Summary:

Forest communication network consists mainly of dirt roads. Acute technical problems with forest roads occur especially for these dirt road which are constructed on cohesive topsoil. Lignite fly-ash may be utilized for successful stabilization of cohesive topsoil dirt roads. Under heavy loads the pavements stabilized with fly-ash often perform unsatisfactorily and as a result failures are noted. The aim of research described in this paper was to develop technical solution for reconstruction of road pavements constructed with admixture of fly-ash and fly-ashslug respectively. Bearing strength variability of fly-ash-soil and fly-ash-slag-soil mixes after failure were considered The mixes crushed then re-compacted with addition of stabilizer as influenced by period and conditions of setting were tested. The stabilizers utilized for the test were both active fly-ash of lignite group IIIC acquired from Konin mining region and coke blast furnace slag. Two kinds of mixtures were tested. These were sandy clay mixed with addition of 14 % lignite fly-ash and the mixture of 10 % lignite fly-ash and 10% furnace slag respectively. The samples were crashed and re-compacted after 14 and 42-day period of curing in optimal and air-dump conditions. After sample curing bulk modules were measured with the utilization of VSS press. This procedure was the basis for assessment of mixture suitability for reconstruction of forest road pavements after failure. Higher bearing performance especially after air-dump curing occurred for sole fly-ash admixture. The technical guidelines for reconstruction of road pavements with utilization of re-used crashed pavement materials were developed. The clayey pavements after failure may be stabilized again in fortnight period after construction. The repair procedure includes re-compaction with adding of water to achieve optimum moisture. In addition, the doses of optimum stabilizer content for the longer than forthright period since road construction were identified.