What is the fck of concrete?

Answer 1

Concrete

The concrete used in structures is characterized by its resistance, the fck. This resistance is measured through the breaking of specimens, and it means to say that a case has a certain fck, the probability of obtaining a lower resistance than that indicated only 5%. It is good to note that the fck, which is the concrete strength is measured by a unit of voltage, ie, a load (force) per unit area. This measure can be given in MPa or kg/cm2. We can say, for example, that a case has fck = 18 MPa. This means that the resistance (fck) of concrete is equal to 18MPa or 180 kgf/cm2.

For specification of concrete for the slab lattice, one must distinguish the concrete used in the manufacture of concrete beams cast in situ to form the ribs of the slab.

The second has an important structural function, as it forms the table compression of the slab, while the first does not always have. The concrete to be released on the spot will be provided by the manufacturer, but its strength should be reported to the engineer responsible for the design of the slab, allowing it to conduct the calculations correctly.

The concrete for casting the beams does not, in most cases, the same structural importance doconcreto to be cast on the spot, except in some cases, such as the continuous slab or sheet, when we squeeze the lower fiber the slab, where the concrete s.apata.

Where no such structural importance, the concrete beams do not need a high compressive strength, but should not miss the purpose of protection of armor that are within the s.apata. Therefore, attention should be paid to asua compactness and avoid the use of beams with poor concreting (maggots).

The concrete that makes up the slabs and concrete lattice supplement must meet the specifications of NBR-12655 and NBR 6118 and NBR 8953 and respecting the provisions of NBR 12,654. The compressive strength will be specified by the structural design, and required a minimum Class C20 to C20 beams and Class of acordocom NBR 6118 for concrete cast on site.

In the case of concurrent execution of specific complementary edo concrete structure, the prevailing higher value of resistance characteristic (fck) specified in the project.

The concrete Class C20 corresponds to the characteristic compressive strength at 28 days of 20 MPa. Beams boom and the combination of the lattice frame, the additional hardware and s.apata concrete. It is the end product quedeverá be delivered by the manufacturer to the customer, along with the filler material and a project demontagem.Deve be designed to carry structural strain after the concreting of the slab, but must also have the stiffness needed to withstand the transport and assembly.