**1. REQUIREMENTS**

a) Specified minimum strength = 20 N/Sq mm

b) Durability requirements

i) Exposure Moderate

ii) Minimum Cement Content = 300 Kgs/cum

c) Cement

(Refer Table No. 5 of IS:456-2000)

i) Make Chetak (Birla)

ii) Type OPC

iii) Grade 43

d) Workability

i) compacting factor = 0.7

e) Degree of quality control Good

**2. TEST DATA FOR MATERIALS SUPPLIED **

a) CEMENT

i) Specific gravity = 3.05

ii) Avg. comp. strength 7 days = 46.5 more than 33.0 OK

28 days = 55.0 more than 43.0 OK

b) COARSE AGGREGATE

i) 20mm Graded

Type Crushed stone aggregate

Specific gravity = 2.68

Water absorption = 1.46

Free (surface) moisture = 0

c) FINE AGGREGATE (Coarse sand)

i) Type Natural (Ghaggar)

Specific gravity = 2.6

Water absorption = 0.5

Free (surface) moisture = 1.4

**3. TARGET MEAN STRENGTH (TMS)**

a) Statistical constant K = 1.65

b) Standard deviation S = 4.6

Thus, TMS = 27.59 N/Sqmm

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**4. SELECTION OF W/C RATIO**
a) As required for TMS = 0.5

b) As required for ‘Moderate’ Exposure = 0.55

Assume W/c ratio of 0.5

**5. DETERMINATION OF WATER & SAND CONTENT**

For W/C = 0.6

C.F. = 0.8

Max. Agg. Size of 20 mm

a) Water content = 186 Kg/cum

b) Sand as percentage of total aggregate by absolute volume = 35 %

Thus,

Net water content = 180.42 Kg/cum

Net sand percentage = 33 %

**6. DETERMINATION OF CEMENT CONTENT**

W/c ratio = 0.5

Water content = 180.42 Kg/cum

Thus, Cement content = 360.84 Kg/cum Adequate for moderate exposure Say 360 Kg/cum

**7. DETERMINATION OF COARSE AND FINE AGGREGATE CONTENT**

Assume entrapped air as 2 %

Thus,

0.98 cum = [180.42+360/3.05 + {1/0.33}*{fa/2.6}]/1000

& 0.98 cum = [180.42+360/3.05 + {1/0.67}*{Ca/2.68}]/1000

Hence,

fa = 584 Kg/cum

Ca = 1223.8 Kg/cum

The final mix proportions of M-20 grade of concrete become:-

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Note: 1 The above recommended mix design must be verified, by actual cube tests.

2 The mix design is based on the quality and grading of the materials actually supplied, by the client.

Any variation in quality and gradation will result in changes in the mix design.

This mix design was submitted by a regular contributor to this site. We are thankful to him for his excellent service.

### Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.
If you have a query, you can **ask a question here**.

i am final yr be student plz send the details the latest admixture for concrete

what is mix ratio for grade 20 concrate

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Friends i am doing 3rd yr in chennai, i need a guide to guide me……….

PLEASE, EXPLAIN HOW TO PLACE REINFORCEMENT ON SITE

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good

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I suggested you to make project on metro plan in crowded city or tri-city just like as chandigrh. It will put a great impression on your teachers. If you chosse that then make a plan that there should be metro iun chd city because of a greate rush.

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pls send me all mix design details

sir how to calculate the triangle concrete capacity

use the formula to calculate triangle.the value you get is equivalent to agg then divide by 2 to get no. of sand.

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please show your detail work conversion to weight