Presumption of Moisture Content in Hardened Cement Paste by Neutron Radiography

The moisture inclination has been generated in the direction from the core to the surface neighbourhood in the concrete section so that the concrete structure may undertake the influence of the external environment under general environment. The drying shrinkage is caused by this reason, and therefore, this behaviour is one factor that concrete crack occurs. However, it was difficult to elucidate these phenomena accurately because the hardened cement paste (HPC) was measured by the gravimetric method, and an internal distribution of moisture content was averaged in current research. On the other hand, the neutron radiography is non-destructive visualization technique in which the attenuate characteristic caused by the interaction of the nucleus and the neutron (capture, scattering, and nuclear reaction) when the neutron penetrates the material used. Especially, it is suitable for the measurement of the moisture existence situation for hydrogen to show the action of strong absorption and scattering. The purpose of this research is to understand the relationship between moisture intensity (relative intensity) and the moisture content by the thermal neutron radiography on the HPC specimen, which adjusted to various W/C ratios and various moisture contents. Moreover, the basic data to evaluate quantitatively the distribution of moisture content in the HPC in the future was acquired. In experiment 1, the relation between the moisture content and the relative intensity was clarified by using theHPC piece set to the moisture content of 0-100%. Next, in experiment 2, the relationship between the moisture content and the relative intensity as thin-wall cylindrical specimen and column specimen was presumed based on the result of experiment 1. Moreover, arbitrary distribution of the moisture content in the section of the thin-wall cylindrical specimen was visualized by Computed Tomography technology as experiment 3. The results were obtained the value of Mass absorption coefficient of the free water, HPC of 1mm in thickness was able to be caught the decrease of the moisture content in drying process and that was evaluated qualitatively which the amount and the distribution of moisture content by the CT method.

کلیدواژه ها:

Neutron radiography ، Hardened cement paste ، Relative intensity ، Moisture content