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

Picture of 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

Picture of 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

Picture of 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

Picture of Mix the Sand and Corn Starch

Mix these ingredients util it becomes a homogeneous mix.

Step 4: Measure 22.5g Water

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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!


DukeOfMarshall (author)2016-01-10

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 (author)DukeOfMarshall2016-01-15

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.

Ampersant made it! (author)2015-12-26

So we're going to Mars someday. A place thats dry, has lots of sand and no available limestone deposits for making cement. It'll be too expensive to transport the necessary ingredients for GPC, but well need the protective cover from UV radiation, storms and micrometerorites. We could use this process to make building materials. If we grow bamboo as an oxygen scrubber, extract the starch, pyrolize the shoots for water and biochar, and follow this formula we get a really good geotextile. Dig a bit deeper and the soils we extract could return even more water to expand the colonies.

YaskK (author)Ampersant2016-01-15

Nice idea indeed and good rounded samples. Few months back I was also discussing use of CoRncrete as a building material in Mars with my Aerospace Engineering freinds. Presently, we are using edible corn starch and we need to use starch from waste for some real application in Mars. As you suggested, starch from Bamboo might be a solution but first we have to check that if that starch can provide a sufficient strength. I apprieciate your idea and I think there is a potential that it can be a reality someday. Good Luck !

κέρωτα (author)Ampersant2016-01-04

bamboo's in a dry land? hahahaha

Ampersant (author)κέρωτα2016-01-04

dcady (author)2015-12-22

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 (author)dcady2016-01-15

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 (author)2015-12-21

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 (author)PeterM132016-01-15

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 (author)2015-12-18

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

JosephS62 (author)joshua.artist2015-12-24

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

YaskK (author)joshua.artist2015-12-24

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 (author)joshua.artist2015-12-20

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 (author)joshua.artist2015-12-20

yes build a house or something

onrecess (author)2015-12-21

I'm thinking of doing this cool project with my elementary students. Can you press your initials onto the top and have it stay, or will it level?

YaskK made it! (author)onrecess2015-12-24

Can you please elaborate your question?

You can prepare nice and smooth blocks and keep it over each other. In this image you can see some of the fun options you can try with CoRncrete. The emoticons are especially liked by students.

fatgnat (author)2015-12-15

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 (author)fatgnat2015-12-24

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 (author)fatgnat2015-12-20

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

ianpaschal (author)fatgnat2015-12-18

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.

YaskK made it! (author)2015-12-24

Some of the Latest CoRncrete samples I made in a Microwave and an oven. I used different colours, shapes and variety of sand.

grolmund (author)2015-12-20

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

YaskK (author)grolmund2015-12-24

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 (author)2015-12-20

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

YaskK (author)SharonG322015-12-24

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.

capeclint (author)2015-12-17

I wonder if using an oven would be better or worse? I'm sure it would be longer though.

YaskK (author)capeclint2015-12-24

Its hard to say if its worst or better, but in a microwave you can make stronger CoRncrete in less time. In an oven, it takes more time but you have the flexibility to make any desired shape. In a microwave there is greater shrinkage or swelling of material making it difficult to form complex shapes.

You can still make a strong CoRncrete in an oven. I have made a CoRncrete with 20MPa strength (comparable to traditional bricks) in oven as compared to 27MPa strength of CoRncrete made in a microwave.

ianpaschal (author)capeclint2015-12-18

Oven is worse. The water dries out before the corn starch gelatinizes making it sort of crumbly.

timmg08 (author)2015-12-17

so I just made a little of this and it is way stronger than I thought it would be. I just made a little puck but I could stand on it with only the spots in the middle where water escaping made it week. I also ran some water over it. it made the outside sticky but it would take quite a long time to disolve it away. definitely don't use this for an outdoor project with out stalling it.

YaskK (author)timmg082015-12-24

Awesome !! I suspect you have used a bit more water which has caused the outburst at the centre. The corn starch you buy in the market also has a significant water (around 8-14%). Hence, the brand of corn starch also matters. Do try it with less water. You can then make a regular shaped CoRncrete. However, you will see that the CoRncrete formed with less water will disintegrate fast when kept in water.

timmg08 (author)timmg082015-12-17

sorry sealing

Me2free (author)2015-12-15

This is pretty cool but I was wondering, have you ever tried it without the microwave?

YaskK (author)Me2free2015-12-24

You can make CoRncrete in oven as well. The timing depends on the quantity of material but for an estimate, It takes around 4-8 hr at 100 deg.C and about 30min-1hr at 175-200 deg.C. Don't heat it beyond 250 deg.C. Also, The mix also hardens when you keep it in sunlight for long time. But it will not be that strong.

Phil_S (author)2015-12-20

Getting all excited by the title "How to make concrete at home" only to find it's really reinforced biscuits. I thought you had come across a revolutionary way to speed up the curing process, when we real concrete mixers know that heat is the concrete cure killer.
I suspect that cement is a lot cheaper than corn starch. You can always mix something like vermiculite into the real stuff to make it fluffier.

Syncubus (author)Phil_S2015-12-20

"Reinforced biscuits" made me LOL.

philipew (author)Syncubus2015-12-21

Yes, reinforced with candy sticks

Randykr (author)Phil_S2015-12-20

Phil-S Actually, the lack of heat is a concrete cure killer, and heat is the concrete cure accelerator. Too much heat will cause concrete mixes to harden too fast, this dramatically decreases strength. Also this is not concrete people... this is merely receipe for good mother-in-law biscuits.

Phil_S (author)Randykr2015-12-20

Have to disagree with that.
Large concrete pours in hot climates usually involves placing cooling pipes in the formwork to slow the cure, as witnessed in the Hoover dam construction where cooling was in place for months, if not years.
Heat might accelerate the drying out with some cure, but the concrete does not develop strength - you can test it easily by mixing some mortar - leave some in the sun and some in the shade (or fridge) - the slow, cool cure is ultimately stronger.

Randykr (author)Phil_S2015-12-20

reread my first sentence... I've placed 10s of thousands of cubic yards of concrete. I started in 1966 worked in MI FL and CA... during all seasons. I have 100s of hours of class time and 10000 + hours of Field experience with concrete. You mis-spoke yourself when you said ""we real concrete mixers know that heat is the concrete cure killer"" Actually Heat will accelerate the cure and a certain amount of heat is required. Concrete cures from a chemical reaction called hydration, that process creates a little heat. In large volume castings like dams, it creates a lot of heat, too much heat can be created, so much heat that it can cook the water in the mixture, in a sense it burns up. In cool climates we add Calcium Chloride (a salt) to the concrete mixture, to create some heat and speed up cure time. Concrete temperature below 41F cure stops, over 86F and it cures too fast. As long as water is present in the mixture and the temp is optimum, the curing process will continue indefinitely. Therefore, Heat will never be a "concrete cure killer " lack of heat or the lack of water will kill the curing reaction. Yet, people place slabs here in FL and CA in 100 degree sun...and in MI they place slabs, or footing in 25 degree weather... lol people ask why is my concrete all cracked up? SMH

steveastrouk (author)Randykr2015-12-21

IIRC, some of the ultra-strong precast tunnel linings are "steam cured", what is that process ?

steveastrouk (author)Phil_S2015-12-20

You can't grow portland cement though.

Lovot (author)steveastrouk2015-12-20

It takes more resources to grow corn than it does to manufacture cement, and the materials use in cement are cheap and plentiful, the main cost is the energy used to obtain and process the raw materials into cement, in addition to that the CornCrete requires microwave radiation to cure properly, so it's not very practical to use in the capacity cement is, and it's cheaper to sinter dirt into masonry than it is to grow corn, so it cannot replace bricks either and that's just the beginning, the CornCrete is very vulnerable to regular water while the alternatives are resistant to water damage. I also suspect it is vulnerable to ants as well due to being held together with starch.

Home Mechanics (author)2015-12-20

Why not use real concrete?

Randykr (author)Home Mechanics2015-12-20

yea novel idea!!! best one I heard all week. And how cheap is a 90 lb sack? LOL

EmmitS (author)Randykr2015-12-21

a lot cheaper than a ninety lb. box of corn starch.

plasticbaldy (author)2015-12-20

Baaaah Humbug. My ex-wife could make concrete in any type of oven with shop bought cake mix.

kirk thill (author)plasticbaldy2015-12-21

Yep, and my wife can make the best rubber motor mounts from a box of macaroni. LOL

goldenskyhook (author)2015-12-21

Wow! I can hardly wait to try this! I already use the 'ible about making silicone molds with cornstarch and 100% silicone caulk. Now I have something to mold in them.

Ha! I'll bet you never dreamed you'd be hosting a p*ss*ng contest between two people who care more about concrete than they do about people's feelings. I'm also baffled at the ones who said "why not just use the real stuff?" Because it's not FUN!

lahines (author)2015-12-21

CoRncrete and concrete (used throughout the method description) are not the same thing. You should correct the text.

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