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Re-think Concrete

 
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies. Thank Post    www.sefindia.org Forum Index -> E-conference on Durability of Concrete - Feb 27 to March 11 - 2012
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chintanp
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PostPosted: Mon Mar 05, 2012 9:23 am    Post subject: Re-think Concrete Reply with quote

Material by design has not been achieved yet. Though we have progressed from


  • No quality control - Stones, as they are naturally occurring - to
  • Some quality control - Bricks, combination of selected earth - to
  • Better quality control - Cement, tested and processed combination - to
  • Still better quality control - Concrete, Designed - empirically

One of the issues with this simplification is that Civil Engineering materials (CEM) seem simple, infact too simple that currently 90% of civil engineering jobs are handled by unskilled and illiterate man-power.

While this was good 50 years back, when a nation needed to be built-up from ruins, it has created a very rudimentary mindset regarding CEM and concrete in particular. This simplicity has been ingrained  so badly that even colleges teach it superficially.

"Concrete is a mixture with cement as binding material and aggregates  occupying most of the volume."


This definition though imperfect on a few grounds, is presented to highlight the following points:


  • OPC is just a type of cement, not the cement or only cement. There have been other types of binding materials like Lime etc that were used for this purpose. Newer or other materials can be used as cements.
  • Aggregates doesnt only mean stones. Any material that exhibits the necessary requirements can be used as an aggregate.

And so are created venues for research. If and most work done in concrete-design is not popular.


Students need to realize that there can be more than one type of concrete. There are infact many-many different uses of concrete requiring a different material everytime like concrete under water, transparent concrete, light-weight concrete, self-compacting concrete etc.

The cost and time of designing a new material every-time might not be justified, but atleast at the academic level, attempts at material deisgn must be made mandatory. Only this will keep the future engineers open to innovations from all fronts.

Designed concrete will take into consideration the environmental condition of exposure, the ingredient material properties, age of structure required etc. leading to improved performance.

If highly durable concrete is required for bridges, where is low-durable concrete required? Is it made with the less life aspect in consideration?

Reducing the cost of concrete in areas where not required may lead to increased work and implementation of high-performance and durable concrete.
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chintanp
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PostPosted: Mon Mar 05, 2012 3:56 pm    Post subject: Self Healing Concrete Reply with quote

Using Fibers as reinforcement : http://www.asknature.org/product/cd6ff82750db9c9c7490b071e5a6b4d4

Using a patented process:
http://www.sciencedaily.com/releases/2009/04/090422175336.htm

Using Bacteria which stay latent until there is water intrusion, after which they fill the cracks with lime like compound:
http://www.google.co.in/url?sa=t&rct=j&q=self%20healing%20concrete&source=web&cd=1&ved=0CEcQFjAA&url=http%3A%2F%2Fwww.ingenia.org.uk%2Fingenia%2Fissues%2Fissue46%2Farnold.pdf&ei=xOFUT8bRMsWtrAfX7oHVDQ&usg=AFQjCNF9l0zcWeoCgTo751FaBdFp1wgIzQ&sig2=1wQjEo8JNL6RZnAU6itgPQ
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Dr. N. Subramanian
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PostPosted: Tue Mar 06, 2012 4:34 am    Post subject: Re: Spray-on solution to earthquake strengthening Reply with quote

Spray-on solution to earthquake strengthening  
      CLAIRE ROGERS
     
Last updated 05:00 05/03/2012
  
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ANDREW GORRIE/Fairfax NZ

BOOSTER: Peter Jones, of Aardvark Concrete Services, sprays Flexus, a flexible concrete used to earthquake-strengthen buildings.


  Spray-on "bendable" concrete sounds oxymoronic, but it's helping earthquake-strengthen the century-old toilets in Wellington's Courtenay Place as they are converted to a pizza bar.
  The concrete, called Flexus, will also be used to shore up vulnerable older buildings in Christchurch.


  Derek Lawley, general manager of Auckland firm Reid Construction Systems, said Flexus had polyvinyl alcohol synthetic fibres sourced from Japan bonded to the concrete to give it tensile strength.


  "You can imagine the old brick buildings or blockwork buildings, under earthquake loads they're very brittle ... and they can end up as a pile of bricks.
  "If we spray this material onto them, we can turn [them] into something that can bend and take the earthquake loads and keep the building together."


  Strengthening unreinforced masonry buildings traditionally involved using reinforcing steel that was then covered with concrete about 10 centimetres thick, Lawley said. But a coat of Flexus could be just 1cm thick meaning there was little change to the building and it was often applied to the interior walls of historic buildings so their facades were not ruined.


  Flexus was also used to make Sir Richard Taylor's Rugby World Cup sculpture in Wellington's Civic Square, create building facades, strengthen the iconic brick chimney at Auckland's Victoria Market, and would be applied to buildings in Christchurch, including ASB Bank in Rangiora and the historic pub Lyttelton Times Cafe, Lawley said.


  The solution was relatively cost-effective, he said, costing roughly $50 a square metre for a 1cm coat.


  The company began using Flexus, which is also being used on wharves and bridges, after developing it with researchers at Auckland University, and in Japan and the United States, and Lawley believed it was the first company in the world to commercialise its application.


  Reid trains regional firms including Wellington company Aardvark Concrete Services to apply Flexus.


  It is setting up a Christchurch reseller.
  Before the Christchurch earthquakes in 2010 and 2011, councils had taken a relatively relaxed approach to earthquake strengthening. A lot more pressure was now being placed on building owners to ensure their properties were up to standard, Lawley said.
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