TECHNICAL INFO » Concrete Quality Control Requirements

Concrete results are evaluated according to the  TS 500 / February  2000  and TS  EN    206-1  Standards.

1 -  Evaluation according to TS 500 / February 2000  Standard      

Evaluation of concrete compressive strength results are based on the values of 28 days. The samples which are taken three at a time, are organized as; G1, G2, G3 ………. Gn according to their collection rank. The parties which come one after the other

P1  ( G1, G2, G3 )   ,   P2 ( G2, G3, G4 )   ,   P3 ( G3, G4,G5 )   ,……..P n-2   

are evaluated according to the conditions below.

a) Average compressive strength for each party

fcm fck +1,0 MPa ( N/mm2 )

fcm = Average strength

fck  = Characteristic strength  ( project strength )

 b)  Minimum group average compressive strength in each party

fcmin ≥ fck – 3,0  MPa ( N/mm2 )

 

The concretes of the parties which applies both of the conditions that are stated above are accepted.

 

Numerical Example        Project strength fck : C20 / 25

P
A
R
T
İ

G
R
U
P

28 Days
15x15x15 cm Cube Pressure Strength

N/mm2

 

Group
Average

 

N/mm2

 

Party

Average

N/mm2

 

Minimum group average of the Party

N/mm2

Evaluation

 fcm ≥ 25+1
fcmin ≥ 25 - 3

RESULT

P1

G1

24-25-25

24.6

25.6

24.6

fcm   = 25.6 < 25+1
fcmin = 24.6 > 25-3

Rejected

G2

25-27-24

25.3

G3

28-27-26

27.0

P2

G2

25-27-24

25.3

26.8

25.3

fcm   = 26.8 > 25+1
f
cmin = 25.3 >  25-3

Accepted

G3

28-27-26

27.0

G4

29-28-28

28.3

P3

G3

28-27-26

27.0

28.1

27.0

fcm = 28.1 > 25+1 
fcmin = 27.0 > 25-3

Accepted

G4

29-28-28

28.3

G5

30-28-29

29.0

 

2 - Evaluation according to TS EN 206-1 Standard.

Samples whose conformity of concrete compressive strength are applied to the 28 days test, are evaluated according to the conditions below.

Chart 14 - Conformity Criterias for Compressive Strength TS EN 206-1 / April 2002

PRODUCT

Number produced in the Group after the pressure strength test 

"n"

1. Criteria

2. Criteria

"n" number test result average

( fcm)
N/mm2

Any single test result ( fci)
N/mm2

Start

3

fck + 4

fck - 4

Constant

15

     ≥ fck + 1.48 . σ

fck - 4

 

Chart 15 – Confirmation Criterias of the Members Belonging to the Group

TS EN 206-1 / April 2002

Test Result Number for Single concrete compound - "n"

3. Criteria

"n" number test result average for a member of the group - fcm
N/mm2

2

≥  fck - 1.0

3

≥  fck + 1.0

4

≥  fck + 2.0

5

≥  fck + 2.5

6

≥  fck + 3.0

 

In the Chart 14 1st Criteria, “n” number of overlapping or not overlapping consecutive test result group – fcm

2nd Criteria, single test result – fci

Conformity is approved by providing those both criterias above.

If the conformity, will be evaluated for the concrete group;

All converted test results which belong to the 1st criteria group will be taken into consideration and applied to the refered concrete.

And 2nd criteria is applied to the original test results.

In order for a concrete to be approved that it belongs to a group, all of the average of test results which aren’t converted belonging to that concrete ( fcm) must be evaluated according to the 3rd criteria which is given in chart 15. Any concrete which doesn’t apply this criteria, is not accepted in the group and independently evaluated for it’s conformity.

In the 1st criteria the coefficient 1,48 in characteristic strength concept, expresses the value of % 5 which is the possibility of getting lesser values than itself . If this coefficient is above TS 500/2000, it will mean that the objective concrete will stay in the safer side, and this will effect the performance of the concrete beneficially.

In the beginning, the standard deviation of at least 35 test results in 3 months time period must be calculated before the production period. This value is taken as the estimated standard deviation for the whole production. The standard deviation along with the production whose conformity control will be checked, is determined in the beginning will be stated as valid on condition that (S15) standard deviation applies to the “ 0,63.σ ≤ S15 ≤ 1,37. σ “ . If S15 is outside these limitation of values, the latest 35 test results of the consecutive production will be used in order to calculate a new standard deviation value.

 

Numerical Example        Project strength : C 20/25

Group

15x15x15 cm Cube Strength

N/mm2

 

Average Strength
fcm
N/mm2

Minimum Single Value 
fcmin
N/mm2

Evaluation
fcm  ≥  fck + 4.0
fcmin   ≥   fck  -  4.0

Result

1

 26   -    28    -   29

27.6

26

27.6 < 25.0+4.0  
26.0   > 25.0 - 4.0

Rejected

2

24   -   25   -   26

25.0

24

25.0 < 25.0+4.0  
24.0  > 25.0 - 4.0

Rejected

3

28   -   30   -  30

29.3

28

   29.3 > 25.0+4.0  
28.0 > 25.0 -4.0

Accepted

4

29   -   28   -   27

28.0

27

28.0 < 25.0+ 4.0  
27.0  > 25.0 - 4.0

Rejected

5

30   -   29   -   31

30.0

29

30.0 > 25.0+4.0  
29.0 > 25.0 - 4.0

Accepted

All Production

Average Strength fcm =28 

Standard Deviation (σ) = 1.5

 

28.0

24

fcm≥fck+1.48x σ
fcm=28>25+1.48x1.5
fcmin=24 > 25 - 4.0

Accepted

 

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