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71 3A 3B 2A 1A 2B 1B Figure 4.6. Site layout with six trenches shown. Figure 4.8. Ductile iron pipes wired and capped. completely, then each of the trenches (row B in Figure 4.6) was mixture CDF1 containing the "off-spec" fly ash was used in completely backfilled with one of the three CLSM mixtures. trenches 3A and 3B. While there was no issue in placing CLSM into the trenches in row A, the pipes in the trenches in row B had to be held in Construction place by a worker to keep them from falling from their sup- The delivery of the ductile iron pipes to the site was arranged ports (wood blocks) during the backfilling. This incident by Hamilton County personnel. The ductile iron pipes illustrates the need for diligence in placing CLSM in utility (152 mm diameter) had an asphalt coating on the outside and applications, where floating or dislodging of pipes/utilities a cementitious coating on the inside. The pipes were capped can occur. Another observation was that, as expected, the to better simulate field conditions. Figure 4.8 shows ductile time required to backfill the trenches that were filled com- iron pipes being capped and wired before they were placed in pletely with CLSM was less than the time required to backfill the trenches. the trenches that had compacted sand around the pipes. After the ductile iron pipes were placed in position, the trenches were backfilled. CLSM was delivered to the site in Test Results ready-mix trucks (S10 and CDF1) and a volumetric mobile mixer (FF1). Mixture S10 was used in trenches 1A and 1B. Cylinders (75 mm 150 mm) were cast for each mixture to Mixture FF1 (flash fill) was used in trenches 2A and 2B, and evaluate their compressive strength at 14, 60, and 90 days. After CLSM CLSM 6'' ductile iron 6'' ductile iron pipe Sand pipe (a) (b) Figure 4.7. Trench cross sections (not to scale).