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Evaluation of asphalt mixtures incorporating electric arc furnace steel slag and copper mine tailings for road construction
Accepted Manuscript Evaluation of Asphalt Mixtures Incorporating Electric Arc Furnace Steel Slag and Copper Mine Tailings for Road Construction Ebenezer Akin Oluwasola, Mohd Rosli Hainin, Md Maniruzzaman A. Aziz PII: DOI: Reference:
S2214-3912(14)00035-X http://dx.doi.org/10.1016/j.trgeo.2014.09.004 TRGEO 29
To appear in: Received Date: Revised Date: Accepted Date:
29 June 2014 15 September 2014 28 September 2014
Please cite this article as: E.A. Oluwasola, M.R. Hainin, M.M.A. Aziz, Evaluation of Asphalt Mixtures Incorporating Electric Arc Furnace Steel Slag and Copper Mine Tailings for Road Construction, (2014), doi: http://dx.doi.org/ 10.1016/j.trgeo.2014.09.004
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Evaluation of Asphalt Mixtures Incorporating Electric Arc Furnace Steel Slag and Copper Mine Tailings for Road Construction Ebenezer Akin Oluwasola1, Mohd Rosli Hainin2, and Md. Maniruzzaman A. Aziz3* 1
Department of Geotechnics and Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia 2 and 3
Faculty of Civil Engineering and UTM Construction Research Centre (CRC), Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia *Corresponding author’s E-mail: [email protected], H/P : +60163673637
Abstract This study evaluates the suitability of using electric arc furnace (EAF) steel slag and copper mine tailings (CMT) as substitution for conventional aggregates used in pavements for roads and highways. Four mix designs containing EAF steel slag and CMT at different proportions were investigated. Mix 1 was 100% granite, Mix 2 consisted of 80% granite and 20% CMT, Mix 3 consisted of 80% EAF steel slag and 20% CMT while Mix 4 consisted of 40% granite, 40% EAF steel slag and 20% CMT. Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were used to evaluate the laboratory performance of the mixtures. The findings reveal that substituting natural granite aggregates with CMT and EAF steel slag improved the performance properties of asphalt mixtures. The mixture containing 80% EAF steel slag and 20% CMT produced the best results. The resilient modulus results show that the resilient modulus of the mixes decreased as the temperature increased. Also, the aging process significantly increased the resilient modulus and dynamic creep modulus values. Thus, the study has revealed that the mining by-products (CMT) and metallurgical by-products (EAF steel slag) can be utilized as aggregates in road construction. Key words: Industrial waste, EAF steel slag, Copper mine tailings, Aging, Sustainability, Green pavements
1. Introduction Transportation system plays a vital role in the development of a country. Having a good road network system enhances the mobility of goods and services which promote economic activities. Among the criteria for a good road transportation system is having quality road and highway pavements. To achieve this, significant quantities of aggregates are being used yearly for the construction of roads and highways. This development has become one of the major concerns for the professionals and agencies in the highway industry. Many studies have been carried out on alternative environmentally friendly materials that are compatible with natural aggregates in terms of performance [1 - 4]. The major constituent in terms of volume and weight of a typical asphalt mixture is aggregate; thus, industrial waste and recycled aggregates are imperative in constructing and maintaining works for roads and highways. The use of industrial waste can alleviate environmental pollution by reducing the accumulation of waste materials, which invariably will also reduce construction costs. Electric arc furnace (EAF)
steel slag is among the more common waste materials used in road
construction [5 - 8]. The use of steel slag has tremendously contributed to green technology as its use has preserved natural ecosystem through a reduction in the amount of dumped wastes and consumption of conventional aggregates in asphalt mix production [9 - 11]. Studies by JEGEL [12] showed that not all types of steel slag are appropriate for use as aggregate in the asphalt mixture. A good number of steel slags were rich in magnesium oxides and free lime, therefore, the tendency for its expansion in humid environments is very high. Appropriate steel slag can be utilized as a partial replacement for conventional aggregate in a number of civil engineering applications. It can be used in soil stabilization [13], concrete mix [4], subbase material [14] and asphalt concretes [15]. It can also be used in warm mix asphalt [2]. EAF steel slag can be processed into fine and coarse aggregate material for use in gapgraded, open-graded and dense graded asphalt mix. At the processing stage, the swelling potential is of prime importance because of the magnesium and free lime in the slag could result in pavement deterioration, if ignored [16]. The ASTM D5106 [17] stated the acceptable qualities of steel slag for use in asphalt mixture. The use of steel slag in the asphalt mix should be limited to partial replacement of natural aggregate because the asphalt mix with 100% steel slag is highly susceptible to bulking and air voids problems because of its angular shape.
Sultan [18] investigated the possibility of using stabilized copper mine tailings (CMT) in road construction. The findings of his study indicated that CMT possesses excellent engineering qualities and can be utilized in highway construction. However, the recent research on CMT had been focused on its utilization in concrete technology. Obinna and Ozgur [19] investigated the properties of concretes incorporating CMT. Their study supported the use of CMT as additive in concrete. Asphalt mix incorporating both EAF steel slag and CMT, may experience aged – hardening like the conventional asphalt mixes due to bitumen oxidation. Aging of asphalt mixtures affects the stiffness of the asphalt binder and may result in excessive stiffness. Characterization asphalt mixtures require that the evaluated samples should be aged to simulate in place properties of the asphalt mix. Aging in the field is significantly affected by the initial voids in the mixture, the densification of the mixture under traffic, the amount of heat applied to the mixture during production and many other factors related to the mixture. Asphalt mix generally undergoes two types of aging processes throughout the service life which are: short term and long term aging [20]. While the short term aging involves subjecting asphalt to a high temperature and air exposure during the production of hot mix asphalt whereas, long term aging involves exposure to the environment such as service pavement for a long period at a relatively lower temperature [21]. Bell et al [22] reported that a stiffer asphalt mixture enhances load distribution properties and improves resistance to rutting, thus, aging might be beneficial. However, in another study conducted by Singh et al [23] revealed that use of aged hot mix asphalt can result in the development of various types of pavement distress such as thermal cracking and fatigue. To evaluate the suitability of the mix incorporating EAF steel slag and CMT as aggregates, a proper mix design should be developed and a series of tests performed to assess their performance. Several studies have been carried out on the utilization of non–conventional aggregates in asphalt mix [24-27], but there is still relatively insufficient study on the performance of asphalt mix incorporating EAF steel slag and CMT as aggregate materials. In this study, Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were carried out on specimens to fulfill the objectives of this study.
2. Experimental Design 2.1 Materials EAF steel slag, CMT and granites are the three types of aggregates evaluated. EAF steel slag and CMT used in this study were obtained from Antara steel and Malaysia Marine and Heavy Engineering (MMHE) Pasir Gudang, Malaysia respectively. While steel slag and granites were used as both fine and coarse aggregate, copper mine tailings can only be utilized as fine aggregate due to its gradation (majorly passes through 1mm sieve). The chemical composition of the aggregates is shown in Table1. PG 76 and 80-100 binders were provided by Shell, Singapore. PG 76 and 80-100 bitumen binders were used in all the mixes. The two grades of bitumen binder were selected because PG 76 bitumen are stiffer than 80-100 bitumen based on their properties as presented in Table 2. In terms of dielectric constant, bitumen grade 80-100 possesses a low dielectric constant while PG 76 binder has high value of dielectric constant [28]. Some conventional tests such as viscosity, softening point and penetration tests were performed. Asphaltic wearing course (ACW 14) mix designation was used in this study. Table 3 displayed the aggregate type and size distribution for the mixes. Figure 1 shows the gradation of the combined aggregates used for all the mixes and Table 4 provides the physical properties of the aggregates.
Table 1: Chemical composition of different type of aggregates
Table 2: Properties of bitumen binder
Table 3:
Aggregate type and particle size distribution of the mixes
Figure 1: Aggregate gradation of combined mixture curve
Table 4: Physical properties of the aggregates
2.2 Sample preparation Four types of asphalt concrete mixes were used in this research. A detailed description of the mix design is shown in Table 3. Prior to the preparations of the samples, the aggregates were dried in the oven for 24 hours at a temperature of 105oC ±1oC to remove any inherent moistures. The heated bitumen was later added into the aggregates. The sample was compacted using a Marshall Compactor by applying 75 blows on each side of the sample. A minimum of three samples was produced to evaluate the reproducibility of the results. A short term oven aging was conducted according to AASHTO R30 – 02 [29]. The loose mixes were conditioned inside the oven for four hours at 135oC ± 1oC. At the end of the aging period, the loose mixes were removed from the oven and compacted using a Marshall Impact compaction. The long term oven aging procedure was carried out on the compacted samples after they were short – term aged. The long term oven aging was also used to simulate 15 years of field aging in a wet-no-freeze climate and 7 years in a dry-freezing climate [30-31]. The compacted specimens were conditioned at 85oC for five days as stated in AASHTO R30 – 02 [29]. After the
aging period, the oven was switched off and allowed to cool to room temperature. Then, the specimens were removed from the oven and tested, which must be at least 24 hours later.
3.
Mix design testing methods
3.1
Marshall stability and Marshall quotient test The Marshall test was basically conducted to assess the Marshall stability and flow of
asphalt mix incorporating EAF steel slag and CMT. The test was performed on the compacted sample in accordance with ASTM D 5581 [32]. The bulk specific gravities and air void contents were measured according to ASTM D C 127 [33]. Thus, from each mixture with the same bitumen content, three samples were conditioned in water at 60oC for a period of 30 minutes. Thereafter, each specimen was loaded to failure. To determine the optimum bitumen content (OBC), the parameters used were maximum Marshall stability, maximum bulk specific gravity, 4% air voids in the total mixture (VTM) and 75% volume in mineral aggregate (VMA). The Marshall quotient (MQ) which is the ratio of Marshall stability (kN) to flow (mm) is a key index to the mixture stiffness. MQ is also a measure of materials resistant to permanent deformation. Thus, a high MQ mixture shows a high tendency of stiffness and can resist creep deformation to a large extent.
3.2
Moisture susceptibility test
AASHTO T 283 [34] described the procedures for the determination of water susceptibility of asphalt mixture. The prepared compacted samples were grouped into two; conditioned and unconditioned. The samples to be conditioned were placed in a saturation vacuum. The pressure of approximately 6.7 kPa was applied for 10 minutes. The specimens were submerged for another 10 minutes in a water bath. To evaluate the effect of the freeze-thaw cycle, each specimen was wrapped with a leakproof plastic bag containing 10 ml of distilled water. The plastic containing the specimen was placed in a freezer at -17oC ±1oC for a minimum of 16 hours. Thereafter, the specimen was submerged in a water bath at 60oC for 24 hours, after which the specimen was placed in a water bath at 25oC for 2 hours with at least 25 mm of water above
the sample. The specimen was later tested for indirect tensile strength (ITS). Prior to the testing of the unconditioned samples, they were submerged in water at 25oC for 2 hours. Resistance to moisture sensitivity was calculated based on ITS ratio, using equation 1
TSR =
( ) ( )
(1)
Where: TSR = Tensile strength ratio ITS conditioned = The average of ITS on the conditioned sample ITS control = The average of ITS of the control sample 3.3
Resilient Modulus test The test was conducted in accordance with ASTM D 4123 – 11 using Universal Testing
Machine (UTM) for unaged and aged samples [35]. The test was conducted at 25oC and 40oC by applying repetitive compressive loads in a harversine waveform on the sample. The resilient modulus at 25oC is somewhat related to fatigue and 40oC related to rutting damage. In general, a lower resilient modulus at low temperature is considered desirable, as the binder becomes more elastic and provides better resistance to fatigue damage. On the other hand, a high temperature is desired in order to have a less viscous binder that can provide a better resistance to rutting damage. Prior to testing, the samples were conditioned for four hours at a selected test temperature. In this study, 1000N peak force was applied as harversine load. Pulse width of 0.1 sec, rest period of 0.9 Sec and assumed Poisson’s ratio of 0.4 were used. A compressive load was applied laterally along the curved plane of a cylindrical sample of asphalt mixture. Each specimen was subjected to two sets of five load pulses. The specimen was rotated after the first reading by 90o. Therefore, the load was applied perpendicular to the direction of the first set during the second set of loadings. The average of resilient modulus of each test was evaluated.
3.4
Dynamic creep test
A dynamic creep test was performed to assess the rutting tendency in asphalt mixes. The test was conducted using compacted specimens in accordance with ASTM D 3497 [36]. Prior to testing, the samples were conditioned at 40oC for four hours. The test parameters used in this study include; a preload stress of 150kPa and axial cycle loading stress of 300kPa. In order to ensure a complete contact between the sample and the load bar, a preloading time of 30 sec was used. The test was set to terminate at 3600 cycles which is sufficient to predict the behavior of asphalt mix in a repeatable axial loading stress. The test was performed by applying a repeated uniaxial load to the test samples. Linear Variable Displacement Transducers (LVDTs) were used to measure the resulting deformations. The results of the creep test were displayed in a graphical form with both strain and displacement on the vertical axis and number of cycles on the horizontal axis. The dynamic creep modulus and creep strain slope (CSS) were calculated using equations 2 and 3 respectively as stipulated in the specifications for Malaysia road works [37]:
#$$%&'( )*&)% +,-'++
! " = ,-)&. ), /011 232%'+4,-)&. ), 5611 232%'+
788 =
%9: ;< =>?@AB @ /0114 %9: ;< =>?@AB @ 5611 %9: /0114%9: 5611
4.
Results and discussion
4.1
Marshall stability and Flow test
(2)
(3)
The Marshall stability test properties of all the asphalt mixes studied in this research are presented in Table 5 as the average of three samples. It was observed that binder PG 76 gave a better result than 80-100 bitumen. The asphaltic mixes containing 4 - 6% in a step of 0.5% bitumen binder by the mass of the aggregate had optimum bitumen content for Mix1, Mix 2, Mix 3 and Mix 4 as 5.04, 5.06, 5.18 and 5.13% respectively for 80-100 binder and 5.11, 5.13, 5.21 and 5.16% respectively for PG 76. The difference in the OBC for the four mixes was not highly significant. However, it was noted in Table 5 that the mix with the highest OBC content
produced the maximum stability and the least flow. This behavior was expected because an increase in bitumen binder in the mix results in air voids reduction between the aggregate particles. This eventually enhanced the compaction of the mix and results in high Marshall stability. As shown in Table 5, in terms of Marshall stability and stiffness /Marshall quotient (MQ) PG 76 binder gave a better performance result. This may be attributed to its viscosity and more so PG 76 is modified bitumen.
Table 5: Results of Marshall Design
The optimum bitumen content of mixes containing either EAF steel slag or CMT was slightly higher than the control mix. This is likely due to the higher porosity of the EAF steel slag and CMT aggregate as compared to the granite though the bitumen content is within the limit stipulated by the Malaysian road standards [37]. In terms of performance based on the Marshall properties studied Mix 2, 3 and 4 were exceedingly better than mix 1 (control). Generally, mix 3 gave the best result followed by mix 4 and 2 respectively. Based, on the physical properties of the aggregates as shown in Table 3, EAF steel slag has a pH value of 11.42, which enhances its affinity with low acidic bitumen because the pH value of PG 76 and 80-100 used in this study was 6.62 and 6.49 respectively. The EAF steel slag and CMT possess higher angle of internal friction, angularity and higher bulk specific gravity comparable to granite. This property enhances better aggregate interlock and qualifies both CMT and EAF steel slag as suitable asphalt paving materials. Mixtures that contain either CMT or EAF steel slag or both also exhibit higher value of the Marshall quotient (stiffness). Thus, such mixes will show higher resistance to permanent deformations and shear stress.
4.2
Moisture susceptibility
The ITS and TSR results are illustrated in Figure 2. The ITS of the specimens drops after moisture conditioning. In this study, Mix 3 samples exhibit higher tensile strength compared to the other mixes. This is probably due to its low air void content. From the other research findings, it is expected that a high air void enables the mixture to have low strength and high deformation [38]. It can be observed that the mixture with 4.8% air void does not provide the same ITS as the mixture with 3.8% air void. The incorporation of EAF steel slag in the asphalt mixes increased the ITS of the mixes. This can be attributed to the improved aggregate structure of the EAF steel slag and CMT. The test results are in conformity with the findings of [39]. The freeze-thaw cycle reduces the tensile strength of the conditioned specimens. The continuity of pores in the EAF steel slag and CMT produced spaces for water absorption. Therefore, when ice forms within the pores of the mix, it may result into the formation of cracks. The presence of pores in aggregates could threaten the resistance against freeze-thaw cycles [40]. However, in this research, the reductions are considered moderate, since the TSR ≥ 80% as recommended in AASHTO T283 [34]. The TSR signal that the moisture susceptibility of asphalt mix incorporating EAF steel slag and CMT does not appear to be a threat.
Figure 2: Tensile strength and TSR for the mixes 4.3
Indirect tensile resilient modulus The average of three specimen test results for indirect tensile resilient modulus values of
the four types of hot mix asphalt mixes is presented in Figures 3 and 4. In general, the results indicate that samples blended with PG 76 bitumen binder have higher resilient modulus values than samples blended with 80–100 bitumen binder.
PG 76 bitumen binder is stiffer and has better tensile strength. Thus, its higher resilient modulus value can be attributed to its stiffness and tensile strength. Among, the four mixes, mix 1 (control) have the least value of resilient modulus at both temperatures. The shape, pH and other physical properties of both EAF steel slag and CMT as displayed in Table 4 can be attributed to higher resilient modulus of mixes 2, 3 and 4 as compared to the control sample. In terms of chemical composition of the aggregates highlighted in Table 1, the value of CaO/SiO2 was 0.076, 5.064 and 0.283 for granite, EAF steel slag and CMT respectively. The higher CaO/SiO2 values for steel slag and copper tailings resulted in higher aggregate – binder adhesion [2].
Figure 3: Resilient modulus of the mixes at 25oC
Figure 4: Resilient modulus of the mixes at 40oC
In general, the resilient modulus of the four mixes decreased when the temperature increased from 25oC to 40oC. According to Tia [41] at low temperature, bitumen becomes brittle and the asphalt mixture tends to crack at lower temperature. Stresses are pronounced in the asphalt mix at cooled surface [42-43]. As a result of the flowing asphalt binder within the asphalt mix, the induced stresses can be reduced to a large extent. The viscosity of the bitumen binder decreases as the temperature increases and this enhances the flow within the mix and reduces stress. At high temperature, bitumen binder may lose its tendency to bind the aggregates together. Thus, the recoverable strain increases with temperature and this would result in lower resilient modulus of the mixes.
Aging studies revealed that sulfoxides, carboxylic acids and ketones increased with oxidative aging. The category and number of oxidative aging products seem to be totally related to the chemistry of the bitumen [44]. This may affect the aggregate particles binding some of the already formed oxidative functional groups. The differences resulted from the oxidative aging can possibly affect the interface chemistry [45].
Therefore, oxidative aging bring forth
significant changes in the chemistry of the asphalt-aggregate interface. Indirect tensile resilient modulus test was performed on short term aging (STOA) and long term aging (LTOA) samples at two different temperatures of 25oC and 40oC. The aging process increases the resilient modulus for both PG 76 and pen 80 – 100 prepared mix. Though, the trend was higher with PG 76 samples as shown in Figures 3 and 4. The increasing resilient modulus of the aging samples may be attributed to binder hardening causing mix to stiffen. It was suggested by Bell and Sosnuvskc [46] that aging was influenced by the aggregates. This agrees with the findings of this research. At 25oC, the resilient modulus of mixes 1, 2, 3 and 4 increased by 53.7, 148, 97.9 and
99.1% after STOA and 85.6, 153.7, 121 and 184.8%
respectively after LTOA. The resilient modulus at 40oC of PG 76 prepared mix 1, 2, 3 and 4 increases by 51.5, 114.5, 21.4 and 58.3%, respectively, after STOA and 55.6, 259.5, 75.8 and 92.8% respectively after LTOA. Thus, this trend shows that the resilient modulus increases with aging higher at 25oC than 40oC. This trend was supported by [46] in their findings that the greater the adhesion, the more the extenuation of aging, thereby confirming that aged EAF and CMT mixes exhibit superior adhesion property compared to aged granite mixes. The results are similar to that of Mohamed [47] which aged HMA modified with crumb rubber produced better resilient modulus than the unaged samples at 0% crumb rubber content.
4.4
Dynamic creep According to He [48] the dynamic creep curve consists of two parts; the curve segment,
which represents the creep strain slope (CSS) at densification of the mix during the test and the stable development of axial strain in the two third line segment of the curve. The initial permanent deformation is not influenced by the load cycle but due to the other two third parts of the linear dynamic creep curve [49]. For these reasons, dynamic creep modulus which is a function of strain and the applied axial stress; and CSS were used to evaluate the mix resistant to
permanent deformation calculated between 1200 and 3600 cycles. Some researchers obtained CSS and creep modulus between 1200 and 3600 cycles [50]. Also, Pasandin and Perez [26] obtained slope of the creep curve between 600 and 1800 cycles and termination occurs at 1800 cycles. The dynamic creep modulus was calculated by dividing the applied axial stress with the differences of strain at 1200 and 3600 cycles. The results of the dynamic creep test are shown in Figure 5. Each value is the average of the three tested specimens. It illustrates that the mixes blended with PG 76 binder are shown to be more superior to those blended with 80-100 binder. Besides that, the dynamic creep modulus increases with aging. For samples blended with PG 76,
Figure 5: Dynamic creep modulus results of the mixture The mix 1, 2, 3 and 4 increased by 111.1, 115.3, 524.5 and 421.9%, respectively, after STOA and 166.7, 168.5, 794 and 668.6% respectively after LTOA. Though, the samples blended with 80-100 binder also experienced increases in dynamic creep modulus with aging, the magnitudes were not as high as that of PG 76. For instance, the mix 1, 2, 3 and 4 increased by 22.9, 9.4, 20 and 25.6% respectively, after STOA and the samples were increased after LTOA by 31.4, 56.3, 72 and 69.8% respectively. The mix susceptibility to permanent deformation with respect to CSS is presented in Figure 6. It can be observed that the CSS reduces with aging. Mixes containing EAF steel slag and CMT show lower CSS than the conventional mixture. The CSS reduces by 24.8, 25.0, 32.1 and 23.9% in Mixes 1, 2, 3 and 4 respectively, after LTOA for 80-100 specimens and 24.3, 31.3, 97.6 and 48.2% in Mixes 1,2,3, and 4 respectively after LTOA for PG 76 specimens. The CSS can be used to evaluate the strain rate of deformation that takes place at the primary stage after the densification. Therefore, the higher the strain rate, the higher the CSS and the lower the resistance to permanent deformation. The mix 1 (control mix) displayed higher CSS than those obtained from the mixture that contain EAF steel slag and CMT. The mix 1 that was blended with 80-100 bitumen shows the highest CSS and thus the least resistant to permanent deformation among the four mixes.
Figure 6: Creep strain slope for the mixes
This trend can be attributed to the good engineering properties of EAF steel slag and CMT. EAF steel slag is more angular in shape and also possesses higher resistance to friction and abrasion. The CSS results also indicated that binder type and content influence the resistance to permanent deformation, this conform with the findings of [48]
5.
Conclusions The study evaluated of asphalt mix incorporating EAF steel slag and copper mine tailings.
Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were conducted for the samples. The findings are summarized as follows: •
Based on aggregate properties, all the testing properties satisfied the standard specification for Malaysia road works [37] except water absorption. According to the Malaysian road specification, the water absorption should not exceed 2%, but the water absorption value for EAF steel slag and CMT was 3.896 and 4.17% respectively. This is because both EAF steel slag and CMT have more pores on their surface area which enable the water to penetrate easily through them. From the moisture susceptibility test results, though, specimens incorporating EAF steel slag and CMT exhibit low TSR, it was apparently clear that the moisture susceptibility of ACW incorporating EAF steel slag and CMT does not appear to be a problem.
•
The use of EAF steel slag and copper mine tailings as aggregate in asphalt mixtures, improves the Marshall stability, Marshall quotient and flow properties. The porosity of EAF steel slag and CMT accounted for the higher OBC value in the Mix 2, 3 and 4. Hence, such mixes will be costly in terms of bitumen consume, though the cost can be saved in terms of the aggregate cost because both EAF steel slag and CMT are byproducts and can easily be obtained at very low price compared to granite.
•
The use of EAF steel slag and copper mine tailings significantly increased the resilient modulus at both temperatures. The excellent attributes of the aggregates accounted for these results. As temperature increases, the difference in resilient modulus is more significant with a decrease in stiffness at 40oC. The samples blended with PG 76 exhibited higher stiffness, thus they are less susceptible to rutting than 80-100 samples.
•
Mix 3 which contained 80% EAF steel slag and 20% copper mine tailings displayed enough resistance to permanent deformation, whether the mix is unaged or aged. The aging process greatly influenced the dynamic creep modulus of the samples and also had a notable effect with CSS.
Finally, based on experimental findings, we remark that EAF steel slag and CMT can improve the performance of asphalt mixtures for road construction. Besides that, utilization of EAF steel slag and CMT will reduce the amount of conventional aggregate used in highway construction and at the same time benefit the environments. Acknowledgements The authors gratefully acknowledge the Universiti Teknologi Malaysia (UTM) for providing financial support for conducting this research through the university research grant vote 07J33. In addition, we are grateful to both Malaysia Marine and Heavy Engineering (MMHE) and Antara Steel in Malaysia and Shell Singapore for providing copper tailings, EAF steel slag and bitumen respectively.
References [1]
Meor OH. and Teoh CY. Effects of temperature on resilient modulus of dense asphalt mixtures incorporating steel slag subjected to short term oven ageing, World Acad. Sci. Eng. Technol., 2007;22: 191–95.
[2]
Ameri M, Hesami S and Goli H. Laboratory evaluation of warm mix asphalt mixtures containing electric arc furnace (EAF) steel slag, Conserv. Recycl., 2013;49: 611–17.
[3]
Andreas L, Diener S and Lagerkvist A. Steel slags in a landfill top cover--experiences from a full-scale experiment., Waste Manag., 2014; 34: 692–701.
[4]
Qasrawi H. The use of steel slag aggregate to enhance the mechanical properties of recycled aggregate concrete and retain the environment, Constr. Build. Mater., 2014; 54: 298–304.
[5]
Sorlini S, Sanzeni A and Rondi L. Reuse of steel slag in bituminous paving mixtures, J. Hazard. Mater., 2012; 209: 84–91.
[6]
Yildirim IZ and Prezzi M. Use of steel slag in subgrade applications, 2009.
[7]
Yi H, Xu G, Cheng H, Wang J, Wan Y and Chen H. An Overview of Utilization of Steel Slag, Procedia Environ. Sci., 2012; 16:791–801.
[8]
Pasetto M and Baldo N. Mix design and performance analysis of asphalt concretes with electric arc furnace slag, Constr. Build. Mater., 2011; 25: 3458–3468.
[9]
Pasetto M and Baldo N. Experimental evaluation of high performance base course and road base asphalt concrete with electric arc furnace steel slags, J. Hazard. Mater.,2010; 181: 938–48.
[10] Liapis I and Likoydis S. Use of Electric Arc Furnace Slag in Thin Skid–Resistant Surfacing, Procedia - Soc. Behav. Sci., 2012; 48: 907–918. [11] Motz H and Geiseler J. Products of steel slags an opportunity to save natural resources, Waste Manag., 2001; 21:285–293. [12] JEGEL. Steel slag aggregates use in hot mix asphalt concrete. Final report prepared for the steelmaking slag Technical Committee, Toronto, Ont. John Emery Geotechnical Engineering Limited (JEGEL), 1993. [13] Manso, J. M., Ortega-López, V., Polanco, J. A., and Setién, J. The use of ladle furnace slag in soil stabilization. Construction and Building Materials, 2013; 40, 126-134. [14]
Xie, J., Chen, J., Wu, S., Lin, J., and Wei, W. Performance characteristics of asphalt mixture with basic oxygen furnace slag. Construction and Building Materials, 2013; 38, 796-803.
[15]
Ahmedzade, P., and Sengoz, B. Evaluation of steel slag coarse aggregate in hot mix asphalt concrete. Journal of hazardous materials, 2009; 165(1), 300-305.
[16]
Norton, J. Use of steel furnace slag in bituminous mixtures. Research Report No. 78 TB23. Michigan Department of Transportation, Lansing, Mich.
[17]
ASTM D 5106. Standard specifications for steel slag aggregates for bituminous paving mixtures. Philadelphia U.S: 2003
[18]
Sultan, H. A. Stabilized copper mill tailings for highway construction. Transportation research record, (734), 1979
[19] Onuaguluchi, O., and Eren, O. Copper tailings as a potential additive in concrete: consistency, strength and toxic metal immobilization properties.Indian Journal of Engineering & Materials Sciences, 2012; 19(2), 79-86. [20] Roberts FL, Kandhal PS, Brown ER, Kim YR, Lee Dad-Yinn and Kennedy T. Hot mix asphalt materials, mixture, design, and construction, Third Edition. Lanham, Maryland: NAPA Research and Education Foundation, 2009. [21] Idham MK, Hainin MR, Yaacob Haryati, M Naqiuddin M Warid and Abdullah ME. Effect of Aging on Resilient Modulus of Hot Mix Asphalt Mixtures, Adv. Mater. Res.,2013;723: 291–97. [22] Bell C, AbWahab Y and Cristi ME. Selection of Laboratory aging procedures for asphaltaggregate mixtures, Strateg. Highw. Res. Program. Natl. Res. Counc., 1994. [23] Singh D, Zaman M and Commuri S. Effect of long term oven aging on dynamic modulus of hot mix asphalt, Geo-Frontiers @ ASCE, 2011; 4773–81. [24] Mills-Beale, J., and You, Z. The mechanical properties of asphalt mixtures with recycled concrete aggregates. Construction and Building Materials, 2010; 24(3), 230-235. [25] Pérez, I., Gallego, J., Toledano, M., and Taibo, J. Asphalt mixtures with construction and demolition debris. Proceedings of the ICE-Transport, 2010; 163 (4), 165-174. [26] Pasandín, A. R., and Pérez, I. Effect of ageing time on properties of hot-mix asphalt containing recycled concrete aggregates. Construction and Building Materials, 2014; 52, 284-293. [27] Collins, R. J., and Ciesielski, S. K. Recycling and use of waste materials and by-products in highway construction 1994; (No. 199). [28] Md. Maniruzzaman BAA, Muniandy R, Abdullah K and Mahmud A. Preliminary determination of asphalt properties using microwave techniques, APRN J. Eng. Appl. Sci., 2010;5. [29]
AASHTO R 30. Standard practice for mixture conditioning of hot mix asphalt:2002
[30]
Airey, G. D. State of the art report on ageing test methods for bituminous pavement materials. International Journal of Pavement Engineering, 2003; 4(3), 165-176.
[31]
Brown, S. F., and Scholz, T. V. (2000). Development of laboratory protocols for the ageing of asphalt mixtures. In Proc. 2nd Eurasphalt and Eurobitume Congress, Session, 2000; 1, 83-90).
[32] ASTM D 5581. Standard test method for resistance to plastic flow of bituminous mixtures using Marshall apparatus. Philadelphia U.S: 2013.
[33] ASTM C 127. Standard test method for density of semi bituminous materials (pyconometer method). Philadelphia U.S: 2012. [34]
AASHTO T 283-02. Standard method of test for resistance of compacted asphalt mixtures to moisture-induced damage: 2007
[35]
ASTM D 4123. Standard Test Method for Determining the Resilient Modulus of Bituminous Mixtures by Indirect Tension Test, Philadephia U.S.: ASTM International: 2011
[36] ASTM D 3497. Standard test method for dynamic modulus of bituminous mixtures. Philadelphia U.S: 2011 [37] Jabatan Kerja Raya Malaysia. Standard specification for Road Works, section 4: Flexible Pavement, 2008; S4-58 - S4-59. [38] Teoh, C.Y. Performance evaluation of steel slag as natural aggregates replacement in asphaltic concrete, Unpublished M.Sc Thesis, University Sains Malaysia, 2008 [39] Asi, I. M., Qasrawi, H. Y., and Shalabi, F. I. Use of steel slag aggregate in asphalt concrete mixes. Canadian Journal of Civil Engineering,2007; 34(8), 902-911. [40]
InDOT Aggregate Properties, Certified Technician Program Training Manual for Hot Mix Asphalt (Construction), Indiana State Department of Transportation, USA, 2004; 31to 3-9.
[41] Tia M. Bituminous materials and mixtures Civil Engineering Handbook. Boca Raton, Florida: CRC press Inc., 2003: 451–36. [42]
Hainin, M.R, Yusoff, N. I. M, Mohd Satar, M. K.L and Brown, E. R. The effect of lift thickness on permeability and the time available for compaction of hot mix asphalt pavement under tropical climate condition, Constr. Build. Mater., 2013; 48: 315–324.
[43]
Ahmad, J, Yusoff, N. I. M, Hainin, M. R, Rahman, M. Y. A, and Hossain, M. Investigation into hot-mix asphalt moisture-induced damage under tropical climatic conditions, Constr. Build. Mater., 2014; 50:567–576.
[44] Kuang, D., Yu, J., Feng, Z., Li, R., Chen, H., Guan, Y., and Zhang, Z. Performance evaluation and preventive measures for aging of different bitumens. Construction and Building Materials, 2014; 66, 209-213. [45] SHRP A - 341 Fundamental properties of Asphalt - Aggregate Interactions, including adhesion and absorption, SHRP, National Research Council, 1993. [46] Bell, C. A., and Sosnovske, D. Aging: binder validation (No. SHRP-A-384). Washington, DC: Strategic Highway Research Program, National Research Council.1994
[47] Mohamed, A.A A study on the physical and mechanical properties of asphaltic concrete incorporating crumb rubber produced through dry process, Unpublished PhD Thesis, Universiti Sains Malaysia.2007 [48] He, G.P. Study the use of reclaimed asphalt pavement (RAP) with foamed bitumen in Hong Kong, PhD Thesis, The Hong Kong Polytechnic University, 2006 [49] Ahmad, J. A study on moisture induced damage and rutting of hot mix asphalt, Unpublished PhD Thesis, Universiti Teknologi Mara, 2010.
Table 1: Chemical composition of different type of aggregates Aggregate type
Oxide content (%)
CaO
SiO2
Fe2O3
Al2O3
ZnO
MgO
MnO
K2O
Na2O
SO3
Cr203
Granite
4.90
64.60
3.80
16.80
-
0.74
-
4.40
3.48
-
-
Steel slag
55.2
10.90
16.80
4.00
3.72
3.06
2.59
0.16
0.75
0.85
0.69
Copper tailings
12.48
44.10
19.00
15.40
0.96
0.87
0.87
1.24
0.46
2.46
-
Table 2: Properties of bitumen binder Parameter Penetration @ 25oC, 1/10mm, 100g Softening point (0C) Viscosity @ 135oC (cP) Viscosity @ 60oC (cP) Specific gravity Mixing temperature Compacting temperature
PG 76 48 61 1800 36200 1.031 170 – 185oC 140 – 160oC
80-100 85 46 400 23200 1.0 130 – 150oC 120 – 140oC
Standards ASTM D5 ASTM D36 ASTM D44
ASTM D70
Table 3: Aggregate type and particle size distribution of the mixes Fraction
Mix 1
Mix 2
Mix 3
(mm)
Granite
Granite
(%)
(%)
14
6
6
-
6
10
14
14
-
5
26
26
3.35
9.5
1.18
EAF
Copper
(%)
Slag (%)
Tailing (%)
-
3
3
-
14
-
7
7
-
-
26
-
13
13
-
9.5
-
9.5
-
4.75
4.75
-
21.5
11.4
10.1
11.4
10.1
5.7
5.7
10.1
0.425
8.5
4.5
4
4.5
4
2.25
2.25
4
0.150
8.5
4.5
4
4.5
4
2.25
2.25
4
0.075
4
2.1
1.9
2.1
1.9
1.05
1.05
1.9
Filler
2
(cement)
Copper Tailing (%)
2
EAF
Mix 4
Slag (%)
Copper Tailing (%)
2
Granite
2
Table 4: Physical properties of the aggregates Testing
Standard
Granite
EAF Steel
Copper
slag
Tailings
Specification
ASTM C 131
10.276
5.100
-
≤ 25%
Flakiness
MS 30
7%
5%
-
≤ 25%
Soundness
AASHTO T 104
3.5%
0.71%
-
≤ 18%
Polished Stone Value
BS 812
52.3%
55.3%
-
≥ 40%
Water Absorption
MS 30
0.756%
3.896%
4.17%
≤ 2%
AASHTO T 182
> 95%
> 95%
-
≥ 95%
Coarse Aggregate
ASTM C127
2.594
2.816
-
-
Fine Aggregate
ASTM C 128
2.585
3.051
3.578
-
BS 1377
10.22
11.42
6.42
-
Loss Angeles Abrasion
Stripping Specific Gravity:
pH
Table 5: Results of Marshall test Property
Mix 1
Mix 2
Mix 3
Mix 4
80-100
PG 76
80-100
PG 76
80-100
PG 76
80- 100
PG 76
O.B.C (%)
5.04
5.11
5.06
5.13
5.18
5.21
5.13
5.16
Air void (%)
4.5
4.8
4.7
4.3
3.8
4.0
4.3
4.4
Bulk specific gravity
2.325
2.276
2.396
2.363
2.577 2.575
2.483
2.364
Marshall stability (kN) 13.70
14.88
15.15
16.97
15.75 21.42
14.10
19.05
Flow (mm)
3.07
2.97
2.17
2.21
2.16
2.30
2.78
MQ (kN/mm)
4.463
5.009
6.982
7.680
7.292 9.872
6.130
6.854
VMA
15.6
17.4
15.4
16.8
18.5
16.8
15.7
2.17
17.9
S2214-3912(14)00035-X http://dx.doi.org/10.1016/j.trgeo.2014.09.004 TRGEO 29
To appear in: Received Date: Revised Date: Accepted Date:
29 June 2014 15 September 2014 28 September 2014
Please cite this article as: E.A. Oluwasola, M.R. Hainin, M.M.A. Aziz, Evaluation of Asphalt Mixtures Incorporating Electric Arc Furnace Steel Slag and Copper Mine Tailings for Road Construction, (2014), doi: http://dx.doi.org/ 10.1016/j.trgeo.2014.09.004
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Evaluation of Asphalt Mixtures Incorporating Electric Arc Furnace Steel Slag and Copper Mine Tailings for Road Construction Ebenezer Akin Oluwasola1, Mohd Rosli Hainin2, and Md. Maniruzzaman A. Aziz3* 1
Department of Geotechnics and Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia 2 and 3
Faculty of Civil Engineering and UTM Construction Research Centre (CRC), Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia *Corresponding author’s E-mail: [email protected], H/P : +60163673637
Abstract This study evaluates the suitability of using electric arc furnace (EAF) steel slag and copper mine tailings (CMT) as substitution for conventional aggregates used in pavements for roads and highways. Four mix designs containing EAF steel slag and CMT at different proportions were investigated. Mix 1 was 100% granite, Mix 2 consisted of 80% granite and 20% CMT, Mix 3 consisted of 80% EAF steel slag and 20% CMT while Mix 4 consisted of 40% granite, 40% EAF steel slag and 20% CMT. Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were used to evaluate the laboratory performance of the mixtures. The findings reveal that substituting natural granite aggregates with CMT and EAF steel slag improved the performance properties of asphalt mixtures. The mixture containing 80% EAF steel slag and 20% CMT produced the best results. The resilient modulus results show that the resilient modulus of the mixes decreased as the temperature increased. Also, the aging process significantly increased the resilient modulus and dynamic creep modulus values. Thus, the study has revealed that the mining by-products (CMT) and metallurgical by-products (EAF steel slag) can be utilized as aggregates in road construction. Key words: Industrial waste, EAF steel slag, Copper mine tailings, Aging, Sustainability, Green pavements
1. Introduction Transportation system plays a vital role in the development of a country. Having a good road network system enhances the mobility of goods and services which promote economic activities. Among the criteria for a good road transportation system is having quality road and highway pavements. To achieve this, significant quantities of aggregates are being used yearly for the construction of roads and highways. This development has become one of the major concerns for the professionals and agencies in the highway industry. Many studies have been carried out on alternative environmentally friendly materials that are compatible with natural aggregates in terms of performance [1 - 4]. The major constituent in terms of volume and weight of a typical asphalt mixture is aggregate; thus, industrial waste and recycled aggregates are imperative in constructing and maintaining works for roads and highways. The use of industrial waste can alleviate environmental pollution by reducing the accumulation of waste materials, which invariably will also reduce construction costs. Electric arc furnace (EAF)
steel slag is among the more common waste materials used in road
construction [5 - 8]. The use of steel slag has tremendously contributed to green technology as its use has preserved natural ecosystem through a reduction in the amount of dumped wastes and consumption of conventional aggregates in asphalt mix production [9 - 11]. Studies by JEGEL [12] showed that not all types of steel slag are appropriate for use as aggregate in the asphalt mixture. A good number of steel slags were rich in magnesium oxides and free lime, therefore, the tendency for its expansion in humid environments is very high. Appropriate steel slag can be utilized as a partial replacement for conventional aggregate in a number of civil engineering applications. It can be used in soil stabilization [13], concrete mix [4], subbase material [14] and asphalt concretes [15]. It can also be used in warm mix asphalt [2]. EAF steel slag can be processed into fine and coarse aggregate material for use in gapgraded, open-graded and dense graded asphalt mix. At the processing stage, the swelling potential is of prime importance because of the magnesium and free lime in the slag could result in pavement deterioration, if ignored [16]. The ASTM D5106 [17] stated the acceptable qualities of steel slag for use in asphalt mixture. The use of steel slag in the asphalt mix should be limited to partial replacement of natural aggregate because the asphalt mix with 100% steel slag is highly susceptible to bulking and air voids problems because of its angular shape.
Sultan [18] investigated the possibility of using stabilized copper mine tailings (CMT) in road construction. The findings of his study indicated that CMT possesses excellent engineering qualities and can be utilized in highway construction. However, the recent research on CMT had been focused on its utilization in concrete technology. Obinna and Ozgur [19] investigated the properties of concretes incorporating CMT. Their study supported the use of CMT as additive in concrete. Asphalt mix incorporating both EAF steel slag and CMT, may experience aged – hardening like the conventional asphalt mixes due to bitumen oxidation. Aging of asphalt mixtures affects the stiffness of the asphalt binder and may result in excessive stiffness. Characterization asphalt mixtures require that the evaluated samples should be aged to simulate in place properties of the asphalt mix. Aging in the field is significantly affected by the initial voids in the mixture, the densification of the mixture under traffic, the amount of heat applied to the mixture during production and many other factors related to the mixture. Asphalt mix generally undergoes two types of aging processes throughout the service life which are: short term and long term aging [20]. While the short term aging involves subjecting asphalt to a high temperature and air exposure during the production of hot mix asphalt whereas, long term aging involves exposure to the environment such as service pavement for a long period at a relatively lower temperature [21]. Bell et al [22] reported that a stiffer asphalt mixture enhances load distribution properties and improves resistance to rutting, thus, aging might be beneficial. However, in another study conducted by Singh et al [23] revealed that use of aged hot mix asphalt can result in the development of various types of pavement distress such as thermal cracking and fatigue. To evaluate the suitability of the mix incorporating EAF steel slag and CMT as aggregates, a proper mix design should be developed and a series of tests performed to assess their performance. Several studies have been carried out on the utilization of non–conventional aggregates in asphalt mix [24-27], but there is still relatively insufficient study on the performance of asphalt mix incorporating EAF steel slag and CMT as aggregate materials. In this study, Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were carried out on specimens to fulfill the objectives of this study.
2. Experimental Design 2.1 Materials EAF steel slag, CMT and granites are the three types of aggregates evaluated. EAF steel slag and CMT used in this study were obtained from Antara steel and Malaysia Marine and Heavy Engineering (MMHE) Pasir Gudang, Malaysia respectively. While steel slag and granites were used as both fine and coarse aggregate, copper mine tailings can only be utilized as fine aggregate due to its gradation (majorly passes through 1mm sieve). The chemical composition of the aggregates is shown in Table1. PG 76 and 80-100 binders were provided by Shell, Singapore. PG 76 and 80-100 bitumen binders were used in all the mixes. The two grades of bitumen binder were selected because PG 76 bitumen are stiffer than 80-100 bitumen based on their properties as presented in Table 2. In terms of dielectric constant, bitumen grade 80-100 possesses a low dielectric constant while PG 76 binder has high value of dielectric constant [28]. Some conventional tests such as viscosity, softening point and penetration tests were performed. Asphaltic wearing course (ACW 14) mix designation was used in this study. Table 3 displayed the aggregate type and size distribution for the mixes. Figure 1 shows the gradation of the combined aggregates used for all the mixes and Table 4 provides the physical properties of the aggregates.
Table 1: Chemical composition of different type of aggregates
Table 2: Properties of bitumen binder
Table 3:
Aggregate type and particle size distribution of the mixes
Figure 1: Aggregate gradation of combined mixture curve
Table 4: Physical properties of the aggregates
2.2 Sample preparation Four types of asphalt concrete mixes were used in this research. A detailed description of the mix design is shown in Table 3. Prior to the preparations of the samples, the aggregates were dried in the oven for 24 hours at a temperature of 105oC ±1oC to remove any inherent moistures. The heated bitumen was later added into the aggregates. The sample was compacted using a Marshall Compactor by applying 75 blows on each side of the sample. A minimum of three samples was produced to evaluate the reproducibility of the results. A short term oven aging was conducted according to AASHTO R30 – 02 [29]. The loose mixes were conditioned inside the oven for four hours at 135oC ± 1oC. At the end of the aging period, the loose mixes were removed from the oven and compacted using a Marshall Impact compaction. The long term oven aging procedure was carried out on the compacted samples after they were short – term aged. The long term oven aging was also used to simulate 15 years of field aging in a wet-no-freeze climate and 7 years in a dry-freezing climate [30-31]. The compacted specimens were conditioned at 85oC for five days as stated in AASHTO R30 – 02 [29]. After the
aging period, the oven was switched off and allowed to cool to room temperature. Then, the specimens were removed from the oven and tested, which must be at least 24 hours later.
3.
Mix design testing methods
3.1
Marshall stability and Marshall quotient test The Marshall test was basically conducted to assess the Marshall stability and flow of
asphalt mix incorporating EAF steel slag and CMT. The test was performed on the compacted sample in accordance with ASTM D 5581 [32]. The bulk specific gravities and air void contents were measured according to ASTM D C 127 [33]. Thus, from each mixture with the same bitumen content, three samples were conditioned in water at 60oC for a period of 30 minutes. Thereafter, each specimen was loaded to failure. To determine the optimum bitumen content (OBC), the parameters used were maximum Marshall stability, maximum bulk specific gravity, 4% air voids in the total mixture (VTM) and 75% volume in mineral aggregate (VMA). The Marshall quotient (MQ) which is the ratio of Marshall stability (kN) to flow (mm) is a key index to the mixture stiffness. MQ is also a measure of materials resistant to permanent deformation. Thus, a high MQ mixture shows a high tendency of stiffness and can resist creep deformation to a large extent.
3.2
Moisture susceptibility test
AASHTO T 283 [34] described the procedures for the determination of water susceptibility of asphalt mixture. The prepared compacted samples were grouped into two; conditioned and unconditioned. The samples to be conditioned were placed in a saturation vacuum. The pressure of approximately 6.7 kPa was applied for 10 minutes. The specimens were submerged for another 10 minutes in a water bath. To evaluate the effect of the freeze-thaw cycle, each specimen was wrapped with a leakproof plastic bag containing 10 ml of distilled water. The plastic containing the specimen was placed in a freezer at -17oC ±1oC for a minimum of 16 hours. Thereafter, the specimen was submerged in a water bath at 60oC for 24 hours, after which the specimen was placed in a water bath at 25oC for 2 hours with at least 25 mm of water above
the sample. The specimen was later tested for indirect tensile strength (ITS). Prior to the testing of the unconditioned samples, they were submerged in water at 25oC for 2 hours. Resistance to moisture sensitivity was calculated based on ITS ratio, using equation 1
TSR =
( ) ( )
(1)
Where: TSR = Tensile strength ratio ITS conditioned = The average of ITS on the conditioned sample ITS control = The average of ITS of the control sample 3.3
Resilient Modulus test The test was conducted in accordance with ASTM D 4123 – 11 using Universal Testing
Machine (UTM) for unaged and aged samples [35]. The test was conducted at 25oC and 40oC by applying repetitive compressive loads in a harversine waveform on the sample. The resilient modulus at 25oC is somewhat related to fatigue and 40oC related to rutting damage. In general, a lower resilient modulus at low temperature is considered desirable, as the binder becomes more elastic and provides better resistance to fatigue damage. On the other hand, a high temperature is desired in order to have a less viscous binder that can provide a better resistance to rutting damage. Prior to testing, the samples were conditioned for four hours at a selected test temperature. In this study, 1000N peak force was applied as harversine load. Pulse width of 0.1 sec, rest period of 0.9 Sec and assumed Poisson’s ratio of 0.4 were used. A compressive load was applied laterally along the curved plane of a cylindrical sample of asphalt mixture. Each specimen was subjected to two sets of five load pulses. The specimen was rotated after the first reading by 90o. Therefore, the load was applied perpendicular to the direction of the first set during the second set of loadings. The average of resilient modulus of each test was evaluated.
3.4
Dynamic creep test
A dynamic creep test was performed to assess the rutting tendency in asphalt mixes. The test was conducted using compacted specimens in accordance with ASTM D 3497 [36]. Prior to testing, the samples were conditioned at 40oC for four hours. The test parameters used in this study include; a preload stress of 150kPa and axial cycle loading stress of 300kPa. In order to ensure a complete contact between the sample and the load bar, a preloading time of 30 sec was used. The test was set to terminate at 3600 cycles which is sufficient to predict the behavior of asphalt mix in a repeatable axial loading stress. The test was performed by applying a repeated uniaxial load to the test samples. Linear Variable Displacement Transducers (LVDTs) were used to measure the resulting deformations. The results of the creep test were displayed in a graphical form with both strain and displacement on the vertical axis and number of cycles on the horizontal axis. The dynamic creep modulus and creep strain slope (CSS) were calculated using equations 2 and 3 respectively as stipulated in the specifications for Malaysia road works [37]:
#$$%&'( )*&)% +,-'++
! " = ,-)&. ), /011 232%'+4,-)&. ), 5611 232%'+
788 =
%9: ;< =>?@AB @ /0114 %9: ;< =>?@AB @ 5611 %9: /0114%9: 5611
4.
Results and discussion
4.1
Marshall stability and Flow test
(2)
(3)
The Marshall stability test properties of all the asphalt mixes studied in this research are presented in Table 5 as the average of three samples. It was observed that binder PG 76 gave a better result than 80-100 bitumen. The asphaltic mixes containing 4 - 6% in a step of 0.5% bitumen binder by the mass of the aggregate had optimum bitumen content for Mix1, Mix 2, Mix 3 and Mix 4 as 5.04, 5.06, 5.18 and 5.13% respectively for 80-100 binder and 5.11, 5.13, 5.21 and 5.16% respectively for PG 76. The difference in the OBC for the four mixes was not highly significant. However, it was noted in Table 5 that the mix with the highest OBC content
produced the maximum stability and the least flow. This behavior was expected because an increase in bitumen binder in the mix results in air voids reduction between the aggregate particles. This eventually enhanced the compaction of the mix and results in high Marshall stability. As shown in Table 5, in terms of Marshall stability and stiffness /Marshall quotient (MQ) PG 76 binder gave a better performance result. This may be attributed to its viscosity and more so PG 76 is modified bitumen.
Table 5: Results of Marshall Design
The optimum bitumen content of mixes containing either EAF steel slag or CMT was slightly higher than the control mix. This is likely due to the higher porosity of the EAF steel slag and CMT aggregate as compared to the granite though the bitumen content is within the limit stipulated by the Malaysian road standards [37]. In terms of performance based on the Marshall properties studied Mix 2, 3 and 4 were exceedingly better than mix 1 (control). Generally, mix 3 gave the best result followed by mix 4 and 2 respectively. Based, on the physical properties of the aggregates as shown in Table 3, EAF steel slag has a pH value of 11.42, which enhances its affinity with low acidic bitumen because the pH value of PG 76 and 80-100 used in this study was 6.62 and 6.49 respectively. The EAF steel slag and CMT possess higher angle of internal friction, angularity and higher bulk specific gravity comparable to granite. This property enhances better aggregate interlock and qualifies both CMT and EAF steel slag as suitable asphalt paving materials. Mixtures that contain either CMT or EAF steel slag or both also exhibit higher value of the Marshall quotient (stiffness). Thus, such mixes will show higher resistance to permanent deformations and shear stress.
4.2
Moisture susceptibility
The ITS and TSR results are illustrated in Figure 2. The ITS of the specimens drops after moisture conditioning. In this study, Mix 3 samples exhibit higher tensile strength compared to the other mixes. This is probably due to its low air void content. From the other research findings, it is expected that a high air void enables the mixture to have low strength and high deformation [38]. It can be observed that the mixture with 4.8% air void does not provide the same ITS as the mixture with 3.8% air void. The incorporation of EAF steel slag in the asphalt mixes increased the ITS of the mixes. This can be attributed to the improved aggregate structure of the EAF steel slag and CMT. The test results are in conformity with the findings of [39]. The freeze-thaw cycle reduces the tensile strength of the conditioned specimens. The continuity of pores in the EAF steel slag and CMT produced spaces for water absorption. Therefore, when ice forms within the pores of the mix, it may result into the formation of cracks. The presence of pores in aggregates could threaten the resistance against freeze-thaw cycles [40]. However, in this research, the reductions are considered moderate, since the TSR ≥ 80% as recommended in AASHTO T283 [34]. The TSR signal that the moisture susceptibility of asphalt mix incorporating EAF steel slag and CMT does not appear to be a threat.
Figure 2: Tensile strength and TSR for the mixes 4.3
Indirect tensile resilient modulus The average of three specimen test results for indirect tensile resilient modulus values of
the four types of hot mix asphalt mixes is presented in Figures 3 and 4. In general, the results indicate that samples blended with PG 76 bitumen binder have higher resilient modulus values than samples blended with 80–100 bitumen binder.
PG 76 bitumen binder is stiffer and has better tensile strength. Thus, its higher resilient modulus value can be attributed to its stiffness and tensile strength. Among, the four mixes, mix 1 (control) have the least value of resilient modulus at both temperatures. The shape, pH and other physical properties of both EAF steel slag and CMT as displayed in Table 4 can be attributed to higher resilient modulus of mixes 2, 3 and 4 as compared to the control sample. In terms of chemical composition of the aggregates highlighted in Table 1, the value of CaO/SiO2 was 0.076, 5.064 and 0.283 for granite, EAF steel slag and CMT respectively. The higher CaO/SiO2 values for steel slag and copper tailings resulted in higher aggregate – binder adhesion [2].
Figure 3: Resilient modulus of the mixes at 25oC
Figure 4: Resilient modulus of the mixes at 40oC
In general, the resilient modulus of the four mixes decreased when the temperature increased from 25oC to 40oC. According to Tia [41] at low temperature, bitumen becomes brittle and the asphalt mixture tends to crack at lower temperature. Stresses are pronounced in the asphalt mix at cooled surface [42-43]. As a result of the flowing asphalt binder within the asphalt mix, the induced stresses can be reduced to a large extent. The viscosity of the bitumen binder decreases as the temperature increases and this enhances the flow within the mix and reduces stress. At high temperature, bitumen binder may lose its tendency to bind the aggregates together. Thus, the recoverable strain increases with temperature and this would result in lower resilient modulus of the mixes.
Aging studies revealed that sulfoxides, carboxylic acids and ketones increased with oxidative aging. The category and number of oxidative aging products seem to be totally related to the chemistry of the bitumen [44]. This may affect the aggregate particles binding some of the already formed oxidative functional groups. The differences resulted from the oxidative aging can possibly affect the interface chemistry [45].
Therefore, oxidative aging bring forth
significant changes in the chemistry of the asphalt-aggregate interface. Indirect tensile resilient modulus test was performed on short term aging (STOA) and long term aging (LTOA) samples at two different temperatures of 25oC and 40oC. The aging process increases the resilient modulus for both PG 76 and pen 80 – 100 prepared mix. Though, the trend was higher with PG 76 samples as shown in Figures 3 and 4. The increasing resilient modulus of the aging samples may be attributed to binder hardening causing mix to stiffen. It was suggested by Bell and Sosnuvskc [46] that aging was influenced by the aggregates. This agrees with the findings of this research. At 25oC, the resilient modulus of mixes 1, 2, 3 and 4 increased by 53.7, 148, 97.9 and
99.1% after STOA and 85.6, 153.7, 121 and 184.8%
respectively after LTOA. The resilient modulus at 40oC of PG 76 prepared mix 1, 2, 3 and 4 increases by 51.5, 114.5, 21.4 and 58.3%, respectively, after STOA and 55.6, 259.5, 75.8 and 92.8% respectively after LTOA. Thus, this trend shows that the resilient modulus increases with aging higher at 25oC than 40oC. This trend was supported by [46] in their findings that the greater the adhesion, the more the extenuation of aging, thereby confirming that aged EAF and CMT mixes exhibit superior adhesion property compared to aged granite mixes. The results are similar to that of Mohamed [47] which aged HMA modified with crumb rubber produced better resilient modulus than the unaged samples at 0% crumb rubber content.
4.4
Dynamic creep According to He [48] the dynamic creep curve consists of two parts; the curve segment,
which represents the creep strain slope (CSS) at densification of the mix during the test and the stable development of axial strain in the two third line segment of the curve. The initial permanent deformation is not influenced by the load cycle but due to the other two third parts of the linear dynamic creep curve [49]. For these reasons, dynamic creep modulus which is a function of strain and the applied axial stress; and CSS were used to evaluate the mix resistant to
permanent deformation calculated between 1200 and 3600 cycles. Some researchers obtained CSS and creep modulus between 1200 and 3600 cycles [50]. Also, Pasandin and Perez [26] obtained slope of the creep curve between 600 and 1800 cycles and termination occurs at 1800 cycles. The dynamic creep modulus was calculated by dividing the applied axial stress with the differences of strain at 1200 and 3600 cycles. The results of the dynamic creep test are shown in Figure 5. Each value is the average of the three tested specimens. It illustrates that the mixes blended with PG 76 binder are shown to be more superior to those blended with 80-100 binder. Besides that, the dynamic creep modulus increases with aging. For samples blended with PG 76,
Figure 5: Dynamic creep modulus results of the mixture The mix 1, 2, 3 and 4 increased by 111.1, 115.3, 524.5 and 421.9%, respectively, after STOA and 166.7, 168.5, 794 and 668.6% respectively after LTOA. Though, the samples blended with 80-100 binder also experienced increases in dynamic creep modulus with aging, the magnitudes were not as high as that of PG 76. For instance, the mix 1, 2, 3 and 4 increased by 22.9, 9.4, 20 and 25.6% respectively, after STOA and the samples were increased after LTOA by 31.4, 56.3, 72 and 69.8% respectively. The mix susceptibility to permanent deformation with respect to CSS is presented in Figure 6. It can be observed that the CSS reduces with aging. Mixes containing EAF steel slag and CMT show lower CSS than the conventional mixture. The CSS reduces by 24.8, 25.0, 32.1 and 23.9% in Mixes 1, 2, 3 and 4 respectively, after LTOA for 80-100 specimens and 24.3, 31.3, 97.6 and 48.2% in Mixes 1,2,3, and 4 respectively after LTOA for PG 76 specimens. The CSS can be used to evaluate the strain rate of deformation that takes place at the primary stage after the densification. Therefore, the higher the strain rate, the higher the CSS and the lower the resistance to permanent deformation. The mix 1 (control mix) displayed higher CSS than those obtained from the mixture that contain EAF steel slag and CMT. The mix 1 that was blended with 80-100 bitumen shows the highest CSS and thus the least resistant to permanent deformation among the four mixes.
Figure 6: Creep strain slope for the mixes
This trend can be attributed to the good engineering properties of EAF steel slag and CMT. EAF steel slag is more angular in shape and also possesses higher resistance to friction and abrasion. The CSS results also indicated that binder type and content influence the resistance to permanent deformation, this conform with the findings of [48]
5.
Conclusions The study evaluated of asphalt mix incorporating EAF steel slag and copper mine tailings.
Marshall stability, moisture susceptibility, indirect tensile resilient modulus and dynamic creep tests were conducted for the samples. The findings are summarized as follows: •
Based on aggregate properties, all the testing properties satisfied the standard specification for Malaysia road works [37] except water absorption. According to the Malaysian road specification, the water absorption should not exceed 2%, but the water absorption value for EAF steel slag and CMT was 3.896 and 4.17% respectively. This is because both EAF steel slag and CMT have more pores on their surface area which enable the water to penetrate easily through them. From the moisture susceptibility test results, though, specimens incorporating EAF steel slag and CMT exhibit low TSR, it was apparently clear that the moisture susceptibility of ACW incorporating EAF steel slag and CMT does not appear to be a problem.
•
The use of EAF steel slag and copper mine tailings as aggregate in asphalt mixtures, improves the Marshall stability, Marshall quotient and flow properties. The porosity of EAF steel slag and CMT accounted for the higher OBC value in the Mix 2, 3 and 4. Hence, such mixes will be costly in terms of bitumen consume, though the cost can be saved in terms of the aggregate cost because both EAF steel slag and CMT are byproducts and can easily be obtained at very low price compared to granite.
•
The use of EAF steel slag and copper mine tailings significantly increased the resilient modulus at both temperatures. The excellent attributes of the aggregates accounted for these results. As temperature increases, the difference in resilient modulus is more significant with a decrease in stiffness at 40oC. The samples blended with PG 76 exhibited higher stiffness, thus they are less susceptible to rutting than 80-100 samples.
•
Mix 3 which contained 80% EAF steel slag and 20% copper mine tailings displayed enough resistance to permanent deformation, whether the mix is unaged or aged. The aging process greatly influenced the dynamic creep modulus of the samples and also had a notable effect with CSS.
Finally, based on experimental findings, we remark that EAF steel slag and CMT can improve the performance of asphalt mixtures for road construction. Besides that, utilization of EAF steel slag and CMT will reduce the amount of conventional aggregate used in highway construction and at the same time benefit the environments. Acknowledgements The authors gratefully acknowledge the Universiti Teknologi Malaysia (UTM) for providing financial support for conducting this research through the university research grant vote 07J33. In addition, we are grateful to both Malaysia Marine and Heavy Engineering (MMHE) and Antara Steel in Malaysia and Shell Singapore for providing copper tailings, EAF steel slag and bitumen respectively.
References [1]
Meor OH. and Teoh CY. Effects of temperature on resilient modulus of dense asphalt mixtures incorporating steel slag subjected to short term oven ageing, World Acad. Sci. Eng. Technol., 2007;22: 191–95.
[2]
Ameri M, Hesami S and Goli H. Laboratory evaluation of warm mix asphalt mixtures containing electric arc furnace (EAF) steel slag, Conserv. Recycl., 2013;49: 611–17.
[3]
Andreas L, Diener S and Lagerkvist A. Steel slags in a landfill top cover--experiences from a full-scale experiment., Waste Manag., 2014; 34: 692–701.
[4]
Qasrawi H. The use of steel slag aggregate to enhance the mechanical properties of recycled aggregate concrete and retain the environment, Constr. Build. Mater., 2014; 54: 298–304.
[5]
Sorlini S, Sanzeni A and Rondi L. Reuse of steel slag in bituminous paving mixtures, J. Hazard. Mater., 2012; 209: 84–91.
[6]
Yildirim IZ and Prezzi M. Use of steel slag in subgrade applications, 2009.
[7]
Yi H, Xu G, Cheng H, Wang J, Wan Y and Chen H. An Overview of Utilization of Steel Slag, Procedia Environ. Sci., 2012; 16:791–801.
[8]
Pasetto M and Baldo N. Mix design and performance analysis of asphalt concretes with electric arc furnace slag, Constr. Build. Mater., 2011; 25: 3458–3468.
[9]
Pasetto M and Baldo N. Experimental evaluation of high performance base course and road base asphalt concrete with electric arc furnace steel slags, J. Hazard. Mater.,2010; 181: 938–48.
[10] Liapis I and Likoydis S. Use of Electric Arc Furnace Slag in Thin Skid–Resistant Surfacing, Procedia - Soc. Behav. Sci., 2012; 48: 907–918. [11] Motz H and Geiseler J. Products of steel slags an opportunity to save natural resources, Waste Manag., 2001; 21:285–293. [12] JEGEL. Steel slag aggregates use in hot mix asphalt concrete. Final report prepared for the steelmaking slag Technical Committee, Toronto, Ont. John Emery Geotechnical Engineering Limited (JEGEL), 1993. [13] Manso, J. M., Ortega-López, V., Polanco, J. A., and Setién, J. The use of ladle furnace slag in soil stabilization. Construction and Building Materials, 2013; 40, 126-134. [14]
Xie, J., Chen, J., Wu, S., Lin, J., and Wei, W. Performance characteristics of asphalt mixture with basic oxygen furnace slag. Construction and Building Materials, 2013; 38, 796-803.
[15]
Ahmedzade, P., and Sengoz, B. Evaluation of steel slag coarse aggregate in hot mix asphalt concrete. Journal of hazardous materials, 2009; 165(1), 300-305.
[16]
Norton, J. Use of steel furnace slag in bituminous mixtures. Research Report No. 78 TB23. Michigan Department of Transportation, Lansing, Mich.
[17]
ASTM D 5106. Standard specifications for steel slag aggregates for bituminous paving mixtures. Philadelphia U.S: 2003
[18]
Sultan, H. A. Stabilized copper mill tailings for highway construction. Transportation research record, (734), 1979
[19] Onuaguluchi, O., and Eren, O. Copper tailings as a potential additive in concrete: consistency, strength and toxic metal immobilization properties.Indian Journal of Engineering & Materials Sciences, 2012; 19(2), 79-86. [20] Roberts FL, Kandhal PS, Brown ER, Kim YR, Lee Dad-Yinn and Kennedy T. Hot mix asphalt materials, mixture, design, and construction, Third Edition. Lanham, Maryland: NAPA Research and Education Foundation, 2009. [21] Idham MK, Hainin MR, Yaacob Haryati, M Naqiuddin M Warid and Abdullah ME. Effect of Aging on Resilient Modulus of Hot Mix Asphalt Mixtures, Adv. Mater. Res.,2013;723: 291–97. [22] Bell C, AbWahab Y and Cristi ME. Selection of Laboratory aging procedures for asphaltaggregate mixtures, Strateg. Highw. Res. Program. Natl. Res. Counc., 1994. [23] Singh D, Zaman M and Commuri S. Effect of long term oven aging on dynamic modulus of hot mix asphalt, Geo-Frontiers @ ASCE, 2011; 4773–81. [24] Mills-Beale, J., and You, Z. The mechanical properties of asphalt mixtures with recycled concrete aggregates. Construction and Building Materials, 2010; 24(3), 230-235. [25] Pérez, I., Gallego, J., Toledano, M., and Taibo, J. Asphalt mixtures with construction and demolition debris. Proceedings of the ICE-Transport, 2010; 163 (4), 165-174. [26] Pasandín, A. R., and Pérez, I. Effect of ageing time on properties of hot-mix asphalt containing recycled concrete aggregates. Construction and Building Materials, 2014; 52, 284-293. [27] Collins, R. J., and Ciesielski, S. K. Recycling and use of waste materials and by-products in highway construction 1994; (No. 199). [28] Md. Maniruzzaman BAA, Muniandy R, Abdullah K and Mahmud A. Preliminary determination of asphalt properties using microwave techniques, APRN J. Eng. Appl. Sci., 2010;5. [29]
AASHTO R 30. Standard practice for mixture conditioning of hot mix asphalt:2002
[30]
Airey, G. D. State of the art report on ageing test methods for bituminous pavement materials. International Journal of Pavement Engineering, 2003; 4(3), 165-176.
[31]
Brown, S. F., and Scholz, T. V. (2000). Development of laboratory protocols for the ageing of asphalt mixtures. In Proc. 2nd Eurasphalt and Eurobitume Congress, Session, 2000; 1, 83-90).
[32] ASTM D 5581. Standard test method for resistance to plastic flow of bituminous mixtures using Marshall apparatus. Philadelphia U.S: 2013.
[33] ASTM C 127. Standard test method for density of semi bituminous materials (pyconometer method). Philadelphia U.S: 2012. [34]
AASHTO T 283-02. Standard method of test for resistance of compacted asphalt mixtures to moisture-induced damage: 2007
[35]
ASTM D 4123. Standard Test Method for Determining the Resilient Modulus of Bituminous Mixtures by Indirect Tension Test, Philadephia U.S.: ASTM International: 2011
[36] ASTM D 3497. Standard test method for dynamic modulus of bituminous mixtures. Philadelphia U.S: 2011 [37] Jabatan Kerja Raya Malaysia. Standard specification for Road Works, section 4: Flexible Pavement, 2008; S4-58 - S4-59. [38] Teoh, C.Y. Performance evaluation of steel slag as natural aggregates replacement in asphaltic concrete, Unpublished M.Sc Thesis, University Sains Malaysia, 2008 [39] Asi, I. M., Qasrawi, H. Y., and Shalabi, F. I. Use of steel slag aggregate in asphalt concrete mixes. Canadian Journal of Civil Engineering,2007; 34(8), 902-911. [40]
InDOT Aggregate Properties, Certified Technician Program Training Manual for Hot Mix Asphalt (Construction), Indiana State Department of Transportation, USA, 2004; 31to 3-9.
[41] Tia M. Bituminous materials and mixtures Civil Engineering Handbook. Boca Raton, Florida: CRC press Inc., 2003: 451–36. [42]
Hainin, M.R, Yusoff, N. I. M, Mohd Satar, M. K.L and Brown, E. R. The effect of lift thickness on permeability and the time available for compaction of hot mix asphalt pavement under tropical climate condition, Constr. Build. Mater., 2013; 48: 315–324.
[43]
Ahmad, J, Yusoff, N. I. M, Hainin, M. R, Rahman, M. Y. A, and Hossain, M. Investigation into hot-mix asphalt moisture-induced damage under tropical climatic conditions, Constr. Build. Mater., 2014; 50:567–576.
[44] Kuang, D., Yu, J., Feng, Z., Li, R., Chen, H., Guan, Y., and Zhang, Z. Performance evaluation and preventive measures for aging of different bitumens. Construction and Building Materials, 2014; 66, 209-213. [45] SHRP A - 341 Fundamental properties of Asphalt - Aggregate Interactions, including adhesion and absorption, SHRP, National Research Council, 1993. [46] Bell, C. A., and Sosnovske, D. Aging: binder validation (No. SHRP-A-384). Washington, DC: Strategic Highway Research Program, National Research Council.1994
[47] Mohamed, A.A A study on the physical and mechanical properties of asphaltic concrete incorporating crumb rubber produced through dry process, Unpublished PhD Thesis, Universiti Sains Malaysia.2007 [48] He, G.P. Study the use of reclaimed asphalt pavement (RAP) with foamed bitumen in Hong Kong, PhD Thesis, The Hong Kong Polytechnic University, 2006 [49] Ahmad, J. A study on moisture induced damage and rutting of hot mix asphalt, Unpublished PhD Thesis, Universiti Teknologi Mara, 2010.
Table 1: Chemical composition of different type of aggregates Aggregate type
Oxide content (%)
CaO
SiO2
Fe2O3
Al2O3
ZnO
MgO
MnO
K2O
Na2O
SO3
Cr203
Granite
4.90
64.60
3.80
16.80
-
0.74
-
4.40
3.48
-
-
Steel slag
55.2
10.90
16.80
4.00
3.72
3.06
2.59
0.16
0.75
0.85
0.69
Copper tailings
12.48
44.10
19.00
15.40
0.96
0.87
0.87
1.24
0.46
2.46
-
Table 2: Properties of bitumen binder Parameter Penetration @ 25oC, 1/10mm, 100g Softening point (0C) Viscosity @ 135oC (cP) Viscosity @ 60oC (cP) Specific gravity Mixing temperature Compacting temperature
PG 76 48 61 1800 36200 1.031 170 – 185oC 140 – 160oC
80-100 85 46 400 23200 1.0 130 – 150oC 120 – 140oC
Standards ASTM D5 ASTM D36 ASTM D44
ASTM D70
Table 3: Aggregate type and particle size distribution of the mixes Fraction
Mix 1
Mix 2
Mix 3
(mm)
Granite
Granite
(%)
(%)
14
6
6
-
6
10
14
14
-
5
26
26
3.35
9.5
1.18
EAF
Copper
(%)
Slag (%)
Tailing (%)
-
3
3
-
14
-
7
7
-
-
26
-
13
13
-
9.5
-
9.5
-
4.75
4.75
-
21.5
11.4
10.1
11.4
10.1
5.7
5.7
10.1
0.425
8.5
4.5
4
4.5
4
2.25
2.25
4
0.150
8.5
4.5
4
4.5
4
2.25
2.25
4
0.075
4
2.1
1.9
2.1
1.9
1.05
1.05
1.9
Filler
2
(cement)
Copper Tailing (%)
2
EAF
Mix 4
Slag (%)
Copper Tailing (%)
2
Granite
2
Table 4: Physical properties of the aggregates Testing
Standard
Granite
EAF Steel
Copper
slag
Tailings
Specification
ASTM C 131
10.276
5.100
-
≤ 25%
Flakiness
MS 30
7%
5%
-
≤ 25%
Soundness
AASHTO T 104
3.5%
0.71%
-
≤ 18%
Polished Stone Value
BS 812
52.3%
55.3%
-
≥ 40%
Water Absorption
MS 30
0.756%
3.896%
4.17%
≤ 2%
AASHTO T 182
> 95%
> 95%
-
≥ 95%
Coarse Aggregate
ASTM C127
2.594
2.816
-
-
Fine Aggregate
ASTM C 128
2.585
3.051
3.578
-
BS 1377
10.22
11.42
6.42
-
Loss Angeles Abrasion
Stripping Specific Gravity:
pH
Table 5: Results of Marshall test Property
Mix 1
Mix 2
Mix 3
Mix 4
80-100
PG 76
80-100
PG 76
80-100
PG 76
80- 100
PG 76
O.B.C (%)
5.04
5.11
5.06
5.13
5.18
5.21
5.13
5.16
Air void (%)
4.5
4.8
4.7
4.3
3.8
4.0
4.3
4.4
Bulk specific gravity
2.325
2.276
2.396
2.363
2.577 2.575
2.483
2.364
Marshall stability (kN) 13.70
14.88
15.15
16.97
15.75 21.42
14.10
19.05
Flow (mm)
3.07
2.97
2.17
2.21
2.16
2.30
2.78
MQ (kN/mm)
4.463
5.009
6.982
7.680
7.292 9.872
6.130
6.854
VMA
15.6
17.4
15.4
16.8
18.5
16.8
15.7
2.17
17.9