This video provides an in-depth exploration of the substance concrete, and the process of how it is made. The narrator explains the difference between cement and concrete, with cement being the glue or matrix and concrete being cement plus aggregate like sand and gravel. He emphasizes that cement is a crucial substance, used more than any other apart from water. Every year, 500 kilograms of cement are created for every man, woman, and child on earth.
The video also delves into the history of concrete, explaining how primitive cement was made from limestone and the discovery of Roman concrete that could harden underwater. The narrator then discusses the modern cement formulation known as Portland cement, which is made by crushing limestone and mixing it with a certain percentage of shale or clay to provide the silicates.
The process of making concrete is shown, from the blasting of quarries for sand and gravel to the mixing of cement powder with these aggregates. The video also explains the importance of maintaining the right consistency of concrete for the customer and how chemicals like superplasticizers are used to adjust this.
The narrator then explains the hardening process of concrete through a chemical reaction known as cement hydration. He concludes by reflecting on the irony that limestone, the core component of cement and concrete, is formed from the skeletons and shells of ancient sea organisms.
In summary, this video provides a comprehensive understanding of the components, history, and process of making concrete, highlighting its importance in modern construction and infrastructure.
1. The speaker is about to be buried in concrete and is explaining the substance to the audience.
2. The speaker differentiates between cement and concrete, stating that cement is like the glue, while concrete is cement plus aggregate (gravel and sand).
3. The speaker mentions that cement is the most important man-made substance on the planet, used more than any other substance apart from water.
4. It is stated that every year, 500 kilograms of cement are created for every man, woman, and child on earth.
5. The speaker explains that concrete is liquid rock, which can be poured into any shape, is strong, durable, and inexpensive.
6. The Roman method of creating cement involved adding volcanic ash called pozzolana to the crushed limestone before heating it.
7. The speaker mentions that the incredible strength, durability, and ability to set underwater of the Roman cement came from the pozzolana.
8. The speaker explains that the strength of concrete increases over time, and samples are tested at 7, 14, and 28 days when the concrete is said to have reached full strength.
9. The speaker describes the process of testing the strength of concrete samples in a hydraulic press, stating that the pressure is increased until they fail.
10. The speaker mentions that the strongest concrete in the world was above 100,000 psi in a competition.
11. The speaker explains that the Portland cement was made by crushing up limestone and then mixing it with a certain percentage of shale or clay to provide the silicates.
12. The speaker describes the process of making concrete, stating that it involves cement powder, sand, and gravel.
13. The speaker explains that the strength of concrete is affected by the sizes and shapes of the aggregate, and that there are strict requirements about these.
14. The speaker mentions that the most common compound in cement is tricalcium silicate.
15. The speaker describes the process of creating concrete, stating that it involves adding water to a dry mixture of gravel, sand, and cement powder.
16. The speaker explains that the pH of concrete can get up to 12 or 13, which is incredibly basic and can dissolve skin and cells.