Building Materials, Third Edition

PWR f   





2w—

—

1. The availability and reliability of the calibration charts.


2. The effects and acceptability of surface damage.


3. The accuracy desired.


4. Economic considerations.


5. Practical limitations such as member size and type, surface conditions, and access to test
   points.

x

2

2x Eh
™/
2„


Information about the in-situ strength of concrete may be required for both under construction
as well as existing concrete structures. For new concrete structures under construction, N.D.T.
may be required under following circumstances:

1. Non-compliance of the material supplied in terms of works specimen test results or other
   specified requirements.


2. Uncertainties concerning the level of workmanship involved in construction operations
   affecting the hardened properties of the in-situ concrete.


3. Quality control of construction.


4. Monitoring of strength development in relation to formwork removal, curing, prestressing,
   load application or similar purposes.
   Existing concrete structure require an examination under the following circumstances:


5. Deterioration of the concrete due to factors such a external or internal chemical attack,
   fire explosion and other environmental effects.


6. To make assessment of the load carrying capacity of an existing structure for change of
   ownership or insurance purpose or in relation to a proposed change of use or alteration.

e/——

2

2x E
™/
2„


Non-destructive methods have following distinct advantages over the prevalent destructive
methods of testing.

1. The measurement can be done on concrete in-situ and thus representative samples are
   not required. In destructive method of testing the change in quality of concrete has to be
   studied on a long-term basis with respect to curing or deterioration due to certain causes.
   A large number of specimens are required which could be tested to destruction, at
   various ages. Since it cannot be guaranteed that all specimens are of the same quality, the
   results obtained may not be very reliable.


2. Non-destructive testing makes its possible to study the variation in quality of concrete
   with time and external influences.


3. In N.D.T. method the concrete is not loaded to destruction. Its quality is judged by
   measuring certain of its physical properties, which are related to its quality.


4. In N.D.T. there is no wastage of material as in destructive methods of testing.

IH3IS‚riyvyq‰

Rheology is the science of flow and deformation of matter and describes the interrelation
between force, deformation and time. The term comes from Greek word rheos meaning to flow.