Handbook on Non Destructive Testing of Concrete Second edition

Abstract

In the inspection of metals, nondestructive testing is an accepted practice. For example, radiographic and ultrasonic techniques are routinely used to identify anomalies in steel pipelines, and there are recognized national and international standards on their use. In the inspection of concrete, however, the use of nondestructive testing is relatively new. The slow development of nondestructive testing techniques for concrete is because, unlike steel, concrete is a highly nonhomogeneous composite material with varying composition and different raw materials. Apart from precast concrete units that, like steel products, are fabricated at a plant, most concrete is produced in relatively small ready-mixed concrete plants and delivered to the construction site. The placing, consolidation, and curing of concrete takes place in the field using labor that is relatively unskilled. The resulting product is, by its very nature and construction method, highly variable and does not lend itself to testing by traditional nondestructive methods as easily as steel products. Despite the above drawbacks, there has been progress in the development of nondestructive methods for testing concrete, and several methods have been standardized by the American Society for Testing and Materials (ASTM), the Canadian Standards Association (CSA), the International Standards Organization (ISO), the British Standards Institute (BSI), and others. The direct determination of mechanical and other properties requires that concrete specimens taken from the structure be tested destructively; therefore, nondestructive methods cannot yield absolute values of these properties. Methods have been developed to measure other properties of concrete from which estimates of mechanical properties or other characteristics related to performance can be inferred. Broadly speaking, there are two classes of nondestructive test methods for concrete. The first class consists of those methods that are used to estimate strength. The surface hardness, penetration resistance, pullout, break-off, pull-off, and maturity techniques belong to this category. Some of these methods are not truly nondestructive because they cause some surface damage, which is, however, minor compared with that produced by drilling a core. The second class includes those methods that measure other characteristics of concrete such as moisture content, density, thickness, resistivity, and permeability. Also included in the second class are such methods as stress wave propagation, ground probing radar, and infrared thermography techniques, which are used to locate delaminations, voids, and cracks in concrete. In addition, there are methods to provide information on steel reinforcement such as bar location, bar size, and whether the bars are corroding. This second edition provides comprehensive treatment of nondestructive test methods that are used to evaluate concrete structures. The opening chapter deals with surface hardness test methods, followed by chapters on penetration resistance, pullout, break-off, maturity, pull-off, permeation, resonant frequency, and pulse velocity techniques. These chapters are followed by a chapter on the combined methods, in which more than one technique are used to estimate strength of concrete. The remaining chapters deal with magnetic, electrical, radioactive, nuclear, radar, stress wave propagation, infrared thermography