Scratch Build – In Progress "Xposure" polished concrete desk....update 03.04.16

Well how to start......

I have long dreamed of building my own computer case and desk. I have been coming to this site for many many years for ideas. I have been blown away by the effort and ideas everyone has on here.

So I have finally got around to doing something my self. I have got about half way through this project. So over the next few days there will be a rather large amount added here which sums up around 3-4 months of work but years of knowledge that I have research and experimented with.

So with out further a do.......

The idea is simple and breaks down into 3 parts.

1- desk top, this is going to be an exposed aggregate concrete. Simply put I will cast concrete and then grind it back to expose the aggregate
2- desk supports, this will be a wooden frame made in 2 sections. A front leg and a wall mounted back which will have the compute mounted on it.
3-wall mounted case, This is the only bit I haven't finalised yet. As it depends on money when its time to build whether I will watercool or aircool.

This is an example of exposed aggregate concrete, however when I'm done mine will be much smoother.



So before I truly decided this was the what I wanted I did a few test pieces.

This shows 3 slabs with one that's been ground down and 2 that are in there cast state. They only show a very rough grind but was enough for me to love it.



10mm aggregate (this is the size of the aggregates not the thickness of the concrete)



mixture of 10mm and 20mm aggregate (this is the size of the aggregates not the thickness of the concrete)



Having decided this was the way I went about designing the desk its self.

What I'm currently on. The wife decided my old desk was too big and took over the room so kicked me behind the door. So space is at a premium!!!!



desk shape 1



Desk shape 2



I decided I liked the shape of the 1st type on shape 2. which lead to the following design



The high back will allow be maybe a shelf or 2 and somewhere to mount my computer with all the wires hidden behind the wood. (I really hate wires so thats one of my key goals is to hid them all).

Having a clear goal I started to build the mould and get really for the casting!!!

I should tell everyone a little about myself it may explain way I have gone this way.................
I work as a concrete technologist at a company which researches and manufactures chemicals to enhance the performance of concrete. So I firstly have knowledge and access to a lot of chemicals that a person the street wouldn't have. I did a lot of testing on the aggregates before I stared this to get the most out of it. From my testing I found that the 20mm concrete looked better but due to the size of the aggregates it broke easily, so to get a better strength and also packing of the aggregate I would stick to 10mm concrete. Next I decide on the mix final mix design (which I won't go into unless people really want to see it), this included a superplasticer, cement dye and nono-silica. Superplasticer allows the removal of some of the water while not affecting how well it flows, this in turn makes the concrete stronger in simple terms."nono-silica" is another material improving the strength proprieties of the concrete.

Another thing I used to improve the strength of the concrete was to add a layer of chicken wire and some rebar. sadly i didn't get a picture as i didn't want my phone covered in concrete.

(if people want to know more on any of the above please let me know on here and I will try to explain the best I can)

I did make a rather large mistake here. I massively over dosed the superplasticer which lead the my first mix making a MASSIVE mass with the water separating out in a big way. There was black dye everywhere the wife went mental, there was no way to save the mix so it was scrapped. But the second mix worked fantastic.









demoulding





Once the concrete was aged alittle all the wood was removed and the concrete was ready for its first grind.



So tonight I will leave this post with an image of the first very rough grind.





As you can see the aggregate is really densely packed and lots of variation.

Really hope everyone likes the first section of my build, there is more to come over the next day or 2 which will take me up to around half way. Plus I have a much better camera on order so pictures will can much much better.

At least the name of the project is a little clearer now!! Xposure!! I am exposing the aggregate in the concrete. Anyone else got a better name? still now sure on it.

 

Really nice first post - no boring boxshots, nice intro to the log, and actual work...

Love the concept of the build, especially the home cast concrete tabletop, not something you see every day!, and it came out great!

Looking forward to the rest of the build

 

@skulth, can you tell me what material/hardware did you use for grinding? And will use for final polishing?

This is interesting project ;-)

 

That looks really sweet! Subscribing to this one!

 

So this was going to be the subject of a later post but there is no time like the present.

Materials wise I have used the following
10mm aggregate is basically pea gravel
Shape sand
Cement wise I used a Cem I high grade industrial
Dyes were Cementone dye, the black this time and later a red.

The mixing order of mixing can be important. Start with the sand, pea gravel and roughly half the water. This allows the materials to wet out and not continue to absorb once the cement was added. The the admixtures, dye and remaining water added. Then mixed fully adding more dye if it was needed. finally poured into the mould. Again if you would like more info on mix design ect let me know.

This is a image of washed pea gravel, there is lots of different colours and shapes and sizes.



I used crush glass later in the project



So tools........

The I have used a basic concrete mixer.



The grinding.... This is basically an angel grind with a variable speed setting. There is a whole set of grinding disc. The disc used are a diamond based with either a metal or resin based carrier. On the bottom row is the really rough grinding discs which are metal bound diamonds this is less than 25-50grit. Then the rest are resin bound diamond discs that range from 50-3000grit. (50,100, 200, 400, 800, 1500 and 3000). Its then very similar to sanding wood. Starting low and building to the higher grit, where each one removes tool marks of the last. The actual grinding is done wet. This particular grinder does have a water inlet, so it was a case of pointing the hose near the place your grinding. It is not ideal but getting a different grind it expensive.

 

this is unique and a fun thing to be following...

 

so next bit it picture heavy.

Fill in the channels left by the wood. This is a red mortar with the crushed glass.



The extra removed



Then grind back to the surface, this time going much much deeper



profiling the sides (look close you can see the tool marks from the rough disk)





grind up to 400grit









grind up to 3000grit





finally, grout the slab up to fill all the really small holes (A grout is just cement and water. I then used a black dye too). I wasn't going to do this otherwise I would have done it at 400grit but have thought on it i decided I would fill in the annoying little holes.







So this is the project to date, doesn't look like much but this has been a fair amount of work. I intend to re-grind at the weekend so more pictures will be added then.

but in the mean time I intend to enjoy a nice cuppa




Any thoughts or questions? If people really want more info on anything like me know.

 

I have a soft spot for everything related to the construction business, after having worked on and off in the business for 10 years now. Will follow this eagerly

 

Love it so far. You should have hunted down a gem/lapidary supplier and got something fancy to dust the top layer with.

 

Jesus how much will this weight ? Very different though, I like

 

I have somewhere I can get this type of material from but been as though this is the first major project I didn't want to waste a ton of expensive material if I cocked it up. Which to be fair I did on the first mix....What a mess.

There are other project I have in mind so next time I will more than likely add something special.

Just the concrete is around the 80 to 100kg.... sooo heavy... but hoping it will be worth it..... only time will tell but so far I'm happy

 

Concrete desk build? I'm in.

 

wooooooooooooooooooooooow

 

Very nice job on the custom worktop, looks awesome.

Is it a 2 or even 3 man job for carrying it though?.

 

Bump

 

Plz, i want to see more!!

 

Sorry I haven't been more active. Been a very busy couple of months.....new job, illness (slipped discs are **** when you work with concrete on a day to day basis), wedding and birthday. Also the desk surface needed time to mature to take the final grind. Anyway with all that out of the way I have found some time to continue.....

So I got some wood!!! and new tools.

I decided to go with pine and anything else was massively expensive.







Tools wise I needed a sander and a router to cut the groves later on. After using both I was very impressed. Last time i used tools like this they were rubbish.





Cats love boxes....The tools gave them new toys..the ginger one has now wrecked the box. shredded it.





The wife was away for a week so I decided to glue up on the kitchen table. (she wasn't impressed I had but oh well). I needed the extra space the garage is a little cramped plus i could get around it all. Never done this before and learn a massive amount for next time.





With the glue dried. The rough sand down could start.



With all the piece given a good sand. The join is actually quite hard to see. very pleased.





That's it for tonight.... well be more tomorrow. will be back to the concrete.

let me know your thoughts.......

 

Mod on and don't waste time, be concrete...
Sorry I could not resist...
Very original!

 

Who'd have thunk that something so smelly and mucky could be so pretty?

Very nice and quite original too

 

@Vault-tec - That's not a nice thing to say about him.

Honestly, your garage looks cavernous. I have to move stuff to work in mine.