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 rea...
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CONCRETE MIX DESIGN.......SHEET

Concrete Mix Design Sheet

With /Without M. Admixture

Grade Fck = _____ N/mm²

Date: ___ / ____ / ____

Site:

  Structure: 

1.    Material Data

   Cement = ____________

M. Admixture = ___________

Controlled Slump= _______mm

   Chemical= ___________

Percentage (P) = ___________ %

Final Slump= _________mm

   Dosage= ________ml/        bag

MSA= _______________  mm

Density= ___________ Kg/ m³

     2.    Control
     a.        Degree of quality control          [ V. Good /Good/ Fair / Poor]                                         
     b.       Standard Deviation (S)     = _________    (Refer Table No. 1)
     3.    Target Mean Strength (Fm)
              Note: Using table no. 1 for standard deviation calculate (Note:  ‘S’ not less than 4)

  Fm = Fck + (S x t) = _____________ + (_____________ x 1.65) = ______________ N/mm².

4.    Water Cement Ratio ( W/C)

Note: Using Fm and Grade of cement calculate W/C ratio from graph no. 1

Therefore, W/C = ____________

5.       Water Calculation (W)

 Water = 2/3 of Uncrushed Aggregate +

1/3 of Crushed Aggregate

            Note: Using Table No. 2, we have,

W= _____________ Lit/m³

6.    Cement Content  ( C )

C = Total Water (W) ÷ Water Cement Ratio =__________ ÷ __________= __________Kg/m³

7.    Total Binder Content (B) *

Cement + M. Admixture = Cement x 1.12 = ____________ x 1.12 = __________Kg/m³

8.    Quantity of Cement and M. Admixture *

B= RC+ (P x RC) =_____________ + (___________ x ___________) = _______Kg/m³

Revised Cement (RC) = _______ Kg/m³,      Flyash (F) = ____________        Kg/m³ 

9.    Revised Water (RW)= Old Water (w) x 0.95 = ____________ lit/ m³  *

W/B ratio = Revised water /Total Binder = _________ ÷ __________ = ________

10.  Calculate Quantity Of Aggregate

Density (D) = Cement (RC) + Revised Water (W) +Aggregate (A) +Mineral Admixture (M)

A = D - RC -RW - M             = _________ - __________ - __________ - _______=                     ______Kg/m³

11.  Calculate Quantity of Sand

Note: Referring graphs no. 2 and using parameters of controlled slump,zone of sand and w/b ratio percentage of Fine Aggregate in mix will be as follows: (For zones refer table no. 3)

Zone Of Fine Sand = ____________

Upper limit (U/l) = ______________,               Lower limit (L/l) = _______________

12.  Gravel Correction

Actual % of Fine agg. (P3) = % of Fine Agg ÷ % passing in 4.8mm I. S. sieve

P3 = ____________ ÷ ____________ = ____________

 

Note:     Upto M30 Take CaI < CaII,     Above M 30 Take CaI > CaII 

             * Use steps only in case of design with Mineral Admixtures (Flyash/GGBS) 

13.  Sieve Analysis                

Material

CaI

CaII

Fine Agg.

All in Grading

Combined FM

%

P1=

P2=

P3=

40mm

 

 

 

 

 

 

 

 

20mm

 

 

 

 

 

 

 

 
10mm

 

 

 

 

 

 

 

 

4.5mm

 

 

 

 

 

 

 

 

2.4mm

 

 

 

 

 

 

 

 

1.2mm

 

 

 

 

 

 

 

 

0.6mm

 

 

 

 

 

 

 

 

0.3mm

 

 

 

 

 

 

 

 

0.15mm

 

 

 

 

 

 

 

 

DLBD

 

 

C.F.M.=

Total (T)

 

     Combined FM (C.F.M) = T ÷ 100 = __________÷ 100 = ___________  (If C.F.M between 5 to 5.2         then O. K)

14.  Calculation of Quantity of Aggregates (Kg/ m³)

Quantity = Percentage (P) x Total quantity of Aggregate (A)

Therefore,             CaI     = P1 x A = __________ x __________ = __________ Kg/ m³

                              CaII   = P2 x A = __________ x __________ = __________ Kg/ m³

Fine Agg (S) = P3 x A = __________ x __________ = __________ Kg/ m³

15.  Cohesion Correction *

j = 13 % of Old Cement Content (C) = C x 13÷100 = ___________ x 0.13 = __________Kg

k= Quantity of Mineral Admixture (M) – j = _________ - __________           = __________ Kg

RS =Revised Quantity of Fine Agg. =S- k= __________ - __________              = ________Kg/m³

16.  Distributing Proportionately in CaI and CaII  *

In CaI = [P1÷ (P1+P2)] x k = [_______÷ (________ + ________)] x ________=_________ Kg

In CaII= [P2÷ (P1+P2)] x k= [_______÷ (________ + ________)] x ________ = ________ Kg

17.  Revised Values of Aggregate ( Adding above values to CaI and CaII) *

RCaI = ___________ + ___________ = __________ Kg/ m³

RCaII = __________ + ____________ = __________ Kg/ m³

18.   Material Calculation /bag

No of cement bag per m3 = __________ Nos.

Material

Quantity

Kg/m³

Quantity /bag by weight

DLBD (Kg/lit)

Quantity / bag Volume

Round

Off (lits)

Cement

 

 

NA

 

 

Mineral Admixture

 

 

NA

 

 

Revised CaI

 

 

 

 

 

Revised CaII

 

 

 

 

 

Revised Sand

 

 

 

 

 

Revised Water

 

 

NA

 

 

     Note: Round off =± 3 So, OK.

19.  Final Mix Design

Grade

CaI

CaII

FaII

Cement

M.Adm.

Water

W/B

C/C

Chemical

 

 

 

 

 

 

 

 

 

 

 

liter

liter

liter

Kgs

Kgs

Liters

 

Kg/ m³

ml

Reference Tables and Graphs

Table No 1: Standard deviation as per IS10262- 1982

Grade

M10

M15

M20

M25

M30

M35

M40

M45

M50

M55

M60

V. Good

2

2.5

3.6

4.3

5

5.3

5.6

6

6.4

6.7

6.8

Good

2.3

3.5

4.6

5.3

6

6.3

6.6

7

7.4

7.7

7.8

Fair

3.3

4.5

5.6

6.3

7

7.3

7.6

8

8.4

8.7

8.8

 

Table No 2: Water demand liters /m ³

 

Slump (mm)

MSA

0 to 10

10 to 30

30to 60

60 to 180

10

160

188.33

213.33

233.33

15

153.3

179.165

201.665

219.165

20

146.66

170

190

205

25

142

165.33

185.33

200.33

30

137.495

160.83

180

195

40

128.33

151.66

170

185

 

Table No 3 Grading limits for fine aggregates ( IS 383 – 1970)

I S Sieve

Percentage Passing

 

Zone I

Zone II

Zone III

Zone IV

10mm

100

100

100

100

4.75mm

90-100

90-100

90-100

95-100

2.36mm

60-95

75-100

85-100

95-100

1.18mm

30-70

55-90

75-100

90-100

0.6mm

15-34

35-59

60-79

80-100

0.3mm

5-20

8-30

12-40

15-50

0.15mm

0-10

0-10

0-10

0-15
 

                                                GRAPH NO 1


                                                            GRAPH NO 2





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