dried in a dryer drum. As the moisture content is reduced, the aggregates release dust that is carried out of the drier and captured in baghouse filters. Since this effectively removes dust from the aggregate, it has become common practice to reintroduce a portion of the baghouse material into the asphalt concrete mix. During the mix design, no distinction is made between pan material collected by sieving and the baghouse fines. These materials are treated as if their effect on the mix is interchangeable (Zaniewski and Reyes, 2003).

5 Use of asphalt plant residue in hot mix asphalt 131 During hot mix asphalt (HMA) production, nearly 1.6% APR per ton emerges as waste. This amount is more in old mixing plants. Because there is wide range of aggregate amount in ton level during HMA production, there is much APR waste aggregation. In Turkey, total production of HMA is 43.5 million tonnes per annum. These values are and 332 for Europe and the USA respectively. On the other hand, mineral filler especially the material passing from mm (No. 200) sieve (generally called P200 material) has a significant effect on the performance of asphalt paving mixtures in terms of permanent deformation, fatigue cracking, and moisture susceptibility. According to ASTM standard specification D , the definition of mineral filler finely divides mineral matter into suitable mineral matter such as rock dust, slag dust, hydrated lime, hydraulic cement, fly ash, loess or other. At the time of use it shall be sufficiently dry to flow freely and essentially free from agglomerations. A great deal of research has been conducted on mineral filler and its effect on asphalt paving mixtures. Baghouse fines can also be considered as mineral fillers. Physical and chemical properties of the dust are extremely important for selecting the fabric that will be used. These include size, type, shape, and density of dust; average and maximum concentrations; chemical and physical properties such as abrasiveness, explosiveness, electrostatic charge, and agglomerating tendencies (McKenna and Turner, 1989). Wastes can be used as wet or dry combination in HMAs. In dry combination method, wastes are added into the mixture while mixing aggregate and bitumen. In wet combination method, specially-treated wastes are added into bitumen previously and the bitumen is modified in this way. Then, this modified bitumen is mixed with bitumen aggregate. In this study, APR was used as dry combination method. APR was added into asphalt concrete in 25, 50 and 100% by weight of filler. Marshall design procedure was applied to specimens. The potential use of APR in asphalt composites for road construction was investigated. 2 Material and method Virgin bitumen graded as 50/70 penetration and the calcareous-based aggregate are used in this study. The properties of this bitumen and aggregate are shown in Tables 1 and 2, respectively. Table 1 Properties of virgin bitumen Properties Test values Standards Penetration at 25 C, 1/10mm 58.2 ASTM D 5-06e1 Ductility at 25 C, cm > 100 ASTM D Loss on heating, % ASTM D 6-95 Specific gravity at 25 C, gr/cm ASTM D Softening point, C 48.5 ASTM D Flash point, C 310 ASTM D 92-02b Elastic recovery, % (25 C) 1.42 ASTM D

6 132 M. Karacasu et al. Table 2 The physical properties of aggregates used in experiments Properties Test values Standards Specific gravity of coarse aggregate, 25 C, gr/cm ASTM C Water absorption of coarse aggregate, % 0.22 ASTM C Specific gravity of fine aggregate, 25 C, gr/cm ASTM C128-07a Water absorption of fine aggregate, % 1.05 ASTM C128-07a Specific gravity of filler, 25 C, gr/cm ASTM C128-07a Los Angeles wearing test, % ASTM C Freezing and thawing test, % ASTM C a Bitumen absorption, % 0.15 ASTM D APR material is obtained from Eskisehir Metropolitan Municipality asphalt plant. The maximum size of APR material is 600 μ. Scan electron microscope (SEM) and the normal images of APR are indicated in Figure 2 and the chemical properties are given in Table 3. Table 3 The chemical properties of APR Element Weight (%) Component Weight (%) C CO O MgO Mg SiO Si CaO Ca Total Figure 2 (a) Normal image, (b) SEM image of APR (see online version for colours) (a) (b) Aggregate gradation used in this study for asphalt mixtures is obtained from Turkish Highway Construction Specifications in Table 4 (GDH, 2006). The Sieve analysis is carried out and aggregate gradation is selected as type 2 wearing course.

7 Use of asphalt plant residue in hot mix asphalt 133 Table 4 Gradation Type 2 wearing course gradation Sieve size Passing requirements, % Passing, % Retained, % inch mm min max 3/4" /2" /8" # # # # # Pan 7 The experimental design procedure used in this study is as follows. The Marshall Test Method was used for determining the resistance to plastic flow of bituminous mixtures prepared with or without APR. Marshall specimens were fabricated in accordance with ASTM D The asphalt concrete specimens with 0%, 25%, 50%, and 100% of APR by weight of filler were prepared and these specimens were named as control specimen (CS), APR-25, APR-50 and APR-100, respectively. Fifty blows were applied on each side of the specimen. 21 specimens were fabricated to determine the optimum bitumen content (OBC) from 3.5% to 6.5% bitumen by weight of aggregate for each APR ratio and CS. Totally, 84 specimens were prepared. Specification of General Directorate of Turkish Highway for Wearing Coarse was used (Table 5). The results for OBC and volumetric properties obtained from the experiments are shown in (Table 6). Table 5 Specification for wearing course (GDH, 2006) Properties of Marshall specimens Specification limits Stability (MS) (kg) min. 900 Air voids (BO) (%) (75; 50 blows) 3 5 ; 4 6 Flow (mm) 2 4 Voids of filled with bitumen (VFA) (%) Voids of mineral aggregate (VMA) (%) min 14 Table 6 OBC and volumetric properties for CS and APR-25, APR-50 and APR-100 CS APR-25 APR-50 APR-100 OBC, % Air Voids, % VMA, % VFA, %

8 134 M. Karacasu et al. 3 Results and discussion First of all, as seen in (Figure 3), OBC decreased when APR increased. It is believed that the increase in APR causes the decrease OBC of the mixture due to chemical properties. As APR may contain bitumen in itself, the level of bitumen used in HMA decreases Thus, OBC values for APR specimens are lower when compared to CS specimens, especially for APR-100. Figure 3 OBC values of specimens The void in the compacted dense-graded HMA specimen at OBC is suggested by most agencies to lie between 3 and 5%. VMA is the total volume of voids within the mass of the compacted aggregate. This total amount of voids significantly affects the performance of a mixture because if the VMA is too small, the mix may suffer durability problems, and if the VMA is too large, the mix may cause stability problems and be uneconomical to produce. As seen in (Figures 4 and 5), both air voids and VMA of mixes containing APR were almost the same as CS. Aggregate gradation affects air voids and VMA. The value results of APR specimen are similar to CS specimens due to filler and APR s having similar properties. Figure 4 Air voids of specimens

9 Use of asphalt plant residue in hot mix asphalt 135 Figure 5 VMA values of specimens Voids of filled with bitumen (VFA) is percent voids filled with bitumen and a redundant requirement for dense-graded HMA. Most states that include percent VFA requirements generally specify that the VFA range from 70 to 85%. Figure 6 illustrates the values of VFA of the specimen. APR specimens have shown decrease in VFA. The VFA decreases with decreasing optimum bitumen content. This is an expected behaviour for HMA. Bulk specific gravity (BSG) value is used to determine weight per unit volume of the compacted mixture. As shown in Figure 7, these values are similar to the values of the APR and CS specimen. Figure 6 VMA values of specimens

10 136 M. Karacasu et al. Figure 7 BSG values of specimens Marshall Stability is defined as the maximum load carried by a compacted specimen tested at 60 C at a loading rate of 51 mm/min. This stability is generally a measure of the mass viscosity of the aggregate bitumen mixture and is affected significantly by the angle of internal friction of the aggregate and viscosity of the bitumen at 60 C (NAPA, 1991). According to the experimental results, APR specimens have shown little increase in Marshall stability and little decrease in flow except for APR-50 in comparison to the CS (Figures 8 and 9). Figure 8 MS values of specimens The Marshall flow is equal to the vertical deformation of the sample. High flow values generally indicate a plastic mix that will experience permanent deformation under traffic, whereas low flow values may indicate a mix with higher than normal voids and insufficient asphalt for durability and one that may experience premature cracking due to mixture brittleness during the life of the pavement (NAPA, 1991). As shown in (Figure 4), Marshall flows are similar to CS and APR specimen.

11 Use of asphalt plant residue in hot mix asphalt 137 Figure 9 Flow values of specimens The Marshall quotient (MQ) is the ratio of stability to flow and represents the ratio of load to deformation. The MQ may be used to give an indication of mixture stiffness while specifying a minimum flow value may prevent mixture susceptible to embrittlement being used (Nicholls, 1998). Figure 5 indicates that variation of MQ with the various CS and APR. A higher value of MQ indicates a stiffer mixture and, hence, indicates that the mixture is likely more resistant to permanent deformation (Hınıslıoğlu and Ağar, 2004). All APR specimens have higher MQ than that of the control mixture as seen in Figure 10. Figure 10 MQ values of specimens 4 Conclusions Based on the findings of the experimental results, the following main conclusions can be drawn: OBC values for APR specimens are lower compared to CS specimens, especially for APR-100. Bitumen is a product derived from petroleum and it is expensive. For this reason, a more economical concrete production can be achieved by using APR. APR specimens have shown little increase in Marshall stability and little decrease in Flow except for APR-50 in comparison to the CS. All APR specimens have higher MQ than that of the control mixture. Although there is no difference between CS and APR specimens, it is recommended that APR can be used as a filler aggregate in asphalt

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