Concrete backgammon chips test specimens are amazingly strong!
Proportions
During my time as a research assistant at Mines, I was also able to fit in some time to make test cylinders of the mix I designed for my custom concrete backgammon chips. (Quick blurb on the project here if you haven’t already checked it out.) I made the mix in a conventional concrete mixer to produce 3 cylinders. The next day, I mixed the same proportions in a kitchen mixer — just enough to fill 1 cylinder. This was closer to the methods used to produce the actual mix for the chips themselves. The materials and proportions I used are listed below:
- Holcim Cement, Type II/IV (only type available)
- Silica Fume
- Quikrete Play Sand, rinsed
- MasterGlenium 7500 (HRWR)
I also tested the Play Sand for absorption (ABS) and specific gravity (SG) and did a sieve analysis in the lab, as I couldn’t find this information from the producer.
Breaking
After returning to my hometown for a while, I finally got a chance to break my specimens in a compression test. The samples were 97 and 98 days old, so they should have been near 100% strength. Due to my lack of knowledge in designing concrete mixes without a coarse aggregate, I was unsure of how well the strengths would turn out. Without much of a basis, I expected around 4000-6000 psi. But — then again, I did try to design these to be as durable as I could make them within the constraints…
The first cylinder kept me in anticipation for the break as it blew past 4000, then 6000 psi. Soon enough it passed 8k, 10k, 12k… I backed up further as time went on, knowing that a higher compressive strength means a louder and more explosive break. Finally, it broke at 13,568 psi with a thorough Type 1 fracture. My next specimen hit 15,856 psi (Type 1)! The final two both broke around 13,500 psi, but with a columnar fracture (Type 3) indicating that the strengths could have been higher. The testing cap was bowed out, which was likely the main issue.
With some research, I found that there are specific ways to test high-performance concrete (HPC) like this one. In the future, I would test according to those guidelines. I never imagined that my simple backgammon chips would be considered HPC, though! My aunt will never have to worry about her chips, well.. chipping! Now those are some OP game pieces.