No Slump Concrete

By:Ibrahim Al MohannaHani Al AnziAbdulaziz Al Mayouf

Content:

• Introduction:• What is a No Slump Concrete, NSC.• Applications of NSC.• Some types of NSC.• Consistency tests for NSC.• Mix proportion design of NSC.

Introduction:

Concrete varies depending on its consistency to:

•Very plastic concrete,•Plastic concrete,•Stiff plastic concrete,•Stiff concrete,•Very stiff concrete, and •Extremely dry concrete.

Workability is decreasing

What is a No Slump Concrete?

No-slump concrete, NSC, is defined as concrete with a consistency corresponding to a slump of 6 mm (1⁄4 in.) or less.

It is very stiff mix, thus have lower paste requirement.

It has poor workability, especially when consolidated by hand rodding.

usually compacted using high frequency vibration.

Application of No Slump Concrete:

It is frequently used in precast where heavy vibration can be easily provided So it can be demolded faster:

Such as:– Precast Pipes.– Precast manholes.

It can be used in cast in place operations where the concrete must maintain its shape unassisted before setting occurs.

Such as:– Slip formed pavement,– Curbs, and– Some architectural operations.

Application of No Slump Concrete:

Some types of No Slump Concrete

•Roller Compacted Concrete, RCC:

Mainly used for water control structures (dams) and pavements.

•Pervious Concrete:

Mainly used for pavement and walkways.

Consistency tests for NSC

Compacting factor test:

1. Concrete is placed in an upper then dropped into a lower hopper then fall into a standard cylinder.

2. The cylinder and concrete weighed (partially compacted weight)

3. The concrete is fully compacted, extra concrete added and then concrete and cylinder weighed again (fully compacted weight).

concretecompact fully ofweight

concretecompact partially ofweight factor Compacting

Vebe test

1. A slump test is performed in a container

2. A clear Perspex disc, free to move vertically, is lowered onto the concrete surface

3. Vibration at a standard rate is applied

Consistency tests for NSC

Vebe time is defined as the time taken to complete covering of the underside of the disc with concrete container

Modified compaction test

Thaulow drop table

Consistency tests for NSC

Mix proportion design of NSC.

Mixing water requirement:

water- cementitious materials ratio:

The selection of w/cm depends on the required strength.

Using the maximum permissible w/cm and the approximate mixing water requirement, the cementitious material content can be calculated by dividing the mass of water needed for mixing by the w/cm.

Mix proportion design of NSC.

coarse aggregate quantity

The largest quantity of coarse aggregate per unit volume

of concrete should be used.

Mix proportion design of NSC.

Designing the mix proportion for NSC is almost the same as the conventional concrete using absolute volume method accept the selection of water content, w/cm ratio and the coarse aggregate volume.

Mix proportion design of NSC.

Thank you

Questions?