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OCR for page 85
85 (a) (b) Figure 4.26. Placement of CLSM into the trenches. nectors attached to the lid of the smaller boxes for extra pro- chlorides, the sites were graded with a motor grader to have a tection and ease of measurement. Connectors in each box are slope of 2 percent. Figure 4.28 shows the general site layout for labeled with numbers 1 to 8. The connectors from 1 to 4 were one of the test sites. attached to the galvanized corrugated steel culverts, starting from the closer end of the trench to the box and connectors 5 Testing Program to 8 were connected to the ductile iron pipe samples. Connec- tors were attached to the counter electrodes of pipes 1 and 8. The flow (ASTM D 6103) and air content (ASTM C 231) of Figure 4.27 shows one of the PVC boxes and connectors. the CLSM delivered to the test site were measured prior to Before the placement of the pipes, the research team planned backfilling the trenches. Cylinders (100 150 mm) were cast to to expose three of the six trenches on each site to chlorides. measure the compressive strength at 4, 7, and 28 days. Samples Therefore, to prevent the chlorides from flowing with rain- were capped with plastic lids after casting. One day after water to the trenches that were not supposed to be exposed to casting, cylinders were transported to a fog room (22C and 98 percent RH) to be held until testing. Compressive strength testing was performed using neoprene pads and displacement- controlled testing equipment. The setting times of the CLSM mixture in the condition I trenches were measured using a needle penetrometer with a 6.45 mm2 needle tip. After backfilling was complete, the location of each piece of pipe was marked using flags. An average of 10.75 kg/m2 sodium chloride was applied to the chloride sections of each site. After the application of chlorides to the backfilled testing sites, half- cell potentials were collected as an indicator of corrosion of the embedded metallic pipes. Half-cell potentials were collected using a coppercopper sulfate (Cu-CuSO4) electrode and a high impedance multimeter. To measure the half-cell poten- tial of a piece of embedded pipe, the electrode was placed on the soil or CLSM surface above the pipe sample, after the multimeter was connected to the corresponding connector in the PVC box. To be consistent, the electrode was placed next Figure 4.27. PVC connection box and connectors. to the identifier flags on the surface identifying the location of