Moisture exudation testing of compacted soil samples is a testing requirement of ASTM D2844, AASHTO T190 and CTM 301. To perform this test, a compressive load is applied to a cylindrical, compacted soil sample until a certain amount of moisture is displaced from the bottom of the specimen. At this point, the load is recorded. This test requires a compression testing machine and a special exudation fixture (pictured below). Older exudation fixtures contain a circle of six contact points on the base plate. When contacted by water, these points will switch-on a light on the indicator box (pictured at right). Newer exudation fixtures contain an additional solid ring on the base plate and a corresponding light on the indicator box. This ring detects free flowing water coming from underneath the mold.

This test requires that the sample be compressed until either five of the six lights are illuminated or three lights and the ring light are illuminated. At this point, the load is recorded and the test is stopped. We've found that this test can be very tedious and inefficient; especially if operators need to sit idle and watch the indicator lights. In an effort to simplify the test and provide better repeatability, we developed a digital interface that allows the indicator box to communicate directly with Partner™ Testing Software. This connection allows our software to monitor the exudation condition - acting as the eyes of the operator. This means users can start a test, walk away, and prepare the next sample; Partner Software will automatically stop the test when exudation occurs and record the load.

For this test we recommend using an Industrial Series 150DX or 300DX compression-only machine, Partner Testing Software (including the GenTest module) and a moisture exudation interface assembly.

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