Introducing Ductile Strip for Durability Enhancement of Concrete Slabs

This paper presents an experimental study on the potential applications of the fiber-reinforced engineered cementitious composite (ECC) in concrete slabs, such as concrete bridge decks and pavements. It is recognized that cracking due to concrete shrinkage and temperature gradient in the transverse direction in concrete slabs strongly influences the fatigue service life of the slabs. In the present study, attempts at localizing cracks, especially shrinkage cracks, into designated strips, where ECC material with strain-hardening and high strain capacity (up to 5%) and high fatigue crack resistance behavior is used, were carried out. As a result, while microstructure damage exists in the ECC strip, the concrete remains intact. This is demonstrated by simulating the shrinkage in concrete under restrained conditions as tensile load acting on a specially designed specimen. Experimental results show that it is possible to achieve the targeted deformation mode with a certain design on the ECC/concrete interfaces and a certain curing period on the ECC-concrete composite slab. Due to the special material properties of ECC, the strain energy produced by shrinkage (under restrained conditions) of hardened cement and temperature changes can be released by the high strain ability of ECC material so that cracking in plain concrete can be avoided. Thus, the fatigue durability of concrete slabs can be improved, resulting in a longer service life. The proposed design concept may be implemented by placing ECC as periodic special joints or “ductile strip” between stretches of concrete slabs. By replacing standard joints, common deterioration (e.g., D-cracking) problems associated with joints may be also eliminated.