How to Make Concrete at Home: CoRncrete TU Delft - TfCD (Sam Smits& Zsolt Hayde)

This instructable helps you to create CoRncrete at home in less then 10 minutes!

For more information about the material read the added description document.

Ingredients needed: sand, corn starch and water

Tools needed: Kitchen scale, mold (which can be put in a microwave), microwave

Step 1: Measure 125g Sand

Sand in CoRncrete is the aggregate. Different kinds of sands can be used making for different looks finishes and strength properties. Different color sands or added pigments can influence the color of the final material.

Step 2: Measure 25g Corn Starch

Corn starch is the cement of this material. It is important to have dried corn starch for it influences the preciseness of the measurements. Grocery store bought corn starch contains a percentage of water therefore less water should be added in this case.

Step 3: Mix the Sand and Corn Starch

Mix these ingredients util it becomes a homogeneous mix.

Step 4: Measure 22.5g Water

Depending on the percentage of water in the corn starch this amount can vary.

Step 5: Mix the Solid Ingredients With the Water

Water is added to gelatinize the corn starch in the mixture. Water and corn starch result in a non-Newtonian fluid.

Step 6: Pour the Mix Inside the Mould

It is important to have a mold which can be put in a microwave. Also think about the draft angle of the mold. If no clear draft angle can be used due to the shape, try to make the mold so that you can cut it off the material once it's solid.

It is a good idea to very softly press the material into the mold to fully fill the shape.

Step 7: Put the Mold in the Microwave and Turn It on for Approximately 3 to 5 Minutes

Heating the mixture start the gelatinization of the material and binds the sand particles together. Depending on the strength of the microwave as well as the amount of material made the heating time can vary. Some experimenting with that might be needed to ensure the perfect result.

You might want to check in between the heating if the material is already solid. You don't want to burn the concrete.

Step 8: Get the Solid CoRncrete Out of the Mold

Careful the material and mold can be very hot!
After getting the mold out of the microwave just pull the concrete out of the mold, or cut the mold away.

And there it is, your finished coRncrete shape!

Step 9: Different Volumes? Repeat the Steps Above Using the Ingredients Ratio

You can of course make more or less concrete by using this method. Remember to use the same ratios for the ingredients:

5 x sand

1 x corn starch

0.9 x water

WARNING! when changing the amount of material the heating time in the microwave also changes! You will need to experiment with this!

Comments

[femalefaust]

About the durability of starch: consider replacing starch/water with a wheatpaste. Wheatpaste is made by boiling a little wheat dissolved in water for a very long time, i have to check on what the minimum is but a day and a half should do. Alternately it is most probably for sale online. In any event it is an incredibly durable glue, even against the elements: wheatpaste is why those broadsides plastered up downtown are still at least partially there, & that is with people actively attempting to remove them.

So I am thinking, as a hybrid experiment, of boiling wheat starch for a very long time, then adding sand.

(there's also gelatin-vinegar, which makes a nice waterproof glue.... what would sand do there?)

Anyway, I came here researching beeswax additives to make cement. If anything excellent comes of my experiments, I hope I remember to check & post back.

Be seeing you,

@femalefaust

[DukeOfMarshall]

Any idea as to how much heat the finished product can withstand? I can definitely see some potential for casting/injection projects, but only if it would hold up.

[YaskK]

The corn starch used in making the CoRncrete can withstand 290 deg C. Sand can withstand higher temperatures. Therefore, According to me it is safer to use CoRncrete upto 200-250 deg. C.

[dcady]

Clearly this is a product with many uses though not necessarily for anything that might be exposed to excess water. But, wow! Think of how many useful things can be made from it, like Christmas ornaments or bricks (if used for indoor building). And it would be great fun to make little colored building blocks (food coloring as someone suggested) with and for my granddaughter. (They would not fall over as easily as the wooden ones do, and I know she'll appreciate that.) Awesome post!

[YaskK]

Please look at my post in the comments to see some of the colouring CoRncrete I have made. I also made some S shaped CoRncrete as a christmas gift.

[PeterM13]

Thiis woud be a good mixture to use in model making like dioramas or model Railroad layouts cheep strong enough and looks like concrete. a little creative work with food coloring or water based paints and it can be any building material. my question is its longetivity and staility during winter/ spring and summer / fall climate adjustments

[YaskK]

This material is not so good in water, hence any outside use might result in the degradation of material. If the weather is dry, the material can stay for a long time. But for now, more experiments will be needed to comment on it. There is a potential that its water resistance property can be improved and I am planning to work on it. Check out my post to see CoRncrete with different colours; it is similar to what you have written.

[joshua.artist]

any word on long term durability, paint-ability, exterior use, say for restoring plaster ornamintation?

[JosephS62]

You could try using another liquid other than water so it shouldn't fall apart in water?

[YaskK]

CoRncrete is not durable in water hence it is not good for outdoor use. However, I would like to comment that I see a possibility to improve its durability and I am planning to work on it soon.

[Lovot]

The cornstarch degrades rapidly in the presence of water, so it's practical uses are limited, set type joint compound, plaster of Paris, and cement are all better suited for just about everything

[Randykr]

yes build a house or something

[fatgnat]

What kind of strength can we expect from this? Just curious whether this will just crumble with a small amount of weight applied, or actually hold it's own.

Good 'ible though!

[YaskK]

You can have strength upto 27MPa, which is comparable/stronger than the fired clay red brick. In a nutshell, It will need a really strong force to completly break it.

[NatalieJ14]

AWESOME! Love the pics of your experimental uses...

[ianpaschal]

I don't remember the exact numbers we measured in the lab but with the right proportions of water and cornstarch it's on par with conventional concrete and brick.

[grolmund]

Neat -ible but, what is the practical application of the finished material?

[YaskK]

I believe you can do a lot with this stuff. It is like a moulding material which can be cast in any shape. It is also possible to make CoRncrete bricks which can be used indoors. Possibility to make it in any colour makes it an interesting material for Architects.

[SharonG32]

Would love to try and see if I could make something for flowers outside. Fun project with kids

[YaskK]

CoRncrete weakens when it comes in contact with water. Presently, its use is limited to indoor use untill unless you live in an area which is relatively dry.