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Experimental investigation on related properties of asphalt mastic containing recycled red brick powder
Construction and Building Materials 25 (2011) 2883–2887
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Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Experimental investigation on related properties of asphalt mastic containing recycled red brick powder Shaopeng Wu, Jiqing Zhu ⇑, Jinjun Zhong, Dongming Wang Key Laboratory for Silicate Materials Science and Engineering of Ministry of Education, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070, China
a r t i c l e
i n f o
Article history: Received 15 July 2010 Received in revised form 10 November 2010 Accepted 24 December 2010 Available online 12 January 2011 Keywords: Asphalt mastic Red brick powder Filler Rheological properties Dynamic Shear Rheometer
a b s t r a c t Some properties of asphalt mastic containing recycled red brick powder (RBP) were investigated in this paper. RBP was used as filler in asphalt mastic. The investigated mastic consisted of asphalt and filler at a mass ratio of 1:1. Penetration, softening point and high-temperature viscosity were tested. Dynamic Shear Rheometer (DSR) was used to conduct frequency sweep test of asphalt mastic. The introduction of RBP resulted in reduced penetration, increased softening point, apparent activation energy, complex shear modulus in the low frequency area and high-temperature viscosity. It indicates that RBP may have some positive effect on high-temperature properties but some negative effect on low-temperature properties of asphalt mastic. It is also believed that the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing limestone mineral filler (LMF). Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction Natural limestone is processed into mineral filler used in asphalt mixture traditionally. But natural limestone resource is being exhausted with the development of cement and construction industry, especially in China [1]. The use of waste powder as filler in asphalt mixture has been the focus of several research efforts over the past few years. Recycled waste lime [2], phosphate waste filler [3], baghouse fines [4], Jordanian oil shale fly ash [5], municipal solid waste incineration ash [6] and waste ceramic materials [7] have been investigated as filler. It was proved that these types of recycled filler could be used in asphalt mixture and gave improved performance. Meanwhile, Chinese brick-making history is over 2000 years and an incalculable number of red bricks have been used in construction and building in China since 1900. Statistics show that 1.43 109 m3 of clay were used and 6 107 tons of standard coal was consumed to produce 6 1011 red bricks in China every year in 1990s [8]. The building demolition has consequently brought a large number of waste red bricks in recent years. China government has limited and gradually prohibited the use of red bricks in residential construction since 1999 for an aim of sustainable development [9]. Recycled red brick powder (RBP), which is obtained from waste red bricks, has been used as filler in asphalt mixture [10]. With the use of RBP, waste red bricks will be recycled
⇑ Corresponding author. Tel./fax: +86 27 87162595. E-mail address: [email protected] (J. Zhu). 0950-0618/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2010.12.040
and utilized efficiently to reduce the pollution of solid waste and conserve mineral and land resources. The main focus of the present investigation was directed towards the properties of asphalt mastic containing RBP. The objective of the research presented in this paper is to evaluate related properties of asphalt mastic containing RBP in terms of: 1. Effect of RBP on high-temperature properties of asphalt mastic. 2. Effect of RBP on low-temperature properties of asphalt mastic. 3. Consequent mixing and compacting temperatures of asphalt mixture. 2. Materials and method 2.1. Materials A base asphalt (AH-70) provided by SK Energy Co. Ltd. of South Korea was used to prepare asphalt mastic, with a penetration of 73 (0.1 mm at 25 °C, 100 g and 5 s), ductility of more than 150 cm (at 15 °C and 5 cm/min) and softening point of 48 °C (ring and ball) according to JTJ 052-2000 [11] of China. Limestone mineral filler (LMF), as control sample, was obtained from Macheng, a town in Hubei Province of Central China. Waste red bricks from demolished buildings were firstly crushed to size of about 50 mm by a hammer and then grinded for 15 min (determined by experiments aiming at the same percentage passing as LMF) by a SMU500 500 mm ball-grinder (made by Shanghai Xinjian Machinery Plant) to obtain RBP. After preparation, LMF and RBP were tested according to JTG E42-2005 [12] of China. Wavelength Dispersive X-ray Fluorescence (XRF) Spectrometer (Axios advanced, made by PANalytical Co. Ltd. of the Netherlands) and JSM-5610LV Scanning Electron Microscope (SEM, made by JEOL Co. Ltd. of Japan) were respectively used to investigate the chemical composition and surface topography of LFM and RBP. Test results are respectively shown in Tables 1 and 2 and Fig. 1.
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Table 1 Filler properties.
Table 3 Shear strain of frequency sweep test.
Test
LMF
RBP
Specification
Percentage passing (%) 0.6 mm 0.3 mm 0.15 mm 0.075 mm Apparent specific gravity Hydrophilic factor
100 98.2 97.2 89.7 2.786 0.66
100 99.7 97.7 87.4 2.715 0.46
100 – 90–100 75–100 P2.50 <1
Table 2 Chemical composition of fillers. Chemical composition
LMF (%)
RBP (%)
SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O TiO2 SO3 P2O5 MnO ZrO2 SrO ZnO BaO Cl Loss
17.950 0.460 0.520 46.90 3.640 0.095 0.087 0.036 0.019 0.037 0.140 Negative 0.021 0.110 Negative Negative 29.730
68.100 16.350 6.040 2.050 1.430 2.380 1.200 0.850 0.110 0.260 0.060 0.053 0.020 0.027 0.072 Negative 0.800
Total
99.745
99.802
Temperature (°C)
10
0
10
20
30
40
50
60
Strain (%)
0.05
0.1
0.2
0.4
0.4
0.5
1
2
2.2. Method In practical engineering projects, the 0.075 mm sieve passing percentage of mineral aggregates gradations is usually around 4.5%. Meanwhile, the optimum asphalt content in practical engineering projects is around 4.5% by the mass of mineral aggregates as well. So the powder–binder ratio of asphalt mastic was fixed on 1.0. Oven-dried LMF and RBP were respectively passed through 0.075 mm sieve. Powders passing the 0.075 mm sieve were got to prepared asphalt mastic samples. At a mass ratio of 1:1, sieved LMF and RBP were respectively mixed with AH-70 base asphalt and then stirred for 10 min at 130–140 °C. Penetration, softening point and high-temperature viscosity are some conventional performance indicators of asphalt evaluated, while some recent researches [13,14] have applied these indicators to evaluating asphalt mastic. Both these indicators and rheological indicators were used to investigate related properties of asphalt mastic in this paper. Penetration (0.1 mm at 100 g and 5 s) at 15 °C, 25 °C and 30 °C, softening point (ring and ball), and viscosity (by DV-II + Pro Brookfield Viscometer, made by Brookfield Engineering Laboratories Inc. of USA) at 135 °C, 155 °C and 175 °C were tested in accordance with JTJ 052-2000. A Dynamic Shear Rheometer (DSR, Physica MCR 101, made by Anton Paar Co. Ltd. of Austria) was used to conduct frequency sweep test at 10 °C, 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C and 60 °C. Strain sweep test was firstly carried out to fix the value of shear strain. The fixed shear strain is shown in Table 3. Under the strain-controlled mode, complex shear modulus (G⁄) and phase angle (d) of asphalt mastic samples were obtained within the frequency range of 0.1–400 rad/s (0.016–63.662 Hz) at each temperature. Samples of 8 mm diameter and 2 mm high were used at 10 °C, 0 °C, 10 °C and 20 °C; samples of 25 mm diameter and 1 mm high were used at 30 °C, 40 °C, 50 °C and 60 °C.
3. Results and discussion It can be seen in Table 1 that all properties of prepared RBP satisfy the requirements of specification. The apparent specific gravity and hydrophilic factor of RBP are both lower than LMF. The former indicates that RBP is more porous or has more folds; and the latter shows that RBP bonds with asphalt better. We can know from Table 2 that SiO2 and Al2O3 are the major component of RBP; and SiO2 and CaCO3 (CaO and Loss result from CaCO3) compose the main percentage of LMF. SEM photographs (Fig. 1) show that the surface of RBP has more folds and the particle distribution of RBP is more homogenous than LMF. All previous results indicate that RBP has higher absorption than LMF.
3.1. Penetration Penetration of asphalt mastic was analyzed by Eqs. (1)–(5). Eq. (1) was used to depict the linear relationship between the common logarithm of penetration (lgPen) and temperature (T). Regression lines and equations were obtained by Microsoft Excel. Based on linear regression equations, Eqs. (2)–(5) were respectively used to
Fig. 1. SEM photographs of fillers ((a) LMF 5000, (b) RBP 5000, (c) LMF 1000 and (d) RBP 1000).
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calculate the penetration index (PIlgPen), equivalent softening point (T800, temperature when penetration is 800 by linear regression equation), equivalent brittle point (T1.2, temperature when penetration is 1.2 by linear regression equation) and flexible temperature range (DT, temperature range between T800 and T1.2) of asphalt mastic.
lgPen ¼ K þ AlgPen T PIlgPen ¼
Table 5 Values of PIlgPen, T800, T1.2 and DT. Samples
PIlgPen
T800 (°C)
T1.2 (°C)
DT (°C)
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
0.29 0.53 0.43
52.4 59.6 61.1
21.3 16.7 14.2
73.7 76.3 75.3
ð1Þ
20 500AlgPen 1 þ 50AlgPen
ð2Þ
T 800 ¼
lg 800 K AlgPen
ð3Þ
T 1:2 ¼
lg 1:2 K AlgPen
ð4Þ
DT ¼ T 800 T 1:2
ð5Þ
where Pen is the penetration of asphalt and asphalt mastic (0.1 mm); T is the test temperature (°C); K and AlgPen are the coefficients of linear regression equations; PIlgPen is penetration index; T800 is equivalent softening point (°C); T1.2 is equivalent brittle point (°C); and DT is the flexible temperature range (°C). Regression lines of penetration are shown in Fig. 2, which illustrates the effect of RBP on penetration of asphalt mastic. It is indicated that RBP decreases the penetration of asphalt mastic. Penetration of asphalt materials increases with temperature. A marked decrease in penetration was obtained by the addition of filler, and the addition of RBP resulted in more significantly decreased penetration than LMF. Linear regression equations of penetration are shown in Table 4. Based on the values of K and AlgPen given in Table 4, the values of PIlgPen, T800, T1.2 and DT for each sample were obtained and shown in Table 5. A significant increase in PIlgPen, T800, T1.2 and DT was observed by the addition of filler. PIlgPen is an evaluating indicator of temperature susceptibility of asphalt materials and must be within the range of 1.5 +1.0 according to JTG F40-2004 [15] of China. PIlgPen of RBP asphalt mastic is lower than LMF, meaning that RBP asphalt mastic is more susceptible to temperature than LMF. T800 and T1.2 are respectively the equivalent temperature of softening and
cracking of asphalt material. Greater T800 value means better high-temperature properties, and lower T1.2 value means better low-temperature properties. As can be observed, T800 and T1.2 of RBP asphalt mastic are higher than LMF, meaning that RBP asphalt mastic softens and cracks at relatively high temperature. As a result, RBP asphalt mastic has the advantage of high-temperature properties and the disadvantage of low-temperature properties. Combining T800 and T1.2, DT was obtained to measure the flexible temperature range of asphalt mastic. RBP is less efficient at increasing DT, meaning that RBP asphalt mastic keeps flexible in a relatively small temperature range. 3.2. Softening point Equivalent softening point (T800) was discussed previously, and softening point is discussed here. Results of softening point test are shown in Fig. 3. As can be observed, a marked increase in softening point was obtained by the addition of filler, and the addition of RBP resulted in more significantly increased softening point than LMF. It is in agreement with the conclusion resulted from the calculation results of T800. When temperature rises, RBP asphalt mastic softens at relatively high temperature and keeps relatively good performance. It indicates that RBP asphalt mastic has a greater capacity to resist to the high temperature deformation. Grabowski and Wilanowicz [16] investigated the relationship between the structure of filler and the stiffening properties of asphalt mastic and believed the softening point of asphalt mastic has some relationship with Rigden void (RV), average grain diameter (Uav) and specific surface area (Ssp) of filler. From this point of view, the significantly increased softening point of RBP asphalt mastic may be explained by the difference in RBP structure, such as RV, Uav and Ssp. However, further study about the structure of RBP should be carried out to support this point of view. 3.3. Frequency sweep test Traffic loading is a dynamic loading and is over a wide range of frequency and temperature conditions. Over such wide frequency and temperature ranges, the rheological properties of the asphalt materials cannot be tested at laboratory scale. Fortunately, the time–temperature superposition principle can be applied to com-
Fig. 2. Regression lines of penetration.
Table 4 Linear regression equations of penetration. Samples
Linear regression equations
Correlation coefficients
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
lgPen = 0.8966 + 0.0383 T lgPen = 0.6984 + 0.0370 T lgPen = 0.6100 + 0.0375 T
0.999 0.998 0.999
Fig. 3. Softening point test results.
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tion of RBP. So RBP asphalt mastic may be relatively easy to crack at low temperature.
Table 6 Empirical values of apparent activation energy. Samples
AH-70 base asphalt
LMF asphalt mastic
RBP asphalt mastic
Apparent activation energy (kJ/mol)
182
186
191
3.4. High-temperature viscosity
pose a smooth curve of the material rheological properties over a wide spectrum of loading frequencies. Master curves represent the material rheological behavior versus loading frequency (or loading time) [17]. Master curves are used to investigate the rheological properties of asphalt mastic as well [18]. In order to get master curves of asphalt mastic, shift factors (aT) was firstly calculated by an Arrhenius-like equation. Eq. (6) describes the dependence on temperature of the calculated shift factors fairly well. Empirical values of apparent activation energy were used to calculate the shift factors. A reference temperature of 10 °C was selected for all samples studied.
lgaT ¼
DEa 1 1 2:303R T T 0
ð6Þ
where T is the test temperature; T0 is the reference temperature, 283 K; DEa is apparent activation energy (J/mol) and R is universal gas constant, R = 8.314 J/(K mol). In order to represent the results well, optimal value of apparent activation energy for each sample was fixed empirically. Table 6 shows the Empirical values of apparent activation energy. Christensen and Anderson [19] calculated the activation energy of asphalt mastic and obtained the value of 250 kJ/mol in 1992. It can be seen in Table 6 that an increase in apparent activation energy was obtained by the addition of filler, and the addition of RBP resulted in more significantly increased apparent activation energy than LMF, which results from the difference in filler structure, and causes the decreased penetration and increased softening point. Shift factor was calculated by Eq. (6); and master curves of complex shear modulus (G⁄) and phase angle (d) were obtained accordingly. G⁄ and d versus loading frequency of asphalt and asphalt mastic are depicted in Fig. 4. It clearly demonstrates that G⁄ increases with frequency. A marked increase in G⁄ was obtained by the addition of filler. The addition of RBP resulted in more significantly increased G⁄ than LMF in Area 1 (low frequency or high temperature area), meaning that RBP asphalt mastic has better hightemperature performance than LMF. It is also shown in Fig. 4 that the addition of RBP resulted in decreased d in Area 2 (high frequency or low temperature area). This phenomenon denotes that viscous portion of G⁄ decreases at low temperature with the addi-
Conventionally, there is a close relationship between the viscosity of asphalt and the mixing and compacting temperatures of asphalt mixture. But Zeng and Wu [20] believes that the viscosity of the asphalt mastic, rather than that of the asphalt, should provide pertinent information on the mixing and compacting temperatures of asphalt mixture. The effect of RBP on high-temperature viscosity of asphalt mastic and the consequent mixing and compacting temperatures of asphalt mixture is discussed here. High-temperature viscosity test was carried out by a Brookfield Viscometer at 135 °C, 155 °C, and 175 °C. There is a linear relationship between the common logarithm of the viscosity values (lgg) and temperature (T). Regression lines and equations were obtained by Microsoft Excel. According to JTJ 052-2000, the mixing and compacting temperatures of asphalt mixture depend on the asphalt viscosity and the asphalt viscosity ranges for mixing and compacting are respectively 0.19–0.15 Pa s and 0.31–0.25 Pa s. Based on the asphalt viscosity ranges, viscosity range of LMF asphalt mastic for mixing and compacting was calculated by linear regression equations. When RBP replaces LMF to be used as filler, the same viscosity range of asphalt mastic must be achieved. So the mixing and compacting temperatures of asphalt mixture containing RBP as filler were calculated by linear regression equations. Regression lines of high-temperature viscosity are shown in Fig. 5, which illustrates the effect of RBP on high-temperature viscosity of asphalt mastic. It is indicated that RBP increases the high-temperature viscosity of asphalt mastic. Viscosity of asphalt materials decreases with temperature. A marked increase in viscosity was obtained by the addition of filler, and the addition of RBP resulted in more significantly increased viscosity than LMF. Linear regression equations of high-temperature viscosity are shown in Table 7. From a slope point of view, a marked increase in the rate of change in viscosity was obtained by the addition of filler, and the addition of RBP resulted in less significantly increased rate of change in viscosity than LMF. Based on the linear regression equations given in Table 7, values of temperature and viscosity for mixing and compacting were ob-
Fig. 5. Regression lines of high-temperature viscosity.
Table 7 Linear regression equations of high-temperature viscosity.
Fig. 4. Master curves of frequency sweep tests.
Samples
Linear regression equations
Correlation coefficients
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
lgg = 2.0489–0.0174 T lgg = 2.9209–0.0197 T lgg = 2.9588–0.0191 T
0.998 0.999 0.999
S. Wu et al. / Construction and Building Materials 25 (2011) 2883–2887 Table 8 Values of temperature and viscosity for mixing and compacting. Samples
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
Mixing process
Compacting process
Temperature (°C)
Viscosity (Pa s)
Temperature (°C)
Viscosity (Pa s)
159–165 159–165 160–162
0.19–0.15 0.81–0.72 0.81–0.72
147–152 147–152 155–157
0.31–0.25 0.98–0.93 0.98–0.93
tained and shown in Table 8. The viscosity ranges of asphalt mastic for mixing and compacting are respectively 0.81–0.72 Pa s and 0.98–0.93 Pa s. The average mixing temperature of asphalt mixture containing RBP is equivalent to that containing LMF. But the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing LMF. 4. Conclusions On the basis of the discussion above, the following conclusions can be drawn: (1) RBP results in increased equivalent softening point (T800), softening point and complex shear modulus (G⁄) in the low frequency (or high temperature) area of asphalt mastic. It indicates that RBP may have some positive effect on hightemperature properties of asphalt mastic because of its increased apparent activation energy. (2) RBP results in increased equivalent brittle point (T1.2) and decreased phase angle (d) in the high frequency (or low temperature) area of asphalt mastic. It indicates that RBP may have some negative effect on low-temperature properties of asphalt mastic. So when RBP are used in extremely cold areas, the low-temperature performance of asphalt pavement needs to be paid attention to. (3) RBP results in increased high-temperature viscosity of asphalt mastic. It is concluded that the average mixing temperature of asphalt mixture containing RBP is equivalent to that containing LMF; but the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing LMF.
Acknowledgements This work presented in this paper was supported by Project of Transportation Construction Technology in Western Area of China
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(2009318811045) from Ministry of Transport of China and International Science and Technology Cooperation Program of China (2010DFA82490) from the Ministry of Science and Technology of China. Authors appreciate the financial support. References [1] Liu FR, Yang FC. Status and demand forecast of limestone resources for cement industry in China. China Non-metallic Min Indust Herald 2004;2:44–8 [in Chinese]. [2] Sung Do Hwang, Hee Mun Park, Suk keun Rhee. A study on engineering characteristics of asphalt concrete using filler with recycled waste lime. Waste Manage 2008;28:191–9. [3] Katamine NM. Phosphate waste in mixtures to improve their deformation. J Transport Eng 2000;126:382–9. [4] Lin Deng-Fong, Lin Jyh-Dong, Chen Shun-Hsing. The application of baghouse fines in Taiwan. Resour Conserv Recycl 2006;46:281–301. [5] Asi Ibrahim, Assa’ad Abdullah. Effect of Jordanian oil shale fly ash on asphalt mixes. J Mater Civ Eng 2005;17:553–9. [6] Xue Yongjie, Hou Haobo, Zhu Shujing, Zha Jin. Utilization of municipal solid waste incineration ash in stone mastic asphalt mixture: pavement performance and environmental impact. Constr Build Mater 2009;23:989–96. [7] Huang Baoshan, Dong Qiao, Burdette Edwin G. Laboratory evaluation of incorporating waste ceramic materials into Portland cement and asphaltic concrete. Constr Build Mater 2009;23:3451–6. [8] CMCC, CMRC. Report on current situation and prospect of China clay brick market in 2009–2010. Beijing: CMCC and CMRC; 2009 [in Chinese]. [9] General office of State Council of China. Notice of several opinions about promoting modernization of housing industry and improve the quality of houses of Ministry of Construction et al. Beijing: Eneral office of State Council of China; 1999 [in Chinese]. [10] Chen Mei-zhu, Lin Jun-tao, Wu Shao-peng, Liu Cong-hui. Utilization of recycled brick powder as alternative filler in asphalt mixture. Constr Build Mater 2011;25:1532–6. [11] RIOH, Standard test methods of bitumen and bituminous mixtures for highway engineering (JTJ 052-2000), Beijing: China Communications Press; 2000 [in Chinese]. [12] RIOH, Test methods of aggregate for highway engineering (JTG E42-2005), Beijing: China Communications Press; 2005 [in Chinese]. [13] Ping Li, Xue Wu, Zheng-qi Zhang. The influence of cement and hydrated lime on the performance of asphalt mortar. In: Icmtma, international conference on measuring technology and mechatronics automation, vol. 3; 2010. p. 885–8 [14] Vansteenkiste Stefan, Vanelstraete Ann. Properties of fillers: relationship with laboratory performance in hot mix asphalt (with discussion). J Assoc Asphalt Pav Technol 2008;77:361–94. [15] RIOH, Technical specification for construction of highway asphalt pavements (JTG F40-2004), Beijing: China Communications Press; 2004 [in Chinese]. [16] Grabowski Wojciech, Wilanowicz Jaroslaw. The structure of mineral fillers and their stiffening properties in filler-bitumen mastics. Mater Struct 2008;41(4):793–804. [17] Wu Shaopeng, Wang Jingang, Zhang Yuan. Preparation and properties of nanoclay/TPS/asphalt ternary binders. Mater Sci Forum 2009;620– 622:497–500. [18] Palade Liviu-Iulian, Attane Pierre, Camaro Sylvie. Linear viscoelastic behavior of asphalt and asphalt based mastic. Rheol Acta 2000;39:180–90. [19] Christensen DW, Anderson DA. Interpretation of dynamic mechanical test data for paving grade asphalt cements. J Am Assoc Pav Technol 1992;61:67–98. [20] Zeng ML, Wu CF. Effects of type and content of mineral filler on viscosity of asphalt mastic and mixing and compaction temperatures of asphalt mixture. Transport Res Record 2008;2051:31–44.
Contents lists available at ScienceDirect
Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat
Experimental investigation on related properties of asphalt mastic containing recycled red brick powder Shaopeng Wu, Jiqing Zhu ⇑, Jinjun Zhong, Dongming Wang Key Laboratory for Silicate Materials Science and Engineering of Ministry of Education, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070, China
a r t i c l e
i n f o
Article history: Received 15 July 2010 Received in revised form 10 November 2010 Accepted 24 December 2010 Available online 12 January 2011 Keywords: Asphalt mastic Red brick powder Filler Rheological properties Dynamic Shear Rheometer
a b s t r a c t Some properties of asphalt mastic containing recycled red brick powder (RBP) were investigated in this paper. RBP was used as filler in asphalt mastic. The investigated mastic consisted of asphalt and filler at a mass ratio of 1:1. Penetration, softening point and high-temperature viscosity were tested. Dynamic Shear Rheometer (DSR) was used to conduct frequency sweep test of asphalt mastic. The introduction of RBP resulted in reduced penetration, increased softening point, apparent activation energy, complex shear modulus in the low frequency area and high-temperature viscosity. It indicates that RBP may have some positive effect on high-temperature properties but some negative effect on low-temperature properties of asphalt mastic. It is also believed that the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing limestone mineral filler (LMF). Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction Natural limestone is processed into mineral filler used in asphalt mixture traditionally. But natural limestone resource is being exhausted with the development of cement and construction industry, especially in China [1]. The use of waste powder as filler in asphalt mixture has been the focus of several research efforts over the past few years. Recycled waste lime [2], phosphate waste filler [3], baghouse fines [4], Jordanian oil shale fly ash [5], municipal solid waste incineration ash [6] and waste ceramic materials [7] have been investigated as filler. It was proved that these types of recycled filler could be used in asphalt mixture and gave improved performance. Meanwhile, Chinese brick-making history is over 2000 years and an incalculable number of red bricks have been used in construction and building in China since 1900. Statistics show that 1.43 109 m3 of clay were used and 6 107 tons of standard coal was consumed to produce 6 1011 red bricks in China every year in 1990s [8]. The building demolition has consequently brought a large number of waste red bricks in recent years. China government has limited and gradually prohibited the use of red bricks in residential construction since 1999 for an aim of sustainable development [9]. Recycled red brick powder (RBP), which is obtained from waste red bricks, has been used as filler in asphalt mixture [10]. With the use of RBP, waste red bricks will be recycled
⇑ Corresponding author. Tel./fax: +86 27 87162595. E-mail address: [email protected] (J. Zhu). 0950-0618/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.conbuildmat.2010.12.040
and utilized efficiently to reduce the pollution of solid waste and conserve mineral and land resources. The main focus of the present investigation was directed towards the properties of asphalt mastic containing RBP. The objective of the research presented in this paper is to evaluate related properties of asphalt mastic containing RBP in terms of: 1. Effect of RBP on high-temperature properties of asphalt mastic. 2. Effect of RBP on low-temperature properties of asphalt mastic. 3. Consequent mixing and compacting temperatures of asphalt mixture. 2. Materials and method 2.1. Materials A base asphalt (AH-70) provided by SK Energy Co. Ltd. of South Korea was used to prepare asphalt mastic, with a penetration of 73 (0.1 mm at 25 °C, 100 g and 5 s), ductility of more than 150 cm (at 15 °C and 5 cm/min) and softening point of 48 °C (ring and ball) according to JTJ 052-2000 [11] of China. Limestone mineral filler (LMF), as control sample, was obtained from Macheng, a town in Hubei Province of Central China. Waste red bricks from demolished buildings were firstly crushed to size of about 50 mm by a hammer and then grinded for 15 min (determined by experiments aiming at the same percentage passing as LMF) by a SMU500 500 mm ball-grinder (made by Shanghai Xinjian Machinery Plant) to obtain RBP. After preparation, LMF and RBP were tested according to JTG E42-2005 [12] of China. Wavelength Dispersive X-ray Fluorescence (XRF) Spectrometer (Axios advanced, made by PANalytical Co. Ltd. of the Netherlands) and JSM-5610LV Scanning Electron Microscope (SEM, made by JEOL Co. Ltd. of Japan) were respectively used to investigate the chemical composition and surface topography of LFM and RBP. Test results are respectively shown in Tables 1 and 2 and Fig. 1.
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S. Wu et al. / Construction and Building Materials 25 (2011) 2883–2887
Table 1 Filler properties.
Table 3 Shear strain of frequency sweep test.
Test
LMF
RBP
Specification
Percentage passing (%) 0.6 mm 0.3 mm 0.15 mm 0.075 mm Apparent specific gravity Hydrophilic factor
100 98.2 97.2 89.7 2.786 0.66
100 99.7 97.7 87.4 2.715 0.46
100 – 90–100 75–100 P2.50 <1
Table 2 Chemical composition of fillers. Chemical composition
LMF (%)
RBP (%)
SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O TiO2 SO3 P2O5 MnO ZrO2 SrO ZnO BaO Cl Loss
17.950 0.460 0.520 46.90 3.640 0.095 0.087 0.036 0.019 0.037 0.140 Negative 0.021 0.110 Negative Negative 29.730
68.100 16.350 6.040 2.050 1.430 2.380 1.200 0.850 0.110 0.260 0.060 0.053 0.020 0.027 0.072 Negative 0.800
Total
99.745
99.802
Temperature (°C)
10
0
10
20
30
40
50
60
Strain (%)
0.05
0.1
0.2
0.4
0.4
0.5
1
2
2.2. Method In practical engineering projects, the 0.075 mm sieve passing percentage of mineral aggregates gradations is usually around 4.5%. Meanwhile, the optimum asphalt content in practical engineering projects is around 4.5% by the mass of mineral aggregates as well. So the powder–binder ratio of asphalt mastic was fixed on 1.0. Oven-dried LMF and RBP were respectively passed through 0.075 mm sieve. Powders passing the 0.075 mm sieve were got to prepared asphalt mastic samples. At a mass ratio of 1:1, sieved LMF and RBP were respectively mixed with AH-70 base asphalt and then stirred for 10 min at 130–140 °C. Penetration, softening point and high-temperature viscosity are some conventional performance indicators of asphalt evaluated, while some recent researches [13,14] have applied these indicators to evaluating asphalt mastic. Both these indicators and rheological indicators were used to investigate related properties of asphalt mastic in this paper. Penetration (0.1 mm at 100 g and 5 s) at 15 °C, 25 °C and 30 °C, softening point (ring and ball), and viscosity (by DV-II + Pro Brookfield Viscometer, made by Brookfield Engineering Laboratories Inc. of USA) at 135 °C, 155 °C and 175 °C were tested in accordance with JTJ 052-2000. A Dynamic Shear Rheometer (DSR, Physica MCR 101, made by Anton Paar Co. Ltd. of Austria) was used to conduct frequency sweep test at 10 °C, 0 °C, 10 °C, 20 °C, 30 °C, 40 °C, 50 °C and 60 °C. Strain sweep test was firstly carried out to fix the value of shear strain. The fixed shear strain is shown in Table 3. Under the strain-controlled mode, complex shear modulus (G⁄) and phase angle (d) of asphalt mastic samples were obtained within the frequency range of 0.1–400 rad/s (0.016–63.662 Hz) at each temperature. Samples of 8 mm diameter and 2 mm high were used at 10 °C, 0 °C, 10 °C and 20 °C; samples of 25 mm diameter and 1 mm high were used at 30 °C, 40 °C, 50 °C and 60 °C.
3. Results and discussion It can be seen in Table 1 that all properties of prepared RBP satisfy the requirements of specification. The apparent specific gravity and hydrophilic factor of RBP are both lower than LMF. The former indicates that RBP is more porous or has more folds; and the latter shows that RBP bonds with asphalt better. We can know from Table 2 that SiO2 and Al2O3 are the major component of RBP; and SiO2 and CaCO3 (CaO and Loss result from CaCO3) compose the main percentage of LMF. SEM photographs (Fig. 1) show that the surface of RBP has more folds and the particle distribution of RBP is more homogenous than LMF. All previous results indicate that RBP has higher absorption than LMF.
3.1. Penetration Penetration of asphalt mastic was analyzed by Eqs. (1)–(5). Eq. (1) was used to depict the linear relationship between the common logarithm of penetration (lgPen) and temperature (T). Regression lines and equations were obtained by Microsoft Excel. Based on linear regression equations, Eqs. (2)–(5) were respectively used to
Fig. 1. SEM photographs of fillers ((a) LMF 5000, (b) RBP 5000, (c) LMF 1000 and (d) RBP 1000).
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calculate the penetration index (PIlgPen), equivalent softening point (T800, temperature when penetration is 800 by linear regression equation), equivalent brittle point (T1.2, temperature when penetration is 1.2 by linear regression equation) and flexible temperature range (DT, temperature range between T800 and T1.2) of asphalt mastic.
lgPen ¼ K þ AlgPen T PIlgPen ¼
Table 5 Values of PIlgPen, T800, T1.2 and DT. Samples
PIlgPen
T800 (°C)
T1.2 (°C)
DT (°C)
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
0.29 0.53 0.43
52.4 59.6 61.1
21.3 16.7 14.2
73.7 76.3 75.3
ð1Þ
20 500AlgPen 1 þ 50AlgPen
ð2Þ
T 800 ¼
lg 800 K AlgPen
ð3Þ
T 1:2 ¼
lg 1:2 K AlgPen
ð4Þ
DT ¼ T 800 T 1:2
ð5Þ
where Pen is the penetration of asphalt and asphalt mastic (0.1 mm); T is the test temperature (°C); K and AlgPen are the coefficients of linear regression equations; PIlgPen is penetration index; T800 is equivalent softening point (°C); T1.2 is equivalent brittle point (°C); and DT is the flexible temperature range (°C). Regression lines of penetration are shown in Fig. 2, which illustrates the effect of RBP on penetration of asphalt mastic. It is indicated that RBP decreases the penetration of asphalt mastic. Penetration of asphalt materials increases with temperature. A marked decrease in penetration was obtained by the addition of filler, and the addition of RBP resulted in more significantly decreased penetration than LMF. Linear regression equations of penetration are shown in Table 4. Based on the values of K and AlgPen given in Table 4, the values of PIlgPen, T800, T1.2 and DT for each sample were obtained and shown in Table 5. A significant increase in PIlgPen, T800, T1.2 and DT was observed by the addition of filler. PIlgPen is an evaluating indicator of temperature susceptibility of asphalt materials and must be within the range of 1.5 +1.0 according to JTG F40-2004 [15] of China. PIlgPen of RBP asphalt mastic is lower than LMF, meaning that RBP asphalt mastic is more susceptible to temperature than LMF. T800 and T1.2 are respectively the equivalent temperature of softening and
cracking of asphalt material. Greater T800 value means better high-temperature properties, and lower T1.2 value means better low-temperature properties. As can be observed, T800 and T1.2 of RBP asphalt mastic are higher than LMF, meaning that RBP asphalt mastic softens and cracks at relatively high temperature. As a result, RBP asphalt mastic has the advantage of high-temperature properties and the disadvantage of low-temperature properties. Combining T800 and T1.2, DT was obtained to measure the flexible temperature range of asphalt mastic. RBP is less efficient at increasing DT, meaning that RBP asphalt mastic keeps flexible in a relatively small temperature range. 3.2. Softening point Equivalent softening point (T800) was discussed previously, and softening point is discussed here. Results of softening point test are shown in Fig. 3. As can be observed, a marked increase in softening point was obtained by the addition of filler, and the addition of RBP resulted in more significantly increased softening point than LMF. It is in agreement with the conclusion resulted from the calculation results of T800. When temperature rises, RBP asphalt mastic softens at relatively high temperature and keeps relatively good performance. It indicates that RBP asphalt mastic has a greater capacity to resist to the high temperature deformation. Grabowski and Wilanowicz [16] investigated the relationship between the structure of filler and the stiffening properties of asphalt mastic and believed the softening point of asphalt mastic has some relationship with Rigden void (RV), average grain diameter (Uav) and specific surface area (Ssp) of filler. From this point of view, the significantly increased softening point of RBP asphalt mastic may be explained by the difference in RBP structure, such as RV, Uav and Ssp. However, further study about the structure of RBP should be carried out to support this point of view. 3.3. Frequency sweep test Traffic loading is a dynamic loading and is over a wide range of frequency and temperature conditions. Over such wide frequency and temperature ranges, the rheological properties of the asphalt materials cannot be tested at laboratory scale. Fortunately, the time–temperature superposition principle can be applied to com-
Fig. 2. Regression lines of penetration.
Table 4 Linear regression equations of penetration. Samples
Linear regression equations
Correlation coefficients
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
lgPen = 0.8966 + 0.0383 T lgPen = 0.6984 + 0.0370 T lgPen = 0.6100 + 0.0375 T
0.999 0.998 0.999
Fig. 3. Softening point test results.
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tion of RBP. So RBP asphalt mastic may be relatively easy to crack at low temperature.
Table 6 Empirical values of apparent activation energy. Samples
AH-70 base asphalt
LMF asphalt mastic
RBP asphalt mastic
Apparent activation energy (kJ/mol)
182
186
191
3.4. High-temperature viscosity
pose a smooth curve of the material rheological properties over a wide spectrum of loading frequencies. Master curves represent the material rheological behavior versus loading frequency (or loading time) [17]. Master curves are used to investigate the rheological properties of asphalt mastic as well [18]. In order to get master curves of asphalt mastic, shift factors (aT) was firstly calculated by an Arrhenius-like equation. Eq. (6) describes the dependence on temperature of the calculated shift factors fairly well. Empirical values of apparent activation energy were used to calculate the shift factors. A reference temperature of 10 °C was selected for all samples studied.
lgaT ¼
DEa 1 1 2:303R T T 0
ð6Þ
where T is the test temperature; T0 is the reference temperature, 283 K; DEa is apparent activation energy (J/mol) and R is universal gas constant, R = 8.314 J/(K mol). In order to represent the results well, optimal value of apparent activation energy for each sample was fixed empirically. Table 6 shows the Empirical values of apparent activation energy. Christensen and Anderson [19] calculated the activation energy of asphalt mastic and obtained the value of 250 kJ/mol in 1992. It can be seen in Table 6 that an increase in apparent activation energy was obtained by the addition of filler, and the addition of RBP resulted in more significantly increased apparent activation energy than LMF, which results from the difference in filler structure, and causes the decreased penetration and increased softening point. Shift factor was calculated by Eq. (6); and master curves of complex shear modulus (G⁄) and phase angle (d) were obtained accordingly. G⁄ and d versus loading frequency of asphalt and asphalt mastic are depicted in Fig. 4. It clearly demonstrates that G⁄ increases with frequency. A marked increase in G⁄ was obtained by the addition of filler. The addition of RBP resulted in more significantly increased G⁄ than LMF in Area 1 (low frequency or high temperature area), meaning that RBP asphalt mastic has better hightemperature performance than LMF. It is also shown in Fig. 4 that the addition of RBP resulted in decreased d in Area 2 (high frequency or low temperature area). This phenomenon denotes that viscous portion of G⁄ decreases at low temperature with the addi-
Conventionally, there is a close relationship between the viscosity of asphalt and the mixing and compacting temperatures of asphalt mixture. But Zeng and Wu [20] believes that the viscosity of the asphalt mastic, rather than that of the asphalt, should provide pertinent information on the mixing and compacting temperatures of asphalt mixture. The effect of RBP on high-temperature viscosity of asphalt mastic and the consequent mixing and compacting temperatures of asphalt mixture is discussed here. High-temperature viscosity test was carried out by a Brookfield Viscometer at 135 °C, 155 °C, and 175 °C. There is a linear relationship between the common logarithm of the viscosity values (lgg) and temperature (T). Regression lines and equations were obtained by Microsoft Excel. According to JTJ 052-2000, the mixing and compacting temperatures of asphalt mixture depend on the asphalt viscosity and the asphalt viscosity ranges for mixing and compacting are respectively 0.19–0.15 Pa s and 0.31–0.25 Pa s. Based on the asphalt viscosity ranges, viscosity range of LMF asphalt mastic for mixing and compacting was calculated by linear regression equations. When RBP replaces LMF to be used as filler, the same viscosity range of asphalt mastic must be achieved. So the mixing and compacting temperatures of asphalt mixture containing RBP as filler were calculated by linear regression equations. Regression lines of high-temperature viscosity are shown in Fig. 5, which illustrates the effect of RBP on high-temperature viscosity of asphalt mastic. It is indicated that RBP increases the high-temperature viscosity of asphalt mastic. Viscosity of asphalt materials decreases with temperature. A marked increase in viscosity was obtained by the addition of filler, and the addition of RBP resulted in more significantly increased viscosity than LMF. Linear regression equations of high-temperature viscosity are shown in Table 7. From a slope point of view, a marked increase in the rate of change in viscosity was obtained by the addition of filler, and the addition of RBP resulted in less significantly increased rate of change in viscosity than LMF. Based on the linear regression equations given in Table 7, values of temperature and viscosity for mixing and compacting were ob-
Fig. 5. Regression lines of high-temperature viscosity.
Table 7 Linear regression equations of high-temperature viscosity.
Fig. 4. Master curves of frequency sweep tests.
Samples
Linear regression equations
Correlation coefficients
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
lgg = 2.0489–0.0174 T lgg = 2.9209–0.0197 T lgg = 2.9588–0.0191 T
0.998 0.999 0.999
S. Wu et al. / Construction and Building Materials 25 (2011) 2883–2887 Table 8 Values of temperature and viscosity for mixing and compacting. Samples
AH-70 base asphalt LMF asphalt mastic RBP asphalt mastic
Mixing process
Compacting process
Temperature (°C)
Viscosity (Pa s)
Temperature (°C)
Viscosity (Pa s)
159–165 159–165 160–162
0.19–0.15 0.81–0.72 0.81–0.72
147–152 147–152 155–157
0.31–0.25 0.98–0.93 0.98–0.93
tained and shown in Table 8. The viscosity ranges of asphalt mastic for mixing and compacting are respectively 0.81–0.72 Pa s and 0.98–0.93 Pa s. The average mixing temperature of asphalt mixture containing RBP is equivalent to that containing LMF. But the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing LMF. 4. Conclusions On the basis of the discussion above, the following conclusions can be drawn: (1) RBP results in increased equivalent softening point (T800), softening point and complex shear modulus (G⁄) in the low frequency (or high temperature) area of asphalt mastic. It indicates that RBP may have some positive effect on hightemperature properties of asphalt mastic because of its increased apparent activation energy. (2) RBP results in increased equivalent brittle point (T1.2) and decreased phase angle (d) in the high frequency (or low temperature) area of asphalt mastic. It indicates that RBP may have some negative effect on low-temperature properties of asphalt mastic. So when RBP are used in extremely cold areas, the low-temperature performance of asphalt pavement needs to be paid attention to. (3) RBP results in increased high-temperature viscosity of asphalt mastic. It is concluded that the average mixing temperature of asphalt mixture containing RBP is equivalent to that containing LMF; but the average compacting temperature of asphalt mixture containing RBP is 6.5 °C higher than that containing LMF.
Acknowledgements This work presented in this paper was supported by Project of Transportation Construction Technology in Western Area of China
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