GRADES OF CONCRETE

         Concrete grades are denoted by the letter 'M' followed by a number, which represents the compressive strength of the concrete in megapascals (MPa) after 28 days of curing. For example, M20 concrete has a compressive strength of 20 MPa 

Nominal Mix Concrete:

         Nominal mixes are predefined ratios of cement, sand, and aggregates. They are generally used for small-scale construction where precise mix design is not critical.

Grades of Concrete	Mix Ratio Cement:Sand:Aggregate	Compressive strength of 150 mm cube at 28 days cured MPa (N/mm2)     Psi
M5	1:5:10	5 Mpa	725 Psi
M7.5	1:4:8	7.5 Mpa	1087 Psi
M10	1:3:6	10 Mpa	1450 Psi
M15	1:2:4	15 Mpa	2175 Psi
M20	1:1.5:3	20 Mpa	2900 Psi
M25	1:1:2	25 Mpa	3625 Psi
M30 and above	Design Mix	30 Mpa	4350 Psi

Grades of Concrete as per IS 456:

         Standard mixes are designed based on specific requirements and are used in structural applications.

Group	Grade Designation	Specified Characteristic Compressive strength of 150 mm cube at 28 days in N / mm2
Ordinary concrete	M10	10
	M15	15
	M20	20
Standard Concrete	M25	25
	M30	30
	M35	35
	M40	40
	M45	45
	M50	50
	M55	55
High Strength	M60	60
	M65	65
	M70	70
	M75	75
	M80	80

Note:  

(1) M5 and M7.5 Grades may be used for lean concrete bases and simple foundations for masonry walls. These mixes need not be designed.

(2) Grades lower than M15 shall not be used in reinforcement concrete.

Selection of Concrete Grades

     The choice of concrete grade depends on the structural requirements, environmental conditions, and specific application. For instance, M20 is commonly used for residential construction, while M40 and above are preferred for commercial and industrial structures.

Different Grades of Concrete -- Concrete Mix Design

Water for Building Construction

 2. Water for Building Construction:

          Water used for mixing and curing shall be clean and free from injurious substances of oils, acids, alkalis, salts, sugar, organic materials (or) other substances that may be deleterious to concrete (or) steel. Portable water is generally considered satisfactory for mixing concrete.  

Quality for Building Construction as per IS 456:2000

Portable Water/River water:

          Generally, quality of water for construction works are same as drinking water/Portable water. Generally, Surface water i.e., River water is generally good for construction.

Quality of Water:

          This is to ensure that the water is reasonably free from such impurities as suspended solids, organic matter and dissolved salts, which may adversely affect the properties of the concrete, especially the setting, hardening, strength, durability, pit value, etc., The water shall be clean and shall not contain sugar, molasses (or) gur (or) their derivates, (or) sewage, oils, organic substances.

          The water quality for construction shall be tested (or) monitored regularly, as it affects the overall strength of concrete. For plain and reinforced cement concrete permissible limits for solids shall be as follows: 

Types of Solid in water	Permissible Limits for Construction
Organic matter	200 mg/l
Inorganic matter	3000 mg/l
Sulphates (So4)	500 mg/l
Chlorides (Cl)	A) 1000 mg/l for RCC work and, b) 2000 mg/l for PCC work
Suspended matter	2000 mg/l

Components in Building Construction

 1. Components in Building Construction

• Site Clearance
• Excavation
• Foundation
• Plinth Beam (or) Slab
• Superstructure Column and Beam
• Brick Masonry Work
• Lintel Over Doors Window
• Floor Slab (or) Roof Structure
• Plastering
• Door and Window Framing and Fixations
• Painting
• Electrical and Plumbing
• Exterior Finishing
• Electrical and Plumbing
• Exterior Finishing
• Internal Finishes
• Boundary Wall and Gates
• Landscaping.

Building Codes & Manuals
1	IS 456	Plain and Reinforced Concrete-Code of Practice
2	IS NBCC	National Building Code of India 2016
3	IS SP 62	Handbook on Building Construction Practices
4	IS SP 21	Summaries of Indian Standards for Building Materials

IS 456: 2000 Indian Standard PLAIN AND REINFORCED CONCRETE - CODE OF PRACTICE (Fourth Revision)

 This IS 456: 2000 deals with the general structural use of plain Concrete and Reinforced Concrete.

SI NO	Materials
1	Cement
2	Fine Aggregate (Sand)
3	Coarse Aggregate (6 mm - 20 mm Graded HBG Metal)
4	Reinforcement (Steel)
5	Plastixers (Admixtures)