1. “Condition Assessment of Concrete with Non Destructive Testing (NDT)”
Hemraj Ramdas Kumavat
Assistant Professor, Department of Civil Engineering, R. C. Patel Institute of Technology, Shirpur. North Maharashtra University , Jalgaon
Research Festival DISTRICT/REGIONAL LEVEL AVISHKAR
INTRODUCTION
NDT :- REBOUND HAMMER TEST
The concrete evaluation is necessary for the proper diagnosis of successful rehabilitation work. Initially, the structure deteriorates due to cyclic temperature variations, physical causes and aggressive chemical attack due to the environment. Later on, if not paid due attention, these deteriorate rapidly and fail to meet the functional requirement for its designed service life.
The structure can be investigated by (NDE) such as rebound hammer which is more useful for classified category of distress. The comparative analysis of rebound hammer test on various members of buildings with life span from 5 yrs to 30 yrs and develop the relationship between rebound hammer number and compressive strength with various grades of concrete for generating fitness model.
Principle: - Rebound of an elastic mass depends on the hardness of the surface against which mass strikes. The plunger of hammer is pressed strongly and steadily against the concrete surface at right angles to its surface, until the spring loaded mass is triggered from the locked position. The distance travelled by the mass as a percentage is defined as rebound number.
Testing of concrete structures ages from 5-10, 10-15, , , yrs
Comparative analysis of rebound hammer test on various members of buildings with life span from 5 yrs to 30 yrs.
Development of relationship between rebound hammer number and compressive strength with various grades of concrete.
Application of relationship for development of equation (rebound number, compressive strength and age of structure) for compressive strength determination
Fitness model of rebound number and compressive strength
Assessment of concrete quality by Rebound Hammer
WORKING OF REBOUND HAMMER
OBJECTIVE
To test actual structure instead of representative cube sample.
To test any number of points and any locations
To assess the structure for various distressed conditions such as damages due to fire, chemical attack, impact, age etc.
To detect cracks, voids, fractures, honeycombs and week locations
To monitor progressive changes in the properties of concrete, reinforcement etc.
To assess overall stability of the structure
METHDOLOGY
Selection of specimen
Mark location of probe
Hammering methods.
Surface preparation
Compressive Strength, uniformity, quality of concrete
Procedure
Beam, column, slab
Top, bottom, left, right
Horizontal, vertically up or down
Removal of plaster and coatings
Impact of hammer
Number of repetition
Application
CONCLUSIONS
The research aims to assess the life span of buildings without demolition and also going to develop e the fitness model of result obtained. Comparative studies of various Building Projects is planned to know the exact solution.
SIGNIFICANCE OF THE STUDY
To use this test method to estimate strength requires establishing a relationship between strength and rebound number. To estimate strength in an existing structure, establish the relationship by correlating rebound numbers measured on the structure with the strengths of cores taken from corresponding locations.
In case of evaluation of concrete by rebound hammer, the results affected by smoothness of test surface, size, shape, and rigidity of the specimens, age of test specimens, surface and internal moisture conditions of the concrete, type of coarse aggregate and cement, carbonation of the concrete surface. These factors need to be considered in preparing the strength relationship and interpreting test results.
CORELATIONSHIP
REFERENCES
IS13311: Part II: 1992: NDT of Concrete-Methods of test: Rebound hammer
ASTM C , Standard Test Method for Rebound Number of Hardened Concrete,
Greene, G.W., Test hammer provides new method of evaluating hardened concrete, ACI J. Proc.,51(3), 249, 1954.
Peter H. Emmons, Gajanan M. Sabnis, Concrete Repair and Maintenance Illustrate, Galgotia Publication Pvt. Ltd., New Delhi