UPDATE: There have been lots of questions about safety and practicality aspects. The pictures here aren't of the final placement of the seat, because they wanted to put it in a bunch of architectural galleries first, so I have added another step addressing things you need to consider for long term placement of something like this.
This was a summer project run within the architecture department at the University of Brighton.
It was a group project, has gone over a year with no further development, so I can't imagine anyone will mind me showing the process here.
If you try this yourself or take inspiration from here please cite 'University of Brighton Architecture Department' as a source.
See here for all the people involved in this project
The Brief:
Design a chair / seat predominately made of concrete.
The Competition:
Consisted of several rounds finally producing a winning design
The Winner:
Was a design for modular blocks which could be stacked to create different seating arrangements.
Development:
The winner couldn't be there for the build so we developed the deign adding lugs onto the bricks to help them fit together more securely.
We then began to experiment with different textures to add to the blocks.
The Build:
Initially took two weeks, then about a month coming in every 3 - 4 days to break the moulds, clean them and cast new blocks.
Read on for details
This was a summer project run within the architecture department at the University of Brighton.
It was a group project, has gone over a year with no further development, so I can't imagine anyone will mind me showing the process here.
If you try this yourself or take inspiration from here please cite 'University of Brighton Architecture Department' as a source.
See here for all the people involved in this project
The Brief:
Design a chair / seat predominately made of concrete.
The Competition:
Consisted of several rounds finally producing a winning design
The Winner:
Was a design for modular blocks which could be stacked to create different seating arrangements.
Development:
The winner couldn't be there for the build so we developed the deign adding lugs onto the bricks to help them fit together more securely.
We then began to experiment with different textures to add to the blocks.
The Build:
Initially took two weeks, then about a month coming in every 3 - 4 days to break the moulds, clean them and cast new blocks.
Read on for details
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We took inspiration for our design from Roman columns. To secure each piece of stone to the one below it they would have lumps projecting out of one stone and holes in the other that would fit snugly together.
We used laminated chipboard and constructed a simple box. In one side of the box we cut out a circle and sunk a small plastic dish in there (sealing it up with silicone).
On the opposite side we placed a plaster filled dish straight on the side.
We made two of these boxes and cast them.
The finished bricks came out really well. To me they look like giant versions of lego 1x1 bricks.
For the final version we used 4 square lugs on top (including 2 lugs on the sides).
We used laminated chipboard and constructed a simple box. In one side of the box we cut out a circle and sunk a small plastic dish in there (sealing it up with silicone).
On the opposite side we placed a plaster filled dish straight on the side.
We made two of these boxes and cast them.
The finished bricks came out really well. To me they look like giant versions of lego 1x1 bricks.
For the final version we used 4 square lugs on top (including 2 lugs on the sides).
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What we ended up doing was renting a concrete grinder for about £20 and using that to take the edges off of all the blocks.
It is possible to round off the corners in the mould, but the way we have ours set up it would take way too long to reset each time.
thank you for your time and consideration
Peace Jeff
I made a few similar projects, and thought I'd share a few suggestions.
First, if you would like the units to be lighter and easier to transport and rearrange, you can insert either an empty box inside the mould (which you won't recover) or alternately, build the bottom first, insert a rectangular tube form (box with no top or bottom) into the center, fill the sides of the mould, forming your "rectangular tube", fill the inner form with packing peanuts or some other light substance for volume, pour additional cement into the inner form, and remove. Then fill to the top of the outer form. Now the center is mostly Styrofoam, and the final block is significantly lighter.
Alternately (or additionally) you might want to consider using hypertufa or papercrete in place of regular concrete. hypertufa is made using portland cement, and peat moss instead of the sand and aggregate. It is very strong and very light.
Papercrete is similar, but uses paper pulp, like pulverized newsprint, instead of peat. It too is very strong and very light.
The outer surfaces on hypertufa are very organic looking and pretty. One idea that works well is to attach moss samples onto the inner sides of the mould prior to pouring the hypertufa. When the unit dries, the moss is embedded into the sides, and continues to grow, creating a nice, soft, natural surface.
To this end, you can add additional reinforcing elements, if it is intended to support much weight. Making it hollow, as detailed above, helps greatly, and also makes drying time not much of an issue, since it can dry from the inside out as well as the outside in. It helps to leave a small hole in the top to let the water vapour out as it cures.
But the real trick of course is just not to use too much water in the first place, as you said. Since the curing of cement is NOT due to it drying out, but rather due to the water being used up as part of the chemical bonding reaction, starting with a dryer mix assures that there will be little to no water vapour that needs to escape.
That's pretty much what they were designed for too.
You could put plastic water bottles in the mold to make it lighter. beats putting them in a landfill.
Also did anyone try to figure out if you could design the nubs and voids so you could stagger the blocks and interlock them horizontally as well as vertically?
The original idea was for series of pillars that were different in height and created setting, but obviously grounds people had concerns over how high they'd let us pile these things, so it because more spread.
So yes considered, but rejected, in line with the original design.
Also here in the US they do have powdered dyes that you can add to the mix to get different colors
I did wonder how many bags of sand and cement you needed to fill a single mold?
And how many castings you were able to get out of a mold?
Once again great job
We cast about 5 / 6 blocks from each mould. they were looking a bit ratty by the end, but I reckon we could have gotten 10 out of each before they started actually becoming unusable.
I think I'd add in some glass or such and make them hollow to reduce weight, cost, and curing issues.
1. the alkali silica reaction between the glass and cement will actually break down the structural integrity of the block overtime and it will eventually fall apart.
- not such an issue in furniture but still not good practice (don't feel bad if you've never heard of this, I only did because my Uni was doing research into it)
2. we don't want to reduce the weight. because this was going to be installed in front of the building, security is an issue. We have to make sure that no one will steal it, and that it won't be knocked over and hurt anyone.
Lighter things like metal and wood benches have to be bolted to the ground, pain.
When we stick a couple of these together they are deemed both heavy enough that no one will run off with one and stable enough they won't fall on someone.
In short, for a home project glass can be a great way to reduce cost and weight, in a live, public project we had to consider different priorities.
Also mixing in polystyrene beads will greatly reduce weight if that's what you need :)
We did also experiment with making a few 'capping blocks' which didn't have the top lugs. We only had one mould for this and so there are only a couple.
Thankfully, I do not have small children, which could be a problem for others.
I disagree. Having the neighbor's kids come over to help. Now depending of there age they could be give different tasks. For the younger one's they could be given the task of collecting things from around the neighbor hood that would be used part of the molds decoration. This would give them pride and a sense of belonging and contributing to the neighborhood. So Invite your neighbors and there kids to come and help, also invite your family and there kids.
Oz is correct, the warmer it is, the quicker they cure. We try to turn over molds every day (start a new cycle.) BTW concrete does not dry, in fact it had better not. It needs the water in a correct ratio mix to form the molecules of cement.
A mold meant to hollow out a larger casting is called a core mold and they are carefully thought out and constructed, with the emphasis on draft, angles that make them easy to pull out.
Starting with white portland is more attractive, and colors mixed with white are much cleaner.
Nice woodworking anyway.
Also, with some slight modifications you could use them as a combo retaining wall/bench.
I wonder if hinges on the outside corners of the molds would work as well as using screws. Just pull the pins to open the molds.
Hollow with open bottoms. Inside corner around the top that fits into the open bottom
to reduce the wieght put a block of polystyreene in the middle
for another variation put coloured powder paint in the concreete mix to give different coloured blocks
Might use them for both seating and thermal batteries.
Keep up the good work.
Bill
A very simple yet elegant design. The blocks stand alone as a piece of art, especially with the natural imprints, or you could construct raised beds or ponds with the cubes. They could also be used to divide a space and coated with yogurt to encourage moss. The possibilites are endless.
Scaling up would be easy to do if needed.
I was thinking of using hypertufa to make the structures lighter and more 'organic'. My garden (really a piece of scrub at the back of the house) needs uplifting and this could be just the thing to do it.
Thankfully, I do not have small children, which could be a problem for others.
Excellent work.