Application of recycled tyre cord in concrete for shrinkage crack control

Abstract

Recently, there has been rauch attention focused on the rapidly deteriorating infrastructure. The main cause of the decay of infrastructure is the deterioration of the materials used in the construction and repair of the structures. In many types of infrastructure, such as highway and airport pavement, cracking behaviour is the most important factor for the determination of durability and lifetime of structures. For example, the control of the crack spacing and width is the main design criterion in continuously reinforced concrete pavement [1]. This type of cracking behaviour is related to environmental strain due to either dry shrinkage or thermal change in concrete structures with restrained boundary condition. Such shrinkage-induced cracking is very common in concrete, especially for large surfaceto-volume ratio structures such as highway pavement, slabs for parking garages, and walls [2]. Cracking can cause several problems in a reinforced concrete structure: durability problems related to the corrosion of rebars, spalling of structure surface, and increased permeability through the cracks, etc. Thus, the control of the shrinkage cracking behaviour in cementitious materials is considered an important factor for long-term structural performance. In the past, research was conducted on the shrinkage behaviour of ordinary concrete and reinforced concrete structures. Recently, attention has focused on fibre reinforced cementitious composites [2-5]. It was found that the effect of discrete fibres is to reduce shrinkage cracking rather than reduce free shrinkage, although 10-25% reduction in free shrinkage in cementitious composites having steel fibre reinforcement has been reported [6, 7]. Shrinkage cracking can, as expected, be significantly reduced by increasing the fibre volume fraction in cementitious composites [8]. In the above mentioned studies of shrinkage behaviour of fibre reinforced composites (FRCs), all composites were reinforced with various types of new virgin fibres including polypropylene and steel. Data on the shrinkage properties of concrete reinforced with recycled waste fibres are not available. Many industrial wastes can be recycled and utilized in building and highway construction. At present, most of these wastes are disposed of in landfills, which is of great environmental concern. For example, about 275 million used tyres are disposed of annually, and 3 billion used tyres have accumulated in waste piles across the United States [9]. No efforts have been made to reuse recycled tyre cord (such as nylon, polyester, and Kevlar), however,