Long-Term Field Performance of Warm Mix Asphalt Technologies (2017) / Chapter Skim
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7 Overview This chapter describes the research approach used in this project. The approach consists of three key components, as illustrated in Figure 2.1: (1)
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8either at the same project location as the WMA pavements or were constructed nearby to provide similar traffic, materials, and structure conditions. Selected Field Projects Two types of field projects were incorporated into this study: five new projects that were constructed in 2011 and 2012, and 23 in-service field projects that were constructed before 2011.
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9 Project MT I-15 TN SR 125 IA US 34 TX FM 973 LA US 61 Construction Year 2011 2011 2011 2011 2012 Warm Mix Type Sasobit, Evotherm DAT, Foaming Evotherm 3G Sasobit, Evotherm 3G Evotherm 3G, Foaming Sasobit, Evotherm 3G Mixing Temp., °F H (315-320)
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10 Project SC US 178 TN SR 46 TX FM 324 LA 116 LA 3191 LA 3121 Construction Month/Year 9/2007 10/2007 2-3/2008 3/2010 11/2008 3/2009 Warm Mix Type Evotherm DAT Sasobit, Evotherm DAT, Astec DBG, and Advera Sasobit, Evotherm DAT, Rediset, Advera Foam Astec Foam Evotherm 3G Production Temp., °F HMA (295) ; Evotherm (240)
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11 Project TX SH 251 TX SH 71 CA HVS 3a CA HVS 3b Construction Month/ Year 8/2008 6/2008 9/2009 9/2009 Warm Mix Type Astec DBG Evotherm DAT Gencor, Evotherm DAT, Cecabase Sasobit, Advera, Astec DBG, Rediset Production Temp., °F H (310)
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12 Notes: "N/A" denotes that information is not available. DF: dry freeze; WF: wet freeze; DNF: dry no-freeze; WNF: wet no-freeze.
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13 Field and Laboratory Characterization of WMA Projects Field Distress Surveys Two rounds of distress surveys were conducted in 2012– 2013 and 2014–2015, for all the in-service projects except for the CA HVS and TX SH 71 projects. The second-round distress survey was also conducted for the newly constructed projects except for the TX FM 973 project due to logistical reasons.
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14 Rut Depth Identification Rut depth was measured within the three 200-ft test sections of the HMA and WMA pavements every 50 ft for both the inside and outside wheel paths. Figure 2.6 illustrates the rut depth measurement process performed in the field.
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15 modulus test. Specimens were tested at temperatures of -10°C, 4.4°C, 20°C, 37.8°C, and 54.4°C and at loading frequencies of 20 Hz, 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz at each temperature for the development of master curves and for use in the statistical analysis.
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16 of the specimens was 1.5 inches in thickness and 3.9 inches in diameter. The volumetric properties of the samples were recorded before conducting the tests.
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17 resistance of the asphalt mixtures. Samples from the TN SR 125 project were compacted in a mobile asphalt laboratory at the plant during construction without reheating.
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18 Binder Extraction and Recovery Asphalt binders were extracted and recovered from the field cores. The extraction process was performed based on AASHTO T 164 Standard Method of Test for Quantitative Extraction of Asphalt Binder from Hot Mix Asphalt and the recovery was conducted according to AASHTO R 59 Standard Practice for Recovery of Asphalt Binder from Solution by Abson Method.
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19 crack length between HMA and WMA. The rut depths were compared based on a practical criterion, a 1⁄16-inch threshold value, because the manual measurement of a rut depth had a precision of 1⁄16 inch.
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20 refers to a high level of correlation between two predictor variables that often exist in a complex field situation and must be avoided in the development of predictive models. Other advantages of the PLS method include simplicity, reliability, versatility, and suitability for relatively small datasets (Peng and Lai 2012)
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