Grout For Prestressing Tendons-Basic Requirement BS EN -447:2007

Grout for prestressing works is used to fill ducts of post-tensioned prestressed concrete.

Several functions of grout are as follows

·????Provide protection to prestressing steel against corrosion

·????Fill voids to avoid water accumulation and any frost damage

·????Where required in the design, provide bond between prestressing steel and ducts

·?????Allowing transfer of compressive stresses in structure, in a direction transverse to internal tendons

Grout should be complied with the requirements given in of EN-447 for following tests, and testing is done in accordance with EN 445

Tests: Sieve test, fluidity, bleeding, volume change, strength, setting time, fluid density.

This standard is divided in to following 4 sections

4- Material

4.1: Cement: EN 197-1 type CEM-1 or any other. The cement type shall be declared.

4.2:? Water: As per EN 1008

4.3: ?Admixture EN 934-4 or 934-2

4.4:? Additions Sec-5, EN 206-1: 2000, Silica fumes EN 13263

5- Batching and mixing of grout

·? Batching at Site (solids mixing) or in factory as ready-mixed grout with mixing of liquid at site

·? Mixing of solids material by mass, and mixing of liquid materials by mass or volume

·? Accuracy of batching:

± 2% for cement, dry admixture and additions

± 1% for water and liquid admixture

6- Properties of grout

6.1: General: The grout shall not contain more than:

·? Chloride (Cl- ) ≤ 0.10 % by weight of cement

·? Sulfate (SO3 2-) ≤ 4.5 % by weight of cement;

·? Sulfide-ions (S2-) ≤ 0.01 % by weight of cement.

6.2: Sieve test: Grout shall be tested according to EN 445 and no lump shall remain in the sieve.

6.3: ?Fluidity: (Test: EN 445) Grout should not change by more than 20 % from immediately after mixing to 30 min after mixing or as per manufacturer recommendation

6.4: ?Bleeding: Test: EN 445,

1) Wick induced method 3 tests.

2) Inclined tube method

Not greater than 3% of initial volume kept at rest for 3 h

6.5: ?Volume changes: Within -1% to +5 % in 24 hours

6.6: ?Strength: Not less than 30Mpa at 28 days, not less than 27Mpa at 7 days, if to be estimated for 28 days at 7 days. Test: EN 445

6.7: ?Setting time: Test: EN 196-3: Initial set ≥ 3h, Final set ≤ 24 h

6.8: ?Fluid Density: Test: EN 445

7- Evaluation of Conformity

7.1: Production Control: Internal control by grout manufacturer for grout fabrication. This requirement applies to grout dry-batched in a factory and to grout batched on site.

7.2: ?Initial type testing: Shall be performed for any grout well before any use on a project for:

·? New mix design

·? Change in material used for the grout

·? Grout is intended to be used in a temperature range for which no prior initial testing has been performed.

7.3: Audit testing: During on-going fabrication of a particular grout, audit testing shall be performed in regular intervals to confirm the validity of the results of the initial type testing. (Table 3 – Extent of audit testing)