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CHAPTER 4 Conclusions and Recommendations This chapter summarizes major findings and deliverables of the pre-implementation phase of the project and presents generic implementation plan for incorporating selected AASHTO procedures into state agenciesâ QA/QC programs. Summary This project constitutes the pre-implementation phase that follows the three experimental and pilot testing phases of project R06B. Specifically, three spectroscopic methods for specific materials classes were identified as promising for field implementation during the earlier phases of the project. These included (1) Fingerprinting of chemical admixtures (retarders, accelerators and water reducers in PCC using ATR FT-IR); (2) QA/QC of traffic paints using the Ti content as determined by portable XRF analysis as the quality parameter; and, (3) Evaluation of moisture and oxidation levels in RAP mixes using ATR FT-IR. The objectives of Phase 4 of the project were to work with two SHAs to further refine the proposed AASHTO methods developed in Phases 1â3, to conduct field tests that would further verify the viability of the methods in real field conditions, and to produce a generic implementation plan for the adoption of the methods by SHAs nationwide. The initial approach of several DOTs to identify the participating agencies showed that there were varied responses to the three proposed methods. In general, the ATR analysis of PCC admixtures was not met with interest by any DOT, including the ones that eventually participated in the field-testing phase. Existing QA/QC procedures are considered adequate and the proposed method was deemed more suitable for adoption by the chemical manufacturers or the concrete mixing plants, not state DOTs. Conversely, the response to the XRF method for paints was encouraging by practically all responding DOTs. This is because of the applicability of the method for a wide variety of materials, the apparent need for more composition-based QA/QC criteria for paints, and the user-friendly nature of portable XRF analysis. Finally, the ATR RAP testing protocol was either hailed as an essential development in the field or as completely redundant. Ultimately, Maine and Connecticut DOTs agreed to fully participate in the implementation phase of the project. The collaboration with the two DOTs proceeded in three steps. First, the draft AASHTO methods were sent to the material engineers to obtain feedback. The received comments were incorporated in the methods, and it was observed that there was no need to produce state-specific testing protocols, since the received comments were generic in nature. Thus, a single updated version of each of the draft AASHTO methods was produced. Then, samples of state-approved materials from all three categories (PCC admixtures, paints, and RAP) were obtained in order to test them in the lab and develop appropriate standards to compare against in the field. For the PCC admixtures, similar results were observed compared to Phase 3, in that highly reproducible ATR spectra could be obtained for the pure compounds. For XRF paints, initial testing showed that the Ti content was specific to the paint type and thus 21
a suitable standard has to be developed in the lab for comparison with field testing. Additionally, detection of diluted paint by water was deemed to be highly successful with this method. Testing of additional samples of glass beads, screws, and other metallic materials supplied by Connecticut DOT showed that XRF has wide applications that meet DOT needs. Finally, lab testing of RAP was performed for a wide range of RAP samples collected from three locations in Connecticut and several locations in Maine. The results from the Connecticut samples indicated that the method yielded higher water contents and increased aging in RAP collected from older stockpiles. The results from the Maine samples, for which no aging information was available, indicated that samples from higher latitudes had a lower degree of oxidation. Overall, the method was deemed successful in producing comparative results of oxidation and moisture in RAP samples. In the next stage, field tests were conducted for XRF of paints in Maine and Connecticut and for ATR for RAP in Maine. Field tests for ATR of PCC admixtures could not be arranged because QA/QC procedures could only take place in private manufacturer or concrete mixing plants, and this was outside the scope of the project. For RAP in Connecticut, the state DOT is not responsible for RAP management; thus, sampling of the stockpiles managed by the company Tilcon were sampled and tested in the lab only. The field results of the XRF analysis yielded data consistent with the lab observations, and positive feedback was obtained from the participating DOT personnel in both states in terms of the ease of handling and interpretation. An important observation was that the measured concentrations in the field were somewhat lower compared with the lab results, which is attributed to the limited thickness of the paint after it is applied and is potentially due to matrix effects. Thus, development of lab-based standards should be done under similar conditions to the expected field conditions. For RAP testing, the operation of the device was found to be straightforward according to the draft AASHTO method, while data interpretation requires some additional training that has to take place prior to going out in the field. R06B Deliverables Revised AASHTO Standards The feedback obtained from the participating DOTs in the project indicated that revisions were necessary in order to render two of the proposed AASHTOs (XRF and ATR for RAP) more user- friendly. However, no comments were received that warranted the production of state-specific protocols. Accordingly, revisions were made to the draft methods developed in Phase 3 and a single updated version of each method was prepared. These are included in Appendix A. Spectral Database for Fingerprinting State-Approved Materials A library of ATR spectra and XRF results for pure materials was created. This library can be used for the identification of those materials in the field. The database will supplement the standards developed under this project and can be potentially available online for QC/QA 22
specialists. The electronic copy of the spectral library will be provided in an electronic version together with a final version of this report. Recommendations for Implementation Recommendations for implementation are provided in the Generic Implementation Plans developed for each method separately in Appendix D. 23
