CLASSIFICATION AND APPLICATION OF SOILS STABILIZED WITH HYDRAULIC BINDER IN ACCORDANCE WITH EUROPEAN STANDARDS

Abstract

Soils being the most widely used materials for road building industry predominantly contribute the improvement of their mechanical and/or technological properties. Relating to the world-wide experience in road building industry, the most effective method for such improvement is treatment of soils with hydraulic binder under optimum water content. Those mixtures being properly compacted set and harden by hydraulic reaction and give stabilized soils. Requirements and classification of hydraulically stabilized soils established by European standards provide wide possibilities for soils application considering their performance in pavement layers. The elaboration of Ukrainian standards identical to the European standards relating hydraulically stabilized soils should permit the elongated life cycle of pavement and also decrease expenses on repairs of road pavements caused by deformation of sub-grade. This article reviews classification and application of hydraulically stabilized soils according to the requirements of European standards. In accordance with European standards, stabilized soils are classified as hydraulically bound mixtures which properties are covered by Specifications on Hydraulically Bound Mixtures (European Standard EN 14227, Part 15). To conform the standard requirements soils should be treated by standard hydraulic binder (or a combination thereof): cement, slag, fly ash, lime, or a standard hydraulic road binder should be applied. Composition and methods of manufacturing (compaction) of specimens of hydraulically stabilized soils give several strength classes of stabilized materials with the highest category characterized by the cubes compressive strength not less than 12 MPa. European standards establish also classification of hydraulically stabilized soils by tensile strength Rt in combination with elastic modulus E; according to that classification the stabilized materials are divided into five categories from T1 to T5. European standards establish also classification of fresh mixtures by immediate bearing index. This value determines the suitability of a compacted layer to support the immediate trafficking. Nevertheless, that requirement may not cover cement-stabilized mixtures for construction of layers which are not intended to be trafficked for 7 days. The in-situ manufacture of stabilized mixtures needs some measures to minimize the inadequacy of properties of a material, or geometry of a layer such as an increased proportion of a binder or an increased layer thickness. Keywords: hydraulically stabilized soils, classification, compressive strength, immediate bearing index, construction of a layer.