What are the ideal soil types for making concrete?

What are the ideal soil types (if any) for making concrete? Do building engineers have their preferences? If so, do countries import soils on that basis?
I look forward to your feedback

Concrete isn’t made out of soil. It’s made out of an aggregate and a binder; soil is neither.

Specifically: washed sand & gravel, Portland cement, and water.

Slight nitpick on Alessan: sand and gravel are both soils. “Soil” also includes lots of other things like silt and clay that are not usually used in concrete. (some processed clay can be used as an additive)

Washed sand and gravel are often imported though. Construction in the gulf countries famously uses imported sand. Desert sand is unsuitable for concrete because it is exceptionally rounded.

Really? I was under the impression that “soil” referred to the mixture of earth, water, microorganisms and organic matter needed to support plant life. I don’t think you want worms and rotting leaves in your concrete.

Sorry, I meant to the civil engineer. I believe geologists say soil has to be able to support vegetation, but to a civil engineer soil is just a natural occurring granular material.

If you have a natural sand or gravel pit, I would still recommend washing and sieving it before making concrete. You definitely don’t want vegetation, or other sources of weakness, in your mix, but I would call the sand a soil before and after cleaning it.

Which natural soil is being referenced here? Simply sand and gravel?

Soil cement is a construction material, a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumble, compacted to high density. Hard, semi-rigid durable material is formed by hydration of the cement particles.

No, that would whatever the local soil is on site. If you’re making a temporary road or landing strip you might till the top surface, mix in cement, and then compact it as much as possible. If you’re doing it for roads it’s a quick and cheap alternative to pavement, so you wouldn’t import soil for that.

I remember reading that “soil concrete” is sometimes used for basketball courts and similar where a hard, but not permanent, surface is desired. When the kids get tired of playing it’s easier to break up and distribute than regular concrete would be.

Mechanics Illustrated maybe 40 years ago.

Sure, but tell a civil engineer that you’re putting ‘soil’ in their concrete and not aggregate and/or sand, and they’ll either lose their shit, or have a Fred Sanford moment.

Hell, they get bitchy about when people call concrete “cement” and say “Cement goes IN concrete”

Check out this guy’s videos Practical engineering - what is concrete?

Yes, yes we do.

I was mostly pointing out that sand and gravel are soils, not that any soil should be an aggregate.

Not that the OP asked, but non-natural aggregates can be used as well. Glass, plastic, iron, and lead shot can be used. There’s also some current research in making concrete more sustainable by using byproducts from other processes like corn husks.

Ahh, soil cement, the favorite building material of The Mother Earth News. Way back when they called it “Earthcrete” and published recipes. It is an alternative when you have limited resources or difficulty transporting material. It isn’t usually permanent when applied on the surface. It is not waterproof. It is not very strong.

On “Building Off the Grid” on TV last year a bicycling club made their floor out of it as they wanted to minimize their carbon footprint so they carried all material by hand (or foot power) using their bikes. It was quite a funny episode. As they walked on their floor after it set up, it simply cracked and mushed up.

They blended it with a contraption that used a bike to rotate a 5 gallon bucket of mix. It took forever with those small batches. I wondered aloud, “why don’t they use a simple pan and hoe like everyone else?” Doesn’t get any greener and has worked for centuries.


You feed those to the livestock to make meat. Or make them into ethanol. Or put them in the still out back and make good old ‘corn likker’. Who the heck would waste them on concrete?

Corn husks aren’t used for any of the above, the corn kernels however, are.

Certainly they are.
Our horses loved eating the husks from sweet corn, it was a real treat for them. Our neighbors pigs were often fed the whole ear of corn, husks & all. And have you ever heard of silage? That’s made from the whole corn plant, even including the leaves & stalk.

Same thing with beach sand plus all that salt that has to be flushed away.

I remember a “this old house” story from years back where they were in coastal California working on a house. Concrete was deteriorated because they’d scooped up beach sand for the mix.

When I was young, most people used what we called “ore sand”. There was a closed down iron mine in a nearby town. When it had been in operation it had produced this huge amount of sand as a waste product. The sand was dumped into a adjacent field the mine had bought for that purpose. The sand was several feet in this field.

So if you were doing any project involving concrete pouring and landfilling, you would drive to the field with some trucks and shovel up all the sand you needed. The stuff was ideal.

This practice no longer exists. Around fifteen years ago, somebody realized the value of this sand that people were taking for free and bought the site in order to sell it commercially.