What is the purpose of keeping tremie pipe’s tip immersed in freshly-placed concrete for about 1m in underwater concreting?

  What is the purpose of keeping tremie pipe’s tip immersed in freshly-placed concrete for about 1m in underwater concreting? The size of tremie pipe is about 300mm with sections having flange couplings fitted with gasket to prevent water leakage. The tremie pipe should be closed initially to prevent water from entering the pipe. It should be designed with sufficient thickness and weight so that it would not be buoyant when empty inside water. The placement of tremie concrete is commenced by putting the closed pipe underwater to the location for concreting, followed by partial filling of tremie pipe with concrete. In order to have tremie concrete flowed out of the pipe, it is necessary to fill the pipe with concrete of sufficient height to overcome the water pressure and frictional head. After that the tremie pipe is raised about 150mm to allow concrete to flow out. To enhance sufficient bonding, each succeeding layer of concrete should be placed before the preceding layer has reached
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DOOR FRAME // POINTS TO BE CONSIDERED AND CARE TO BE TAKEN WHILE ERECTING THE DOOR FRAME//HOW TO CALCULATE DOOR FRAME HEIGHT

FOLLOWING POINTS TO BE CONSIDERED AND CARE TO BE TAKEN WHILE ERECTING THE DOOR FRAME:

1) Before fixing of door frame, apply black Japan (coal tar) over the rough surface of the door frame which is touching to the RCC member/block masonry and Primer to be applied on finished surface of door frame, if painting coming on the door frame, so that application of black Japan (coal tar) and primer to be done at ground level only. Do not take materials up without application of black Japan (coal tar) and primer. 

2) Different types of Holdfast and their uses.

3) Fix the hold fast to the door frame for both 7’ & 8’ door frame as per given figure for different situation of block masonry.


4) Sometimes door frames width may be same for different locations i.e. Kitchen and Bedroom, but Rebate size may be different. For eg. Kitchen door frame Rebate = 47mm,& Bedroom door frame Rebate = 42mm. Hence one has to ensure that door frame of correct rebate is erected. It is some times observed that door frame rebates are not checked and frame of wrong rebate is erected. Of frame Considering only width.




5) Now erect the door frame keeping margin of internal plaster and check the plumb both inside (Rebate portion area) and outside of the door frame. (which is flushing to the plaster finish).

6) Give the necessary support by wooden prop to the frame to keep incorrect position and level.


7) Put the concrete around door leg bottom. (which is inserted ½” in the slab to avoid displacement of door frame leg).

 

8) Carry out block work upto approx. 3’6” height touching door frames.

9) Do the holdfast concreting with farma simultaneously with block masonry as per required height, on same day. Next day do the balance block work upto required height with maintaining of door frame plumb. If found half of the door frame is not in plumb give the necessary support and get it incorrect position and plumb and do the block masonry with hold fast concreting upto beam bottom.

10) During the block masonry do not disturb the door frame.

ERECTION OF DOOR FRAME

CASE   – 1 For door frames 7’2½” in height.

Clear height from finish floor level to door frame top       = 7’0”

Finish Margin                                                                       + 2”

To be inserted in the slab                                                     + ½”

Door Frame Height                                                         = 7’2½”

Floor Height     3100

Beam Depth     -700

Clear Height  = 2400

Door Frame Height                                                         7’2½” = 2200

Reference Level (Khachra level on column)                                -1400

                                                                                                        800

Door frame to be inserted in the slab                                             - 10

                                                                                                        790

So mark the 790 mm level on door frame from top of the door frame and match with 1400 mm R.L. (khachra level) marked on adjacent column and if clear height between beam bottom to slab top = 2400mm, check the gap between bottom and door frame top. It should be minimum 200mm for one layer of block masonry.

CASE – 2 For door frames 7’11” in height.

Clear height from finish floor level to door frame top      = 7’8½”

Finish Margin                                                                       + 2”

To be inserted in the slab                                                    + ½”

Door Frame Height                                                           = 7’11”

Floor Height 3100

Beam Depth -700

Clear Height = 2400

Door Frame Height                                             7’11” = 2410 mm

Reference Level (Khachra level on column)                 -1400 mm

                                                                                       1010 mm

Door frame to be inserted in the slab                              - 10 mm

                                                                                       1000 mm

So mark the 1000 mm level on door frame from top of the door frame and match with 1400 mm Reference level (khachra level).

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