Short-Term Laboratory Conditioning of Asphalt Mixtures (2015) / Chapter Skim
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C-1 Preliminary Laboratory Experiment A preliminary laboratory experiment was conducted at the beginning of this project to evaluate the effects of binder absorption, aggregate size, binder source, binder grade, and conditioning protocol on the stiffness and strength of asphalt mixtures subjected to various laboratory short-term oven aging (conditioning) protocols.
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C-2 Factors Level Values Aggregate Type (Water Absorption) Abs-1: 0.7% Abs-2: 3.5% NMAS NMAS-1: 9.5 mm NMAS-2: 19 mm Binder Source Binder A Binder V Binder Grade PG-1: PG 64-22 PG-2: PG 70-22 Conditioning Protocol STOA-1: 2 h @ 275°F (135°C)
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C-3 The statistical analysis results by JMP statistical package (SAS product) for MR as the response variable are presented in Figure C-1.
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C-4 As illustrated in Figure C-2, for all mixtures, the stiffness of mixtures with higher absorptive aggregates was higher than or equivalent to that of mixtures with lower absorptive aggre gates. Since two types of aggregates had different levels of binder absorption, mixtures with those two aggregates were designed differently and, thus, with different optimum binder contents.
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C-5 Mixture Label Binder Absorption FTbe 9.5-A-70-2h Low-Brownwood 18.8 High-Georgetown 14.6 9.5-A-64-2h Low-Brownwood 16.8 High-Georgetown 14.4 9.5-A-70-4h Low-Brownwood 18.8 High-Georgetown 14.6 9.5-A-64-4h Low-Brownwood 16.8 High-Georgetown 14.4 19-A-70-2h Low-Brownwood 19.6 High-Georgetown 14.3 19-A-64-2h Low-Brownwood 20.0 High-Georgetown 13.6 19-A-70-4h Low-Brownwood 19.6 High-Georgetown 14.3 19-A-64-4h Low-Brownwood 20.0 High-Georgetown 13.6 9.5-V-70-2h Low-Brownwood 19.1 High-Georgetown 14.6 9.5-V-64-2h Low-Brownwood 18.9 High-Georgetown 14.4 9.5-V-70-4h Low-Brownwood 19.1 High-Georgetown 14.6 9.5-V-64-4h Low-Brownwood 18.9 High-Georgetown 14.4 19-V-70-2h Low-Brownwood 20.1 High-Georgetown 13.7 19-V-64-2h Low-Brownwood 19.0 High-Georgetown 14.4 19-V-70-4h Low-Brownwood 20.1 High-Georgetown 13.7 19-V-64-4h Low-Brownwood 19.0 High-Georgetown 14.4 Table C-4. Calculated effective binder film thickness results.
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C-6 The effect of binder source on mixture MR results is illustrated in Figure C-4. All mixtures with Binder A were significantly stiffer than or equivalent to those made with Binder V
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C-7 The statistical analysis results for the IDT strength obtained by JMP are shown in Figure C-7. As indicated by the "Effect Tests" table in Figure C-7, among the 15 factor/level combinations considered, the main effects of binder absorption, binder source, binder grade, conditioning protocols, and the two-way interactions between binder absorption and NMAS, NMAS and binder source, and NMAS and binder grade on IDT strength are significant at a = 0.05.
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C-8 Figure C-7. JMP output of fitting model for IDT strength.
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C-9 the mixtures increased the mixture stiffness, while the opposite trend was observed for other cases. Therefore, it was anticipated that a more significant effect of NMAS on mixture IDT strength might be associated with the interaction with other main factors.
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C-10 Figure C-11. Effect of binder grade on mixture IDT strength.
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C-11 with less conditioning time. Therefore, the extended short-term conditioning for loose mix was able to significantly increase the mixture stiffness and strength.
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