Concrete Crack

Cracking of concrete does not come as a big surprise; and to a great extent, that might be true.Cracking of concrete can happen in different stages: It can happen before hardening of concrete, and it can happen in an old concrete structure.

Crack Depth Measurement in Concrete

It is important to evaluate the depth of cracks, to make sure if surface cracking is well propagated into concrete or not. The effectiveness of repair methods such as epoxy injection relies on accurate prediction of crack depth. Different methods have been developed over years to evaluate the depth of cracks in concrete.

I. Visual Examination of Concrete Cores

In this method, dye is injected (using pressure) into surface cracks. Later, concrete cores will be taken from the area under investigation. The sample is studied under microscope for determining the depth of cracks in concrete. “Crack depth measurement in reinforced concrete using ultrasonic techniques”

II. Impact Echo

In Impact-Echo test, a stress pulse is generated at the surface of the element. The pulse spreads into the test object and is reflected by cracks, flaws or interfaces, and boundaries. The surface response caused by the arrival of reflected waves, is monitored using a high precision receiving transducer . When stress waves travel within the concrete element, a part of emitted acoustic waves by the stress pulse on the surface is reflected over the boundary layers, where different the material stiffness changes. The data recieved by the transducer is normally analyzed in the frequency domain to measure the wave speed and the thickness. This procedure has been standardized as the ASTM C1383,

III. Ultrasonic Pulse Velocity Ultrasonic Pulse Velocity (UPV) is an effective non-destructive testing (NDT) method for quality control of concrete materials, and detecting damages in structural components. The UPV methods have traditionally been used for the quality control of materials, mostly homogeneous materials such as metals and welded connections.

With the recent advancement in transducer technology, the test has been widely accepted in testing concrete materials. Ultrasonic testing of concrete is an effective way for quality assessment and uniformity, and crack depth estimation.

UPV method can be used for estimating the depth of surface cracks. To do so, each transducers should be place on one side of the crack, for a given distance. Then, the distance between transducers is change in the same trajectory. the UPV measurement will be repeated for different spacing of transducers.