ᐅ Concrete slab, insufficient cement content in the concrete mix
Created on: 14 Jun 2020 15:06
E
Eriwan2
Hello, I am quite inexperienced with construction and very worried about the following issue:
I want to build a swimming pool in my garden, measuring 3x5x1.5 meters (10x16x5 feet), using Styrofoam formwork blocks that will be filled with concrete.
A friend who works in construction helped me pour the base slab (20cm (8 inches) thick) over the weekend, and for various reasons, we had to mix the concrete ourselves from cement and gravel.
I read online that the ideal mix ratio is 1 part cement to 4 parts gravel by weight, and this is exactly what my friend had told me before. He mixed the concrete, and I did the pouring.
Now that the slab is finished, I checked the delivery notes. When I calculate everything, we used exactly 8 tons of gravel and 1.25 tons of cement. But for a 1:4 ratio, we should have used 2 tons of cement.
He says this is not a problem and gave me explanations I don’t fully understand. (For example, there was some water in the gravel, so we actually used less gravel than was delivered. The gravel was indeed damp, but as a layperson, I am still very concerned if this will truly hold.
Does anyone have experience with this and could please share some advice?
I want to build a swimming pool in my garden, measuring 3x5x1.5 meters (10x16x5 feet), using Styrofoam formwork blocks that will be filled with concrete.
A friend who works in construction helped me pour the base slab (20cm (8 inches) thick) over the weekend, and for various reasons, we had to mix the concrete ourselves from cement and gravel.
I read online that the ideal mix ratio is 1 part cement to 4 parts gravel by weight, and this is exactly what my friend had told me before. He mixed the concrete, and I did the pouring.
Now that the slab is finished, I checked the delivery notes. When I calculate everything, we used exactly 8 tons of gravel and 1.25 tons of cement. But for a 1:4 ratio, we should have used 2 tons of cement.
He says this is not a problem and gave me explanations I don’t fully understand. (For example, there was some water in the gravel, so we actually used less gravel than was delivered. The gravel was indeed damp, but as a layperson, I am still very concerned if this will truly hold.
Does anyone have experience with this and could please share some advice?
In the past, the well-known 1:1 mixes—1 shovel of cement to one wheelbarrow of sand—often lasted a very long time with a lot of hope, and I live in a house like that that is about 150 years old. Depending on the substrate, I don’t think there will be any problems. If there are concerns, just add another 5cm (2 inches).
K
Koordinator30 Jun 2020 20:38More important than the amount of cement is the water content and the quality of compaction. The less water used and the better the compaction, the better the result and the less cement is needed.
Additionally, the question is whether the concrete slab is purely structural or if it has static requirements and demands.
Should the slab be waterproof? If yes, forget about it!
The planned wall will not be waterproof.
Additionally, the question is whether the concrete slab is purely structural or if it has static requirements and demands.
Should the slab be waterproof? If yes, forget about it!
The planned wall will not be waterproof.