Use of Stress Wave Technique to Monitor and Predict Concrete Strength Development

摘要

The feasibility of using stress wave technique, a nondestructive testing technique, to monitor and predict the strength and modulus development of Portland cement concrete was investigated. The measured quantity of this technique is the dynamic modulus of elasticity. The dynamic modulus can then be related to the strength parameters and static modulus obtained from conventional testing on the molded specimens or drilled cores. In this investigation, the laboratory tests on molded concrete specimens and cores were carried out with the simplified free-free resonant column method and the field or in-place tests on concrete elements were conducted with a hand-held device called the Portable Seismic Pavement Analyzer. In all instances, the maturity of the concrete as a function of curing time and temperature (time-temperature factor) was measured. A database, containing results from about 1000 specimens made from low, medium and high-strength concrete mixes, has been developed. Preliminary relationships between the dynamic modulus and the strength and static modulus parameters are proposed in the basis of the type of coarse aggregate. Unlike a strength-maturity relationship that is usually very specific to a particular mix under a particular curing condition, a dynamic modulus-based relationship is mainly affected by the nature of the coarse aggregate and, to a lesser extent, by other parameters such as curing condition, admixture, and water-cement ratio. The technique used in this study has shown to be a rapid, simple and very economic means for estimating the strength and modulus development of concrete and determining the time required to open a repaired or newly constructed concrete pavement to traffic.