Wednesday, November 3, 2010

Biocementation of Sand for Marine Engineering

I am surprised that I have not come across this a lot sooner.  My interest has been real for over thirty years.

What it boils down to is that it is possible to treat a body of sand multiple times to produce or alternately grow a stony material that ultimately looks like marble.

It immediately solves a huge civil construction problem in that sand consolidation is always a method of choice when it is available.

Here they show that applying this to road building is completely feasible.  This means that an entire roadway can be built up at the same speed with no imported asphalt to finish the surface.  No more heating machines.

The real payoff has to be in the area of ocean engineering.   Dikes are obvious applications, but using it in combination with artificial seashell accretation on a wire substrate allows us to produce sand holding cells that can then be cemented.  Such a process allows us to build up a full blown barrier reef that is as wide as desired and as deep as necessary and presenting to the sea a coral reef structure quite able to withstand hurricanes.

A working crew could lay down from a barge a section of metal framework unto the sea bed every season and initiate the accretation process.  The next season, another crew could pump in the treated sand to initiate consolidation.  This process could be repeated several times in a season and into the next season as needed.  Once fully established, it is no trick to repeat the whole process and build up an additional layer.

It would consume a lot of cheap chicken wire and low grade rebar but that is the only direct material expense.  Forming container sized cells appears a pretty good idea in order to minimize the amount of steel.

Earlier posts in this blog discuss the use of low voltage direct current to accrete a dense layer of calcium carbonate and manganese sulphate.  Once a good layer has been established, it may even be smart to use a liner bag that is then filled with pumped sand and inoculants so as to fill up the cell.  Maintaining the current will build out the accretation while the sand consolidates as a unit and as the plastic finally disintegrates allowing the structures to properly bind.

I see ample merit in commencing this process along the Gulf coast in particular.  There losses are a problem and hurricane inundation commonplace.  A barrier reef a couple of miles offshore even would solve both problems forever.  It would also massively improve the fishery and prospectively expand mangrove forests into the swamps adjacent.

I also see ample merit in applying the method on all other coasts.  Massive lagoon fisheries are established, coastal mangrove forests are grown to the full extent of their range and the threat of storm surges are mastered.

Imagine placing barrier reefs in the North Sea in front of Holland and the mouth of the Thames.  I suspect the fishery alone will justify the effort.

Again, these can be built out at an annual increment of even a mere mile or two or even less.  Accumulation over even centuries will complete the task eventually.  It can be a small drain on societies resources yet a provider of accumulating perpetual benefits.

NOVEMBER 01, 2010

* This bacterium uses an enzyme to make its surroundings less acidic, which is a good environment for them to grow", said Ms Whiffin. The by-product of this reaction is calcium carbonate, or limestone

* Ms Whiffin believes her biotechnology work will have many applications, not only for restoring historical buildings, but also mine shafts and other industrial structures.

* In 2002, a Dutch company responded to Ms Whiffin's website and shipped sand samples from Holland for testing.

* They were impressed by the capability of the bacteria to cement sand samples from Dutch dykes that protect the land from rising sea levels.

* a similar technique is being used to clean up strontium spills in the United States at the moment.

The biggest block they have made as of 2009 was in a shipping container, just to prove that it can not only work in the laboratory

A major practical application for the biocementation technique will be in mining. It doesn’t need oxygenation. In theory we could solidify the sea bed before drilling for oil. We could also drill tunnels in the sand, we could make the sand harder so it doesn’t cave in.

There was a 2008 patent

After biocementation treatment, Koolschijn sand indicated a shear strength of 1.8 MPa and a stiffness of 250 MPa, which represents an 8-fold and 3-fold respective improvement in strength compared to unconsolidated sand. Significantly lower strength improvements were observed in sand mixed with peat. 

The construction industry is slow to adopt new technology, so this will need to penetrate some unique niches where there is no established or adequate alternative. The mining and dike applications look to be first and perhaps some desert experiments in Dubai and the UAE where they are already looking at creating artificial water tables on a large scale (waterproof sand).

NOVEMBER 01, 2010

Sandstone roads could replace regular asphalt. The resulting roads are 20% more reflective and can reduce the urban heat island effect by 2-3 degrees celsius. The project is a part of the iida awards 2010 competition, organized by designboom in collaboration with incheon (south korea) metropolitan city. 

Scientists have produced a method of creating a biological substitute to asphalt, that could be produced at much lower costs, and have the same behavior as a paving material.

The new “sandstone” road surface is produced by using sand and a specific type of bacteria. The idea belongs to designers Thomas Kosbau and Andrew Wetzler, who are the winners of the Korean green design competition the iida awards.

The team says that mixing common sand – one of the most abundant resources on the planet – with a solution containing the microorganism Bacillus Pasteurii could result in a cementing process that turns the mix into biologically-engineered hardened sandstone.

After the two are mixed, the solution is sprayed on yet another layer of sand. The microbes act again, solidifying the layer underneath, and resulting in a tough, road-worthy material that can sustain heavy traffic.

Additionally, given the low cost of manufacturing the material, it will be a lot cheaper to repair it as well. When cracks appear, all maintenance crews will have to do is spray some of the bacteria solution within, and leave the road to solidify again.

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