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Showing posts with label testing. Show all posts
Showing posts with label testing. Show all posts

Sunday, February 3, 2019

February 03, 2019

SLUMP TEST OF CONCRETE ｜ HOW TO DO SLUMP TEST OF CONCRETE AT SITE

SLUMP TEST OF CONCRETE ｜ HOW TO DO SLUMP TEST OF CONCRETE AT SITE                                     


OBJECTIVE:                                                                                                          
This method of test specifies the procedure to be adopted, either in the laboratory or in the field during work, for determining the workability of concrete where the nominal maximum size of aggregate does not exceed 38 mm.                                                                                                           
SLUMP TEST OF CONCRETE ｜ HOW TO DO SLUMP TEST OF CONCRETE AT SITE
Slump test

APPARATUS:                                                                                                         
Metal slump cone of at least 1.6mm thickness provided with a suitable base plate and also handles for lifting it from the moulded concrete test specimen vertically                                                                                                 

Internal dimension of the cone should have the following sizes:                                                                                                      

                        Bottom diameter     - 20 cm                                                                           
                        Top diameter          - 10 cm                                                                            
                        Height                     - 30 cm                                                                           

            Tamping rod of 16 mm diameter 0.6m long and rounded at one end.                                                                                              
PROCEDURE:                                                                                                        
1. Firstly decide the frequency of slump value to be taken during concreting.                                                                                                         
2. Oil the interior surface of the slump cone with a mould releasing oil to prevent adhesion of the concrete.                                                                                                
3. Place the slump cone on a levelled surface.                                                                                                
4. Collect the sample thoroughly in a wheelbarrow with sampling scoop.                                                                                                      
5. Remix the sample thoroughly in a wheelbarrow with sampling scoop.                                                                                                        
6. After remixing immediately fill the slump cone in layers approximately one- quarter of the height of the cone.                                                                                                   
7. Each layer shall be compacted with the tamping rod by 25 strokes distributed in a uniform manner over the cross-section of the cone and for the second and subsequent layers tamping rod shall penetrate into the underlying layer.                                                                                                        
8. After compacting the top layer, the concrete shall be struck off level the top of the slump cone, using a trowel. Any mortar, which may have leaked out between the mould and the base plate, shall be cleaned away.                                                                                                           
9. Unscrew the slump cone from the base plate and remove it immediately from the concrete by raising it slowly and carefully in a vertical direction.                                                                                                   
10. After the concrete subsides place the slump cone on the plate in a reverse position and places a scale on it. Measure the height between the top of the mould and the highest point of the specimen being tested.                                                                                                      


REPORTING OF SLUMP VALUE:                                                                                                        
The slump measured shall be reported in terms of a millimetre of subsidence of the specimen during the test. Any slump specimen, which collapses or shears off laterally, shall be repeated with another sample. If in the repeat test also, the specimen shears the slump shall be measured and the fact the specimen sheared shall be reported. Take corrective action to make the mix cohesive.                                                                                                  

                                    
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February 03, 2019

MAKING AND CURING CONCRETE CUBES AS PER IS:516-1959

MAKING AND CURING CONCRETE CUBES AS PER IS:516-1959



OBJECTIVES:                                                                                                        
This method covers the procedure or making and curing of concrete cubes as per IS: 516- 1959.                                                                                   
                
APPARATUS:                                                                                                         
Wheelbarrow, sampling scoop, trowel, cube mould of 15x15x15 cm size and tamping bar 16mm in diameter, 0.6 m long and bulleted point at the lower end.                                                                        


PROCEDURE:                                                                                                        
1. Decide the number of samples to be taken during concreting (as per table no. 15.2.2 of IS: 456-2000)                                                                                                  
2. Oil the interior surface of the mould with a mould releasing oil to prevent adhesion of concrete.                                                                                                 
3. Collect the sample in a wheelbarrow after mixing the concrete properly in the transit mixture.                                                                                                  
4. Remix the sample thoroughly in a wheelbarrow with sampling scoop.                                                                                                       
5. After remixing immediately fill the mould in layers approximately 5 cm deep.                                                                                                   
6. During filling the mould, the scoop shall be moved around the top edge of the mould as the concrete slides from it in order to ensure a symmetrical distribution of the concrete within the mould.                                                                                                      
7. Each layer shall be compacted with the tamping rod by minimum 35 strokes distributed in a uniform manner over the cross-section of the mould.                                                                                                  

8. After compacting the top layer, the top surface of the concrete shall be finished level with the top of the mould using a trowel.                                                                                                            

9. Store the cube moulds in a place which is free from vibration and cover the surface of the concrete with a piece of damp sacking for initial 16 to 24 hours.                                                                                                       


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Saturday, January 19, 2019

Testing of Cement before concreting at the site / What are the site test you can do of cement before concreting
January 19, 2019

Testing of Cement before concreting at the site / What are the site test you can do of cement before concreting

Testing of Cement before concreting at the site / What are the site test you can do  of cement before concreting


1. DATE OF PACKING
•Date of manufacture should be seen on the bag. It is important because the strength of cement reduces with age.
•2. COLOUR
•The cement should be uniform in colour. In general the colour of cement is grey with a light greenish shade. The colour of cement gives an indication of excess lime or clay and the degree of burning.
•3. RUBBING
•Take a pinch of cement between fingers and rub it. It should feel smooth while rubbing. If it is rough, that means adulteration with sand.
•4. HAND INSERTION

•Thrust your hand into the cement bag and it should give a cool feeling. It indicates that no hydration reaction is taking place in the bag.
•5. FLOAT TEST
•Throw a small quantity of cement in a bucket of water. It should sink and should not float on the surface.
•6. SMELL TEST
•Take a pinch of cement and smell it. If the cement contains too much of pounded clay and silt as an adulterant, the paste will give an earthy smell.
•7. PRESENCE OF LUMPS
•Open the bag and see that lumps should not be present in the bag. It will ensure that no setting has taken place.
•8. SHAPE TEST
•Take 100g of cement and make a stiff paste. Prepare a cake with sharp edges and put on the glass plate. Immerse this plate in water. Observe that the shape shouldn’t get disturbed while settling. It should be able to set and attain strength. Cement is capable of setting under water also and that is why it is also called ‘Hydraulic Cement’.
•9. STRENGTH TEST
•A block of cement 25 mm*25 mm and 200 mm long is prepared and it is immersed for 7 days in water. It is then placed on supports 15000 mm apart and it is loaded with a weight of 340 N. the block should not show any sign of failure.

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Monday, January 14, 2019

January 14, 2019

The initial Setting time of the Cement testing procedure in details

The initial Setting time of the Cement testing procedure in details

picture of vicat apparatus

OBJECTIVE:

This method covers the testing procedure for determining the initial setting time of cement.


APPARATUS:

Vicat apparatus conforming to IS: 5513-1969 with dashpot, non-absorbent mixing plate, measuring cylinder, gauging
trowel and stopwatch.

PROCEDURE:

1. Take the Vicat apparatus and fit the standard consistency plunger (needle type). Lower the stem and check if the reading
is zero when the plunger touches the non-porous resting plate (glass plate). If not adjust it to zero.
2. The temperature of cement and water and that of the testing room shall be preferably within the range of temperature
3. Coat the non-porous resting plate (glass plate) with petroleum jelly. Place the mold after coating lightly with petroleum
jelly on the non-porous resting plate (glass plate)
4. Take 300 g of cement.
5. Prepare a neat cement paste mixed with water which is 0.85 times that of standard consistency (i.e. standard consistency
=30%). Water for initial setting time =0.30x300x0.85= 76.5 ml.
6. The time from adding water to dry cement until starting to fill the Vicat Mould should be within 3 to 5 minutes.
7. Start the stopwatch as soon as you start adding water and mixing the cement paste. The mixing should be done using
stainless steel trowel which is available with lab equipment dealers.
8. Fill the vVicat Mould completely with the cement paste made and smooth off the surface of the paste make it level to the
top of the Mould.
9. Place the Mould under the needle (1 mm square) together with a non-porous resting plate and cement paste make it level to
the top of the Mould.
10. Lower the needle gently to touch the surface of the block and release quickly. Make sure that the dashpot works
properly.
11. Initially, the needle will pierce completely into the test block .Repeat this procedure until the needle fails to penetrate
into the test block by 5± 0.5 mm from the bottom of the mould.
12. The time started from mixing water to the cement to the time when the needle fails to penetrate test block by 5 ± 0.5
mm is described as the initial setting time.
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