Revised Macro-cracking Criterion for Massive Non-reinforced Self-compacting Concrete Structures Under Thermal Load Based on Extensive Experimental Testing and Field Observations

The Supercontainer is a reference concept of the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS) for the post-packaging of vitrified high-level waste and spent fuel destined for deep geological disposal. The behaviour of this massive concrete structure was studied using macro-scale modelling, based on extensive experimental testing at lab-scale and validated by means of an experimental program, using realistic scale models. One of the objectives of this study was to predict and overcome possible cracking of the different cementitious layers in the container. The experimental program used half-scale models of the Supercontainer constructed in two main phases: (i) the construction of a non-reinforced concrete buffer with an inner cavity using a self-compacting concrete mixture, and (ii) the embedment of a heat-emitting source in the cavity of the buffer to simulate the heat-emitting conditions of a real overpack. This paper provides a brief discussion of the test setup used in the experimental program as well as the instrumentation, concrete mixing and the casting process during the two construction phases of the experiment. The macro-cracking criterion used to predict cracking onset and evolution in the cementitious layers is critically reviewed by comparing the simulated tangential and axial stresses in the axi-symmetrical container with in-situ experimental measurements.