Читать книгу Monument Future - Siegfried Siegesmund - Страница 348

Controlled structural impregnation and consolidation of porous materials require a reliable technique that enables the assessment of consolidation effects, especially the penetration depth of consolidating agents.

Consolidation effects are typically tested on specimens extracted from the treated bodies in the form of drilled cylindrical cores or cuboids cut from the object. The specimens are further cut into thin slices beginning at the treated surface and continuing along the depth. The slices are then tested using destructive methods – typically as discs or short beams loaded in bending (Drdácký & Slížková 2008). The determined strengths indicate changes in mechanical characteristics of the treated material along the depth.

The individual specimens are also suitable for non-destructive laboratory investigation of the penetration depth of consolidants using ultrasonic measurement in the transmission mode (Sasse & Snethlage 1996).

Such monitoring should ideally be performed during the consolidation process, i. e. after each impregnation cycle. It is practically impossible, however, to cut samples from an object after each treatment cycle.

A semi-destructive method that exploits the measurement of resistance to drilling is also used for in-situ testing of stone, but the specific character of the method prevents repeated application at identical points, and the monitored data is thus 234unreliable due to the heterogeneity of the tested material. Ultrasonic measurement, on the other hand, can provide integral information across a larger domain of treated stone objects, and the monitored data is less sensitive to small-scale heterogeneity within the material.

This paper introduces a new portable ultrasonic double-probe for recording changes in material properties along a depth profile and assessing consolidant penetration depth.