Used in construction for over 2,000 years, concrete is one of the world`s oldest composite materials. Much of the nation`s concrete infrastructure is over 40 years old, and the demand for accurate and reliable means of testing the structural integrity of concrete has never been greater.
The testing of concrete, however, presents numerous problems. Widely-used conventional methods such as pulse-echo and pitch and catch are of limited effectiveness. The aggregates contained in concrete cause scattering of sound waves and multiple reflections that greatly reduce the effectiveness of conventional tests. The use of reinforcing bar (rebar) in concrete structures can also cause severe problems for conventional testing methods.
NLA testing methodology avoids these problems entirely by evaluating the overall mechanical properties of concrete over a given region, instead of attempting to determine the location of single defects. To NLA methodology, reflections from aggregates become irrelevant and rebar effectively invisible. Furthermore, laboratory and field experiments have shown that NLA technology can detect surface and interior micro-cracking in concrete caused by less than 20 percent of its maximum compressional loading.