KARSTEN

Measurement of capillary water absorption with the Karsten test tube

Introduction

A summary of the article "Determination of capillary water absorption with measuring tubes according to Karsten and Mirowski" from the book "Leitfaden Naturstein-Monitoring" [1] published by IRB-Verlag in 2011 with regard to the measuring method for estimating the coefficient w with the Karsten test tube supplemented by the mathematical background of the evaluation procedure.

The knowledge of the capillary water absorption is of great interest for the condition assessment of many monitoring objects, e.g. for the effectiveness check of a hydrophobization, for the assessment of the necessity and effectiveness of cleaning measures or for the evaluation of grouts, replacement mortars and slurries. Relevant parameters are the water absorption coefficient w [kg/(m²√h)], the water penetration coefficient B [cm/√h] and the water absorption capacity CTE [vol.-%], which are mathematically linked. They can be determined with accuracy only by laboratory measurements on object specimens of defined geometry according to relevant standards. However, destructive sampling, such as core sampling, is often unacceptable for monument objects. On the object, however, the parameters of capillary water absorption can be estimated non-destructively using the Karsten test tube.