BS EN 13791 gives rules for in situ

[S K CHAN]

BS EN 13791 gives rules for in situ checking if the hardened concrete in structure could achieve the designed compressive strength conform to the class of concrete.

If the measured in-situ values are expressed as equivalent cube strengths, it will usually be found that they are less than the strengths of cubes made of concrete from the same mix which are compacted and cured in a standard way.

In-situ compaction and curing will vary widely, and other factors such mixing, bleeding and susceptibility to impurities are difficult to predict.

Based on BS6089: 2010, the minimum individual in-situ strength value is given as 0.85*(fck -4 ) = 23.8 MPa for compacted concrete i.e. for superstructure casting.

What will be the minimum compressive strength for non-compacted concrete for cast in-situ bored pile?

 

[HTURKAK]

-Compressive strength classes range usually used for bored piles is between C20/25 and C45/55.

- Refer to consistency ranges given in ( DIN EN 1536:2010 table 4 — Target values of consistence and tolerances for fresh concrete in different conditions ) ..

- Suggest you to look DIN EN 1536 for Execution and Quality controll of Bored piles

 

[S K CHAN]

Hi Hturkak

Assuming that C32/40 concrete is used for the casting of bored pile, what will be the minimum in-situ compressive strength to be achieved for the hardened concrete of the bored pile?

In other words, if core sample of the hardened concrete of bored pile is taken and tested for unconfined compressive test, what is the expected compressive strength required for the concrete core sample?

 

[HTURKAK]

I disagree with your assumption and i have suggested you, to look DIN EN 1536 . If you looked to the consistency requirements you could see that the slump (H ) varies 150 to 200 mm..

Do you think the strength of bored pile concrete , if the slump H=200 mm and concrete placed by tremie pipe in submerged conditions, will be less than cubes made of concrete from the same mix which are compacted and cured ?

[quote
Assuming that C32/40 concrete is used for the casting of bored pile, what will be the minimum in-situ compressive strength to be achieved for the hardened concrete of the bored pile?][/quote]

The answer is EN 206 defines class C30/37 with fck cyl = 26 , fck cube = 31 Mpa. Refer to table 2 of EN 13791 .

 

[S K CHAN]

The value of the design compressive strength of bored pile, fcd is given as 0.515fck cyl in EN1992-1-1.

For class C30/37, fcd = 15.45 MPa.

Should the value of in-situ compressive strength of bored pile concrete be not lesser than 15.45 for class C30/37 concrete?

 

[HTURKAK]

Today , i saw your post..
I could not see the same figures in EN1992-1-1.

The value of the design compressive strength is defined as ; fcd= αcc fck / γc

αcc = Look to the National Annex. The recommended value is 1.0

γc = (partial material factor for concrete )= 1.5 ( for persistent loads )

For class C30/37 fcd= fck / γc=30/1.5=20 MPa.

2.4.2.5 Partial factors for materials for foundations .... (2) The partial factor for concrete γC given in 2.4.2.4 (1) should be multiplied by a factor, kf, for calculation of design resistance of cast in place piles without permanent casing.
The recommended value of kf is 1,1
In case of CIP pile without permanent casing

fcd= =30/(1.1*1.5)=18 MPa.