Feasibility Assessment of Recycled Products Use in Portland Cement Concrete
GOULIAS D and AL-HOSAIN A, Brooklyn Polytechnic University, USA
For some years municipalities are phased with the ever increasing problem of disposing recycling materials, such as glass, plastic, rubber. The discharge of these materials into expensive and continuously decreasing number of landfills generates significa
For some years municipalities are phased with the ever increasing problem of disposing recycling materials, such as glass, plastic, rubber. The discharge of these materials into expensive and continuously decreasing number of landfills generates significant pressure to communities in identifying potential applications for these waste products. Federal, State and local government, recognising this need, often promote the use of these recycled products through either incentives or mandates. The 1991 Intermodal Surface Efficiency Act, with the mandate on the tire rubber for federally funded highway projects, is one example. Today, more than 200 million passenger tires are discharged every year in the U.S., from which only a small portion is being reused. The investigation on the use of tire rubber in asphalt mixtures is being recently intensified. Tire rubber, in the form of crumb rubber and/or tire chips is being used either for binder enhancement or aggregate replacement on asphalt mixtures (Goulias et. al., 1994). The use of this recycled product in Portland cement concrete was not investigated to the same degree. In a recent study evaluating the effects of rubber particles in Portland cement concrete with traditional destructive testing, it was concluded that while rubber content reduced strength characteristics provided a more ductile failure due to the increased amount of energy absorbed by concrete cylinders (Eldin et al., 1993).
Today, several NDT methods are available for evaluating Portland cement concrete in the field and the laboratory. These methods, depending on the technique, are able to evaluate elastic parameters and properties of concrete such as hardness, resonant frequency, rebound characteristics, ability of pulse waves to propagate through concrete, and other, (Malhotra 1976). The Resonant frequency method involves the determination of the fundamental resonant frequency of vibration of concrete for determining among other, Poisson's ratio, Young's modulus of elasticity and modulus of rigidity, (dynamic modulus). Objective of this study was first to evaluate, with such NDT technique, the properties of concrete filled with different content of commercially available crumb rubber particles, and second, couple these results with data from compression testing for relevant comparisons between the parameters obtained by the two techniques.
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