Wednesday, March 12, 2008

Building a ferro cement structure,Vietnam.2006

Dr Tuan, from the Forestry Science Institute of Vietnam, asked me to design a structure over the fertigation system (a basic ventury setup) downhill from the 40,000 liter water tank so stuff could be stored and locked without the worry of theft.The locals are pretty light fingered around the farm.While doing some earthworks here,the dozer broke down with a broken fan belt and over heated.I couldn't really move it without further damaging the motor so I had to leave it where it was.The next morning I went to the machine and both batteries and the alternator were missing.Some local people had been there during the night and pinched them.

Anyway,as some tanks had been constructed here by Darren and the workers I thought I would try a building from ferro cement also.I drew a quick design for the contractor based on something similar in Australia we use for a nursery,minus the cement.
The structure was to sit next to an access way to the ridge dam.I designed one side of the building with a retaining wall to retain the material for the access track.As the majority of the traffic on this track was motorcycles,and the track was quite wide,the retaining wall should hold well.The steel wire would go on the outside of the blocks used for extra strength.So the steel wire was straightened (as it comes rolled up in 200kg parcels) and the foundation laid after I went in with the Komatsu 'baby' excavator (baby meaning small) to dig and level the footings.
Local rock blocks were used and cost about 10c each.The manual labour involved in this task is amazing.Boulders are sourced from however far away then people start chiseling away with hammers and spikes to break them down.No hydraulic rock breakers used here,just good old fashioned jail yard toil.As the boulders split or fracture they are then broken smaller to about 200/300mm X 100mm X 100mm.Then they are loaded by hand onto a farm tractor trailer and brought to site and again unloaded by hand,usually where the tractor parked,not necessarily where exactly needed and then possibly moved by hand again to their final resting place.
The local contractor had also built some culverts for me also from the same rock.Usually one load of rocks is about 500 pieces.Any more than that the tractor gets out of controll on the road.
Above is Mr Sun who worked for the contractor.He was a really bright young bloke and a great worker.I was supprised one day when I saw him all dressed up riding a motorcycle outside the farm when I had also only just saw him working on the structure.I found out later that he is a twin.His brother totally opposite to he.Liked wearing fancy clothing,didn't like work and a real casanova.Really great guys though.
So the steel wire was joined together in a 200mm grid fashion and then snake wire was layed inside and out to be the support for the mortor when it gets applied.Some supports were fitted temperarily inside the structure to stop the roof from collapsing under the weight of the mortor.Mind,the complete wall thickness was only 25mm,but when set is as strong as.The mortor is applied to the outside and allowed to set and then repeated on the inside.The mortor has a good rough bonding surface on the inside from the outer layer being forced through the snake wire.

Then we had a finished product.It was really cool inside and a good place to have a rest at lunch.Dr Tuan was really happy with the finish as was Darren.It was also possible to mould some gutters onto the side to collect water from the roof and store in a small tank for hand washing.A door was put on and then ready for use

The finished structure was able to hold my 90kg weight and some more.All it needed was a coat of white wash and some plants to shade it.A great job done by all.

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