A Week in/of Review: Week 3, SCM Emissions and Money Matters

This week, I worked on these parts of the project:

1. Researching other factors of SCM usage besides supply, such as costs (both monetary and environmental).

2. Adjusting previous supply calculations to better reflect real world situations.

3. Figuring out the CSA burning and concrete-making schedule.

4. Creating a plan for making small test cubes in the school lab.

Investigating and Comparing SCM Costs

When considering the use of materials (especially in a scale as large as concrete), the science working may only be 10% of the equation. The other 90% is constituted by cost-efficiency, ease of use, industry standards, etc. This is why I’m looking at these other factors. Without seeing the whole playing field, how can we know the best moves to save the planet?

According to Nick, the issue is lots of pricing of materials is done on an order-to-order basis, so finding standard prices was an issue. Still, I was able to find enough information to make graphs of relative costs of various SCMs, as seen in the bar graph below.

As we can see, Fly Ash has been fairly cheap. In fact, in the past, companies were paid to take Fly Ash from the coal plants in which it was produced. Now, prices are on the rise as sustainability becomes more important and demand rises. In the US, the supply is getting to the point where landfill Fly Ash supplies are being used. Nick mentioned that Fly Ash prices can even get to $190 per metric tonne, so I’ll keep looking for information regarding these higher prices.

Blast furnace slag can replace up to 80% of cement in concrete, and used to be more available in the US, but since the Steel Belt turned into the Rust Belt, most slag from steel/iron production is now found in China, where cement fairly cheap. Of course cement could be shipped overseas to the west coast where cement is more expensive, since bulk-shipping by sea is fairly efficient.

Silica Fume

Silica fume is just really expensive in general, and Nick told me its only used in very specific situations requiring ultra-high strength.

Rice Husk Ash

Rice Husks don’t have too many large-scale commercial uses at the moment, and so as waste products, their prices can be fairly low, especially in rice-producing countries in Asia. But, if demand grows, the price could as well. We’ll have to keep an eye on that in the future.

Coconut Shell Ash

Coconut Shell Ash, also not being used commercially at a large scale, was difficult to find prices for, so I had to find bulk prices online on the Chinese site Alibaba, then use this as the higher estimate to estimate a lower price, based on the percentage difference between RHA high and low prices, since both are similar agricultural products. One advantage CSA may have over RHA is that it grows on the coasts already, so less land transportation costs (way more expensive and emission-heavy than by sea). Plus, coconuts are largely produced by non-China countries, so future shaky relations may not affect the supply as much.

Important Factor: Transportation Emissions and Cost

As I was saying before, transportation can play a role in the cost and emissions of SCMs, so it’s an important consideration to make when comparing them as well (coupled with geographical information, which I’ll be looking more into this week).

 

 

 

 

 

 

Basically, we want to minimize transportation in general, and if we are to transport materials over a longer distance, it’s best to go by boat or rail, not by truck. This is why many US cement factories are situated by rivers.

Updates:

• Burning of the CSA is going slower than expected, more details below, but basically I’ve delayed making the mixes at Cemex until 3/28 (a week later than plans before) and making the mixes at lower percentage replacements than before:

  Currently, around 6.5 kg of fully burned CSA has been produced, which is fairly far from the 20-25 kg of material used last time. What this means is that we either:

  1. Push the concrete-making day at Cemex back from 3/21 (although I’ll be in Japan from the 29th to April 8th)…

  2. And/or reduce the amount of burnt CSA needed at for the testing. This could be done by getting rid of the shrinkage mold testing (leaving only cylinder molds for compressive strength testing) and by reducing the replacement percentages of cement with CSA (previously 15, 25 and 35%)

  This testing is an important part of my project, so it’s essential to balance getting it right/up-to-standard and getting it done in time. Hopefully the steel containers hold up, and I’ll update again soon.

• I’m planning on making various highly experimental concrete mixes at school with ice cube trays as proxies for cube molds. I’ll try things like using extreme acids and bases on the CSA before making concrete. I’ll also try making zero-cement concrete with the CSA (geopolymer)

Thanks for reading and see you next week!

Max Polosky