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Concrete Mix Design – M 20 Grade Of Concrete

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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

sieve_analysis_m20_grade_of_concrete

c) FINE AGGREGATE (Coarse sand)
i) Type Natural (Ghaggar)
Specific gravity = 2.6
Water absorption = 0.5
Free (surface) moisture = 1.4

sieve_analysis_fine_m20_grade_of_concrete

3. TARGET MEAN STRENGTH (TMS)
a) Statistical constant K = 1.65
b) Standard deviation S = 4.6
Thus, TMS = 27.59 N/Sqmm

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 %

adjustments-m20-grade-concrete

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:-

mix-design-concrete-m20

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.

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Comments
  • Anand May 13, 2016 at 12:58 pm

    Plz explain how 320 kgs of cement is used instead of 400kgs of cement for m20 concrete in kpwd sr …

  • gopi May 29, 2016 at 1:13 am

    I need a brief description about mix design details.please send me

    • MUNIYAPPAN.K June 30, 2016 at 12:36 pm

      which type of concrete mix design sir…?like M35,M40 etc…

  • GTH RAYA June 21, 2016 at 1:30 pm

    I need a brief description about mix design details.please send me

    • MUNIYAPPAN.K June 30, 2016 at 12:49 pm

      which type of concrete mix design sir…?like M35,M40 etc…

    • MUNIYAPPAN.K June 30, 2016 at 12:50 pm

      A mix of M-80 Grade suitable for pumped concrete is to be designed with the following materials and detail.

      1. OPC 53 Grade, 7-day strength 52.5 N/mm2, Spgr 3.15

      2. Silica Fume Specific Gravity 2.20

      3. Standard deviation for the mix 5.0 N/mm2

      4. Grading and properties of river sand and 12.5 mm crushed aggregate are given in Table-1

      5. Superplasticizer based on modified Polycarboxylate, specific gravity 1.06, liquid pH 6.0. With the given set of materials, it was found that at a dosages of 2.5 % bwc it gives a reduction of 30% of water for the required slump of 100 mm after one hour at the average day site temperature of 37 degree C.
      Continue Reading »
      Filed under Concrete Engineering, Mix Design, Research Papers | 1 Comment
      Mix Design For Concrete Roads As Per IRC:15-2011

      By
      Kaushal Kishore, Materials Engineer, Roorkee

      ABSTRACT:
      The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concrete mixes is described in the paper.

      INTRODUCTION:
      Usual criterion for the strength of concrete in the building industry is the compressive strength, which is considered as a measure of quality concrete. However, in pavement constructions, such as highway and airport runway, the flexural strength of concrete is considered more important, as the stresses induced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of the world specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexural strength. Therefore, there is a need to design concrete mixes based on flexural strength.

  • sunilkumar June 29, 2016 at 9:39 am

    sir, in 1.REQUIREMENTS…..b)durability requirements……ii)minimum cement content=300kgs/cum
    please let me know how/on what basis you have taken minimum cement content=300kgs/cum

  • Sanjay Raundal July 28, 2016 at 11:40 am

    Sir pl clarify the limits for crushed sand passing below 150 micron is revised as 0 to 20 but in all in aggregate it is kept same i. e. 0 to 6 why not limits revised

  • Er. Vijayananda S. Hiremath September 26, 2016 at 8:15 am

    i wanted to know the suitable proportion of contents of basalt crushed stone which can be used for construction purpose.

  • francis October 26, 2016 at 11:59 am

    I would like to know all the classes of concrete and their corresponding proportions. Secondly, how is the volume of entrapped air estimated during a concrete mix design? Thnx

  • hemant November 10, 2016 at 12:14 pm

    Hi sir,
    This hemant i am new in this field plz help me out and i just want to know, the required material for M20 Grade, 300x300x450 high rcc block,

    like : Cement grade, & Qty, M20 Aggregate, Qty, Sand Qty. and required water..

    Thanks
    Hemant

    • joydev sen March 4, 2017 at 7:11 am

      Please do L×b×h.

  • ramchandar January 8, 2017 at 3:28 am

    how much mm sand using for 2 coat plastering?

  • om prakash yadav February 11, 2017 at 12:23 am

    what is the reason behind using 53 grade cement in m20 concrete?

  • Er.Yogesh March 8, 2017 at 4:43 am

    how may calculate the strength per day of cube .?

  • Sunil March 13, 2017 at 12:34 pm

    How days water apply the concreat foe setting

  • M.Venkatesh March 24, 2017 at 11:01 am

    sir plz send acceptence criteria for M25 grade concrete

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