NEW RESULTS ON EARLY-AGE CRACKING RISK OF SPECIAL CONCRETE

The Center of Building Materials (cbm) at the Technische Universitaet Muenchen has many years of experience in the early-age cracking risk of concrete. So far most of the investigations have been focused onmass concrete with regard to its semi-adiabatic thermal behavior—the development of uniaxial restraint stress during hardening has been determined in the cracking frame, simulating the centre of an approx. 50 cm-thick concrete. New results on the early-age cracking risk of special concretes with regard to their specific conditions or composition that is different to that of ordinary mass concrete will be shown in this paper. These special concretes are self-compacting concrete, pavement concrete, high-strength concrete and in particular ultrahigh-performance concrete with a compressive strength of up to 200 MPa at an age of 28 days. Furthermore, a test-based calculation method using the finite element method (FEM) was developed to predict, for example, the thermal restraint stress in concrete structures under various weather and curing conditions. The restraint stress distribution at any location in the concrete can be calculated realistically by applying appropriate rheological models for which “true values” of particular early-age concrete properties are required, which have to be determined experimentally.