Examination of the infrared spectra of synthetic kaolinites, with various degrees of substitution of hydroxyls by OD groups, allows a more detailed attribution of the stretching bands due to inner-surface hydroxyls of kaolinite. Among the three innersurface OH groups of the unit cell, two are nearly perpendicular to the sheet and give coupled vibrations which are responsible for the bands around 3695 and 3670 cm−1; the band near 3655 cm−1 is due to the other hydroxyl, which is lying close to the sheet.

Various kaolinites, a dickite and halloysites have been treated by DMSO in presence of D20 and subsequently washed by D20. This procedure allowed to record OD stretching bands which are due specifically to the intercalated fraction and, for the washed samples, to the fraction of the solid which has been intercalated and has subsequently collapsed.No structural difference is found between the intercalated materials prepared from the various minerals. Washing usually restores the starting mineral; however, for a non-tubular halloysite, DMSO intercalation and subsequent washing gave a product similar to kaolinite.

Due to the impact-echo defectoscopy tests of a massive block of underreinforced concrete steel bars of diameter 22 and 32 mm were detected. This fact is described in the paragraph, and results are provided through a visualization of b-scanning. The effect of a concrete cover layer and of the reinforcement diameter is clear on the sensitivity of the method. Because of various parameters of the reinforcement, impactors of a different ball diameter were employed. With a ball of diameter 12 mm, 8 mm and 5 mm reinforcement at the depth of about 50 to 60 mm was detected.KEY WORDS: Impact-echo, concrete, non-destructive testing of steel bar detection.

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This paper focuses on testing the possibility of using portable betatrons in the radiography of reinforced concrete structures of greater thicknesses. The experiments were carried out in cooperation with the Research Institute of Introscopy in Tomsk (Russia).