Operation Drivway - Lessons Learned

Posted by blainegarrett

September 7, 2008

I have not written lately about my adventures in the lizard bricks. That doesn’t mean I have not been working on them. However, today I think I came to the realization that I need to start over. The key issue is that the limbs keep breaking off, even with the concrete. This is mostly due to the joints being to narrow compared to the depth of the bricks. This would be fine in application since the interlocking nature of the bricks will displace the weight of a vehicle, etc. However, the breakage occurs when removing the bricks from the mold.

So, the plan is to start over from scratch with a new clay version bigger than the original to make wider limbs. I am anticipating the end brick will be twice as large. This will have the benefit of covering more area, resulting in fewer bricks being made. Either way, here are some lessons learned:

Goods:

The proof of concept is valid - this can work.
The “level” version I made works slick and will prevent stubbed toes. I need to remember this when making the next one.
The mold and the concrete accurately capture the detail of the clay version. I could put a wee bit more effort into the next version to make it more detailed.

Bads:

Premixed concrete is not the way to go since it has too many big rocks. My best bet is to buy pea gravel, portland, and sand and mix it myself. I did this in the final trial and it worked slick.
Hardening time : I am probably going to need to let each brick harden for a week or so to give it the proper strength to be removed from the cast.
With the above said, this drastically cuts my production time down and I probably need multiple molds to compensate (I would like to eventually get this driveway done).
When making the mold, I need to not be stingy and try to fill gap areas with empty space (such as beer bottles). This is more of a pain in the butt and potentially leads to a weak mold - especially if I switch to a softer polymer.
Softer mold : I also probably want to use a softer polymer. Due to the shape of the bricks, the limbs probably count as “under cuts” and thus I need to use a less ridged mold to prevent breakage when pulling them out.
I probably need to match the size of the brick with a container that I will use as the cast to get the optimal size of the mold. Preferably, a round container… perhaps a cardboard concrete pillar mold or something more hexagon shaped.
The mold probably needs to be cut into pie-shaped chunks to more easily remove them from the cast. This might be a non-issue with softer mold mix and a larger cast. However, it is something to consider.

Other:

I might want to use barn nails to reinforce the joints like re-bar.
Using mold release on the concrete casts is probably a good idea, however I doubt this would have solved my problem with the breakage.
The original probably should be slightly tapered so that it is narrower at the top so there is less resistance pulling out the mold. Again, since the limbs protrude outward horizontally, this probably isn’t going to solve the breakage issue either.

Anywho. I might try this again very soon since I still want to be making bricks all winter. Assuming the bricks are twice the size, then I probably only need 250 of them. If I have 5 molds, it will take me 50 pouring sessions to do it. If I need to let the casts harden in the mold for a week, I am looking at another year of this or so. These are just estimates, but off the top of my head, it looks like maybe the driveway will be done Fall 2009, which is only slightly longer than I was expecting anyway. Radular. Anywho, wish me luck