Over recent years significant emphasis has been placed on the use of recycled products in highway and construction materials. Waste materials, such as tire rubber, plastic, and glass may be used with conventional materials either as aggregate replacement or binder enhancement. For portland cement concrete, rubber from granulated tires may be used as an elastic aggregate modifying the brittle failure of concrete and increasing its ability to absorb higher amounts of energy before failure. The replacement of coarse aggregate with rubber particles may significantly compromise strength characteristics of concrete due to the high compressibility of rubber particles, generating localized stresses and bonding problems between the rubber particles and the cement matrix. To the contrary, the use of fine graded rubber as partial replacement of fine aggregates may produce a ductile behavior with large deformations prior to full disintegration of concrete and affect to a lesser degree the strength loss.
An experimental study is being conducted to evaluate the effects of incorporating crumb rubber, very fine tire rubber particles, into Portland cement concrete. The objective of the study is to evaluate the effects of rubber aggregate into portlant cement concrete (PCC) properties. Initially, the rubber content replacing fine aggregates into the concrete mix was investigated by examining the concrete failure characteristics and the amount of energy absorbed during testing. The destructive testing results of the rubber-filled concrete were then coupled with nondestructive testing (NDT) evaluation. The scope of this effort was first to use a well-accepted NDT method for evaluating this specific PCC type, and second, to correlate strength and static elastic modulus to parameters evaluated from the dynamic NDT testing. These relationships may be used for estimating concrete strength and static elastic modulus from NDT results. Nondestructive testing techniques are relatively simple and quick to perform and provide the advantage of using the same samples again and again. NDT techniques are also of particular value in quality control testing.