Flexural Tests on Consolidation Effects on Stone

This paper describes laboratory verification tests for determining the efficiency of various consolidation treatments on Czech quartz sandstone. It compares material data acquired using circular discs and rectangular plates. While the application of rectangular plates enables the testing not only of strength but also of other material characteristics – e.g., moisture, water saturation or temperature dilation parameters – on identical specimens, the biaxial bending easily applicable only for mechanical testing gives data better describing material unisotropy. At the same time the influence of two different modes of consolidation agent application was taken into account – namely, capillary rise and brushing, which is typically used in conservation practice. Furthermore, cylinders and cubes were treated with the consolidation agents in order to determine their depth penetration ability. After maturing, the cylinders and cubes were cut into thin slices after being tested with ultrasonic measurements to determine differences in wave velocity across the specimen along the depth profile of the treated bulk. The experimental data were compared to ultrasonic tests as well as theoretically computed strength, for which a FEM model was used in the case of biaxial bending. Differences in consolidation effects are also discussed in relation to the chemical characteristics of the applied consolidation agents which were based in the case under study on ethylsilicate compounds and thus produced various amount of acting SiO₂ gel inside the porous system. Both techniques were found to be useful in the testing of consolidation agents being developed before their introduction into conservation practice.