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61 CHAPTER 4 Field Evaluations of CLSM Introduction Long-term strength gain/excavatability Short-term strength gain/constructability This chapter summarizes the studies on the field perfor- Corrosion of metals in CLSM mance of CLSM and the use of the data collected and experi- Productivity and cost (especially relative to compacted fill) ence gained to validate and improve upon the test methods, Resistance to freezing and thawing specifications, and guidelines developed in the laboratory Construction issues (i.e., floating of pipes) portion of the study. An overview of the research approach Settlement and objectives is provided, followed by discussions on the Use of by-product materials studies performed at six field sites throughout the United Environmental issues States. Lastly, some of the main findings of the overall field Permeability (for various reasons, including drainage and efforts are presented. leak detection) After identifying the key unresolved technical issues re- Research Approach garding CLSM and selecting agencies to participate in the The key deliverables of this research project will be useful field testing, the research team developed a field testing pro- only if they are eventually applied in the field. Thus, a com- gram, as shown in Table 4.1. This program encompasses the prehensive field testing program was included in the latter most important technical issues and includes the CLSM ap- stages of this project, which aimed to gain insight into specific plications relevant to this project. More emphasis was placed technical or practical issues regarding CLSM. The objectives on the most common CLSM applications, such as backfill, of the field testing plan included the following: whereas less emphasis was placed on less common applica- tions, such as bridge approaches. The test matrix shown in Close the gap in understanding of CLSM by addressing key Table 4.1 captures the main technical issues and addresses several common interests with the field testing partners. Un- research needs Assess applicability and efficiency of test methods devel- less otherwise noted, the test methods, specifications, and guidelines developed under this project were implemented in oped in laboratory the various field tests. Assess appropriateness and validity of test methods, specifi- The researchers recognized from the onset of this field test- cations, and construction guidelines developed in labora- ing program that not all of the long-term data (e.g., corrosion) tory and through a synthesis of current practice would be generated or collected during the finite duration of this project. However, they attempted to generate and synthe- Field Testing Plan size as much relevant data as was feasible; in some cases, field tests were continued beyond the completion of this project Several technical issues were identified in the early stages and will be monitored and evaluated through research collab- of this project as requiring significant attention in the labo- orations formed as part of this project. This information, ratory portion of this project; some of these issues were fur- when available, will be presented to the relevant AASHTO ther deemed to be important enough to address in actual committees for review and possible inclusion in future CLSM field trials: construction.