Cellulose Fibre Degradation in Cellulose/Steel Hybrid Geotextiles under Outdoor Weathering Conditions

Risks from rockfall and land sliding can be controlled by high-tensile steel nets and meshes which stabilise critical areas. In many cases, a recultivation of the land is also desired. However, high-tensile steel meshes alone are not always sufficient, depending on the location and the inclination of the stabilised slope, to achieve rapid greening. Cellulose fibres exhibit high water binding capacity which supports plant growth. In this work, a hybrid structure consisting of a nonwoven cellulose fibre web and a steel mesh was produced and tested under outdoor conditions over a period of 61 weeks. The cellulose fibres are intended to support plant growth and soil fixation, and thus the biodegradation of the structure is highly relevant, as these fibres will become part of the soil and must be biodegradable. The biodegradation of the cellulose fibres over the period of outdoor testing was monitored by microscopy and analytical methods. The enzymatic degradation of the cellulose fibres led to a reduction in the average degree of polymerisation and also a reduction in the moisture content, as polymer chain hydrolysis occurs more rapidly in the amorphous regions of the fibres. FTIR analysis and determination of carboxylic group content did not indicate substantial changes in the remaining parts of the cellulose fibre. Plant growth covered geotextiles almost completely during the period of testing, which demonstrated their good compatibility with the greening process. Over the total period of 61 weeks, the residual parts of the biodegradable cellulose web merged with the soil beneath and growing plants. This indicates the potential of such hybrid concepts to contribute a positive effect in greening barren and stony land, in addition to the stabilising function of the steel net.