Beam-hardening correction method for quantifying moisture content in cement paste based on X-ray radiography

Abstract

The X-ray spectrum changes while traveling through specimen, and this phenomenon, known as the beam-hardening effect, breaks the linear relationship between the intensity variety on radiographs and material thickness. In the detection of water transport in cement-based materials, this effect leads to inaccurate results of the quantitative moisture distribution inside the sample, and it is difficult to eliminate this effect by gravimetric calibration. To solve this problem, this paper proposed a calibration strategy for the attenuation coefficient curve of cement-water two-phase specimens, and provided a heuristic mathematical model for fitting the 2D attenuation coefficient surface of cement paste specimens. The experiments showed that for zones close to saturation, beam-hardening leads to an overestimation of moisture content, while for a zone with a low water content, the X-ray radiography results without correction tend to underestimate it. After correction, the method showed a quantitative result close to that of the gravimetric method, and maintained a good stability in samples of different thickness.