Quantification of Cement Hydration through Neutron Radiography with Scatter Rejection

The unique capabilities of neutrons to penetrate materials opaque to X-rays and at the same time to interact with hydrogen make neutron radiography a technique of choice for the nondestructive quantification of hydrogen-containing substances. However, scattering rather than absorption of neutrons by hydrogen atoms can substantially decrease the accuracy of this quantification. Various post-experiment data processing techniques were developed to correct and mitigate the effects of scattering. A complementary “hardware” solution is to simply eliminate the detrimental scattering component from the detected signal through the use of neutron collimators. Compact polycapillary collimators, merely a few millimeters thick, enable accurate, high spatial resolution quantification for a wide range of neutron scattering materials. This paper demonstrates the improved quantification of water absorption with sub- 100 μm spatial resolution in 1 ×1×2 cm³ Portland cement samples. A compact polycapillary neutron collimator (2 mm thick) was used for scatter rejection in our experiments. The results of these measurements indicate that such devices can be attractive for studies where samples must be placed in quite close proximity (e.g., only a few centimeters or closer) from the neutron detector active surface.