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82 7000 1A 2A 1B 2B 1C 2C 6000 5000 Compressive strength (kPa) 4000 3000 2000 1000 0 0 50 100 150 200 Time (days) Figure 4.20. Unconfined compressive strength of cylinders from one night's construction (1A, 1B, and 1C) and from one week later (2A, 2B, and 2C). elastic modulus is proportional to the square root of the com- an extensive field application. The overall experience shows pressive strength. One interesting result is that the upper that rapid-setting CLSM can be an extremely useful and ver- 350 mm of the rapid-setting CLSM at bridge approach 2B was satile material for rapid construction, but also that care should significantly softer than its lower fill, perhaps because of the be taken in designing and constructing field installations, with addition of more water in the upper fill. suitable quality control/quality assurance, to ensure long-term This section summarized a laboratory- and field-based eval- performance. uation of rapid-setting CLSM for use in bridge approach applications. The study was unique in that it first involved Field Test at Texas A&M University diagnosing the cause of a failed field application of the ma- terial and then used the information and experience gained in Introduction this exercise to design a mixture that was successfully used in A comprehensive, long-term field test was performed at the National Geotechnical Experimentation Site located at the Texas A&M University Riverside Campus, which is about 18.0 Asphalt concrete Upper Fill Lower Fill 12 km west of the main university campus in College Station, 16.0 Texas. The objective of the field testing was to investigate the 14.0 CLSM strength gain, excavatability of CLSM, and the long- Modulus (GPa) 12.0 term corrosion performance of ductile iron pipes and gal- 10.0 vanized corrugated steel culverts backfilled with CLSM. It 8.0 was recognized from the onset that because of the long-term 6.0 nature of corrosion, long-term field data would be needed. 4.0 Because the site is strategic to Texas A&M University (where 2.0 all the laboratory corrosion testing was done, as described in 0.0 Chapter 3) and the research team has unlimited access to the Bridge-1A Bridge-1B Bridge-2A Bridge-2B test location, the research team anticipates that it will continue Figure 4.21. Average moduli of backfill to monitor the corrosion studies long after this NCHRP proj- and asphalt pavement measured in situ ect has concluded. This site also was unique in that it allows using SASW. for the controlled (and measured) application of chlorides to