UNDERWATER CONCRETING

Prepacked Concrete(Grouted Concrete)

Prepacked Concrete

• Placing coarse aggregate only in forms and thoroughly compacting it to form prepacked mass.

• Mass is grouted with cement mortar of required proportions.

• Mortar grouts the concrete and displaces water and fill the voids.

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Requirements

• Well graded aggregate to produce dense and compact concrete.

• The aggregate should be wetted before being placed.

• Aggregates up to maximum size of 80 mm .• Fine sand, pozzolanic filler material and a

chemical agent.• An air entraining agent .

Methods of Grouting

• The mold is filled partially with grout and coarse aggregates can be deposited in the grout.

• The grout can be poured on top surface of the aggregate and allowed to penetrate to the bottom.

• Pumping the grout into aggregate mass from the bottom.

Benefits of Grouting

• The prepacked concrete exhibit lower drying shrinkage and higher durability.

• Resistance from freezing and thawing.• Rate of development of strength is slow but

eventual strength is same so it is used for underwater construction.