hardened concrete

Question 1

is a type of evaluation that determines how a component will behave under pressure until it fails

Answer 1

Destructive testing

Question 2

assesses an object’s behavior but does so without the need of damaging it.

Answer 2

Non-destructive testing

Question 3

Non-Destructive Tests

Answer 3

Rebound Hammer
Ultrasonic Pulse Velocity

Question 4

Destructive Test

Answer 4

Compression Test

Question 5

is a non-destructive method of testing concrete which provides a quick indication of compressive strength of the subjected surface.

Answer 5

Rebound hammer testing

Question 6

RHT procedure

Answer 6

Preparation: Clean the surface of the concrete to remove any loose particles, dust, or debris. If the surface is too smooth, roughen it with a grinder or papel de liha (sandpaper).

Calibrate the hammer: Press the hammer onto a hard, flat surface to make sure the needle on the dial reads zero. If it doesn’t, adjust the instrument accordingly. (80±2)

Test locations: Determine the locations where you will conduct the test. It’s recommended to test at least 3 spots on the concrete surface to ensure accuracy.

Conduct the test: Hold the hammer perpendicular to the concrete surface, with the impact plunger touching the surface. Press the trigger to release the plunger, which will hit the surface with a spring-loaded mass. The rebound energy will cause the plunger to bounce back, and the hammer will record the rebound distance.

Record data: Record the rebound values on a data sheet, making sure to label each value with its corresponding test location.

[Interpretation: Use the rebound values to estimate the compressive strength of the concrete. Consult the manufacturer’s instructions or a conversion chart to convert the rebound values into compressive strength values.]

Question 7

influencing factors (hardened concrete)

Answer 7

Type of Aggregate
Type of Cement
Surface and moisture condition of the concrete
Curing and Age of concrete
Carbonation of concrete surface

Question 8

Helps engineers in the quality control of newly constructed and existing concrete structures. Evaluate the integrity and quality of concrete materials and structures.

Answer 8

Ultrasonic pulse velocity

Question 9

ultrasonic pulse velocity method could be used to establish:

Answer 9

the homogeneity of the concrete,
the presence of cracks, voids, and other imperfections,
changes in the structure of the concrete which may occur with time,
the quality of the concrete in relation to standard requirements,
the quality of one element of concrete in relation to another, and
the values of the dynamic elastic modulus of the concrete.

Question 10

upv applications

Answer 10

Durability of Concrete
Defining internal flaws
Segregation
Honeycombing
Compaction of Concrete
Workmanship

Question 11

factors affecting resulst (upv)

Answer 11

Quality of the Testing Surface and Tramsducer Contacts
Path length of the pulse
Dimension of the specimen tested
Presence of reinforcement in concrete
Size of the aggregates used
Moisture content of tested concrete
Concrete Age
Cement Type

Question 12

upv apparatus

Answer 12

upv meter

Question 13

upv procedure

Answer 13

Preparation of Specimen: Concrete Surface Preparation

1. Locate the dry location on the concrete surface.
   1.2. Use a grinding wheel to remove any plaster or other coating from the concrete surface.
   1.3. Divide the entire structure in suitable grid markings of 300 mm

Ultrasonic Measurement: Placement of the Two Transducers on a Concrete Surface

a.) Direct transmission method (Fig. A): Both transducers are placed on opposite faces of the concrete surface
b.) Semi-direct transmission method (Fig. B): Both transducers are placed on adjacent faces of concrete surface
c.) Indirect or surface transmission method (Fig. C): Both transducers are placed same face of the concrete surface

Procedure of Ultrasonic Pulse Velocity Test for Different Transducer Arrangements

3.1. Measure the distance between the grid points where the transmitting and receiving transducers are to be placed. (L)
3.2. Apply typical acoustical couplants like petroleum jelly, grease, or liquid soap between the concrete surface and the face of each transducer.
3.3. Switch on the ultrasonic pulse velocity meter then press the transmitter and receiver transducers on the predetermined grid points of the concrete surface.
3.4. Record the traverse time (T) displayed on the ultrasonic pulse velocity meter.

Question 14

is used to determine how a product or material reacts when it is compressed, squashed, crushed or flattened by measuring fundamental parameters that determine the specimen behaviour under a compressive load.

Answer 14

compression testing

Question 15

benefits of using compression testing

Answer 15

To determine batch quality
To determine consistency in manufacture
To aid in the design process
To reduce material costs and achieve lean manufacturing goals
To ensure compliance with international and industry standards

Question 16

age at test (ct)

Answer 16

Tests should be done at recognized ages if the test specimens, usually being 7 and 28 days.
The ages should be calculated from the time of the addition of water to the drying of ingredients.

Question 17

no. of specimens (ct)

Answer 17

At least three specimens, preferably from different batches, should be taken for testing at each selected age.

Question 18

ct procedure

Answer 18

Test specimens are stored in water at a temperature of 24° to 30°C for 48 hours before testing. They are tested immediately on removal from the water whilst they are still in a wet condition.

The dimensions of each specimen should be noted before testing.

No preparation of the surfaces is required.

The bearing surfaces of the compression testing machine should be wiped clean.

The axis of the specimen should be carefully aligned with the centre of the thrust of the spherically seated platen.

The load should be applied without shock and increase continuously at a rate of approximately 140kg/sq.cm/minute until the resistance of the specimen breaks down and no greeter load can be sustained.

Question 19

measures the force required to bend a beam under three point loading conditions.

Answer 19

flexural test

Question 20

used as an indication of a material’s stiffness when flexed.

Answer 20

flexural modulus

Question 21

determines the flexural strength of concrete by the use of a simple beam with third-point loading. Results are reported as the modulus of rupture (MOR), which is the flexural strength of the concrete sample just before it yields.

Answer 21

astm c78

Question 22

ft procedure

Answer 22

Test specimens are stored in water at a temperature of 24° to 30°C for 48 hours before testing. They are tested immediately on removal from the water whilst they are still in a wet condition.

The dimensions of each specimen should be noted before testing.

Place the specimen on the loading points.

Center the loading system in relation to the applied force.

Bring the block applying force in contact with the specimen surface at the loading points.

Applying loads between 2 to 6 percent of the computed ultimate load.

Employing 0.10 mm and 0.38 mm leaf-type feeler gages, specify whether any space between the specimen and the load-applying or support blocks is greater or less than each of the gages over a length of 25 mm or more.

Eliminate any gap greater than 0.10mm using leather shims (6.4mm thick and 25 to 50mm long)

Capping or grinding should be considered to remove gaps in excess of 0.38mm

Load the specimen continuously without shock till the point of failure at a constant rate (Indian standard specified loading rate of 400 Kg/min for 150mm specimen and 180kg/min for 100mm specimen, stress increase rate 0.06+/-0.04N/mm2.s according to British standard).

Question 23

An indirect way of evaluating the tensile test of concrete.
To determine the tensile strength of concrete to determine the load at which the concrete members may crack.

Answer 23

splitting tensile strength test

Question 24

It is employed when the diameter or the largest dimension of the upper bearing face or the lower bearing block is less than the length of the cylinder to be tested.

Answer 24

plate or supplementary bearing bar

Question 25

splitting tensile test procedure

Answer 25

Initially, take the wet specimen from water after 7, 28 of curing; or any desired age at which tensile strength to be estimated.

Then, wipe out water from the surface of specimen.

After that, draw diametrical lines on the two ends of the specimen to ensure that they are on the same axial place.

Record the weight and dimension of the specimen.

Set the compression testing machine for the required range.

Place plywood strip on the lower plate and place the specimen.

Align the specimen so that the lines marked on the ends are vertical and centered over the bottom plate.

Place the other plywood strip above the specimen.

Bring down the upper plate so that it just touch the plywood strip.

Apply the load continuously without shock at a rate within the range 0.7 to 1.4 MPa/min (1.2 to 2.4 MPa/min based on IS 5816 1999)

Finally, note down the breaking load(P)