NDT In Construction

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1. INTRODUCTION:
1.1 Non-destructive Testing:
Civil engineering is a field in which the use of the NDT can be developed. They also can become an important tool to assist the professionals considering the quality control of new buildings. The NDT methods are used in various researches. NDT do not only allow the evaluation of aged and spoiled structures; they also can be used in quality control of new structures. The method allows doing the tests at the same place, making possible a continuous monitoring in the structures and a determination of possible variations during a period of time. Once the structures are monitored, the life-time can be predicted, and consequently, the treatment and the recovery become more easy and economic.
The widely …show more content…

The correlation between the NDT and the structure strength can be established. The correlations are particular for a certain type of concrete and must be used with caution. Concrete properties can vary considerably depending on the nature and proportions of its materials, the construction methods and the loading and environmental conditions. In order to prevent and control the concrete deterioration, it is interesting to establish continuous monitoring strategies, which might be a powerful tool to increase the service life of concrete. This implies the development of control methods which are able to determine the quality and the condition state of concrete. UPV methods can play an important role in this area, since they allow us to monitor the density and homogeneity of the material, providing information about the strength evolution and about the existence of internal flaws and defects. The UPV methods have been used in inspection operations and monitoring of concrete structures. This test allows to measure and to control a series of basic parameters to determine the concrete quality. However, interpreting the result of this type of test need to be made in a criteriously form and demand a specific knowledge of the influential factors. In order to collaborate with the development of the models that consider these …show more content…

This natural settlement causes excess mix water and entrapped air to be displaced (called bleeding), and the lighter materials migrate toward the surface. If finishing operations start prematurely and close or seal the surface before bleeding is completed, air and/or water are trapped under the densified surface mortar. As concrete hardens, subsurface voids develop where the water or air is trapped. These voids create weakened zones right below the surface that can eventually detach during slab use. Very thin mortar layers over delaminations may even detach when struck with a hammer, as you try to sound out the extent of the delaminated area.
If the delamination is isolated to just one spot, it might not affect the performance of a concrete slab. But if it's widespread, then you have a more serious problem that should be addressed.
Delaminations come in various forms and degrees of severity. Blisters are small, isolated delaminations usually 1 to 3 inches in diameter (Photo 1). Blisters frequently happen when relatively sticky mixes with higher percentages of fines are placed. They occur in areas subject to moderate to high rates of evaporation and that are finished too soon.
When finishing operations occur too early, uniformly over the slab, a delamination problem can be quite widespread and affect larger zones of a slab surface (Photos 2 and

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