Evaluating Applications of Field Spectroscopy Devices to Fingerprint Commonly Used Construction Materials (2013)

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209 A p p e n d i x O Quantitative Analysis of GpC Results Polymer-Modified Asphalt Binders and Hot-Mix Asphalt The chromatogram of the asphalt binder modified with styrene–butadiene–styrene (SBS) (Figure O.1) showed SBS peaks at an earlier elution time (15 to 19 min, as highlighted by the red box on figure) than asphalt binder (25 min). Figure O.2 shows a normalized chromatogram of SBS peaks that became larger as the amount of SBS increased. The peak areas for 1% SBS, 3% SBS, and 6% SBS were calculated and divided by the peak area corresponding to neat PG 64-22 binder. The peak area ratios for 1%, 3%, and 6% SBS were 0.00087, 0.0044, and 0.0085, respectively, which indicates a linear relationship with an R2 = 0.99 (Figure O.4). After the GPC method successfully identified the SBS com- ponent of the polymer-modified binder prepared in the lab, the SBS-modified PG 64-22 binder was mixed with aggre- gates to prepare three polymer-modified hot-mix asphalt (HMA) samples with concentrations of 1%, 3%, and 6% SBS, respectively. After the HMA mix was prepared, the binders were extracted from the HMA using D-chloroform solvent and injected into the GPC column. Figure O.3 shows a blown-up chromatogram for extracted SBS-modified bind- ers with an obvious increase in the SBS-related peak area with increased amounts of SBS. The SBS-related peak areas for 1% SBS, 3% SBS, and 6% SBS were normalized to the area under the peak corresponding to a neat PG 64-22 binder and yielded values of 0.0011, 0.0020, and 0.0055, respectively. Figure O.4 compares the normalized peak area values for SBS-modified binders and their corresponding mixes. The linear trends presented in the figure show high correlation for both binders and HMA mixtures. In conclusion, GPC chromatogram can be used not only to qualitatively assess the presence of polymer modifiers but also to quantify the polymer content in asphalt binders and HMA mixtures. RAP–Containing Asphalt Binders and HMA Evaluating the oxidation level in recycled asphalt pavement (RAP)-containing asphalt binders and HMA mixes was an important part of the Phase 2 experimental design. Initially, RAP-modified binder blends were produced by mixing neat PG 64-22 binder with the RAP binder extracted from the RAP supplied by Tilcon-Old Castle Company from two separate stockpiles located in Manchester and Waterbury, Connecticut, which are denoted by TLCM and TLCW. Figure O.5 shows GPC chromatograms of the neat PG 64-22 and two RAP-modified blends. The shoulder seen in the figure suggests a minor peak for the component with a higher molecular weight eluting after 21 min, as opposed to the main peak corresponding to the main component (neat binder) eluting after 25 min. A higher molecular weight may indicate the presence of oxidatively cross-linked material resulting from the oxidation of RAP. The next step was to quantify the amount of RAP added to the virgin HMA mix based on an analysis of the GPC chro- matograms of the HMA mixes prepared with different RAP contents. For this purpose, samples of HMA mixes with con- centrations of 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 80% RAP were prepared. The binders were extracted from the resulting mixtures and the extracted components were injected into the GPC column. Figure O.6 shows a blown-up chromatogram of the RAP-modified HMA samples at elution times ranging from 21 to 22 min. The shoulder, located at an approximate elution time of 21 min, seems to be increasing with the increase of RAP. The deconvolution of GPC spectra into separate RAP (21.7 min) and virgin binder (24.8 min) peaks is illustrated in Figure O.7. Figure O.8 shows the relationship between the RAP con- tent and the area ratio of the RAP peak relative to the binder peak. The trend in Figure O.8 shows a large spread of values Quantitative Analysis of GPC and NMR Data

Figure O.1. GPC chromatogram of PG 64-22 binder modified with 3% SBS. 0 5 10 15 20 25 30 35 0.00 0.05 0.10 In te n si ty Time, min PG 64-22E + 3%SBS 15 20 11 35 67 21 99 42 Time, min SBS (Kraton D) Figure O.2. Close-up of GPC chromatogram of normalized SBS peaks for PG 64-22 binders modified with 1%, 3%, and 6% SBS. 14 16 18 20 22 0.00 0.02 0.04 0.06 PG 64-22E + 6%SBS PG 64-22E + 3%SBS PG 64-22E +1%SBS In te n si ty (a. u.) Time, min PG 64-22E SBSUV Figure O.3. Zoomed GPC chromatogram of normalized SBS peaks for 1%, 3%, and 6% SBS-modified HMA mixes. 0251 -0.005 0.000 0.005 HMA + 6%SBS HMA + 3%SBS HMA + 1%SBS In te n si ty (a. u . ) Time, min Figure O.4. Linear relationship between SBS concentration and GPC peak area. Figure O.5. GPC chromatogram of RAP-modified asphalt binder blends. 0 5 10 15 20 25 30 35 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 64-22W 64-22W + TLCM 64-22W + TLCW In te n si ty (a. u . ) Time, min Figure O.6. Blown-up chromatogram of RAP-modified HMA samples. 20 21 22 23 0.0 0.2 0.4 0.6 Virgin Aggregate 80% 40% 100% 10% 20% N or m al iz e d In te ns ity Time, min 0% RAP content in Aggregate 210

211 Figure O.7. Deconvolution of GPC peaks for binder extracted from RAP-modified HMA mixes. 15 20 25 30 0.0 0.2 0.4 0.6 0.8 1.0 N o rm a liz ed In te n si ty Time, min RAP Virgin Binder Figure O.8. Effect of RAP content on GPC peak area values. The blue boxes are markers for the data points. 0.0 0.2 0.4 0.6 0.8 1.0 0.096 0.098 0.100 0.102 0.104 0.106 0.108 0.110 Pe a k R AP / P e ak Bi n de r RAP content slope = 0.00011± 0.00003 p-value < 0.05 R2 = 0.72 around the trend line with a fairly low correlation (R2 = 0.72) between the RAP content and GPC peak area values. This may be explained by the nonuniform distribution of oxidized RAP particles within the HMA sample or by the variability in the properties of RAP obtained from different paving projects. Quantitative Analysis of nMR Results Polymer-Modified Asphalt Binders and HMA Initially, the nuclear magnetic resonance (NMR) chemical shifts were obtained for pure SBS to identify peaks that were unique for this polymer and to verify its formula (Figure O.9). Figure O.9 shows two prominent peaks, located at 2.1 ppm and 5.4 ppm, related to the butadiene component of SBS and a sharp peak at 1.4 ppm associated with the terminal methyl of styrene. These peaks were used to identify the presence of SBS in the polymer-modified PG 64-22 binder and HMA mix produced with this binder. Three samples of SBS-modified PG 64-22 binder with 1%, 3%, and 6% SBS content were dissolved in D-chloroform and analyzed in a Bruker DRX 400 NMR system. Figures O.10, O.11, and O.12 show NMR spectra for these samples. The integration values of the butadiene protons (peaking at 2.1 ppm) and those of the aliphatic protons of virgin binder (peaking between 1.5 and 1.2 ppm) are both reported at the bottom of the plot. Table O.1 summarizes the ratios of these values for 1%, 3%, and 6% SBS concentrations. The results Figure O.9. NMR spectrum and chemical composition of Kraton D1101 SBS. 1.02.03.04.05.06.07.0 f1 (ppm) SBS (Kraton D) 1 2 3 4 5 6 7 8* 9 CH310 1 2 *3* 4 B2, 4, 6 B A A1 B3, 5 A3 B7, 8 Figure O.10. NMR spectrum for 1.5% SBS-modified PG 64-22 binder. 67 .5 1. 0 0. 0

212 Figure O.11. NMR spectrum for 3% SBS-modified PG 64-22 binder. 34 . 8 1. 0 - 0. 1 Figure O.12. NMR spectrum for 6% SBS-modified PG 64-22 binder. 14 .8 1. 0 0. 2 Table O.1. SBS Concentration in Binder as Measured by NMR SBS Content as Prepared in Laboratory (%) Integration Ratio SBS– Binder SBS Content as Measured by NMR (%) Absolute Error (%) 1 1:67.5 1.48 0.48 3 1:34.9 2.87 -0.13 6 1:14.8 6.76 0.76 Table O.2. SBS Concentration in Extracted Binder as Measured by NMR SBS Content as Prepared in Laboratory (%) Integration Ratio SBS– Binder (%) SBS Content as Measured by NMR (%) Absolute Error (%) 1 1:118.6 0.84 0.16 3 1:39.1 2.56 -0.44 6 1:20.0 5.00 -1.0 clearly show that NMR yields the correct ratio of SBS concen- tration in samples prepared in the lab with small deviations that can be attributed to the variability associated with sam- ple preparation. Tracking down the source of this variability was not possible because of time and expenditure issues related to using the stationary NMR equipment to repeat the experiment. The SBS-modified binders were used to produce HMA mixtures from which the binder was then extracted and eval- uated by the NMR system. The integrated ratios of the buta- diene peak to the virgin binder peak were deduced from the NMR spectra and compared with the actual SBS concentra- tion, as summarized in Table O.2. The absolute error values for the extracted binder presented in the table indicate a level of accuracy similar to that of the virgin binder. Furthermore, the error does not exceed 1%, which corresponds to the level of reliability achieved with the Fourier transform infrared method. Although portable NMR devices were not available for evaluation in this study, it seems reasonable to assume that, in the future, NMR spectroscopy can be used in the field for both the qualitative and quantitative analysis of polymer- modified binders and asphalt mixtures. RAP-Containing Asphalt Binders and HMA NMR spectroscopy proved to be successful not only for the identification of hydrocarbons but also for the identification of oxygen-containing functional groups based on a chemical shift in the neighboring hydrogen atoms. Therefore, the NMR system was used for the analysis of RAP-containing asphalt binders and HMA mixtures. Figure O.13 shows the NMR spectra of an RAP-modified binder blend with a char- acteristic peak at 3.8 ppm corresponding to the CH group attached to carbonyl (C=O). Figure O.14 shows the NMR spectra of a 20% RAP-containing HMA mix where the peak assigned to the RAP at 3.8 ppm is hardly detectable. The attempts to establish a correlation between the amount of oxygen and the RAP content in mixes have not yet been suc- cessful. Therefore, it can be concluded that, while the increased

213 Figure O.13. NMR spectrum for RAP-modified binder blend. 1.02.03.04.05.06.07.0 Shift, ppm RAP TLCW HCC=OCR Figure O.14. NMR spectrum for 20% RAP-containing HMA mixture. Figure O.15. NMR spectrum for AD-here LOF 65 antistripping agent. 5 .1 7 .0 3 .1 0 .1 AD-here 65 6.0 5.0 4.0 Shift, ppm 3.0 2.0 1.0 Figure O.16. NMR spectrum for PG 64-22 binder with 1% of AD-here LOF 65. 14 7.7 - 1.0 6.5 5.5 4.5 3.5 AD-here 65 64-22 + AD-here65 Shift, ppm 2.5 1.5 0.5 presence of oxygen-containing functional groups can be tracked using NMR, it can be only done qualitatively given the available data. Binders with Antistripping Agents The NMR method proved to be useful for identifying the presence of antistripping agents in asphalt. To verify this, the NMR spectra of pure antistripping agents were first obtained to identify the characteristic peaks (Figure O.15). Next, a sample of virgin PG 64-22 binder with an addition of 1% anti stripping agent was prepared and tested. The resultant NMR spectra (Figure O.16) showed the characteristic peak at very low intensity. The team concluded that because of the extremely low concentration of antistripping agents used in the industry (0.25% to 1% of weight), quantifying the amount of these additives using the NMR method does not seem practical.