The effects of using alkali-silica reaction (ASR) affected recycled concrete
aggregate (ASR-RCA) in hot mix asphalt (HMA) were investigated in this study.
Dilatometer and modified beam tests were performed to determine the possibility of new
ASR occurring in reactive aggregates within the HMA or re-expansion of existing gel.
The Lottman test and micro-calorimeter were used to determine the moisture
susceptibility of HMA made with ASR-RCA. A differential scanning calorimeter
(DSC) with thermogravimetric analysis (TGA) was used to evaluate the drying of an
artificial gel and x-ray diffraction (XRD) was used to check for the potential presence of
gel in the filler fraction of the ASR-RCAs. Micro-deval and freeze-thaw tests were
evaluated for their potential to indicate the presence of excess micro-cracks or ASR gel.
Expansion testing indicated that both ASR-RCAs were still reactive with 0.5 N
NaOH solution saturated with calcium hydroxide (CH) at 60 degrees C. Dilatometer testing of
HMA specimens in NaOH CH solution at 60 degrees C indicated a reaction between the asphalt
binder and the solution, but little, if any, ASR. The lack of expansion in the modified
beam test supports the binder-solution interaction. However, dilatometer testing in
deicer solution at the same temperature indicated that some ASR may have occurred
along with the primary binder-solution interaction. The volume change characteristics
associated with the binder-solution interaction with and without ASR was supported by
the change in pH and alkali concentration of the test solution.
DSC/TGA testing indicated that the artificial gel dehydrated at approximately
100 degrees C. XRD analysis of the filler indicated that some gel may have accumulated in this
fraction. Moisture damage testing indicated good resistance to moisture damage by
HMA mixtures made with ASR-RCA especially compared to a virgin siliceous
aggregate. Micro-deval and freeze-thaw tests can detect the presence of micro-cracks
due to ASR in ASR-RCAs as higher mass loss than the virgin aggregate.
The potential distress mechanisms that may occur when using ASR-RCA in an
HMA pavement were identified. Results obtained using accelerated laboratory
conditions were extrapolated based on anticipated field conditions. Guidelines for the
mitigation of potential distresses in HMA made with ASR-RCA are presented.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-08-8504 |
| Date | 2010 August 1900 |
| Creators | Geiger, Brian James |
| Contributors | Mukhopadhyay, AnAl K., Zollinger, Dan G. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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