The purpose of the present paper is to obtain a practical expression for estimating the compressive strength of concrete the nondestructive testing method combining rebound number evaluation of the -I L L .n strength of concrete members or structures. with ultrasonic pulse velocity and to discuss its applicability to Experimental investigations were carried out to examine the effects of factors such as water-cement ratio, the maximum size and volume fraction of coarse aggregate, the curing condition and age of concrete. Accuracies of the prediction expressed in concrete strength are proposed. The equations are applied for empirical formulae are examined by multiple and practical equations for estimating the evaluating the-strength distribution in a concrete column and in an existing concrete building.

During the past 40 years in-situ/non-destruc-tive testing of concrete has achieved increasing acceptance for the evaluation of existing concrete structures with regard to their uniformity, durability and other properties. This paper reviews critically the available in-situ/non-destructive tests for estimating concrete strength and for determining properties other than strength, and discusses their implications. The methods discussed for estimating concrete strength in-clude surface hardness and penetration resistance tests, pullout, ultrasonic pulse velocity, break-off, combined methods, and maturity techniques. The tests reviewed for determining properties other than strength include magnetic, electrical, radioactive, pulse echo, radar, microwave absorption, acoustic emission, nuclear, infrared thermography, and permeability methods. Some of the tests described are relatively easy to perform whereas others require sophisticated equipment and trained personnel, and there are others which are still in the development stage. Regardless of the type of test used, it is emphasized that interpretation of test data must be performed by specialists rather than by technicians performing the tests. Unless comprehensive laboratory correlations have been established between the strength parameters to be predicted and the results of in-situ/non-destructive tests, the use of the latter to predict compressive or flexural strength of concrete is discouraged.

Non-destructive concrete testing methods provide construction engineers and concrete technologists with useful tools for quality control of concrete and for evaluating the strength and durability of existing structures. This annotated bibliography, chronologically arranged, compiles literature published from 1975 to 1983 on innovations and modifications of non-destructive methods used for the testing of concrete. Attention was focused on the new methods used for monitoring concrete deterioration, crack development and corrosion of reinforcement. The journals, symposia and books selected for review have international stature, and contain state-of-art experimental works from diverse laboratories. Authors' abstracts or their translations are included when possible, to assist the. Concrete engineer in determining the applicability of a method to provide needed data. The study was made possible with a Canadian government contract awarded to the senior author.

able and First, the main test susqested appplies low air pressure to ease over time for a siven depth as a measure of the air-permeability. And hre .40, compressive strength respectively 10 MPa (1450 psi) , 26 MPa (3770 psi), and 86 MPa (12500 psi) all types of concretes having 90% The paper describes methods, theory, and port apparatus for estimating gas-permeability of concrete in situ, the users’ preliminary field experiences.the surface of the concrete, and monitors the pressure incr We present a theory of induced transient air flow in concrete substantiate the theory by laboratory measurements in qualities of concrete ( w/c-ratios 1.00, 0.55 and 0 relative humidity). We also outline field experience with The relative humidity must be monitored and, if nee corrected for. Second, other types of in-situ test applications of reveal other properties, including microcracks and porositie the outer surface layer, resistance to carbonation of concreting for a depth of down to 50 mm. The ded,gas s in the reinforcement cover, and bleeding below aggregates during

A reliable in-situ testing method such as break-off provides a more accurate estimate of the concrete strength of the structure than site-cured and laboratory-cured standard specimens. Considerable discrepancy was observed between strength measured in the structure and on separate specimens cast from the same mix. The test method also proved to be useful when testing bonding strength of concrete overlays and epoxy coating to concrete.