Home Trust Development Ltd.

2.2.1. Core Test:
Steps to the Core Tests:
The reinforcement will be detected at planned location with the help of Rebar Locator to avoid cutting of reinforcement.
The Core cutting equipment will be fixed at the planned location and core is extracted.
The Cores are transported to the laboratory and visual observations of cores are recorded for interpretation purpose. Reinforcement bars, if encountered, are cut off.
The Cores are removed from water cut to the required L/D ratio of 2, wherever possible, exactly perpendicular to the longitudinal axis.
Both the ends are prepared by grinding up to the tolerance limit as specified for flatness and parallelism.
A thin layer of plaster of Paris is applied to ends to ensure proper contact.
And the cores will be ready for compression testing.

2.2.2. Rebound Hammer Test:
Steps to carry out Rebound Hammer Test:
The plaster is removed at test locations.
For testing, smooth, clean, dry surface without any defect like honeycombing cracks and hollow sound is selected.
The area of approx. 300 mm x 300 mm is rubbed with carborandum stone to remove loosely adhering scales, or remains of plaster mortar, if any.
In this area 12 points at approximate 30 mm apart are selected in grids.
By holding the rebound hammer at right angles to surface of the concrete member 12 readings are taken at selected points.
Of these readings, abnormally high and abnormally low results are eliminated and average of the balance readings is worked out.
Taking into consideration the factors influencing hardness of the concrete surface like moisture condition of the surface, carbonation, test location within the member, direction of test etc. corrected rebound number is worked out.
The compressive strength of concrete against each rebound number is obtained from graph prepared on correlation established between rebound numbers at core test locations and equivalent cube strength values.
The statistical analysis is carried out for this set of values of compressive strengths obtained by above method.

2.2.4. Carbonation Test Procedure:
The powder of concrete is obtained by drilling inside into concrete at selected location. Then the collected powder is made moist and then phenolphthalein indicator is dropped on it to check any colour change. If the colour changes to pink, indicates that concrete is not affected by carbonation & if no colour change is observed, indicates concrete is affected by Carbonation. We can also apply phenolphthalein indicator on the collected core to see the colour changes.

3.2. Reinforced Concrete Wing Walls:
This strengthening method is to install small wall panels which may not be considered shear walls with boundary columns. The objective of this strengthening method is to increase seismic performance of existing buildings by changing the existing independent columns to columns with wing wall for upgrading their strength. It is also possible to install wing walls to carry axial load of a column and to eliminate a problem of second-class prime elements, whose failure leads to building collapse.

However, there is a case that the seismic capacity of building is determined by the performance of existing beams, even though seismic performance of column is upgraded by installing wing walls. Thus, it shall be counted in the design.
Especially, buildings with short distance in beams shall be carefully designed to eliminate shear failure in beams due to beam shortening after installing walls adjacent to columns. It is possible by installing wing walls to upgrade the second-class prime elements, whose failure leads to building collapse. For example, installing wing wall in the direction of lateral load concerned to increase its strength is an effective retrofitting method when they are extremely brittle columns. To enhance the axial load carrying capacity of a column, wing walls are often provided in the direction perpendicular to the lateral load concerned.