/ belinda_carr
Chapters
0:00 Introduction
1:13 Invention of geopolymers
1:40 Waste materials
3:08 Chemical reaction
3:35 Geopolymer projects
4:35 Advantages
6:27 Sponsorship
7:11 Disadvantages
8:12Conclusion
Scientists use a variety of waste materials, industrial byproducts, and minimally processed natural materials instead of Portland Cement. These waste products are difficult to dispose of and they can affect the environment if left untreated. So, using them to significantly reduce the carbon footprint of concrete is an excellent idea. Let’s take a look at some of these waste or low energy materials.
- Fly ash or pulverized fuel ash or PFA which is a fine, powdery residue from coal burning power plants. It is mainly composed of silicon dioxide, aluminum oxide and calcium oxide.
- Metakaolin which is produced when china clay or kaolin is heated to 1500 degrees Fahrenheit or 800 degrees Celsius. It can be used to make tiles and traditional concrete.
- Ground granulated blast furnace slag or GGBS which is a by-product of the steel industry. It is high in calcium silicate hydrates CSH which improves the strength, durability and appearance of concrete.
- Palm oil fuel ash or POFA which is produced by burning palm oil shells and husks. It is a hazardous material that is usually sent to landfills, but it can be used to make cement.
Advantages
- Geopolymers are apparently stronger in tension and compression.
- They are resistant to various alkalis, salts, acids and corrosive substances. They also have a high sulfur resistance due to the lack of сalcium compounds in its structure.
- Geopolymers have excellent waterproof properties. Its pores are smaller than 50 nanometers so big molecules like water can’t enter in the geopolymer matrix
- It is also fire resistant. Unlike Portland cement, water in geopolymer concrete evaporates and does not explode the concrete from inside.
- Foamed geopolymer concrete can also have superior thermal insulation thanks to the trapped air inside the blocks.
- They can reduce the carbon footprint of concrete by up to 90%. For every 1 ton of Portland cement made, around 0.9 tons of CO2 is released. Conversely, for every 1 ton of geopolymer cement made, only 0.2 tons of CO2 is released.
- Geopolymers will help us stop mining and extracting raw materials from the earth because we can use waste and by-products of existing industries.
- It can speed up construction because it develops about 50% of its strength in the first 3 days.
Disadvantages
- There isn’t enough waste material to meet the demand for cement. The global consumption of cement is about 4 to 5 times the generation of industrial wastes like fly ash and slag.
- Another issue is the lack of standard and uniform waste materials. For example, fly ash will have a different alumina-silica ratio than slag, so their geopolymer cement mixes will perform differently.
- They are difficult to make because the geo-polymerization process is sensitive. Chemicals like sodium hydroxide are harmful to humans so the process requires special handling.
- And finally, the biggest drawback in my opinion is that they are up against powerful Portland cement manufacturers, some of whom have a monopoly in the concrete industry. They have control over code requirements and marketing which allows them to easily suppress competition.
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SOURCES:
• 7 questions à Joseph Davidovits sur l...
https://www.youtube.com/watch?v=znQ bk_yBHre4
• Geopolymers: what are geopolymers mad...
• Brisbane West Wellcamp Airport projec...
• EFC geopolymer pavements at Wellcamp ...
• Video
• Video
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