CRACK HEALING OF EARLY AGE CRACKS IN CONCRETE

Abstract

A combined experimental and numerical study is performed on crack healing in hydrating concrete. The aim of the research is to investigate under which conditions cracks that are formed in concrete at very early age can heal again when the cement hydrates further. To study this phenomenon, three-point-bending tests are performed on prismatic concrete specimens at early age to create cracks with a specified crack opening. After the test the specimens are matured further under water with and without compressive loading to close the cracks. Several weeks after the first test the specimens are tested again to investigate the amount of healing and further development of mechanical properties. From the tests it can be concluded that the mechanical properties of the concrete are recovered to a large extent for cracks made after 1 day of hydration, loaded in compression afterwards and healed under water. This is the case for concrete with both BFSC and OPC. If the degree of hydration of the specimens is higher at the moment of cracking, the strength gain is less. A numerical study is performed to investigate the mechanism of self-healing. The results of the simulations indicate that ongoing hydration is responsible for the crack healing observed in the tests.