Concrete is made of a combination of cement, an aggregate such as gravel, and water. If that mixture dries too quickly, then cracks can form within it as it cures. Now, however, scientists have determined that the use of coal-ash spheres can help keep that from happening.

Looking for a cheaper, more abundant form of such porous aggregates, researchers at Philadelphia’s Drexel University turned to the “fly ash” waste that is produced when coal is burned at power plants. Led by Asst. Prof. Yaghoob Farnam, they combined the ash with bonding chemicals, formed it into tiny spheres, then baked those spheres at a temperature of 1,160 ºC (2,120 ºF) for a few minutes.

https://newatlas.com/environment/spora-coal-ash-concrete/

> Looking for a cheaper, more abundant form of such porous aggregates, researchers at Philadelphia’s Drexel University turned to the “fly ash” waste that is produced when coal is burned at power plants. Led by Asst. Prof. Yaghoob Farnam, they combined the ash with bonding chemicals, formed it into tiny spheres, then baked those spheres at a temperature of 1,160 ºC (2,120 ºF) for a few minutes.

This technology was old when I was learning about concrete in University in 1977.

It’s quite good technology.

mollwollfumble said:

> Looking for a cheaper, more abundant form of such porous aggregates, researchers at Philadelphia’s Drexel University turned to the “fly ash” waste that is produced when coal is burned at power plants. Led by Asst. Prof. Yaghoob Farnam, they combined the ash with bonding chemicals, formed it into tiny spheres, then baked those spheres at a temperature of 1,160 ºC (2,120 ºF) for a few minutes.

This technology was old when I was learning about concrete in University in 1977.

It’s quite good technology.

The power station I worked at made quite a tidy sum selling fly ash to Pozzolanic for inclusion in concrete.

mollwollfumble said:

> Looking for a cheaper, more abundant form of such porous aggregates, researchers at Philadelphia’s Drexel University turned to the “fly ash” waste that is produced when coal is burned at power plants. Led by Asst. Prof. Yaghoob Farnam, they combined the ash with bonding chemicals, formed it into tiny spheres, then baked those spheres at a temperature of 1,160 ºC (2,120 ºF) for a few minutes.

This technology was old when I was learning about concrete in University in 1977.

It’s quite good technology.

I was going to say that, but AFAIK no-one was using fly-ash formed into porous spheres to reduce drying shrinkage in 1977 (or even 2017).

The Rev Dodgson said:

mollwollfumble said:

> Looking for a cheaper, more abundant form of such porous aggregates, researchers at Philadelphia’s Drexel University turned to the “fly ash” waste that is produced when coal is burned at power plants. Led by Asst. Prof. Yaghoob Farnam, they combined the ash with bonding chemicals, formed it into tiny spheres, then baked those spheres at a temperature of 1,160 ºC (2,120 ºF) for a few minutes.

This technology was old when I was learning about concrete in University in 1977.

It’s quite good technology.

I was going to say that, but AFAIK no-one was using fly-ash formed into porous spheres to reduce drying shrinkage in 1977 (or even 2017).

> they combined the ash with bonding chemicals, formed it into tiny spheres, then baked those spheres at a temperature of 1,160 ºC (2,120 ºF) for a few minutes.

That’s a point. Fly ash naturally is in tiny spheres, and is naturally considered a non-shrink material.

But you’re right, I hadn’t heard of anybody preprocessing fly ash by combining it with bonding chemicals and high temperature baking to transform it from smaller spheres into larger spheres. That makes sense.