Concrete Mix Design

Mix Design Procedure (IS -10262 2009)

Theory

•  The concrete mix design consist of selection of optimum proportion of cement, FA, CA and water to produce a concrete of specified properties. 
•  The most specified properties of concrete are compressive strength, workability, durability. 
•  As we know that strength is governed by w/c ratio of concrete.

Factor Affecting  Concrete Mix Design

1. Grade of concrete 
2. Type of cement
3. Cement content 
4. Size, shape, and grading of aggregate.

Steps For Mix Design

1. Determine target mean strength of concrete 
2. Determine W/c ratio from strength requirement. 
3. Determine water content from workability 
4. Determine cement content and check for durability 
5. Determine volume of aggregates. 
6. From concrete mix proportions so obtained, trial mixes with suitable adjustments are made to arrive at the final mix proportions. 

CONCRETE MIX DESIGN(Example as per IS 10262 2009)

STEP-01.   TARGET MEAN STRENGTH

F'ck=Fck+ 1.65S

• F'ck = Target mean compressive strength at 28 days N/mm2 
• Fck = characteristics strength at 28 days N/mm2 
• S = standard deviation  N/mm2 
• S is based on grade of concrete. 
• Fck = grade of concrete N/mm2

Table 1 from IS 10262-2009

STEP-02.   W/C RATIO

• W/C Ratio from IS 456-2000 Table 5.
• Based On experience adopt W/C Ratio(fig. 1), Which should be less than Maximum W/C Ratio given. 

Table 5 from IS 456-2000

Fig. 1 Adopt W/C  based on experience 

STEP-03. WATER CONTENT

• Water content select based on maximum size of aggregate (from Table 2)

Table 2 Water content (IS 10262 2009)

• Water Content also based on Slump Value of Concrete.

Slump Value	Increment water
25-50	0 %
50-75	3 %
75-100	6 %
100-125	9 %

• Water content reduce 29%-30%, if use plasticizer or super-plasticizer.

STEP-04.   CEMENT CONTENT

• Calculate cement content with W/C ratio and water content.
• It should be based on exposure condition. 
• Calculated cement content should be more than minimum cement content.

STEP-05.   VOLUME OF C.A. AND F.A

                 

    Volume of aggregate base on.

•  Coarse aggregate --- size 
• Fine aggregate ----- zone 

Table 3. IS 10262-2009

Note:-Volume of Aggregate shown in Table 3 is for W/C Ratio  0.5

Condition - 1 

• As w/c ratio is decrease ---- CA volume will be increase  and vice-versa. 
• For every  change of w/c ratio 0.05 ------ the CA volume will change by 0.01 
• So, if reduction of w/c for every 0.05 ---- the CA volume will increase by 0.01 

Condition - 2

• If concrete is pumpable Volume of CA will reduce by 10%

STEP-06. CALCULATION OF VOLUME.

DOWNLOAD

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