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The material studied was an ASTM C109 mortar [3] with a water/cement ratio of 0.485 and a sand/cement ratio of 2.75. The sand grains ranged between 300-600 micrometers in diameter. Once the sample was made it was cured for 1 day and then exposed to a 10 % solution of sodium sulfate for about six weeks. To stop further hydration and sulfate attack at a selected testing time the specimen was potted with an ultra-low viscosity resin using a two-step replacement procedure [4]. This procedure also minimizes the occurance of drying shrinkage cracking. First, the pore solution is replaced with ethanol and then the ethanol is replaced with resin. The resin was cured at 60 degrees centigrade for 24 hours. A cylindrical sample speciman, 3.5mm in diameter, is then cored from the original mortar to be scanned. Note, tomography does not require the potting procedure, as specimens could be scanned dry or wet.