Untreated Wood Ash as a Structural Stabilizing Material in Forest Roads

• Main Authors: Karl Stampfer, Gerald Bohrn
• Format: Article
• Language: English
• Published: University of Zagreb, Faculty of Forestry 2014-01-01
• Series: Croatian Journal of Forest Engineering
• Online Access: https://hrcak.srce.hr/file/177903

Due to the euphoric use of »green« energy produced by biomass power plants, up to 350 000 tons of ash are accumulated as a waste product every year in Austria and the estimated costs for landfilling are 1.7 million € per year. For this reason, methods must be found for the utilization of wood ash. One solution is to use it as a stabilizing material in forest roads. The pozzolanic characteristic of ash is used to bind the gravel in the road base. Wood ash is expected to reduce the need for gravel on forest roads and at the same time to enhance the load bearing capacity of forest roads. Two different untreated wood ashes were used in two mixture ratios, each on a 50 meter long forest road section, to investigate the load bearing capacity. The ashes were selected by their different properties: high lime and low heavy metal content, production of ashes in Austrian biomass power plants with various furnace technologies and disposal costs. Mixing depth was 0.50 m and the road base was covered by a 0.10 m thick surface layer. Elastic moduli of these sections were measured before the application, and repeated monthly by using a light falling weight deflectometer. After the first vegetation period, the mean elastic modulus of the sections mixed with dry bed ash showed an improvement. The increase of the initial mean load bearing capacity of 32.0 MNm-2 was 65% for 15/85 mixture and 76% for 30/70 mixture. The results for the fluidized bed ash sections fell short of expectations. Only 95% of the initial value could be reached for both mixing values.