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35 replies
7k views
35 replies
C30/37 w/c 0.5 xc4+xf3 Must not be troweled?
If I ask the constructor that question, he will probably answer yes you need it and not back down because he thinks it should be that type. It takes another person to review his work if I'm going to get the right answer.
Is c30/37 bad for concrete floors or?
Is c30/37 bad for concrete floors or?
You should not ask a yes/no question. You should ask him to justify his choice.M MackanM said:
C30/37 is probably a "stronger" concrete than necessary. However, it may be needed in terms of structural load-bearing capacity. Please ask for a motivation and not just a yes. Then, you don't have to follow the constructor regarding the air content, but if by any chance there are unexpected issues with cracks in the slab, it might be a bit troublesome to get anything since you're not following the plans. However, one should not deviate from the strength without consulting.
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Hello, it's probably too late now.
If the concrete is an indoor structure, you absolutely don't need any air in it. Air is used in structures exposed to cold periods (permanent or cyclical). We're talking years. A microscopic pore system will form, allowing the bound water to expand when it freezes.
This should not be confused with the air you use the vibrator to remove.
You absolutely don't need air to cast a structure that will be indoors (like a foundation slab in a house).
The concrete must be protected against early freezing, meaning it must not freeze before reaching a compressive strength of 5 MPa. Ice crystals will form, and further strength growth can fail.
This is achieved fairly quickly if you have heat in the concrete and cover the surface with, for example, a concrete curing mat.
Remember that the concrete winter is counted from +5 degrees. Lower outdoor temperatures will cause the strength growth to be extremely slow unless the concrete is insulated or heated.
The idea that finishing would destroy the pore system is possibly correct (I don't know).
If the concrete is an indoor structure, you absolutely don't need any air in it. Air is used in structures exposed to cold periods (permanent or cyclical). We're talking years. A microscopic pore system will form, allowing the bound water to expand when it freezes.
This should not be confused with the air you use the vibrator to remove.
You absolutely don't need air to cast a structure that will be indoors (like a foundation slab in a house).
The concrete must be protected against early freezing, meaning it must not freeze before reaching a compressive strength of 5 MPa. Ice crystals will form, and further strength growth can fail.
This is achieved fairly quickly if you have heat in the concrete and cover the surface with, for example, a concrete curing mat.
Remember that the concrete winter is counted from +5 degrees. Lower outdoor temperatures will cause the strength growth to be extremely slow unless the concrete is insulated or heated.
The idea that finishing would destroy the pore system is possibly correct (I don't know).
If you are casting a foundation slab in a house, it is usually the w/c ratio that governs the strength of the concrete. The water-cement ratio controls the relationship between the water and the cement in the concrete. The less water there is, the higher the strength in the mix.
You typically want to have a low w/c ≤ 0.50 for drying purposes, especially in bathrooms.
In the project I'm working on now, the requirement for strength is c30/37 from the structural engineer for the slabs. But we know from experience that we need to go down to w/c 0.40 in the bathrooms to reach 85% RH before applying the waterproofing. With w/c 0.40, the strength of the concrete increases to c40/50.
You typically want to have a low w/c ≤ 0.50 for drying purposes, especially in bathrooms.
In the project I'm working on now, the requirement for strength is c30/37 from the structural engineer for the slabs. But we know from experience that we need to go down to w/c 0.40 in the bathrooms to reach 85% RH before applying the waterproofing. With w/c 0.40, the strength of the concrete increases to c40/50.
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