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

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10 Review of Spectroscopic Applications to Construction Materials This chapter presents the major findings from the literature search on the state-of-the-art theory and practice for finger- printing the most common materials used in highway con- struction. The full literature review of the principles of several spectroscopic techniques and a discussion on their applica- bility to testing highway construction materials is provided in Appendix E. The chapter also compares the laboratory and field testing devices in terms of their applicability, complexity of usage, sensitivity, and reliability. A detailed description of each device can be found in Appendix E as well. Overview of Spectroscopic Techniques Spectroscopy generally relies on the interaction of light with matter. Electromagnetic waves of different wavelengths inter- act with atoms and molecules in different ways that are gov- erned by physical laws. Each material has a unique chemical composition and structure, consisting of elements combined in predictable amounts and, for most crystalline materials, spatial configurations. The type and physical arrangement of elements in a compound dictate the outcome of its interaction with light at different wavelengths. Targeting a material with radiation of known wavelength and observing the outgoing signal can be used to infer the chemical properties of the material and potentially its amount within a mixture. Fig- ure 3.1 shows different regions of electromagnetic spectra employed by the spectroscopy methods covered in this study. Each method is briefly presented below. Infrared spectroscopy relies on the absorption of IR radia- tion (0.78 to 1,000 µm) by vibrating molecular bonds of differ- ent atoms (e.g., C–H, C–O, N–H, S–H, S–O, and so forth). The chemistry and molecular bonds in a compound dictate the characteristic wavelengths of IR absorption and the degree of absorption, which can be used to fingerprint the material. Raman spectroscopy also relies on the interaction of light (near infrared, visible, or ultraviolet range) with molecular vibra- tions, exploiting the effect named after C. V. Raman, which refers to the shift in energy of a laser beam as it interacts with different modes of vibration in a system. Similar to IR, inter- pretation of Raman spectrum relies on the comparison of characteristic frequencies and intensities of pure compounds with the experimental spectrum. Both IR and Raman spectros- copy are suitable to analyzing materials with molecular bonds that vibrate in the desired frequencies, typically organic compounds and inorganic compounds with covalent bonds. NMR spectroscopy employs the radio frequency range (60 to 800 MHz for hydrogen nuclei) to measure the energy of pho- tons. The difference between the resonance frequency of the nucleus and a standard (usually, carbon-13 or hydrogen-1) is called the chemical shift of a nucleus, which is measured in parts per million (ppm) and denoted by d. Measuring the chemical shift enables the identification of chemical elements. XRF is the emission of characteristic “secondary” (or fluores- cent) X-rays from a material excited by high-energy X-rays (wavelength 0.01 to 10 nm) or gamma rays (wavelength <0.01 nm). The energy and intensity of the emitted X-rays depend on the type and concentration of elements in a sample; thus XRF is used to quantify the elemental composition of a sample. Stationary XRF can quantify elements with Z > 11 (Na), while portable XRFs such as the one owned by the research team can quantify elements with Z > 15 (P). X-ray diffraction relies on the interaction of X-rays of a cer- tain wavelength with crystalline materials (i.e., materials that have a periodic, predictable physical structure). The reflected (or diffracted) X-ray beam has a direction and intensity that is a function of the interatomic distances in the material and the chemical composition. Interpretation of XRD patterns thus relies on the comparison of diffracted angles and intensities of pure materials with the observed peaks in the pattern. XRD is typically used to analyze inorganic solid materials, including cements, soils, aggregates, and mineral ores. C h A p t e R 3 Findings and Applications

11 Chromatographic methods physically separate the compo- nents of a mixture and distribute them between two phases. One phase remains stationary (a solid, a gel, or a liquid sol- vent), while the other phase (a liquid or a gas) moves in a defi- nite direction. The separation principle in size-exclusion chromatography (SEC) is determined by the selective perme- ation of the polymers into and out of the mobile-phase filled pores of the column packing. The separated compounds can be detected by coupling the chromatographic column with a detector that identifies each compound separately. A summary of the specifications of the respective devices for each method can be found in Appendix E, Table E.2. On the basis of the review of the spectroscopic equipment, the following preliminary conclusions were drawn: • GPC, high-performance liquid chromatography (HPLC), and gas chromatography (GC) are useful for separation and qualitative analysis before further identification by other spectroscopic methods. Portable chromatographs are avail- able for use in field and mobile laboratories. • Infrared and Raman analyzers can be used for the analysis of a range of materials in the liquid, solid, or gas phase (mid-IR only). Several field portable systems are available. • The handheld XRF systems are available for the identifica- tion of chemical composition of metal-containing materials, while compact XRD instruments have been developed for testing mineral aggregates. Both can be operated in outdoor conditions at temperatures above freezing. • Most of the NMR equipment for analyzing solid-state matter is laboratory-based and cannot be used in the field. However, benchtop (or semiportable) time-domain NMR analyzers are available that appear to be useful for the anal- ysis of liquid-state substances, such as fractionated asphalts. Summary of Spectroscopic Applications to Construction Materials A quantitative analysis of the bibliographic database that includes 240 references was conducted to determine the most commonly used spectroscopic method as applied to specific material categories. The pie chart in Figure 3.2 shows the dis- tribution of the publications by spectroscopic method. Many studies reported more than one method of material analysis, because none of the spectroscopic methods could provide full characterization of a material (i.e., both chemical composition and physical properties). For example, most asphalt studies used chromatography as a preparation method for further evaluation of asphalt fractions by FTIR or NMR. The pie chart in Figure 3.2 indicates that most studies employed FTIR and SEC (41% and 22%, respectively) for chemical characteriza- tion of materials. XRF spectroscopy was least used for con- struction materials, presumably because of their predominantly organic nature. The distribution of bibliographic sources by materials and methods is provided in Figure 3.3. FTIR and chromatography were most often used for research on asphalt materials. Among the other categories of construction materials, PCC and aggregates were more often reported to be evaluated by XRD, XRF, Raman, and FTIR. The absence of NMR studies for epoxies, paints, and soils can be explained by the high cost Figure 3.1. Electromagnetic frequencies employed by spectroscopic methods. Figure 3.2. Distribution of bibliographic sources by spectroscopic methods.

12 of NMR equipment. Another important observation from the literature review is that researchers have been more suc- cessful in the qualitative rather than the quantitative analysis of chemicals compounds, because the quantification of com- ponents in construction materials requires the development of calibration curves using pure compounds. Spectroscopic methods are used primarily by academic and industrial researchers because of equipment availabil- ity and resources required for these analyses. Nevertheless, a few ASTM and AASHTO standards exist for the FTIR and XRF testing of paints and polymers in construction and they are used by some transportation agencies in the United States (e.g., Virginia and Texas). It is plausible to assume that with advances in the manufacturing of reli- able portable devices (e.g., portable FTIR, XRF, XRD, Raman, and NMR), more agencies will be interested in the future in using fast and nondestructive spectroscopic methods for QA/QC purposes. Federal and Local Standards for Spectroscopic Testing in the United States The literature review included the ASTM and AASHTO standards relevant to spectroscopic testing of transporta- tion construction materials. Additionally, the research team identified several local specifications developed by SHAs. Out of 26 standards summarized in Appendix E, Table E.3, only seven are used by SHAs to test highway construction materials, primarily portland cement and its products and paint coatings. Two procedures were developed by FHWA for asphalt-related materials. A search of all 50 SHAs web- sites revealed that nine states share their locally developed (or modified ASTM and AASHTO) standards, including Arizona, California, Kentucky, Louisiana, Maryland, Wash- ington, and West Virginia (see Appendix E, Table E.4). Summary of Literature Review The objective of this project was to evaluate the suitability of various spectroscopic techniques for fingerprinting transpor- tation construction materials in the field. Effectively, the lit- erature review covered the underlying principles of the most commonly used spectroscopic methods, as well as the current practice of their application to the analysis of asphalt, port- land cement, and other construction materials. In addition, the research team prepared an overview of the available equip- ment with emphasis on portable devices for the feasibility study. Tables E.5 and E.6 in Appendix E show the universality ranking of the methods most applicable to transportation construction materials. On the basis of the quantitative com- parison, it appears that the methods that can be applied to most materials are FTIR, XRF, Raman, NMR, and SEC-HPLC. The quantitative comparison though does not exclude other discussed methods that can be very productive in some particular applications. The literature also indicates that some techniques are more favorable for the analysis of particular materials than others. FTIR was successfully used to determine fundamental Figure 3.3. Distribution of bibliographic sources by material and method.

13 properties of both asphaltic materials and portland cement. XRD has been traditionally used to investigate the portland cement composition rather than for the analysis of asphalt components. The suitability of Raman technology for the asphalt analysis should be evaluated further in this study, because literature references were not adequate to establish this. In the majority of published studies, the researchers suc- ceeded in the qualitative rather than quantitative analysis of chemical compounds. Finally, a number of portable devices (GPC, HPLC, and GC chromatographs, FTIR and Raman spectrometers, and XRD-XRF analyzers) were identified as potential candidates for the feasibility study in Phase 2. Analysis of the national standards for spectroscopic test- ing indicated that several procedures developed by the ASTM and AASHTO were used by the SHAs to test highway construction materials, primarily portland cement and its products and paint coatings. A search through the 50 SHAs websites revealed that nine states share their locally developed (or modified ASTM and AASHTO) standards online. The search indicated the need for developing new procedures that could replace the often complicated and time-consuming chemical tests and thus allow faster and more accurate measurements. Survey and Workshop Results Preliminary Survey Results The preliminary survey included a questionnaire that was sent to the SHRP 2 coordinators in 50 SHAs and 16 responses were received. The survey included questions on three fundamental issues: • What materials are the most challenging in terms of their quality control in the field? • What analytical procedures are currently used by state agencies? • What testing constraints are common under field condi- tions, and what features of the QA/QC procedures and related devices are desirable to address these requirements? The complete answers on the questionnaire and analysis of the preliminary survey are provided in Appendix F. Overall, the survey indicated that • Some departments of transportation are familiar with spectroscopy methods; • Asphalt- and portland cement-related materials and paints are the most challenging in terms of QA/QC; and • Test duration, personnel training, and equipment cost are the biggest concerns when implementing new procedures. Workshop Results In addition to the preliminary survey, a workshop with experts from both SHAs and industry was held before finalizing the experimental protocol for this project. The workshop concen- trated on both qualitative and quantitative requirements for the field QA/QC procedures that would be implemented as a result of this project. Table F.3 in Appendix F presents a sum- mary of findings from the workshop. On the basis of the results of the workshop, a set of desired testing and equipment parameters, such as sample preparation, test duration, reli- ability, training effort, and equipment price, was developed. It helped to rank practicality of the spectroscopic devices to be chosen for laboratory and field evaluation. More details on the discussion during the workshop are provided in Appendix F. Finalizing Design of Experiment for Proof of Concept The literature review, SHAs’ responses to the questionnaire, input from the workshop participants, and the experience of the research team contributed to the design of the experimen- tal matrix, as shown in Figure 3.4. Table A.2 in Appendix A Figure 3.4. Flowchart for the experimental design.

14 lists the spectroscopic devices chosen for the proof-of-concept experiments in Phase 2. Both portable and stationary equip- ment were included in the experimental protocol to compare detection limits, accuracy, and precision. Although it was expected that the stationary equipment in the laboratory would be accurate and robust, technological improvements may allow for the use of portable equipment now or in the future. Appendix A provides detailed descriptions of the materials, equipment, and testing protocols evaluated in Phase 2. Table A.4 in Appendix A summarizes the results of the evaluation of spectroscopic equipment in terms of com- pliance with suitability criteria. The list of material categories and spectroscopic methods for proof-of-concept testing is summarized in Appendix A, Table A.2. The individual testing objectives for each material– method combination were established on the basis of the input from the workshop participants. For each type of material, at least two brands were chosen for the final test matrix shown in Table A.1. The brands included in Table A.1 were obtained by surveying the APL/QPLs that were available on 34 out of 50 SHA websites. Figures A.8 through A.17 in Appen- dix A summarize the findings from the APL/QPL survey. The most successful pairs of material–method combina- tions identified in the laboratory phase were proposed for field testing. The following guidelines were established for the selection process: • Fulfillment of a specific objective for a particular combina- tion of method and material, as stated in Table A.2; • Full compliance with specific procedure parameters, such as minimum sample preparation, time, and labor effective- ness (details are provided in Table A.4); • Full compliance with specific equipment characteristics, such as accuracy, reliability, duration of measurement (details are provided in Table A.4); and • Equipment portability (size and weight) and costs (details are provided in Table A.4). Concurrently, generic laboratory testing protocols were developed for each spectroscopic method to be further refined under real-time field conditions (see Appendix B). Field Needs Survey Results To verify the relevance of the testing matrix to the needs of transportation construction professionals, an additional survey of the 50 SHAs was conducted before the final phase of the project, field verification, was initiated. Participants were asked to rank the need for a particular material QC objective from 1 (low) to 5 (high). The research team used survey outcomes to finalize the scope of work for the field phase of the project, as summarized in Table 3.1. The detailed results of the survey can be found in Appendix G. Figure 3.5 summarizes the distribution of average field need scores between SHAs, where the average score is calcu- lated as the average score from a given state to all 10 material categories listed in Table 3.1. Twenty-seven out of 33 surveyed respondents assigned the score of 3 or higher to the proposed Table 3.1. Scope of Work for Field Phase with SHA Ranks Material Category Objective Average Score Rank Structural coatings and pavement markings Verification of chemical composition 3.05 2 Verification of presence of solvents/ diluents 2.73 3 Epoxy adhesives Verification of chemical composition 2.68 3 PCC Verification of presence of admixture in fresh/cured PCC mix 2.65 3 Curing compounds for PCC Verification of chemical composition/ degree of cure (water content) 2.76 3 Polymer-modified asphalt Binders, emulsions, and mixtures Verification of type/class of polymer modifier 3.45 1 Determination of polymer content 3.52 1 Antistripping agents Verification of presence/type 3.55 1 RAP Verification of RAP presence in mixture 2.30 4 Determination of RAP content in HMA 3.05 2 Mean average score 3.0 SD of mean 0.4

15 field tests. The overall scores varied from 1.0 (Texas) to 4.8 (North Carolina), with an average value of 3.0 ± 0.4 (stan- dard deviation). Table 3.1 provides the averages and standard deviations for each field test objective as assigned by all states. It shows that scores varied between materials from 2.3 to 3.55, with an aver- age value of 3.0 ± 0.4. The ranks in Table 3.1 were assigned by dividing the test objectives into four distinctive groups. The first group (rank = 1) includes verification of the presence and determination of content of polymer additives and antistrip- ping agents in asphalt binders, emulsions, and mixtures, with the scores around 3.5. The second group (rank = 2) contains fingerprinting of structural coatings and pavement mark- ings and determination of RAP content in asphalt mixes with the score around 3.0. The third group (rank = 3) comprises scores within 1 SD below the mean (score > 2.6). This group includes fingerprinting of PCC-related materials (chemical admixtures, curing compounds, epoxy adhesives) and verifi- cation of presence of water, solvents, or diluents in liquids. The only item that fell below the threshold of 2.6 is verifica- tion of presence of RAP with a score of 2.3. Fingerprinting of Pure Materials Verification of chemical composition was pursued for the materials with known chemical structures provided by the manufacturers. If such information was not available, the sig- nature spectra were obtained for comparison with unknown samples or mixtures. As shown in Table 3.2, analysis using a portable ATR FTIR instrument either verified the structure or provided unique spectra for all materials. The characteris- tic IR absorption peaks for pure additives (i.e., chemical admixtures, curing compounds, and polymers) served as an indicator of their presence in complex materials, such as PCC and polymer-modified asphalts. The portable Raman analyzer was only successfully used to evaluate the composition of liquid materials that did not fluoresce. Analysis of traffic paints and epoxies with the por- table XRF device provided the concentration of the primary metals in pigments and fillers (Ti or Zn) that can be used as indicators for QA/QC of these materials. The stationary GPC system was suitable to fingerprint the materials with molecu- lar weights higher than 1,000 Da. All organic materials in which phase separation did not occur were successfully eval- uated by the stationary NMR system. The GPC chromato- grams and NMR spectra of pure materials can be found in Appendices L and M, respectively. The following text provides expanded discussion on the characteristic spectral features of the materials in Table 3.2 for each method. The ATR and Raman signature spectra can be found in Appendices I and J, while the XRF numerical results are provided in Appendix K. In addition, an electronic version of spectral data was provided to SHRP 2 administration and is located at www.trb.org/Main/Blurbs/167279.aspx. Epoxy Paints and Adhesives Epoxy Structural Coatings and Pavement Markings Typical epoxy-based coating systems consist of epoxy resin, solvent, pigment, and sometimes metal filler (e.g., zinc pow- der). The product may be supplied in separate components. As the paint dries, the solvent evaporates and the hardened (oxidized) epoxy creates a thin film on the surface. Two brands of structural coatings—Carbozinc 859 and Scotchkote—were tested with FTIR. The former is a three-part organic zinc-rich epoxy coating, whereas the latter is a fusion-bonded epoxy. The epoxy pavement marking brands were Epoplex LS50 for white and yellow lane markings. The Figure 3.5. Summary of average field need survey scores per SHA.

16 signature spectra of individual material components (Parts A and B) were obtained (see Appendix I). Next, a sample of each product was prepared following the mixing directions pro- vided in their material safety data sheets (MSDS) (see Appen- dix H). The spectra of mixed samples were collected in liquid state (from the container and after surface application) by the spectroscopic methods listed in Table 3.2. Although all meth- ods except XRD were applicable for identification of epoxy paints, only portable ATR, Raman, and XRF could test dried paint in both laboratory and field environments. These three techniques yielded highly repeatable results that could be inter- preted qualitatively (absorption peaks by ATR and Raman) or quantitatively (metal content by XRF). The presence of epoxy resin in a coating material is easily detected by FTIR because of the triple absorption in the region between 1,530 and 1,680 cm-1. An aliphatic solvent yields very strong IR absorption peaks located between 650 and 900 cm-1 that decrease while paint is drying. Oxidative hardening of an epoxy can be tracked by the increase in carbonyl absorption around 1,650 to 1,750 cm-1. The signature spectra of dried paint may vary in the intensity of peaks but not in their loca- tion (see Figures I.1 through I.4 in Appendix I). RTA’s Raman analyzer can be used to characterize components of a struc- tural coating by a maximum intensity Raman shift peak as listed in Appendix J, Table J.1, provided the signal-to-noise ratio is sufficiently high (i.e., normally greater than 10). XRF analysis was successful to differentiate between differ- ent epoxies and paints based on their metal content. An average of 74 ± 2 wt% for Zn was found to be a typical con- centration for Carbozinc 859 and Scotchkote had 6 to 7 wt% concentration of titanium dioxide. Last, a consistently dif- ferent Ti content was found in Epoplex LS50 white and yellow paints (30.4 ± 0.4 wt% and 5.2 ± 0.09 wt%, respectively). More details on the epoxy and paint evaluation by XRF can be found in Appendix K. Epoxy Adhesives Two-component epoxy adhesives are typically used in PCC for bonding, patching, and crack repairs. Part A is typically an epoxy resin, whereas Part B is an amine-based hardener. Besides the hardener component, the chemical structure and hence spectra of epoxy adhesives are similar to those of epoxy paints. The ready-mixed product hardens in a very short time (about 11 min), and the process is accompanied by heating up to 60°C. Therefore, spectroscopic evaluation of the mixed product presents a challenge, because portable equipment typically does not operate under these conditions. In this study, portable ATR and Raman instruments were success- fully used to fingerprint components of Ultrabond 1100 and Sikadur 31 (see links to MSDS in Appendix H). The signature ATR and Raman spectra of the components can be found in Appendices I and J, respectively. The evaluation of dried Ultrabond 1100 was implemented in the field phase of the project, as discussed in the section on field verification of laboratory results. Table 3.2. Summary of Success in Spectroscopic Fingerprinting of Pure Materials Material Category Portable Methods Stationary Methods ATR FTIR Raman XRF XRD GPC NMR Structural coatings and pavement markings Yesa Yesb Yes na Yesa Yes Epoxy adhesives Yes Yesb na na No Yes Chemical admixtures for PCC Yes Yes No na No Yesc Curing compounds for PCC Yes Yes na na Yes Yesc Polymer additives for asphalt binders Yes Yes na na Yes Yes Antistripping agents in asphalt concrete Yes Yes na na No Yes Note: na = not applicable. a Organic constituents only. b Not applicable for solids and fluorescing constituents. c In some cases, phase separation is expected.

17 Waterborne Paints Waterborne traffic paints typically have several components: polymer binder, pigment, filler, water, organic solvent, and other minor additives. Pigments often consist of transition metal elements, such as Ti, Cr, and Fe. The organic paint components can be identified by FTIR, Raman, and NMR spectroscopy, whereas metals can be quantified by XRF. This study evaluated two brands of polyacrylic waterborne paints: (1) 3M All Weather (see link to MSDS in Appendix H) and (2) Ennis FAST DRY (no MSDS available). Both products were supplied with white and yellow pigment. The signature ATR and Raman spectra of these products can be found in Appendices I and J, respectively, while typical metal content as measured by XRF is provided in Appendix K. Figures I.5 through I.7 show example spectra of a polyacrylic waterborne paint. The structure of liquid paints sample can be identified on a FTIR spectrum by the medium-wide water- associated OH band (~3,400, ~3,250, and ~1,640 cm-1) and strong sharp carboxylate-associated (~1,730 and ~875 cm-1) absorption bands. The evaporation of water can be tracked by observing the reduction in the intensity of the OH vibrations in a freshly painted marking line (about 15 to 30 min after application). According to ATR FTIR analysis, the 3M and Ennis paints had similar compositions. The white and yellow polyacrylic paints could be differen- tiated by XRF using their Ti content as a criterion. For exam- ple, Ennis white paint in the liquid form had an average Ti concentration of 4.92 ± 0.05 wt%, while Ennis yellow paint sample yielded a Ti content of 2.12 ± 0.04 wt%. Chemical Admixtures in Concrete Four chemical admixtures typically used in the United States were evaluated: W. R. Grace’s ADVA 190 (superplasticizer), Euclid’s AIR MIX 200 (air entrainer), Accelguard 80 (set accel- erator), and Eucon Retarder 75 (set retarder). The technical and chemical information on these products can be found in the corresponding MSDS using links provided in Appendix H. For the purpose of fingerprinting, all admixtures were tested as aqueous solutions. As shown in Table 3.2, only ATR and Raman analyses yielded meaningful spectra for all admixtures. NMR samples were prone to phase separation during analysis because of the high water content. The main challenge with identifying concrete admixtures by ATR and Raman is their relatively close chemical composition (i.e., abundance of C–H, C–O, and O–H bonds in their struc- ture). Nevertheless, the ATR signature spectra were distin- guished as follows (see corresponding spectra in Figures I.10 through I.13 in Appendix I): • ADVA 190 has a strong and wide absorption band at ~1,090 cm-1 attributable to CH2–O vibrations of polyether. • AIR MIX 200 differs from ADVA 190 and Eucon Retarder 75 by the absence of the band around ~1,080 to 1,050 cm-1 and by distinctive shoulders at ~1,780 cm-1 and ~1,540 cm-1 attributable to carbonyl and C–N components of tall oil (a mixture of mainly acidic compounds like turpentine found in pine trees). • Retarder 75 has a prominent terminal carboxylate in its structure, and it yields a characteristic split of the water band (~1,650 and ~1,600 cm-1) and a strong split band at ~1,080 and ~1,040 cm-1 because of vibrations of the multiple hydroxide (OH) groups. • Accelguard 80 is characterized by a strong and wide band at ~1,331 cm-1 attributable to nitrogen dioxide (NO2) and two medium and sharp peaks at ~1,050 and ~830 cm-1 associated with nitrate (NO3 -) as well as by the absence of hydrocarbons. The Raman spectra of the admixtures in the discussion are provided in Appendix J. The typical Raman shift peaks and corresponding signal-to-noise ratios are listed in Table J.1 It appears that Accelguard 80 can be identified by Raman with higher probability because of its much higher signal-to-noise ratio as compared with the rest of the considered admixtures. Curing Compounds Curing compounds are applied to concrete surfaces to create a film that retains water in the concrete to ensure full hydra- tion of the cement. The curing compounds are typically water-based wax emulsions. Consequently, water and the organic wax component can be identified by ATR FTIR and Raman spectroscopy. The wide and strong IR absorption band in the region between 3,200 and 3,400 cm-1 coupled with a single peak at ~1,640 cm-1 wave numbers is usually associated with the hydrogen-bonded OH group in water. The multiple peaks between 2,800 and 3,000 cm-1, as well as a double peak at ~1,455 and ~1,375 cm-1, indicate the presence of aliphatic hydrocarbons (wax). Measuring the ratio of wax-related peak intensities to water-related ones (e.g., A1455/A1640) can be used to track the water content in a curing compound. Raman analysis is similar to ATR analysis in that it indi- cated the presence of wax in curing compounds by a triple Raman-shift peak between 2,800 and 3,000 cm-1 as well as by two single peaks at ~1,440 and ~1,300 cm-1. Raman analy- sis was more sensitive to the hydrocarbon component and less sensitive to water than ATR. Two brands were evaluated in Phase 2: (1) WR Meadows’s Sealtight 1100 Clear and (2) ChemMasters’ Safe-Cure 1200. Their ATR and Raman fingerprint spectra can be found in Appendix I (Figures I.14 and I.15) and Appendix J (Figures J.15 and J.19), respectively. In addition, field ATR measurements were performed on a PCC surface with TAMMSCURE applied,

18 as described in the section on field verification of laboratory results. Polymer Additives to Asphalt Polymer additives have been increasingly used to improve asphalt durability and resistance to rutting. The following three polymer products commonly used for asphalt modifica- tion were included in the experimental design: DuPont Elvaloy 4170, Kraton D1101 styrene–butadiene–styrene (SBS), and BASF’s Butonal styrene–butadiene (SB) latex. The Elvaloy is a vinyl acetate/carbon monoxide/ethylene copolymer, while Kraton and Butonal products are manufactured from styrene– butadiene polymer. More details about these products can be found in the MSDS (see link in Appendix H). The pure polymer samples were scanned by portable ATR and Raman to obtain the “signature” spectra (see Appendices I and J, respectively). The major IR absorption peaks were used to identify the presence of a polymer and determine its concen- tration in the polymer-modified asphalt binders and HMA mixtures, as discussed in the next section. Raman could not be used for the evaluation of polymer-modified asphalts because of the high opacity of asphalt binders. A typical ATR FTIR spectrum of Elvaloy exhibits several distinctive absorption peaks. The polyethylene chain is characterized by sharp peaks at 2,920, 2,850, and 724 cm-1. The carbonyl peak at 1,735 cm-1 coupled with a double peak at 1,240 to 1,270 cm-1 represents the acetic component in Elvaloy. Finally, two peaks at ~1,640 and ~1,560 cm-1 are associated with vinyl vibrations. When added to asphalt binder, Elvaloy 4170 still shows two distinctive peaks at ~1,240 and 1,735 cm-1, which can be used for positive iden- tification of this additive. The most distinctive chemical bonds in a typical SB- based polymer are aromatic C–H bonds in polystyrene (PS) and trans-alkene (vinyl) C–H bonds in polybutadiene (PB). The out-of-plane vibrations yield prominent IR peaks at ~700 and ~965 to 970 cm-1 for PS and PB, respectively. The PS and PB peaks can be easily identified on both Kraton’s and Butonal’s spectra in Figures I.18 and I.19, respectively, in Appendix I. The obvious difference between those two polymers is the presence of emulsifier in Butonal, which is characterized by strong bands associated with OH vibra- tions at ~3,400 and ~1,645 cm-1. The double peak at 2,850 to 2,880 cm-1 on a typical Raman spectrum of Elvaloy is associated with the ethylene functional group and yields the highest intensity (see Figure J.22 in Appendix J). The two single peaks at ~1,440 and ~1,300 cm-1 are also attributed to aliphatic hydrocarbon chains. The other pronounced peaks at ~1,120 and ~1,060 cm-1 are associated with stretching vibrations of the carbon skeleton in Elvaloy. The Kraton and Butonal polymers have a common SB component, which is identified by strong and narrow peaks at ~1,000 and ~1,670 cm-1 (see Figures J.21 and J.23). Butonal can be dif- ferentiated from Kraton by the peak at ~470 cm-1, which is most likely due to the carboxylic emulsifier. Antistripping Agents for Asphalt Applications Antistripping agents in asphalt mixtures increase the adhesion of asphalt binder to aggregate and reduce moisture damage. The antistripping agents tested in this project were Akzo Nobel’s Kling Beta and ArrMaz’s AD-here, both amido amine- based concentrated liquids. Highly repeatable signature spec- tra were obtained for both materials using the portable ATR FTIR, as shown in Figures I.20 and I.21 in Appendix I. The ATR analysis indicated that Kling Beta and Ad-here differed in aromaticity (note the difference in the region around 800 cm-1). This difference affected their viscosity; hence there are slightly different applications (see links to MSDS in Appendix H for more information). The two chemicals appeared to have similar chemical struc- ture. Thus aliphatic hydrocarbons were identified by the ATR at 2,924, 2,854, ~1,460, and ~725 cm-1, whereas double peaks at ~1,650 to 1,550 and 1,130 to 1,070 cm-1 were assigned to amido and amino groups, respectively (see Figure I.22). The ATR FTIR spectrum of an Ad-here sample obtained from the manufacturer (lab sample) is compared in Figure I.22 with a sample obtained from a storage facility. One can observe stronger absorption bands for the aliphatic hydrocarbons along with significantly lower absorption for amido-amino functional groups. This suggests that the field sample may be contaminated with asphalt binder or, alternatively, diluted by an aliphatic solvent to reduce the viscosity of the anti- stripping agent. Raman analysis yielded a representative spectrum for Kling Beta (see Figure J.13 in Appendix J). However, the high opacity of AD-here additive precluded Raman analysis. Identification and Quantification of Additives and Contaminants in Complex Materials One of the main objectives of spectroscopic investigations in this project was the identification and quantification of addi- tives and contaminants in mixtures. Specifically, the presence of water in waterborne paints, chemical admixtures in PCC, polymer modifiers, antistripping agents, RAP, and contami- nants in asphalt products were of interest. Table 3.3 compares the spectroscopic methods in terms of their success for each mixture. ATR FTIR analysis performed well for all cases except to detect diesel contamination in asphalts. The stationary GPC and NMR systems were successful in the detection of all additives in asphalt products except antistripping agents

19 (most likely because of their extremely low concentration in the mixtures). Quantification of chemical admixtures in PCC and antistrip- ping agents in asphalts by ATR was not found practical because of the low concentrations prescribed by the manufacturers. In addition, diesel fuel contamination in asphalt binder could not be identified using FTIR because of the overlapping bands of the two materials. However, a quantitative analysis of the FTIR spectra obtained for polymer-modified binders and RAP-containing asphalt products yielded reasonable results. The same level of success was achieved by the quantitative analysis of GPC chromatograms and NMR spectra for these materials, as described in the Appendix O. The next sections summarize the results of the most successful ATR quantita- tive analyses. Curing of Epoxies Three types of epoxies were evaluated by the Bruker ALPHA ATR FTIR spectrometer to investigate the feasibility of tracking changes in their chemical composition in situ: (1) three-part, organic, zinc-rich epoxy coating system (Carbo- zinc 859); (2) fusion-bonded epoxy (Scotchkote); and (3) two-part high-strength epoxy bonding adhesive (Ultrabond 1100). The signature spectra of those materials were previ- ously obtained in the laboratory. Next, the testing specimens were fabricated by mixing ingredients in accordance with manufacturer’s instructions and applying the coating to a metal plate. The probes for ATR testing of Carbozinc and Scotchkote systems were taken by scrapping a small amount of an epoxy from the plate immediately and after 20 to 60 min of the air curing. The Ultrabond adhesive was probed after 10 min of curing because of rapid hardening. The results of spectral analysis for cured epoxies are discussed next. The three spectra shown in Figure 3.6 indicate the evapo- ration of toluene solvent by a drastic decrease in the IR absor- bance at 738 and 698 cm-1, and the hardening and oxidation of the epoxy base by an increase in the absorbance at 1,728 and 1,276 cm-1. Nevertheless, the presence of epoxy resin can be tracked even after an hour of air-curing, as evident by Table 3.3. Summary of Success in Spectroscopic Identification and Quantification of Additives and Contaminants Material Category Objective Portable Methods Stationary Methods FTIR Raman XRF XRD GPC NMR Epoxy coatings, paints, and adhesives Presence of solvents Yes na na na No Yes Waterborne paints Presence of water Yes na na na na na PCC Identification of admixture in PCC mix Yesa na No na na na Quantification of content No na No Yesb na na Curing Compounds for PCC Identification of curing membrane on PCC surface Yes na na na Yes na Polymer-modified asphalt binders, emulsions, and mixtures Identification of polymer and water in product Yesb Noc na na Yes Yes Quantification of content Yes na na na Yes na HMA concrete Detection of contaminants (e.g., motor oil, diesel fuel) No Noc na na Yes Yes Antistripping agents in binders and mixtures Identification of antistripping in product No No na na No Yes Quantification of content No Noc na na No na Oxidation in RAP Verification of presence in mixture Yes Noc na na Yes Yes Quantification of content Yesc na na na Yesc na Note: na = not applicable. a For concentrations greater than 0.4%. b High variability in results is expected. c Not applicable for solids and fluorescing constituents.

20 the IR absorption peaks at 1,662, 1,608, and 1,580 cm-1. Fig- ure 3.7 tracks changes in the ATR FTIR spectrum of Ultrabond 1100 adhesive after 10-min curing. It shows that virtually all characteristic absorption peaks of the adhesive can be posi- tively identified within 10 min (onset time) from the time of application. Curing process is characterized by the evapora- tion of solvent as evident by a reduced intensity of the associ- ated peaks between 2,800 and 3,000 cm-1 at ~830 cm-1. Also, consolidation of the adhesive can be tracked by the increase in amino-related absorption of hardener at 1,130 to 1,070 cm-1 wave numbers. Waterborne Paints and Curing Compounds An ATR study of Ennis FAST DRY white paint was performed on samples taken from a storage tank before application, from newly painted pavement marking, from an old white lane at the same facility. The ATR FTIR spectra of the three Figure 3.6. Changes in the ATR FTIR spectra caused by curing of Carbozinc 859 epoxy coating system. Figure 3.7. Changes in the ATR FTIR spectra caused by curing of Ultrabond 1100 epoxy adhesive.

21 samples are compared in Figure 3.8. The waterborne vinyl acrylate structure of a liquid sample from a tank can be easily identified by the medium-wide water-associated (~3,400, ~3,250, and ~1,640 cm-1) and strong sharp carboxylate- associated (~1,730 and ~875 cm-1) absorption bands. Note that the evaporation of water can be tracked by observing significant reduction in the intensity of the OH vibrations in the freshly painted white line (about 15 to 30 min after application). Consequently, no water can be detected in the old paint several months after application. Figure 3.9 superimposes the ATR FTIR spectra of the pure chemical (TAMMSCURE curing compound), the sample scratched from the freshly covered PCC surface, and the sam- ple of the dried PCC surface. Each spectrum represents an average of three replicate probes from each sample. It is obvi- ous from Figure 3.9 that characteristic peaks (2,938, 2,856, Figure 3.8. Comparison of the ATR FTIR spectra of Ennis FAST DRY white paint sampled from tank, freshly applied white marking, and old white line surface. 28 56 29 38 14 55 13 74 Figure 3.9. ATR FTIR spectra of TAMMSCURE curing compound before and after application to a PCC surface.

22 1,455, and 1,374 cm-1) associated with hydrocarbon resin and aliphatic naphtha components of TAMMSCURE (see MSDS) can be tracked on the ATR FTIR spectra of both freshly cov- ered and dried PCC surfaces to which the curing compound have been applied. Chemical Admixtures in Fresh Concrete This study employed four chemical admixtures that are typically used in the United States: W. R. Grace’s ADVA 190 (superplasticizer), Euclid’s AIR MIX 200 (air entrainer), Accelguard 80 (set accelerator), and Eucon Retarder 75 (set retarder). Table 3.4 summarizes technical and chemical infor- mation on these products. All admixtures were supplied as aqueous solutions. The PCC batches (2 kg each) were pre- pared using Type 2 portland cement supplied by Lafarge North America and local fine and coarse aggregates of nomi- nal maximum aggregate size of 4 and 12.5 mm, respectively. Five PCC batches, one control with no admixtures and one for each admixture from Table 3.4, were mixed in proportions shown in Table 3.5 with total weight of about 1.8 kg per batch. The admixtures were first mixed with batch water in pro- portions recommended by their manufacturers and then added to the dry batch mix. To obtain the IR spectra of PCC samples modified with a chemical admixture, about 1 g of fine PCC fraction (cement–sand–water–admixture) was placed directly on the internal reflection element (IRE) and a fixed load was applied to a sample to ensure its full con- tact with the IRE. The fingerprint ATR FTIR spectra of the admixtures in discussion were obtained in the laboratory as discussed ear- lier in this report. Identifying the characteristic IR absorp- tion bands of the admixtures in the ATR FTIR spectra of their corresponding PCC mixes is a challenging task. Only ADVA 190 and Accelguard 80 could be positively identified as additives by the characteristic IR absorption bands shown in Figures 3.10 and 3.11. An apparent reason for that is a much higher concentration of those admixtures (0.4 and Table 3.4. Chemical Composition of Admixtures Admixture Type Product Name Manufacturer Chemical Components (wt%) Chemical Functionalities Superplasticizer (high-range water reducer) ADVA 190 W. R. Grace & Co. Water (90–99) Carboxylated polyether (1–10) H2O;–COO–;–CH2–O–CH2 Air entrainer AIR MIX 200 (AIR 200) Euclid Chemical Water (>60) Tall oil, sodium salt (10–30) 4-Chloro-3-methylphenol (<1) H2O; –CONaO–; –C6H3OH;–CH3; –Cl Set accelerator Accelguard 80 Euclid Chemical Water (40–70) Calcium nitrate (40–70) H2O; Ca(NO3)2 Set retarder Eucon Retarder 75 Euclid Chemical Water (>60) Sodium gluconate (30–60) 4-Chloro-3-methylphenol (<1) H2O; –CHOH–;CH2OH; CONaO; –C6H3OH; –CH3; –Cl Table 3.5. Summary of PCC Batch Proportions Batch 1a 2 3 4 5 Admixture type None ADVA 190 AIR 200 Eucon Retarder 75 Accelguard 80 Water–cement ratio 0.5 0.45 0.45 0.45 0.45 Design water 8.3% 7.60% 8.30% 8.30% 8.20% Type 2 cement 16.6% 23.70% 18.40% 18.40% 18.30% Batch water 8.7% 7.90% 8.70% 8.70% 8.60% Stone 34.7% 41.10% 34.60% 34.60% 34.40% Sand 40.0% 26.80% 38.20% 38.20% 37.90% Admixture 0.0% 0.43% 0.070% 0.13% 0.72% Total 100.00% 100.00% 100.00% 100.00% 100.00% a Batch one is the control.

23 0.7 wt% of the batch weight for ADVA 190 and Accelguard 80, respectively) as compared with AIR 200 and Eucon Retarder 75 with 0.07 and 0.13 wt%, respectively (see Table 3.5). The ATR testing of fresh PCC mix samples verified feasi- bility of identification of the presence of high-range water reducers (HRWR) and nonchloride (NCL) set accelerators in fresh PCC mixes. In knowing that HRWR chemicals pre- serve rate of hydration, the presence of HRWR can be veri- fied by the relatively strong IR absorption peaks at 933, 874, and 828 cm-1 associated with formation of the primary hydration product [calcium–silicate–hydrate (C–S–H)], as shown in Figure 3.12. Furthermore, a closer look at the zoomed-in spectra in the region between 1,500 and 1,300 cm-1 reveals relatively weak but visible peaks associated with admixtures. For instance, the three peaks at 1,455, 1,280, and 1,250 cm-1 can be related to the presence of HRWR, while the two peaks at 1,410 and 1,330 cm-1 indicate the pres- ence of NCL accelerator. Figure 3.10. Composition of the ATR FTIR spectrum of PCC sample modified with ADVA 190. Figure 3.11. Composition of the ATR FTIR spectrum of PCC sample modified with Accelguard 80.

24 Polymers in Asphalt Products The major objective for spectroscopic evaluation of polymer- modified asphalt products was identification of polymer type and, if possible, determination of polymer content in asphalt binders, emulsions, and HMA mixtures. Two SB- based polymers—Kraton SBS and BASF’s Butonal NX1138— were used in this study to produce polymer-modified binders in the laboratory. In addition, two styrene–butadiene rubber (SBR) latex-modified binders (of different performance grades [PG]) as well as the SB-modified cationic rapid setting emul- sion CRS-1P were supplied by a refinery and evaluated in the laboratory. The spectra of polymer-modified emulsions, polymer-modified binders (PMB), and polymer-modified asphalt mixtures collected in the laboratory were compared with those obtained in the field setting from the real paving projects. The results of spectral analysis of these materials are discussed separately in the next two subsections. Styrene–Butadiene-Modified Emulsions Figure 3.13 superimposes the ATR FTIR spectra of the polymer-modified emulsion CRS-2 in two states: (1) sampled from the tank and (2) applied to stone aggregate (Novachip seal technology). The two main emulsion components are eas- ily identified by strong and wide water bands centered around 3,300 and 1,640 cm-1 and doubled aliphatic binder peaks at about 2,920, 2,850, 1,455, and 1,375 cm-1. The SBS additive can be detected by two characteristic peaks at 967 and 700 cm-1 associated with polybutadiene and polystyrene, respectively. The spectra of the Novachip stone coated by the CRS-2 emul- sion clearly indicate the absence of water after the emulsion breaks on the aggregate. Note that the wide band at 1,600 cm-1 is associated with the aromatic carbon skeleton of the binder. For the polymer, the polybutadiene peak is obscured by the signal from silicate component of the aggregate at ~990 cm-1. However, the SBS presence can still be verified by a weak yet distinctive peak at about 695 cm-1. Figure 3.14 compares the ATR FTIR spectra of two polymer- modified asphalt emulsions tested in the laboratory and in the field by two separate Bruker ALPHA ATR FTIR spectrometers. Note that practically no difference in chemical composition of the two samples is indicated. However, the higher water con- tent in CRS-1P relative to CRS-2 can be deduced by the signifi- cantly lower intensity of the absorption bands associated with the aliphatic binder. Nevertheless, the presence of polymer is clearly indicated by the SBS-related peaks at 966 and 695 cm-1. Because asphalt emulsions are chemically stabilized sys- tems, their balance can be easily disturbed with exposure to air. Therefore, sampling and scanning of those products with the ATR FTIR was a challenging task. During storage, the bitumen can segregate from the water. Figure 3.15 pre- sents three spectra for CRS-1P: the agitated emulsion and the water-segregated and binder-segregated components of the same product. The presence of the SB polymer is easily indi- cated by a distinctive peak at ~965 cm-1. The absorbance peak at ~1,640 cm-1 is assigned to water while the two peaks at ~1,460 cm-1 and ~1,380 cm-1 correspond to the stretch- Figure 3.12. ATR FTIR spectra of hydrated PCC sample with HRWR and NCL admixtures.

25 ing vibrations of aliphatic hydrocarbons in asphalt binder. Last, one can notice that spectra of both stirred emulsion and its binder-segregated portion show highly intensive absorbance at ~1,740 and ~1,250 cm-1, which indicates presence of carboxylate emulsifier in the polymer-modified emulsions. In conclusion, although segregation of the asphalt emulsion is most likely to preclude the quantitative analysis of its spectra during FTIR testing, it is still possible to identify its major components (i.e., water, binder, and polymer additive). Styrene–Butadiene-Modified Binders This study employed various original asphalt binders modified with SBS and SBR polymers. The PMB samples were mixed in the laboratory as well as supplied by a refinery. Table 3.6 Figure 3.13. ATR FTIR spectra of pure emulsion from tank (CRS-2) and Novachip coated aggregate. Figure 3.14. ATR FTIR spectra of polymer-modified emulsions.

26 summarizes the asphalt binders and the modifiers used for aging experiments. The PG of asphalt binders ranged from PG 52-34 to PG 64-28. Note that the virgin binders PG 58-28 and PG 64-22 were obtained from two different refineries: Nu Star in Rhode Island and West State Asphalt from Washington State. Two types of polymer—Kraton SBS D1101 and BASF Butonal NX1138—were added to the original asphalt binders in proportions ranging between approximately 1 and 3 wt%. The SBR latex-modified and neat asphalt binders were sup- plied by Hudson Asphalt Group, Providence, Rhode Island. The SBS- and Butonal-modified asphalt binders were prepared in the laboratory, as described in the following text. To prepare the SBS-modified samples in the laboratory, about 400 g of base bitumen (PG 64-22 or PG 58-28) was pre- heated in an oven to a temperature of 160°C for about 1.5 h. Then the sample in a stainless steel flask was put in a heating jacket and stirred at 175°C ± 5°C using a high-shear mixer for about 2 h. The Kraton SBS pellets were added gradually within 5 min after stirring started. The liquid Butonal latex was added to the preheated bitumen sample at 135°C ± 5°C and stirred at lower speed (about 1,000 rpm) for 1 h. For both polymers, a sample was taken from the flask every 0.5 h and the ATR FTIR spectrum was measured to track the dispersion of the polymer. Three different replicate batches were prepared for each labo- ratory combination of bitumen and polymer concentration. Finally, each produced PMB batch was divided into three 6-oz cans for sampling and ATR FTIR spectrometry. To evaluate the effect of the temperature and pressure on the chemical composition of PMB, two accelerated aging methods were used in this study: rolling thin film oven–aged (RTFO) air blowing and pressure aging vessel (PAV) condi- tioning. The aging cycle for each sample included RTFO for 85 min followed by PAV for 20 h. Each sample was scanned by the ATR FTIR spectrometer before and after every step in the aging cycle. The spectra of virgin and aged samples for each PMB with maximum polymer concentration are superim- posed in Figures I.27 through I.30 in Appendix I. The primary objective of spectral analysis was to identify a polymer type by the characteristic IR absorption peak. In addi- tion, calibration equations for the quantification of polymer content in binders listed in Table 3.5 were developed based on the Beer-Lambert law (Equation 2.3 in Chapter 2). The molar Figure 3.15. ATR FTIR spectra of CRS-1P asphalt emulsion. Table 3.6. Summary of Polymer-Modified Binders Bitumen PG Grade Modifier Name Modifier Amount Added Preparation PG 64-22 Kraton SBS D1101 0, 1, and 3 wt% Laboratory PG 58-28 BASF Butonal NX1138 (SB latex) 0, 1.5, and 3.3 wt% Laboratory PG 52-34 SB latex (source unknown) 1.5 wt% Refinery PG 64-28 SB latex (source unknown) 3.3 wt% Refinery

27 extinction coefficients (or coefficient of absorptivity, e) for polystyrene and polybutadiene were determined as a ratio of IR absorbance value, A, at ~965 and ~700 cm-1, correspond- ingly, over the polymer content, c, multiplied by the IR light path length, l, as shown in Equation 3.1. The path length was calculated as 0.25 power of wavelength (1/wave number). e A cl = ( . )3 1 Figure 3.16 graphically compares the calibration slopes for SBS-modified PMBs between different binder sources (east versus west) and different polymers. It can be seen that calibra- tion slopes for polystyrene peak (A700) do not differ between east and west. This suggests that in this study, no dependence of absorptivity on the binder source was observed. It should be noted that other quantitative methods of spec- tral analysis were evaluated in this study to establish reliable calibration equations. One was peak-to-peak ratio. This method correlates the normalization of PB or PS absorption peak intensity to that associated with aliphatic CH stretching or bending vibrations that did not change with increase in polymer concentration (e.g., A966/A1377 and A700/A2920). Another so-called semiquantitative method involved normal- ization of valley-to-valley integrated absorption bands cen- tered at ~965 and ~700 cm-1 for PB and PS, respectively. The two methods are described in Appendix N and can be applied to any complex material or compound. Using peak-to-peak ratio rather than direct peak values as measured by ATR did not noticeably improve the goodness of fit for calibration equations (see Figure N.1 in Appendix N). Therefore, it is recommended that directly measured A966 Figure 3.16. Calibration equations for SBS-modified PMB based on polybutadiene and polystyrene absorption.

28 and A700 peaks be interchangeably used for quantification of SB polymers in PMBs. When the team studied the effect of oxidative hardening on PMBs, no noticeable change in polymer content resulting from oxidation was found for PMBs with the SB content up to 3.5 wt% (see Figure K.5 in Appendix K). Styrene–Butadiene-Modified Hot-Mix Asphalt Mixtures An attempt to identify polymer modifiers in HMA mix- tures from the analysis of FTIR spectra was done using HMA mixtures produced in the laboratory with polymer- modified binders. The PG 64-22 east binder modified with 1, 3, and 6 wt% SBS was preheated to 163°C and mixed with aggregates to produce the HMA mixtures. The FTIR spectra were obtained for each mix a week later at about 20°C. The two IR absorption peaks at ~965 and ~700 cm-1 were expected to serve as indicators of the presence of PB and PS in the mix. However, no PB peak could be extracted from the ATR FTIR spectra of the mix samples and no cor- relation between peaks at ~695 to 700 cm-1 and SBS con- centration was found. Further investigation was conducted by means of two-dimensional correlation spectroscopy to allow a closer look at the chemical composition of the HMA samples. Figure 3.17 presents the two-dimensional correla- tion spectroscopy plot for SBS-modified HMA samples. Note that, on the one hand, there is no correlation observed between absorption bands at 965 and 695 cm-1. On the other hand, strong correlation between two peaks at 695 and 793 cm-1 indicates the presence of quartz in either sili- ceous limestone or granite aggregate. Field evaluation of HMA samples was conducted during paving operations on I-84 near Farmington, Connecticut. The mix including PG 76-22 SBS-modified binder was sam- pled from two separated trucks immediately after unload- ing. Figure 3.18 presents the normalized (to 2,920 cm-1 peak value) ATR FTIR spectra of two samples taken from the paver within 15 min of each other. One can see that absorp- tion peaks of the two samples are matching, which suggests they have identical chemical composition. The peak at about 2,180 cm-1 indicates the presence of carbon dioxide from entrapped hot air. In addition, minor oxidative hardening caused by mixing and placement of the HMA can be detected by the peak at about 1,700 cm-1. The rest of the peaks are associated with the binder (2,961, 2,921, 2,853, ~1,600, 1,455, and 1,375 cm-1) and filler and aggregates (~1,000, 793, 637, 585, 530, and 467 cm-1). Figure 3.19 presents a closer look at two SBS-modified HMA samples: (1) prepared in the laboratory and (2) obtained from the field. There are two small but not negligible peaks at ~967 and ~695 cm-1, which can be associated with the presence of SBS polymer in the PG 76-22 binder. The spectrum of the field sample, however, does not positively indicate the Figure 3.17. Two-dimensional correlation spectroscopy plot for SBS-modified HMA samples.

29 presence of SBS. It should be noted that polybutadiene peak at 967 cm-1 is likely to be obscured by the strong and wide band centered around 1,000 cm-1 that is associated with the silicate component of the aggregates. Furthermore, the peak near 700 cm-1 can be associated with the presence of quartz in siliceous aggregates rather than with polystyrene-related IR absorptions. The direct ATR measurements on HMA samples showed that quantification of SBS content in the fresh mix appears impractical for two reasons. First, the weight percent content of the polymer compared with the mix sample weight is extremely low (around 0.002 wt%), which makes identifying the SBS peaks a challenging task. Second, the polymer content is usually governed by a binder grade specification. Therefore, it appeared logical to verify poly- mer content in an extracted binder sample as discussed in the next section. Polymer-Modified Binder Extracted from Hot-Mix Asphalt The experiment on quick extraction of PMB was conducted on Novachip street paving project in Rocky Hill, Connecti- cut. About 5 g of HMA passing No. 16 (1.18 mm) sieve size was added to 15 mL of stabilized dichloromethane (DCM) for spectroscopic applications, manually shaken for 2 min, and then left for 15 min to allow sedimentation of sus- pended filler particles. The liquid phase of the solution Figure 3.18. ATR FTIR spectra of HMA field samples. Figure 3.19. Zoom-in on SBS-associated absorption bands in laboratory and field samples of polymer-modified HMA.

30 was probed by pipetting two to three drops on the ATR sampling plate. The ATR FTIR spectra of the sample were collected twice: immediately and within 1 to 2 min from the moment of placement. Figure 3.20 compares the ATR FTIR spectra in the finger- printing region (1,800 to 400 cm-1) of a DCM-extracted PG 76-22 binder sample obtained immediately and 1 min after placing the sample on the ATR plate. It is shown that the only three characteristic absorption peaks attributed to DCM, which are at 1,263, 739, and 706 cm-1, do not inter- fere with characteristic peaks of the aliphatic component of the binder (1,455 and 1,377 cm-1) or with the absorption of filler particles. However, the DCM solvent peaks do obscure the signal from the aromatic hydrocarbons (860 to 725 cm-1) and, if present, from the polystyrene component of the SBS polymer (expected around 700 cm-1). When the sample is allowed to cure for 1 min, the solvent evaporates completely, making it possible to identify both binder aromatics and the SBS-related peak. Oxidation in Recycled Asphalt This study targeted the following two objectives related to recycled asphalt pavements: • Feasibility of the identification of elevated oxidation level in the RAP-modified binder blends and HMA mixes by means of a portable infrared spectrometer, and • Possibility of the determination of RAP content in binder blend–HMA mix based on the concentration of the oxidized chemical functionalities. Two types of samples were prepared in the laboratory (see Table 3.7): (1) binder blends containing 15 to 40 wt% RAP Figure 3.20. Identification of SBS polymer in asphalt binder PG 76-22 extracted from HMA. Table 3.7. Summary of RAP-Modified Materials Material Category Brand/Material Name Composition Neat asphalt binders mixed with RAP binders Virgin PG 64-22 West (VB) RAP Tilcon Waterbury (RAP1)/Manchester (RAP2) 60% VB : 40% RAP1 70% VB : 30% RAP1 80% VB : 20% RAP1 70% VB : 30% RAP2 80% VB : 20% RAP2 85% VB : 15% RAP2 RAP-containing HMA mixes Virgin PG 64-22 West (VB) Virgin aggregate (VAGG) RAP Tilcon North Brantford (RAP) 5.0% VB : 95.0%VAGG : 0.0% RAP 4.6% VB : 85.8%VAGG : 9.6% RAP 4.3% VB : 76.6%VAGG : 19.1% RAP 3.9% VB : 67.3%VAGG : 28.8% RAP 2.8% VB : 38.9%VAGG : 58.3% RAP 2.0% VB : 19.6%VAGG : 78.4% RAP

31 binder and (2) loose HMA samples modified by up to 80 wt% RAP. The infrared spectra were collected using a Bruker ALPHA FTIR spectrometer equipped with a single reflection diamond ATR accessory. About 0.1 g of a RAP-modified sample (binder blend or HMA mix) was put directly on the ATR prism and a fixed load was applied to a sample to ensure its full contact with the diamond. Twenty-four scans were averaged for each sam- ple within the wave number range of 4,000 to 400 cm-1 at a resolution of 4 cm-1, and the resultant averaged spectrum was recorded. Three replicate probes from each sample were scanned to establish standard deviation of the method. To track the changes in chemical composition of the RAP- modified binder blends and HMA mixes attributable to an increase in RAP content, the ATR FTIR spectrum of each sample was analyzed both qualitatively and quantitatively. The qualitative analysis involved identifying characteristic IR absorption bands for the functional groups typically present in binders. Beside the aliphatic (CH, [CH2]n, and CH3) and aromatic (C=C and arCH) binder components, the oxidation products such as hydroxyls (OH), dicarboxylic anhydrides (O=C–O–C=O), ketones (C=O), and sulfoxides (S=O) were identified in both binder blends and HMA. Last, the charac- teristic absorption bands associated with mineral aggregate component were determined. Figures 3.21 and 3.22 provide detailed spectra for a 40 wt% RAP-modified binder blend and a 80 wt% RAP-modified HMA, respectively. Of particu- lar interest was an increase in the IR absorption for the oxi- dized functional groups, such as phenolics hydroxyl, carbonyl, and sulfoxide, as shown in Figure 3.23. To quantify spectral changes attributable to RAP presence in binder blends, bands area for OH, C=O, and S=O function- alities were first valley-to-valley integrated within the limits (a) (b) Figure 3.21. Comparison of ATR FTIR spectra of neat and RAP-extracted binders and their 60/40 blend (1).

32 shown in Figure 3.23. The individual integrated areas of the oxidized functionalities were then normalized to the sum of all band areas to calculate individual oxidation indices (1). A similar approach was implemented to a quantitative analysis of the RAP-modified HMAs. The only difference was associated with using SiO absorption band instead of S=O band because of their large overlap. Figure 3.23 sup- ports justification of such an approach by showing a steady increase in OH, C=O, and SiO absorption intensity with an increasing RAP content in HMA. On the basis of the multiple correlation analysis of the oxi- dation indices against RAP content (C_RAP), two best-fit linear models with a similar goodness of fit (R2 of 0.97 to 0.98) were developed. The first model (Equation 3.2) where only the sulfoxide index (ISO) is used for prediction yields slightly better standard error, while the second model (Equa- tion 3.3) accounts for all major oxidation products using sum of hydroxyl, carbonyl, and sulfoxides indices (IOH+ ICO+ ISO) as a predictor. The two models produced similar standard error of 5% to 7%. C RAP SO_ . . ( . )= − +0 236 0 400 3 2I C RAP OH CO SO_ . . ( . )= − + + +( )0 095 0 190 3 3I I I The evaluation of the effect of RAP content on the oxida- tion level in RAP-modified HMA samples revealed significant deviation from the linearity and higher variability for car- bonyl index. Nevertheless, the correlation analysis suggested both carbonyl index and its combination with silicate index as an independent variable being the best candidates for pre- dicting RAP content in HMA. The linear prediction models in Equations 3.4 and 3.5 yielded R2 values of 0.72 and 0.86 with standard errors of 15% and 11%, respectively. C RAP CO_ . . ( . )= − +0 191 1 117 3 4I C RAP CO SiO_ . . . ( . )= − + +1 48 0 76 0 025 3 5I I Two reasons would explain a lower agreement in prediction models in HMA. First, a much higher standard error for HMA data as compared with binders’ data is mostly governed by nonuniformity of replicate samples because of variation in particle size. Second, there can be a lack of interaction between binder adsorbed to RAP particles and the virgin binder. In summary, it can be recommended to use ATR measure- ments of the IR absorption oxidized functional groups in RAP binder blends to predict RAP content in the field samples using the following step-by-step procedure: Step 1. Extract binder from a representative pure RAP sample. Step 2. Obtain a representative sample of a virgin binder. Step 3. Perform ATR measurement and calculate OH, CO, and SO indices for both virgin and pure RAP binder samples as described above and elsewhere (1). Step 4. Determine intercept and slope of the calibration line from the plot of sum of oxidation indices versus 0% and 100% RAP content. It should be noted that it is necessary to have a pure RAP sample for developing concentration model. Furthermore, it is understood that a given model is applicable only for a given RAP source. Finally, it is found to be feasible to detect elevated oxidation level in RAP-modified HMAs; however, the quanti- fication of RAP in HMA based on the ATR measurements appears to be impractical. Reliability of portable Spectroscopic Measurements The repeatability and reproducibility of test results or the most successful material–method combinations were evaluated in both laboratory and field environment. The evaluation of (a) (b) Figure 3.22. Typical ATR FTIR spectra of 80 wt% RAP-modified HMA mix (1).

33 (a) (b) (c) Figure 3.23. Integration limits for (a) hydroxyl (AROH), (b) carbonyl (ARCO), and (c) silicate/sulfoxide (ARSiO) absorption bands (1).

34 repeatability concerned the variation in measurements taken by a single operator or instrument on the same item and under the same conditions. The reproducibility of test results was judged by the level of variability in the results measured by independent operators on the same equipment. The repeat- ability was measured by the coefficient of variation (COV) in the absorbance of the primary components (major peaks) between the probes produced by one operator. The reproduc- ibility was evaluated by COV in mean absorbance between the independent operators who tested the same material. It should be noted that because of the schedule constraints, only a lim- ited number of materials were included in the repeatability and reproducibility study, as summarized below. The main findings of the variability study are separately discussed for portable ATR and XRF/XRD instruments, while the details are provided in Appendix P. Variability in Attenuated Total Reflectance Results The first round of ATR testing indicated that repeatability of FTIR results for pure materials and components and simple compounds (i.e., those materials that can be easily finger- printed) was not an issue. The repeatability of the FTIR results for the materials and components of known composition was high, with variation not exceeding 5% of the absorption peak intensity. This did not apply to complex mixtures where phase separation was possible or the concentration of additive was extremely low. The effect of difference in sample preparation was also a concern. Therefore, the second round of testing in the repeatability and reproducibility study concerned com- posite materials, such as structural coating systems, pavement markings, portland cement concrete with admixtures, and polymer-modified binders. All those products were prepared in the lab according to the proportions as summarized in Table 3.8. More details on the variability in ATR measure- ments on particular materials are provided in Appendix P. The conclusions from the variability study follow. Epoxy Paints On the one hand, as shown in Tables P.2 and P.3 in Appendix P, repeatability (within-variation) of the ATR results for epoxy paints was comparable with their reproducibility (between- variation) and remained within 3% to 10% for major paint components. On the other hand, the within-variation in solvent-associated IR absorption could reach 25%. Further- more, no difference between within-variations and between- variations suggested that no operator dependence was a factor of variability in the ATR measurements on liquid paint sample. It was noted, however, that the variation in the pressure applied to a sample placed on the ATR crystal before scanning signifi- cantly affected the absorbance values obtained for spectra of hardened epoxy-based pavement markings. This could be explained by the stiffness of the epoxy film preventing full con- tact between the sample and ATR crystal, thus reducing the Table 3.8. List of Materials Tested by ATR FTIR in the Reproducibility and Repeatability Study Material Category Brand/Material Name Composition Material State Test Objective Structural coatings Carbozinc 859 2 PartA:1 PartB: 10 Filler Powder Reproducibility study Scotchkote 1 PartA:1 PartB Solid Reproducibility study Pavement markings 3M White 100% Ready Liquid Reproducibility study Epoplex LS50 Yellow 2:PartA:1 PartB Solid Reproducibility study PCC with admixtures Lafarge Type 2 cement/local aggregates/AIR 200/Eucon Retarder 75 8.0% water 17.0% cement 31.9% stone 35.2% sand 0.2% AIR 200 Wet mix Repeatability study Lafarge Type 2 cement/local aggregates/Eucon Retarder 75 8.0% water 17.0% cement 31.9% stone 35.2% sand 0.3% AIR 200 Wet mix Repeatability study Reproducibility study Polymer-modified asphalt binders PG 64-22 modified by Kraton SBS PG 64-22 East + 1% SBS PG 64-22 East + 3% SBS PG 64-22 East + 6% SBS PG 64-22 West + 1% SBS PG 64-22 West + 3% SBS PG 64-22 West + 6% SBS Viscous solid Repeatability study

35 signal intensity. This observation was reflected in developing a test procedure for pavement markings by recommending of the use of pressure applicator with solid samples as a general rule for ATR testing. Portland Cement Concrete with Chemical Admixtures The coefficient of variation for three replicates of air-entrained PCC prepared in the same proportions varied between 10% and 40%, as shown in Tables P.4 and P.5 in Appendix P. This was eventually attributed to the nonuniform water content in the samples, nonhomogeneity of PCC in general, and extremely low (0.4 to 0.5 wt%) concentration of an additive within a sample. It was also found that the variability in the concentration of major absorption bands was inversely pro- portional to the concentration level. In spite of a similarly high level of variability in ATR measurements on the field samples, the identification of presence of high-range water reducer and nonchloride set accelerator in the fresh PCC samples still was possible. Polymer-Modified Asphalt Binders The case of polymer-modified binders represented more homogeneous mixtures. Consequently, the variation in the concentration of the major component (binder) as mea- sured by the ATR FTIR did not exceed 5%. However, the variation in oxygen content (ketones and sulfoxides) and polymer content (SBS) reached 30% (see Table P.6 in Appen- dix P). It was also found that the variability in the signal associated with additives and functional groups increased proportionally to their concentration in a sample. This phenomenon can be attributed to the nonuniform oxida- tion during the storage of binder samples. Another reason could be a nonuniform distribution of the polymer net- work within the binder phase, which may occur because of differences in sample preparation. On the basis of the analysis of variability in ATR measure- ments in this study, it can be concluded that repeatability of the results within the same batch or sample of a simple com- pound is not a concern. However, sample preparation and handling are the main factors of the variability in the ATR results obtained from different samples of a complex mixture. Therefore, while definitely being suitable for fingerprinting pure materials and simple compounds, the ATR FTIR spec- trometer cannot be positively recommended for quantitative analysis under the field conditions. Variability in X-Ray Fluorescence Results A two-step approach was adopted for the analysis of vari- ability in XRF measurements. Single measurements were first employed to establish proof-of-concept that XRF can yield measurable results for each material. When an element was detected in prominent concentrations that would not likely have interferences from other field materials and were significantly higher than the method detection limit, XRF was considered a promising QA/QC method. In the next step, 10 measurements were obtained for each material to determine the precision of the method. Because the por- table XRF device owned by the research team was deemed to be successful to different extents in the evaluation of epoxy structural coating systems and pavement markings, only the results for these materials are summarized below. A more elaborate discussion of the XRF results is provided in Appendix P. Several replicates of each mix were investigated for both the error associated with preparing different mixes and the variability within a single mix. The mixtures were prepared in the laboratory in accordance with manufacturer guidelines (see Tables P.7, P.9, and P.11 in Appendix P). Next, 10 probes from a sample batch were compared to establish mean and standard deviation in concentration of major metal oxides. Both soil and mining modes produced highly repeatable measurements (within 5% variation of mean), of Ti for epoxy paints as shown in Tables P.10, P.12, and P.13 in Appendix P. Field measurements on white and yellow pavement markings prepainted on the asphalt surface yielded slightly higher but still acceptable standard deviation of about 11% of the mean Ti content (see Tables P.2 through P.5 in Appendix P). In conclusion, the portable XRF owned by the team produced highly reliable results for heavy metal content in metal-based paints. Portable Versus Stationary Results One objective of the laboratory phase of the experiments in this project targeted the comparison between portable and station- ary spectroscopic instruments. The instruments were compared for detection limits and method precision. Two spectroscopic methods for which both portable and stationary equipment was available were infrared spectroscopy and X-ray diffraction technique. The most important findings follow, while more details on the comparison between portable and stationary IR and XRD measurements are provided in Appendix P. Portable Versus Stationary Infrared A direct quantitative comparison of the FTIR spectra produced by the portable ATR FTIR and stationary transmission IR spec- trometers was not possible because of the differences in tech- nology and sample preparation. Nevertheless, the qualitative assessment of the absorbance spectra produced by both meth- ods revealed that both devices identified major absorption

36 bands for a given material at the same wavelength (see Fig- ures P.1 and P.2 in Appendix P). Note that two types of sam- ples, liquid paint and solid binder, were evaluated. Therefore, it was concluded that the portable ATR FTIR spectrometer is capable of producing at least the same quality of IR spectra as the stationary IR spectrometer. Portable Versus Stationary X-Ray Diffraction Samples of crystalline materials such as portland cement, mineral aggregates, and ready-mixed concrete were tested by portable and stationary XRD instruments. The spectra of these samples are compared in Appendix P in Figures P.3 through P.8, while the quantitative results are summarized in Tables P.16 through P.21. It appeared that the stationary XRD equipment provided better results for resolution then the portable XRD, especially when longer scanning times were employed. Nonetheless, the portable instrument was successful in identifying all major phases qualitatively. The quantitative analyses yielded some discrepancy between the stationary and portable equipment but remained within reasonable error. The largest obstacle would be that the software statistics showed that the portable XRD equipment had a signal-to-noise ratio too low to trust the numerical goodness of fit. Therefore, the investigation of heterogeneous materials, such as natural aggregates and concrete, showed that it is not practical to apply the XRD method in the field for QA/QC purposes. Field Verification of Laboratory Results This section briefly summarizes the outcomes of the final phase (Phase 3) of this project: field verification of the labora- tory results. It describes the scope of work and provides the conclusions. The full report of the field verification phase can be found in Appendix Q. Objectives and Scope The main goal of field experiments was to verify the applica- bility of portable equipment identified as successful in labo- ratory to the testing of construction materials in field conditions at a level of quality that satisfies current QA/QC criteria. Effectively, the following were the objectives for field experiments in Phase 3: • Conduct field testing to demonstrate that the spectroscopic techniques recommended in Phase 2 can be transferred to field application. • Document all test procedures and protocols for the suc- cessful techniques and applications. • Recommend reasonable modifications to the equipment for improved implementation of the technologies. Table Q.1 in Appendix Q summarizes project types, locations, and labor and equipment details for the field experiments conducted in Phase 3. Field Experimental Protocol The portable devices recommended for field verification were the Bruker ALPHA spectrometer with a single-reflection diamond ATR accessory, the Innov-X Alpha XRF analyzer, and RTA’s Fourier transform Raman spectrometer. These instruments are described in detail in Appendix A. The field setup for the three devices included using an independent power source (built-in for Raman and XRF and external battery for ATR). The Raman analyzer was equipped with an extended 5-m-long probe, which allowed for taking mea- surements directly from the surface if needed. Typically, the ATR and Raman spectrometers were set in the trunk of a minivan and connected to a laptop and an external bat- tery. The XRF instrument with a built-in personal digital assistant was used in the handheld mode by attaching the scanner to the tested surface. As a rule, no sample preparation was necessary for any material except using DCM solvent to extract PMB from HMA. The ATR sampling mode was used for substances in liquid, thin film, or powder form, such as paints, chemical admixtures to PCC, asphalt binders and emulsions, and cement mortars. To obtain spectra for those materials, several drops of a liquid or approximately 0.5 g of a solid were placed on the ATR sam- pling plate and 24 co-averaged scans were collected at a resolu- tion of 4 cm-1. In the case of thin films and powders, pressure was applied to the sample to ensure full contact with the ATR prism surface. The portable Innov-X Alpha XRF analyzer owned by the team was used for testing traffic paints in field applications. Exchangeable alloy, soil, and mining measurement modes allowed for the detection of typical heavy metal concentra- tions in both liquid (laboratory tested) and solid (in situ tested) paint samples. To obtain concentration quantities, cured pavement markings were tested by applying the XRF instrument to the surface and collecting data over 90-s time intervals. Liquid paint samples were collected from the tank and tested in the laboratory (on arrival from the field) in their as-received state by placing 15 to 30 g of each sample in an XRF sample holder. Field measurements of Raman spectra of traffic paints, curing compounds, and chemical admixtures to PCC were recorded using RTA’s Fourier transform Raman spectrometer operating at 1,064-nm laser excitation at 500 mW. Resolution was set at eight wave numbers (cm-1) for all collections. Col- lection was performed using RTA’s FTIR software operat- ing in continuous collection mode. A 5-m, steel-jacketed, fiber-optic probe was used for collection. Given the poten- tial interference of ambient light, spectral analysis consisted

37 Table 3.9. Summary of Portable Equipment Evaluation Featurea Target Value FTIR Raman XRF XRD Accuracy Minimum 1% <0.5% <2% <1% <1% Goal <0.5% Duration of measurement Maximum 1 h ∼1 min ∼1 min 6–12 min 15 min Goal ∼5 min Effort involved Maximum 1 person 1 person 1 person 1 person 1 person Goal 1 person Amount of prior training Maximum 1 day 1 h 1 h 1 h 1 h Goal 0.5 day Reliability Minimum Depends on material (90%) 99% (software failure) Depends on materialc 99% (software failure) 99% (software failure) Goal 95% Time to get results Maximum Depends on construction process (1 h) ∼5 min ∼5 min ∼5 min ∼5 min Goal ∼5 min Price range Maximum $50,000 ∼$25,000 ∼$60,000 ∼$37,000 $45,000 Goal <$20,000 Device weight Maximum 50 lb ∼16 lb ∼20 lb ∼4 lb (handheld) ∼15 lb (benchtop) ∼27 lb Goal <20 lb Sample preparation Maximum Solvent As isb As isb As is (liquids) pulverization (solids)b Crushing (solids) Goal As isb a Accuracy: Agreement between a measurement and the true or correct value. Duration of measurement: Time between start and end of testing cycle. Effort involved: Personnel required to perform the test. Amount of prior training: Time required to make personnel familiar with a testing procedure. Reliability: Unlikelihood of equipment failure during the test. Time to get results: Time between the beginning of the sample preparation and the end of the analysis of the test results. Price range: Cost of the equipment. Device weight: Mass of the equipment including the case or enclosure. Best time for QA/QC: Stage of the manufacturing and application process when the test is most timely. Sample preparation: Processing and manipulating the material before the test. Minimum and maximum: Acceptable threshold value from the user perspective that given equipment should produce. Goal: Desirable target value from the user perspective that given equipment should produce. b Pulverization of granular materials (aggregates) is required for better quality. c Failure to get the signal for fluorescent materials or because of thermal emission.

38 of first evaluating those contributions and determining the appropriate background removal techniques to yield spectra consistent with those of controlled laboratory conditions. Summary of Field Results A summary of the field results follows. 1. On the basis of the results of the field verification experi- ments, it can be concluded that, predominantly, the exper- iments conducted in the field phase of this project verified the methodology and reproduced the results similar to those in the laboratory phase. 2. Specifically, the compact ATR FTIR spectrometer, handheld XRF instrument, and RTA’s Raman analyzer were successful in the identification of chemical structure, or fingerprint- ing, of both simple and complex organic compounds, such as epoxy coatings and adhesives, curing compounds, and waterborne traffic paints. 3. Furthermore, such complex composite material as PCC yielded meaningful ATR absorbance spectra, which allowed for the identification of chemical admixtures in fresh mix samples, provided their concentrations were higher than 0.5 wt%. 4. Verification of polymer presence in asphalt binders and emulsions was possible using the ATR FTIR spectrometer. While identification of polymer in an HMA mix presented a challenge, the fast binder extraction procedure in the field with using DCM solvent appeared to be a feasible alternative to direct evaluation of polymer-modified HMA. 5. Although successful in fingerprinting pure materials, RTA’s Raman analyzer demonstrated some safety issues, due to potential damage to the operator’s eye by open laser light beam and issues with handling the Raman probe when not in the collecting mode. Summary of technical performance of portable Instruments This section summarizes the results of the technical evalu- ation of the portable spectroscopic devices. The evaluation concerned the ability of portable FTIR, Raman, XRF, and XRD devices to comply with qualitative and quantitative requirements of field QA/QC procedures. The qualitative and quantitative requirements were accuracy, time, and labor involved in testing; level of training required; and other parameters. These requirements were established in the pre- liminary phase of the project based on the feedback of the professionals who participated in the workshop organized by the team. Table 3.9 compares the actual parameters achieved in the laboratory and in the field with the target values. As shown in Table 3.9, all devices evaluated in this study comply with the previously established technical cri- teria, suggesting that the team chose the equipment cor- rectly. However, final recommendations for the use of these instruments are based on their success in producing reli- able and interpretable results that can be used for QA/QC purposes on a daily basis. Reference 1. Yut, I., and A. Zofka. Spectroscopic Evaluation of Recycled Asphalt Pavement Materials. Presented at 91st Annual Meeting of the Trans- portation Research Board, Washington, D.C., 2012.