Structural Health Monitoring by Non Destructive Techniques On Concrete

Abstract

The concept of nondestructive testing (NDT) is to obtain material properties “in place” specimens without the destruction of the specimens and to do the structural health monitoring. NDT using Rebound hammer, Ultra pulse velocity, Halfcell potential, core cutter, carbonation depth, rebar locator, Rapid chloride penetration test, electric resistivity meter test and vibration base analysis by data analoger are very popular and highly effective in conducting structural health monitoring. The structure can be investigated by using a visual inspection, NDT, laboratory and field test performance. In this article a review of these tests have been provided to conduct effective structural health monitoring of a RCC structure. The estimation of mechanical properties of concrete can be carried out by several methods; destructive and nondestructive. In this context, the crushing of the samples is the usual destructive test to determine the concrete strength. The rebound hammer test and the ultrasonic device are used in the field of nondestructive tests to determine respectively the compression strength and the ultrasonic pulse velocity (UPV) in the concrete. In this work, eight concrete compositions were used to prepare cylindrical specimens (16 cm x 32 cm) by varying the water/ cement ratio and the cement dosage. An experimental study was conducted to determine the compressive strength of concrete by destructive (compression) and nondestructive (rebound hammer) tests at different ages (7, 14 and 28 days). In addition, the influence of several factors on the modulus of elasticity determined by pulse velocity test was investigated. These factors mainly included the age of concrete and the water/ cement ratio. The results showed that the difference between the resistance values obtained by destructive and nondestructive methods decreases with increasing age of concrete. The dynamic modulus of elasticity increases with the curing time of the concrete until the age of three months. In addition, a simplified expression has been proposed to estimate the rebound number from the value of the dynamic modulus of elasticity determined by pulse velocity test.