METHODS FOR TESTING HYDRAULICALLY BOUND MIXTURES IN ACCORDANCE WITH THE EUROPEAN NORMS
Authors:   N.P. Shulgin State Road Research Institute State Enterprise, Tereshchenko Tatiana , Illiash Serhii ,   N.P. Shulgin State Road Research Institute State Enterprise
Published: May 2023

Hydraulically bound mixtures have been widely used for road building industry in base layers of flexible and rigid pavements to enhance the bearing capacity and ensure the stability of base layers when built in complicated ground-hydrogeological conditions. This article continues the cycle of publications regarding hydraulically bound mixtures, deals with an analytical review of methods for its testing and represents possibilities to choice the strategy for construction a road pavement layer from bound material. The methods for testing hydraulically bound mixtures can be divided, in general, into methods for testing fresh mixed material (the mixture itself) and those for testing bound materials. The strategy for construction a road pavement layer from bound materialcan be correctly chosen applying methods for testing fresh mixtures for workability and immediate bearing index which are not implemented in the native practice of road building industry. A value of the mixture workability represents the period of time from its manufacturing to compaction in a layer during which that layer could be re-worked, if required. In comparison with the appropriate national requirements based only on the setting times of a hydraulic binder, the workability criterion is more precise and valuable and allows to widethe above mentioned time period. Immediate bearing index (IBI) sets the mechanical stability of a compacted mixture and shall be used to evaluate the ability of a mixture layer to withstand the traffic immediately after compaction. IBI criterion is valuable while constructing the road pavement layer using slow hardened hydraulic binder or when the rapid construction technology is a matter. After implementation, these standard methods for tests of fresh mixtures will permit the improved economical performance and quality of road pavements construction. The fundamental classification of hydraulically bound mixtures is based on their mechanical strength.The mechanical properties of hardened materials, in accordance with European Norms, shall be tested in unconfined compression or in tension – direct or indirect one. The indirect tensile strength shall be determined as splitting tensile strength only. One more criterion for fundamental classification is the modulus of elasticity of hardened materials that shall be determined when carrying out the compressive or tensile testing. Given these criteria, hardened materials can be classified by one of the two substantive methods: by classes relating the compressive strength or by classes relating the relationship “tensile strength/modulus of elasticity”. In the national system of standards, the materials bound by the mineral binders are classified by complex of their compressive and bending tensile strengths. Among these methods, the classification by the relationship “tensile strength/modulus of elasticity” is the most reliable one that ensures the modeling regime closest to the performance of bound material in the pavement layer. Together with that, the method approved in the national system of standards gives the correct classification of bound materials and considers all the requirements of national building codes relating road pavements designing. Keywords: hydraulically bound mixture; fresh mixture compacity; fresh mixture workability; immediate bearing index; compressive strength; tensile strength; modulus of elasticity.