Fundamental Properties of Asphalts and Modified Asphalts, III

Figure 2-2.2.13. PA spectra RA/AAD-1 asphalt mastic. Top: 20% RA/80% AAD-1. Second
from top: 50% RA/50%AAD-1. Third from top: 80%RA/20%AAD-1.
Bottom: 90%RA/10%AAD-1. Variable number of separate scans averaged
(256 co-added scans per spectrum), OPD velocity 1.0 cm/sec, gain (7).
Spectral subtraction can be performed to obtain the spectrum of the aged AAD-1 asphalt. An
example is illustrated in figure 2-2.2.14. The top spectrum in the figure is 20% RD
aggregate/80% aged AAD-1 asphalt mixture, the middle spectrum is pure RD aggregate, the
bottom spectra is the difference spectrum. The difference spectrum was obtained by using the
limestone band at 1800 cm -1 , which is common to both the mixed spectra and the reference
spectra, and subjectively adjusting the scaling factor (0.64 in this case) until the band appeared
flat.
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