M20 grade Standard concrete and concrete of grade M20 are appropriate for Reinforced Cement Concrete (RCC) projects such as slabs, beams, and columns. High-strength concrete can be used in high-rise constructions. However, it must comply with certain requirements.
The minimum strength required by the American Concrete Institute (ACI) for a column of this size made from RCC is 20 MPa (300 psi). Higher strengths may be required for special applications. For example, if the column is being used as the base for a building overhang, a higher strength might be required.
The type of reinforcement used in RCC depends on its ultimate load. For columns under moderate loading conditions, normal reinforcing methods are sufficient. For columns under high loads, additional reinforcement should be added to the top plate to prevent failure by buckling. The ACI recommends either plain or corrugated metal sheets as the top surface treatment for RCC columns. Corrugated metal sheets provide greater resistance to crushing damage than plain metal plates. They also allow the use of thinner concrete layers because there's less risk of spalling.
Plain concrete columns are adequate for light duty service but they have the disadvantage of lower resistance to crushing damage compared to corrugated ones. This means that they require thicker walls which increase the overall weight of the structure.
For routine labor, the ratios are 1.5:3 and 1:2:4. For foundations and bulk concrete constructions, the ratios are 1: 3: 6 and 1: 4: 8. Concrete grades lower than M20 are not permitted in RCC work, according to IS 456: 2000.
The required strength of concrete for rigid-core construction depends on the design pressure expected on the roof. The rule of thumb for RCC is that the average daily load should be equal to 20 percent of the total weight of the roof. For example, if the roof weighs 100 tons, then its maximum design pressure should not exceed 2,000 pounds per square foot (psf).
Concrete required for RCC projects should be strong enough to withstand the compressive stress imposed by the overlying roof deck without failing. This means that M50/60 concrete with a minimum of 30 minutes of reinforcement is sufficient for most applications.
Higher strengths may be necessary for special designs such as deep roofs or high wind areas. Also, lower strengths may be needed for interior floors or base courses where less pressure is applied.
The required strength of concrete for rigid-shell construction depends on the size and weight of the shell. Heavy shells require heavier concrete which in turn requires stronger reinforcement.
Responses RCC requires a minimum grade of concrete, M20, with a cement-to-fine-aggregate-to-coarse-aggregate ratio of 1:1.5:3, or 1 part cement, 1.5 parts fine aggregate (sand), and 3 parts coarse aggregate. What is the minimum concrete grade for an RCC slab? Responses RCI requires a minimum concrete grade of C50, which means it can be any type of concrete as long as it has a minimum compressive strength of 50MPa.
The minimum required concrete strength depends on the design requirements for the project. For example, if you plan to use the slab as a road surface, then it makes sense to require a stronger concrete than one used in a garden wall. Concrete strength is measured in MPa (megaPascals). A common minimum requirement is 60MPa for pedestrian areas and 80MPa for vehicle lanes.
In terms of actual numbers, that means the total weight of the slab should be at least 2000kg / 4400lb, and its maximum thickness should not be less than 30cm / 12". The density of ordinary concrete ranges from 2400 to 3000kg/m3, so this means that the slab must have at least 6300kg or 13500lb of material.
The cost of the building or structure mostly determines the concrete grades. M20 or M15 COLUMN AND BEAMS M15 or M20 for floor concrete, depending on the projected load. They must be developed in accordance with IS 456:2000 starting at M30 or M60. The minimum reinforcement required depends on the projected load and the type of joint used.
The type of joint used between floor slabs affects the required depth of reinforcement. For example, a simple lap joint requires only half the depth of reinforcement required for a complex joint such as a dovetail. The requirements for reinforcement are also affected by the type of floor covering used. A carpeted floor requires less reinforcement than a wood floor. The thickness of the floor slab also affects the required depth of reinforcement. Floor slabs under 2 inches thick do not require reinforcement. Slabs over 2 inches but less than 4 inches thick can be reinforced with rebar up to 1-1/4 inches in diameter. Thickness ranges from 4 to 6 inches require 2-inch-diameter rebar up to 1-3/8 inches deep.
A column below ground level does not need to have reinforcement if it will not be exposed to any significant loading. A basement floor can have thin concrete with no reinforcement at all, provided it is flat and free of dips or rises. Basement floors are usually supported by footings or walls at each end.