292 Improvement of Soil Properties, Bratislava on June 4 – 5, 2007 TREATMENT OF SOILS WITH THE RBI-81 AND RENOLITH ADDITIVES Milorad Jovanovski, Spasen Gjorgevski, Jovan Papic, Josif Josifovski ABSTRACT: This paper presents the results from field and laboratory testing on low bearing natural subsoil and coarse grained material for pavement layers, stabilised with additives type RBI-81 and RENOLITH. The effect of improvement of mechanical properties such as Californian Bearing Ratio, Uniaxial Compressive Strength etc is analyzed for several soil types. The methodology of testing is briefly explained. The improvement of named soil properties is 2,36 - 4 times. Adequate recommendations about possible using of additives RBI and RENOLITH, are discussed for cases of improvement of low bearing subsoil, as well as for coarse grained material which can be used in pavement layers. The favorable aspects of the treatment with such additives, as well as limitations are noted. The problem needs a close communications between Geotechnics, Geology, Chemistry and Civil Engineering experts, in order to minimize the expenses for construction of the roads and the ecological influences on the natural media. 1. Introduction During the design of traffic infrastructure, several main aspects of the natural foundational media are of primary technical and economical interest. One of them can be the problem of low-bearing capacity subsoil, which has a direct or indirect influence on the technical solution and economical impact on the project. The other one can be a problem with providing of an adequate coarse-grained material for pavement layers because of the strict technical criteria, that must be satisfied for such materials. Having in mind that the Geotechnical Department from the Faculty of Civil Engineering at Skopje, R.Macedonia, during several years worked on some road projects in the country with specific types of additives called RBI and RENOLITH, in the paper the experiences from the tests are presented. This is a relatively new technology for stabilisation of the natural soil or pavement layer of the roads, based on the reaction of the ecological stabilisers with a natural soil. In general, the following effect with treatment of the low- bearing subsoil with this stabilizer: -Decreasing of the dry unit weight, -Increasing of the strength properties, -Decreasing of the soaking of water, Finally, the effect in soil improvement is expressed in a higher bearing capacity of low bearing soil or reducing in the thickness of the pavement layers. _________________________________________________________________________________________________________________ Prof. Milorad Jovanovski, Prof. Spasen Gjorgevski, Assist. Jovan Papich & Assist. Josif Josifovski, Faculty of Civil Engineering, Skopje, blvd.Partizanski odredi N o 24,1000,Skopje,Macedonia, E-mail:jovanovski@gf.ukim.edu.mk