Bill Gates pointed out that China has used 6.6 gigatons of cement in the last three years compared to 4.5 gigatons the USA has used in 100 years. Not only is that a lot of cement, it is in a very short time.

## Mass and Volume of Cement

How much is 6.6 gigatons? I'm not a big fan of the "ton" unit since there are several different definitions. In this case, I suspect intended definition of the ton is a unit of mass equivalent to 907.18 kilograms. That's just an assumption. However, with that assumption the Chinese have used 5.99 x 10^{12} kilograms of cement.

There's still a problem. It's difficult to show mass, but it's pretty easy to visualize volume. If I know the density of cement, I can use that to find the volume of cement used by China (and the USA). The Engineering ToolBox lists cement with a density of about 2300 kg/m^{3}. Using that, I get the volume of China cement as:

If I do the same thing for the cement used by USA, I get 1.77 x 10^{9} kg.

## Visualizing Volume

If I were going to use a bunch of cement, I would just make a giant cement cube. The length of each side would just be the cube root of the volume.

Does that look crazy? Maybe a little bit. China used 1.47 times the amount of cement (again in just three years) but their giant cement cube is only 1.13 times taller. That's not crazy. Take 1.13 to the third power, what do you get? Yup, you get 1.47. It all works.

So, what would this giant cement cube look like? Using Google Earth, I can draw this cement cube. I'm not sure why, but I put it in Chicago next to the Willis Tower (about 8km from downtown)