self compacting concrete 1

[pechetty]

hi!
i'm interested in self compacting concrete.could some one give me details about mix proportioning procedure for a required target strength. please also give me details ab't various sites about scc.

Pechetty.

 

[dicksewerrat]

Never heard of this. Self leveling conrete though, just a slump of 15"+

 

[Ron]

A 15" slump? Now there's a trick!

 

[Taro]

Self-Compacting Concrete (or Self-Consolidating Concrete) does not use a standard slump test. Instead a ASTM C143 slump flow test is used. When the slump cone is raised, the diameter of the resulting spread is measured. The concrete should flow without aggregate segregation.

 

[Zambo]

A high slump is required, as mentioned earlier this is measured with a flow test. Aim for a slump around 175 to 225mm in your mix design. Bear in mind this is for particluar uses such as bored piles and because of the high cement content (to keep the water/cement ratio low) the mix is expensive. Use a water reducing plasticiser to achieve the required flowability. In general if possible better to use a normal slump concrete of between 50 to 100mm and compact with internal or external vibrators.

Zambo

 

[SirAl]

There are proprietary products such as 'Agilia' by LaFarge that basically flow into place. A contractors dream.. "A 4-corner slab pour" No screeding required! Flows around a congested rebar configuration. Forget about mix design/proportioning however. Such products are Top Secret!

 

[Taro]

Be careful about using SCC for slab pours if you haven't used it before. The mix does not bleed and the finishers can have a hard time. It is particularly well suited for vertical elements (walls, columns, etc.) especially in congested areas. Placing SCC is as easy as filling up a bathtub but the forms need to be watertight.

 

[Zambo]

SirAl and Taro thanks for educating me, very interesting. I've carried out a couple of web searches, seems technique developed in Japan, but now fairly common in States also. Wonder how the cost of materials against savings in labour compares.

Zambo

 

[Taro]

Our local supplier charges a $20 (U.S) per cubic yard premium for SCC compared to a conventional mix with comparable strength. There also may be a higher formwork cost. However, the placing costs are much lower. Our local supplier recommends pouring walls with vertical drop of 20 feet and horizontal runs of 40 feet, no vibration required. So the total in-place cost of the concrete may not be higher than conventional concrete.

 

[Ginger]

There is a good paper on SCC in precast works in the Feb 2003 edition of CONCRETE published by The Concrete Society. In the paper the benefits of SCC are laid out.

http://www.concrete.org.uk

http://www.concreteon-line.com