Investigation of the Neutron Surface Moisture Gauge for Determining Moisture Contents of Building Materials, Plane, Thin, and Homogeneous

Abstract

Fundamental experimental investigation was done to make clear of several problems in determining surface moisture contents in 10-15cm depth of plane and homogeneous building materials by neutron surface moisture gauge.
Fast neutrons emitted by the source of radium/beryllium 5mc, are preliminarily moderated by paraffin wax, and moderated neutrons are radiated into medium in which moisture contents to be measured.
As fast neutron moderated to some extent before radiated into medium, effective measuring volume of medium is reduced, that is, effective depth is controlled to some surface thickness in medium concerned fit to measure surface moisture contents. In this experimental investigation, relations between moisture contents and thickness of samples are checked by changing the thickness of paraffin wax moderators, being moisture contents of samples kept low. Samples consist of aluminum mould boxes containing sugar and standard sand mixed to keep desired moisture contents, except concrete samples of no mould boxes.
Mixing ratio is determined by calculation based on moisture contents in one molecule of sugar.
In our determination of moisture contents in the sample of 15cm thickness and 10% moisture content, accuracy is kept within ±1.5%, taking count time 5 minutes in one measurement.