Hi everyone,

i'm 27 years old and based in South America.
My mother bought a Russian portable foamed concrete machine from Stroybeton (500L drum system with foam generator). 
The unit had previously been sent for repair and we were told it was fixed, but several components were missing and some parts were not properly assembled.
The manual was entirely in Russian, including technical drawings and exploded diagrams. 
I translated everything myself to understand the system and rebuilt it correctly.

I am not a mechanic or engineer, but I rebuilt and modified the machine myself:

- Realigned shafts
- Reworked closures and seals
- Reassembled missing components
- Adapted parts to make the system reliable

Mechanically, the system now works correctly.


Discharge modification:
Originally the system used a 5-meter discharge hose (approx. 100 mm diameter).
The original hose is no longer available, and I am not interested in using the unit for pumping floors or filling wall cavities. My focus is exclusively block production.

So we modified the discharge:

Shortened the hose
Installed approx. 1 meter of pipe
Added a shut-off valve with elbow
The mix now flows directly into the molds


Why I care about quality:

There are already people here producing similar lightweight blocks.

I obtained test blocks from one producer.
They were initially hard and dense. I stored them for three months under the roof, protected from weather and direct sunlight.

After three months, the blocks had significantly deteriorated. They became weak and started crumbling by hand.

That is exactly the kind of quality I do NOT want to produce.

If we do this, I want long-term stable blocks — not something that looks good for a few weeks and then loses strength. Also I want to let them rest for few months to see how they doing in the drying process.


Foam Specification:

Manufacturer specification: 60–80 g/L
Measured foam density:
1 liter = approx. 80 grams

The foam is stable. It is not extremely dense, but it holds structure well, remains stable over time, and bubble size appears consistent (neither too fine nor too coarse).

Manufacturer Mix Tables
(Original tables are for the 1000L units – values below are divided by 2 for my 500L machine, we only tried 600kg/m3 and 800kg/m3)

400 kg/m³ 
Cement Portland: 175 kg
Sand: 0 kg
Mixing water: 55 L
Foam volume: approx. 420–430 L

600 kg/m³ 
Cement Portland: 175 kg
Sand: 105 kg
Mixing water: 55 L
Foam volume: approx. 360–370 L

800 kg/m³ 
Cement Portland: 175 kg
Sand: 200 kg
Mixing water: 65 L
Foam volume: approx. 310–320 L

1000 kg/m³
Cement Portland: 175 kg
Sand: 280 kg
Mixing water: 60 L
Foam volume: approx. 270–280 L
Foam density (manufacturer): 60–80 g/L
Measured foam density: ~80 g/L

Current Problems:

I'm not sure how long and when to mix, should I start mixing the foam directly into the Cement-Mix or wait until the  foam is in the machine and mix then? The Manual says not longer then one minute mixing after adding the foam.

Earlier: Mixed too long → foam collapsed → blocks soft and crumbly.

Now: Base slurry feels relatively thick before foam addition and doesn't mix completely so density varies.

During discharge:
- First output very dense and heavy
- Later output lighter and foam-rich
- Batch not homogeneous
- Density varies within the same drum
- It appears slurry and foam are not forming a stable, uniform cellular structure.

Since these machines are sold worldwide, I assume the issue lies in my mix design or mixing process.


My Questions:

Should the base slurry be significantly more fluid before adding foam?

Is increasing water by 5–10% reasonable?
Ideal mixing time after foam addition in a 500L drum?

Could shortening the discharge hose reduce secondary mixing and contribute to visible segregation?

What would you consider critical for long-term durability in 600–1000 kg/m³ foamed concrete blocks?

I cannot realistically test small lab batches because the mixing behavior is completely different from the 500L production drum.

Any practical advice from experienced producers would be greatly.

Please remember that I'm still in testing phase and that the momentarily buildup will be changed as soon as I get my working space done.

Thank you.

Trying to start foamed concrete production (400–1000 kg/m³) with 500L Stroybeton mixer – density separation and long-term durability concerns