Determination of Mixing and Compaction Temperatures ... - ijcebm

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International Journal of Civil Engineering and Building Materials (ISSN 2223-487X) Vol. 2 No.4 2012 © 2012 International Science and Engineering Research Center in ASTM D 2493 is found suitable as the mastic viscosity is a well-defined linear function of temperature in the coordinates for plain asphalt equi-viscous range. With increasing use of mineral fillers in the asphalt paving industry, which incorporates various additives that stiffen binders, this method can used to predict reasonable asphalt mixtures mixing and compaction temperatures shift from that of neat binders. A reasonable determination of the mixing and compaction temperature master curve from asphalt mastics is important to avoid construction problems, due to heat damage of asphalt, and lead to the release of unacceptable levels of “blue smoke” and cause difficulties in compaction. Description of Materials and Experimental Procedures Asphalt cement. The source of the plain asphalt binder as well as mineral fillers is from Jiangsu production plant in China and properties of No. 70 petroleum asphalt binder are shown in Tab.1. All the asphalt binder tests were done in accordance with the testing procedures as outlined in JTJ 052- 2000 [3]. The asphalt binder was tested before conducting experiments for this research to verify conformity with the standard specifications for use of such materials as outlined in specification JTG F40-2004 [4]. It can be seen from the test results that the asphalt binder met the requirements for No. 70 penetration grade asphalt binder. It must be mentioned that no characterization tests were done on the commercial mineral fillers supplied for the purpose of this project. However, all the fillers are as a result of the calcination process that occurs and due to the presence of calcium content in these fillers, there is a possibility that a chemical reaction takes place with plain asphalt and results in certain properties of the asphalt-filler mastic. Table 1 Properties of No. 70 petroleum asphalt binder Test Unit Standard Tested Value Penetration (25°C, 5s , 100g ) 0.1 mm 60~80 71 Penetration index PI - -1.8~1.0 0.084 Softening point (R&B) min °C 43~44 44.8 Ductility at 15°C min cm 100 >100 Wax content max % 3.0 - Flash point max °C 260 310 Solubility in trichloroethylene % 99.5 - min Density (15°C ) g/cm 3 Actual 1.005 After TFOT Change in mass max % ±0.8 - 0.36 Penetration ( % of original) % 58 59.6 Retained ductility 15°C min cm 15 - Testing procedures. Six dust to binder ratio specimens were prepared in the laboratory for use with each mineral filler. The dust to binder ratios ranged from 0.0 up to 1.5 in ratio increments of 0.3 by weight of asphalt. A brookfield programmable viscometer DV-II was used to test for viscosity at 135, 165, and 195°C per dust content [5]. The steps and procedures as outlined in ASTM D4402 test No. TP48 and JTJ 052-2000 of China, test No. T 0625 were used. Two brookfield specimen volumes of 8ml and 10ml were prepared for testing with SC4-21 and SC4-27 spindles respectively. The 8ml brookfield specimens were prepared for testing at 0.0 and 0.3 dust to binder ratio contents and 10ml for 0.6, 0.9, 1.2, and 1.5 respectively. The asphalt filler mastic samples were produced by adding the correct weight per sample to the heated plain asphalt. The mineral fillers prior to mixing were heated to 100°C for 24hrs to ensure moisture free particle surfaces. The mixing time was restricted to 15 minutes to minimise further hardening due to the short aging process and was done in the brookfield viscometer cylinders of either 8ml or 10ml based on the mineral filler to binder mix ratio. 160
International Journal of Civil Engineering and Building Materials (ISSN 2223-487X) Vol. 2 No.4 2012 © 2012 International Science and Engineering Research Center Test Results and Analysis Viscosity. Three asphalt mastic specimen per dust content were tested at three different temperatures 135, 165, and 195°C and the average viscosity per testing temperature at a specific dust content was recorded in centipoises as the viscosity of the asphalt mastic specimen at a test temperature and dust content. The order of testing was from lowest mineral filler content and temperature to highest. A linear relationship between viscosity (log-log scale) and temperature is established for each mineral filler dust to binder ratio content using the equation below. V i = A + VTS( Ti ) (1) Where V is viscosity in (Pa·s), A is the regression intercept,Tiis temperature of interest, (°C) and VTS is the regression slope of viscosity temperature susceptibility.Using least squares regression method, the linear eq. 1 is established per dust to binder content as shown in table 2. The figures generated for each mineral filler are shown in figures 1 to 3. At 0.170±0.02 Pa·s and 0.280±0.03 Pa·s equi-viscous lines, the temperatures for asphalt mixtures mixing and compaction are established at any dust to binder ratio content for each specific mineral filler as shown in the figures below. Depending on the type and content of mineral filler recommended for use with No.70 (Penetration grade), the required asphalt mixtures mixing and compaction temperatures can be read off from the particular asphalt mastic graph. It should be noted that a linear regression equation for mineral filler to binder ratio of 1.5 for hydrated lime is missing because the mixture at such a high content of hydrated lime was too stiff to work. Hydrated lime has a higher specific gravity than other mineral fillers hence the method based on weight other than volume of mineral filler proved to work well for low specific gravity fillers such as limestone and Portland cement. Filler to binder ratio 0 0.3 0.6 0.9 1.2 1.5 Table 2 Viscosity at different type and content of mineral fillers Test Temp . o Viscosity (Pa.s) Viscosity equation Vi = A + VTS(Ti) C Hydrated Lime Lime stone Portland cement Hydrated Lime Limestone Portland Cement 135 0.42 0.42 0.42 165 0.11 0.11 0.11 Vi=1.24-0.006Ti Vi=1.24-0.006Ti Vi=1.24-0.006Ti 195 0.04 0.04 0.04 135 0.9 0.59 0.6 165 0.2 0.16 0.2 Vi=2.6-0.0133Ti Vi=1.73-0.0088Ti Vi=1.68-0.0083Ti 195 0.1 0.06 0.1 135 3.1 0.85 1.0 165 0.8 0.23 0.3 Vi=9.1-0.0467Ti Vi=2.48-0.0127Ti Vi=2.94-0.015Ti 195 0.3 0.09 0.1 135 14 1.45 2.1 165 3.2 0.37 0.5 Vi=41.58-0.215Ti Vi=4.26-0.0218Ti Vi=6.16-0.0317Ti 195 1.1 0.14 0.2 135 27.4 2.41 4.6 165 5.4 0.59 1.1 Vi=82.18-0.428Ti Vi=7.12-0.0367Ti Vi=13.58-0.07Ti 195 1.7 0.21 0.4 135 - 3.69 12.8 165 - 0.86 3.0 - Vi=10.94-0.0565Ti Vi=37.81-0.195Ti 195 - 0.3 1.1 161
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