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• In theory, the pore solution extraction follows the procedure described by Barneyback and Diamond (1981).
• Clean and dry all parts of the assembly as shown in Figure 28. Ensure that the pore solution channel connecting to the canal and to the outlet is cleaned and unblocked. Place the Base (1) onto the lower head machine and assemble the Pore solution collector (2) and the Sample Cell (3) in the order as shown in Figure 28. Align them with the axis of the universal test machine.
• Spray some lubricating agent onto the inner surface of the sample chamber (3) and the surfaces of the steel cylinder (4).
• Dry the surfaces of the companion specimen. Make crushed samples from the specimen with particles varying in size from about 5 mm to 25 mm.
• Put as many crushed samples as possible into the sample chamber in three layers. Each layer should be compacted with an appropriately sized cylinder or rod. Finally, leave a 10 mm space between the samples and the top of the sample chamber.
• Place a Teflon pad into the sample chamber on top of the crushed sample. Insert the steel cylinder into the sample chamber. Place the protective steel pad on top of the cylinder and verify that the setup is aligned with the axis of the universal test machine.
• Connect a new empty syringe to the pore solution outlet of the sample cell (3) to collect the solution.
• Apply compressive load to the cylinder through the protective pad at a moderate rate (e.g., 20-40 klb/min). Regularly check the syringe. Expel any air and reinstall if necessary. Record the load as the first pore solution drop comes out.
• Continue compression loading and pore solution collecting until no more pore solution comes out or until the load is close to the maximum safety limit (e.g., 650 klb for a 1,000 klb capacity).
• Gently unload the machine. Place the Cell (sample chamber) on two supports (e.g., concrete beams) and remove the core of compacted samples from the sample chamber by applying compressive load to the steel cylinder (Figure 29). Additional cylinders are usually needed as shown in Figure 29.
Figure 29 – Removing the compacted sample core from the sample chamber
• A minimum of 2 ml. of pore solution is needed for analysis. If necessary, more than one sample extraction can be made from the same specimen to obtain a sufficient quantity of pore solution.
• Tightly seal the syringe holding the pore solution, or transfer it into a sample bottle and tightly seal the bottle. Then place the pore solution sample in a refrigerator at a temperature between 4°C and 8°C.
• As soon as possible after the extraction, send the pore solution to a qualified laboratory for ion analysis.
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