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November 19th, 2010

UPDATE: Video of the week: Chemistry of concrete

Published on November 19th, 2010 | By: pwray@ceramics.org

We’ve received a lot of feedback questioning some of the science presented in this video.

I forwarded some of the comments on to the producers and requested a response. I just received the following response from the lab at University of Nottingham:

“[Professor Martyn Poliakoff] has been away in Africa but I’ll ask him to look (I am the film-maker, not a scientist). He receives many emails from viewers but always tries to reply.

“Worth noting our videos are for a very wide audience and often contain just a few curious nuggets designed to inspire further interest – unfortunately the whole story never fits in a YouTube video… the comments you refer to are obviously from true ‘concrete fans’ who feel very passionately about detail.”

While we anxiously await Poliakoff’s return, watch the video yourself and let us know what you think.

 

[flash http://www.youtube.com/watch?v=b43Iz2OoUNk preview=force]

Here is the latest and greatest installment of chemist Martyn Poliakoff of University of Nottingham in his Periodic Table of Videos. The Chemistry of Concrete describes the chemistry behind the hardening process that occurs after you mix silicon dioxide, lime, aggregate and water.

Poliakoff is the narrator of a 118-part series of short videos called The Periodic Table of Videos, which is a popular science project intended to familiarize the public with the periodic table. The site is worth checking out. Each short video offers an informative quick lesson in the element presented.

 


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3 Responses to UPDATE: Video of the week: Chemistry of concrete

  1. Charles L. Ammann says:

    The lack of this professor’s knowledge about this topic along with his willingness to expound on it is truly frightening.

    It should not be published here (or anywhere else).

    I hope the ACerS editors will do a lot better in the future.

  2. Wagner M. Silva says:

    The given information in the video is really so misleading, that the video should not be published here. Dr. Poliakoff describes an ancient lime mortar as a modern cement; whereas it is not even comparable to the Roman example which he gave (the romans used pozzolanic earths from volcanic areas, something similar to blast furnace slag). The Chemistry of Cement, though its use over more than one century, is a very complex subject, not fully understood, that involves the formation of nano-scale structures whose role is not fully depicted.
    Moreover, the description of the rheology of the concrete is so completely false, that I wonder how he got this picture. He also does not comment the role of the C2S hydration over time on the increase in the mechanical resistance, and so on and so forth…

  3. Dr. Martyn Poliakoff needs to go back to school concerning the manufacture of, chemical reactions in and hardening processes of cement.

    Portland cement, one kind of hydraulic cement, is a complex calcium silicate based material wherein complex oxides of Ca, Si, Al, Fe, S and minor amounts of other elements (Mg, Na, K, etc.) are combined using heat to become new manufactured minerals, then intimately ground together, burned to incipient melting at about 2,700F, and after which are inter-ground with gypsum to make a powder which when mixed with water and even if maintained under water, will harden and stay hard.

    The verbal description Dr. Poliakoff offers about CaCO3 being heated and then adding SiO2 to form hydraulic (or Portland) cements is highly misleading if not simply wrong, as he describes calcining of lime (CaCO3 –>> CaO + CO2) and not the manufacturing process of cement. The more important chemical reactions have to do with the early reactions involving the solubility of gypsum and chemical reactions with calcium aluminate materials and then longer term reactions of calcium silicates reacting with water to form complex calcium-silicate hydrates. Finally, while carbonation of concrete is not uncommon, it is a relatively minor issue. Hydration reactions and reaction rates and secondary reactions are far more important than carbonation as well.

    There is an enormous amount of misinformation regarding lowly cement materials: let’s not further confuse the situation by incorporating it with what is probably a wonderful general overview of the elements in everyday products.

    Thanks

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