Using magnetism to control the structure of concrete

  1. So this is my idea:

    make concrete using iron sand, preferably one with a decent ferromagnetic interaction.

    As the concrete sets, apply a magnetic field. The ferromagnetic particles align to the field creating a structure within the concrete.

    Possible to coat the iron sand in a retarding agent, like sugar, to slow the development of bonds which has an effect of improving strength.

    Hopefully this will produce a concrete that is still cheap with good tension performance, particular in bending.
  2. jcsd
  3. What is the point of forming such a structure?

    Try the fiber concrete technology, it may be interesting
  4. Bobbywhy

    Bobbywhy 1,908
    Gold Member


    Interesting proposal! True, if you add powdered iron, for example, into your concrete mixture and then apply a magnetic field while it cures there will be a pattern of iron particles fixed in the concrete. But grains are not connected to one another, so they will not add any tensile strength when the concrete cures (hardens).

    Your suggestion “to coat the iron sand in a retarding agent, like sugar, to slow the development of bonds...” does not make any sense to me.

    In our science museum experiments to visualize magnetic fields we have used iron filings (powdered iron) mixed in liquid jello (say, yellow in color). We then fixed a strong magnet outside the plastic container. This causes the particles to align themselves along the magnetic field lines. Then we put the whole thing in the refrigerator and waited for the jello to “set”. Then when removing the magnet we could see the particles fixed along the magnetic field lines easily. Now, if you imagine similar action in the concrete mixture, you can imagine there is no interconnected structure, so there would be no change in the tensile strength of the concrete. Concrete is not considered to be a flexible material, so bending does not seem to be possible.

    Don’t let this deter you from trying new ideas! There is an old saying “Necessity is the Mother of Invention.” That means when you come across a problem and invent a new solution, this is innovation! Keep on experimenting! Don’t be shy about posting your questions or doubts here on Physics Forums. Members here are always ready to assist a true searcher wanting to learn more science.

  5. Bobbywhy,
    You would be a great teacher if not already you are.

    It's very important to provide proper motivation for those creative youngs, who has the fountain of ideas. Most of that ideas has no proper grounding due to unsufficient knowledge and luck of experience. It's easier to criticise, targetting self-confidence, which mostly leads to idea-generating blocking, rather than critic review.

    By the way, magnetizm structurizing may do solid in a bit differ condition:

    About 200C and some pressure there is a reactions: Fe(CO)5 <=> Fe+5CO

    If we put Fe(CO)5 or Ni(CO)4 at those conditions and in a magnetic field, then will slightly increase temperature, I suppose it may produce a microfibre on the domain scale.
    Doing the same in 3 steps for XYZ dimensions probably may produce stable skeleton?

    (Beware of the Fe(CO)5 and especially Ni(CO)4 high toxicity)
    Last edited: Feb 7, 2013
  6. Bobbywhy

    Bobbywhy 1,908
    Gold Member

    Graniar, thanks for the kind words.

    The two homoleptic metal carbonyls you mention are precursors of thousands of organometallic species. Do you have any evidence that these materials would form stable skeletons? Why would you want to reinforce concrete with these dangerous poisonous volatile compounds? Have you investigated how concrete is now reinforced commonly? Will you please offer some rational justification for your proposal?

    Iron pentacarbonyl is a yellow liquid trigonal bipyramidal molecule and is toxic. If inhaled it may cause lung irritation, toxic pneumonitis, or pulmonary edema.
    From Wikipedia:
    “When heated Fe(CO)5 converts to Fe3(CO)12, a green solid.” (and not to Fe + 5CO.)
    “Fe(CO)5 is toxic, which is of concern because of its volatility (vapour pressure: 21 mmHg at 20 °C). Iron pentacarbonyl Like other metal carbonyls, Fe(CO)5 is flammable.”

    Nickel tetracarbonyl, a tetrahedral molecule is a colorless liquid and the most toxic substance found in industrial processes.
    From Wikipedia:
    Nickel carbonyl may be fatal if absorbed through the skin or more likely, inhaled due to its high volatility.

  7. Sure, I wouldn't!
    Just thinking about possible improvement of that experiment in your scientific museum, you mention above.

    I think, the fiber concrete technology is best when local strength needed.
    Otherwise ordinary ferroconcrete is better for strength/cost ratio.
  8. Nevertheless, there may be a reason to produce metall aerogel from carbonils without any magnetic fields
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