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 1012 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/m3. 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 109 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)

Screen capture from Google Earth showing a giant cement cube. Screen capture from Google Earth showing a giant cement cube.

That's a pretty big block of cement but nearly as big as a mole of salt crystals (in South Florida). I wonder if it was all poured at once, how long would it take to cool down? (cement gets hot when it hardens) You could see this block from quite a distance, but Google Earth doesn't render the buildings from that far away. Notice the Willis Tower right next to the cement? The listed height of this tower is 442 meters.

Maybe a giant cube of cement is a silly thing to do and a waste of cement. What if it was used to make a giant parking lot? How big would that parking lot be? I guess I need to make an assumption first. How think would the cement need to be in a parking lot? This parking lot is going to be super awesome. I am going to make it 0.25 meters thick (or maybe it's going to be a sucky parking lot if I underestimated the required thickness).

Since I know the volume, if I divide by 0.25 meters, I get a surface area of 1.2 x 1010 m2. What would that look like? Again, back to google maps. I wanted something you would recognize. So, here it is.

Screen capture from Google Earth with edited cement covered Hawaii.

I present to you the Big Island of Cement Parking Lot Hawaii. It's not exactly the correct area, but it's close enough. I didn't take into account the elevation changes due to the mountain Mauna Kea, but you can figure that out as a homework.

There was the option to draw this parking lot over a recognizable city like Los Angeles, but it's already covered in cement parking lots.

Homework ——–

Here are some other questions for you to consider.

If all of this China cement was used to make one road, how long would that road be?

If China kept using cement at this three year rate, how long would it take them to cover all the land in the world with cement parking lots.

Estimate the amount of cement used in a building. How many buildings have been created in China during the past three years?

How many cement trucks are there in China?

What percent of China's cement was used to build the 3 Gorges Dam? Estimations required (don't just look it up). (Hat Tip to Bill for suggesting this)

Homepage Image: Tine Steiss/Flickr