Concrete Grading and Mix Ratio for your building or structures.

The materials used in reinforced/unreinforced concrete are commonly weighed and mixed in large concrete mixers or small batches that are mixed by hand or in a portable mixer.

British standard 5328: specify concrete, including ready-mixed concrete, gives a range of mixes, prescribed mixes of cement, fine and coarse aggregates by volume or weight as they are measured with accurate method of measuring the proportion of cement to aggregates but allowing for close control of the water content.

Prescribed mixes are designed by the letters and numbers i.e. C7.5P, C10P, C15P, C20P, C25P, C30P, etc.

· The letter C stands for compressive

· The letter P for prescribed and

· The number indicates the 28-day characteristics cube crushing strength in Newton’s per-square millimeter (N/mm²⁾ that the concrete is expected to attain.

By Weight and By Volume:

By weight – for designed mix or for jobs of relative importance

By volume – The concrete is specify as a ratio of cement to fine aggregate to coarse aggregate.

Typically, i.e. 1:2:4 or 1:1 ½: 3.

Concrete should be specified using characteristics strength Fck.

Example:-

Strength classification of concrete;

	*CLASS-* *DESIGNATION*	*MIX RATIO*	*(Fck)* *CHARACTERISTIC STRENGTH* *(N/mm²)*	*GROUP* *(as per* *IS: 456-2000)*	*NORMAL LOWEST CLASS FOR USE AS SPECIFIED*
1.	Grade 5 (C₅)	1:5:10	5	Lean Mix
2.	Grade 7.5 (C_7.5)	1:4:8	7.5	Lean Mix
3.	Grade 10 (C₁₀)	1:3:6	10	Ordinary concrete
4.	Grade 15 (C₁₅)	1:2:4	15		Light weight concrete
5.	Grade 20 (C₂₀)	1:1½:3	20		Plain concrete
6.	Grade 25 (C₂₅)	1:1:2	25	STANDARD CONCRETE	Reinforced concrete
7.	Grade 30 (C₃₀)	DESIGNED	30		Reinforced concrete in foundation
8.	Grade 35 (C₃₅)		35
9.	Grade 40 (C₄₀)		40
10.	Grade 45 (C₄₅)		45
11.	Grade 50 (C₅₀)		50
12.	Grade 55 (C₅₅)		55
13.	Grade 60 (C₆₀)		60	Very High Quality Concrete

Comments

Construction Procedure of Surface Road Side Drainage-PART 1 (with picture)

Surface water ( i.e., rain water) that falls on the ground surface such as; open field, paved areas or road surface, roof tops etc are channeled to a main drain naturally or through a constructed channel which is referred to as drainage. Procedure for construction of a common drainage (trench) (1m x 1m U drainage) (reinforced). includes; I. Marking Of Alignment: The surveyor marked out the alignment for the trench to be dug. II. Digging/Excavation: The surveyor marked out the dept of the trench to be excavated with a mechanical excavating machine. For a 1m x 1m drainage, the mathematical process of obtaining the required dept is to sum together the dept of the required drain + base + blinding. For dept: A drain of dept1000 mm, base of 150 mm and blinding of 50 mm. Hence 1000mm + 150mm + 50mm = 1200mm (1.2 m) So an excavation of 1200mm (1.2m) is required from the to level of the road surface. For width:

Construction Procedure of Surface Road Side Drainage-PART 2 (with picture)

V. Next step is laying of concrete base on the blinded surface and the positioned reinforcement. A concrete base of 150 mm is to be laid or cast on the blinded floor, concrete grade C20 of ratio 1:2:4 is allowed (See concrete grading and mix ratio). A guiding panel is placed into position to guild in the laying of the concrete base in order to achieve a uniformly alignment base edge, thickness and width, also to manage concrete material while pouring. The base is cast with the U shape reinforcement bottom in between the concrete base achieving concrete cover below and above. VI. After setting and drying of the concrete base, next is to position the side wall panel form work. The floor base is marked to give the required one meter (1000 mm) internal width where the panel will be positioned. The panel wall spacing is 100mm, and wall height of 1000mm (1 meter), the panel is lubricated, clipped and prepared to accept the Concrete.

Ring / Pipe Culverts Construction procedure

Culvert is an open/close drain structure that allows water to flow below a road. It’s like a tunnel carrying a stream of water flow. A Ring/Pipe Culvert Procedure for construction of a common Ring/Pipe Culvert (road junction culvert) includes; I. Marking Of Alignment: - The surveyor marked out the alignment for the trench to be dug. II. Digging/Excavation: The surveyor marked out the dept of the culvert to be excavated with an excavating machine. For a 1m pipe culvert, the mathematical process of obtaining the required dept is to sum together the total width of the pipe + base + blinding. For dept: A pipe of width 1000 mm, base of 150 mm and blinding of 50 mm (though optional). . Hence 1000mm + 150mm + 50mm = 1200mm (1.2 m) So an excavation of 1200mm (1.2m) is required from the to level of the natural ground (sub grade level) surface. For width: A minimum of (2.5 x width) m is advisable.

Construction Hints

Search This Blog