SuperPlasticiser 1% by weight of cement, 23% reduction in water achieved, SpGr 1.145

These are the steps you will take:

STEP 1 : TARGET MEAN STRENGTH

For SEVERE exposure RCC using 20mm coarse aggregate we need to atLeat use M30 Grade of concrete (As per Table 5 of IS 456 2000)

 So lets design M30

Target Mean Strength Fckt = Fck + 1.65xS

Fck = 30MPa (for M30)

Standard deviation for M30= 5.0 (Table 1 IS 10262 2009)

Fckt = Fck + 1.65×5.0

Target Mean Strength= 30+ 1.65*5.0=38

STEP 2 : CALCULATION FOR WATER CONTENT

For 20mm Aggregates MAX Water Content =186.0 (Table 2 10262 2009)

This value is for Slump within the range of 25-50

For Every 25mm increase in slump we will increase

water by 3%

Current Slump is :100 Which is :50 mm above 50mm

Increase Water Content By :6.00%

186.0+(6.00*186.00)/100 =197.16 Kg/m³

With the Admixture 23% reduction is achieved So

New Water Content = 197.16-(23/100)

Water Content = 151.81 Kg/m³

STEP 3 : SELECTION OF WATER CEMENT RATIO

For REINFORCED Concrete and SEVERE exposure

condition MAX W:C=0.45 (As per Table 5 of IS 456 2000)

STEP 4 : CALCULATION OF CEMENT CONTENT

Cement=WaterContent/w:C

Cement Content=151.81/0.45 = 337.36 Kg/m³

(As per Table 5 of IS 456 2000)Minimum Cement Content is 320

Since

337.36 >320 OK

STEP 5 : CALCULATION OF RATIO OF AGGREGATES

For 20mm Coarse and Zone 2 Fine,Volume of Coarse to Total Aggregates=0.62(Table 3 10262 2009)

This value is for w:C =0.50 our w:C=0.45

Increase Coarse Ratio by 0.01 for every decrease of 0.05 in W:C

For 0.45 there is a decrease of 0.05

So Increase Factor= 0.01

New Coarse Ratio = 0.62 + 0.01 = 0.63

Fine Agg Ratio=1-Coarse Agg Ratio=0.37

DESIGN MIX CALCULATIONS

Vol of Cement= WT OF CEMETN/(SPGR of

CEMENT*1000)=337.36/(3.14*1000)=0.11

Vol of Water=Wt of Water/1000

=151.81/1000

=0 .15

Vol of Admixture = Wt of ADM/(spgr*1000)=0.003

TOTAL AGGREGATE Vol(e) = 1-(Cement+Water+Admixture)=0.74

Wt of Coarse Aggregate=e*CoarseRatio*SPGR*1000

= 0.74*0.63*2.45*1000=1138.79 Kg/m³

Wt of Fine Aggregate=e*FineRatio*SPGR*1000

=0.74*0.37*2.50*1000=682.47 Kg/m³

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STEP 1 : TARGET MEAN STRENGTH

For MODERATE exposure RCC using 20mm coarse aggregate we need to atLeat use M25 Grade of concrete (As per Table 5 of IS 456 2000)

 So lets design M25

Target Mean Strength Fckt = Fck + 1.65xS

Fck = 25MPa (for M25)

Standard deviation for M20-M25 = 4.0 (Table 1 IS 10262 2009)

Fckt = Fck + 1.65×4

Target Mean Strength= 25+ 1.65*4.0=31.60

STEP 2 : CALCULATION FOR WATER CONTENT

For 20mm Aggregates MAX Water Content =186.0 (Table 2 10262 2009)

This value is for Slump within the range of 25-50

For Every 25mm increase in slump we will increase

water by 3%

Current Slump is :100 Which is :50 mm above 50mm

Increase Water Content By :6.00%

186.0+(6.00*186.00)/100 =197.16 Kg/m3

STEP 3 : SELECTION OF WATER CEMENT RATIO

For • REINFORCED Concrete and MODERATE exposure

condition MAX W:C=0 50 (As per Table 5 of IS 456 2000)

STEP 4 : CALCULATION OF CEMENT CONTENT

Cement=WaterContent/w:C

Cement Content=197.16/0.50 = 394.32 Kg/m3

(As per Table 5 of IS 456 2000)Minimum Cement Content is 300

Since

394.32>300 OK

STEP 5 : CALCULATION OF RATIO OF AGGREGATES

For 20mm Coarse and Zone 2 Fine,Volume of Coarse to Total Aggregates=0.62(Table 3 10262 2009)

This value is for w:C =0.50 our w:C=0.50 OK

Fine Agg Ratio=1-Coarse Agg Ratio=0.38

DESIGN MIX CALCULATIONS

Vol of Cement= WT OF CEMETN/(SPGR of

CEMENT*1000)=394.32/(3.14*1000)=0.13

Vol of Water=Wt of Water/1000

=197.16/1000

=0 .20

TOTAL AGGREGATE Vol(e) = 1-(Cement+Water)=0.68

Wt of Coarse Aggregate=e*CoarseRatio*SPGR*1000

= 0.68*0.62*2.45*1000=1028.76 Kg/m3

Wt of Fine Aggregate=e*FineRatio*SPGR*1000

=0.68*0.38*2.50*1000=643.40 Kg/m3

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In a future article we are going to design the M30 concrete mix 

STEP 1 : TARGET MEAN STRENGTH

For MILD exposure RCC using 20mm coarse aggregate we need to atLeat use M20 Grade of concrete (As per Table 5 of IS 456 2000)

 So lets design M20

Target Mean Strength F_ckt = F_ck + 1.65xS

Fck = 20MPa (for M20)

Standard deviation for M20-M25 = 4.0 (Table 1 IS 10262 2009)

F_ckt = F_ck + 1.65×4

Target Mean Strength= 20+ 1.65*4.0=26.60

STEP 2 : CALCULATION FOR WATER CONTENT

For 20mm Aggregates MAX Water Content =186.0 (Table 2 10262 2009)

This value is for Slump within the range of 25-50

For Every 25mm increase in slump we will increase

water by 3%

Current Slump is :100 Which is :50 mm above 50mm

Increase Water Content By :6.00%

186.0+(6.00*186.00)/100 =197.16 Kg/m³

STEP 3 : SELECTION OF WATER CEMENT RATIO

For • REINFORCED Concrete and MILD exposure

condition MAX W:C=0 55 (As per Table 5 of IS 456 2000)

STEP 4 : CALCULATION OF CEMENT CONTENT

Cement=WaterContent/w:C

Cement Content=197.16/0.55 = 358.47 Kg/m³

(As per Table 5 of IS 456 2000)Minimum Cement Content is 300

Since

358.47>300 OK

STEP 5 : CALCULATION OF RATIO OF AGGREGATES

For 20mm Coarse and Zone 2 Fine,Volume of Coarse to Total Aggregates=0.62(Table 3 10262 2009)

This value is for w:C =0.50 our w:C=0.55

Decrease Coarse Ratio by 0.01 for every increase of

0.05 in w:C

For 0.55 there is an increase of :0.05

So Decrease Factor=0.01

New Coarse Ag Ratio=0.62-0.01=0.61

Fine Agg Ratio=1-Coarse Agg Ratio=0.39

DESIGN MIX CALCULATIONS

Vol of Cement= WT OF CEMETN/(SPGR of

CEMENT*1000)=358 47/(3.14*1000)=0.11

Vol of Water=Wt of Water/1000

=197.16/1000

=0 .20

TOTAL AGGREGATE Vol(e) = 1-(Cement+Water)=0.69

Wt of Coarse Aggregate=e*CoarseRatio*SPGR*1000

= 0.69*0.61*2.45*1000=1029.23 Kg/m³

Wt of Fine Aggregate=e*FineRatio*SPGR*1000

=0.69*0.39*2 50*1000=671 46 Kg/m³

If you want a free tool with which you can create Concrete Mix Designs without doing any calculations just enter your requirements and it will do the calculations for you and it will also generate human readable calculations within seconds 

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In a future article we are going to design the M30 concrete mix 

• Ordinary Portland Cement (OPC)
• Portland Pozzolana Cement (PPC)
• Rapid Hardening Cement
• Quick setting cement
• Low Heat Cement
• Sulphate resistant cement
• Blast Furnace Slag Cement
• High Alumina Cement
• White Cement
• Colored cement
• Air Entraining Cement
• Expansive cement
• Hydrophobic cement

1. Ordinary Portland Cement(OPC)

Ordinary Portland cement is the most widely used type of cement, which is suitable for all general concrete construction. It is the most commonly produced cement around the world.  This cement is suitable for all kinds of concrete construction.

2. Portland Pozzolana Cement(PPC)

Portland Pozzolana Cement is prepared by grinding volcanic ash or pozzolana with Portland cement. It is also produced by adding pozzolana with the addition of gypsum

This cement has a high resistance to chemical attacks on concrete and thus, it is widely used in marine structures, sewage works, sewage works etc 

3. Rapid Hardening Cement

Rapid hardening cement attains high strength in the early days. it is used in concrete where formwork are removed at an early stage. This cement has increased lime content and contains higher C3S content and finer grinding, which gives higher strength development than OPC at an early stage.

The strength of rapid hardening cement at 3 days is similar to 7 days strength of OPC.Thus you can remove formwork earlier, which increases the rate of construction.

4. Quick Setting Cement

Quick Setting Cement sets earlier but its rate of strength gain is similar to ordinary Portland cement. If you want to complete the work in very short time you will use quick setting cement

5. Low Heat Cement

Low heat cement is produced by maintaining the percentage of tri-calcium aluminate C3A below 6% by increasing the proportion of C2S. C3A is mainly responsible for heat of hydration, so lowering its percentage lowers heat generation due to hydration. If you are using concrete in mass such as in dams you would use low heat cement. 

6. Sulphate Resisting Cement

Sulphate resisting cement is used to reduce the risk of sulphate attack on concrete and thus is used in the construction of foundations, canals, culverts etc. where the soil has high sulphate content. This cement has reduced contents of C3A and C4AF.

7. Blast Furnace Slag Cement

Blast furnace slag cement is obtained by grinding clinkers with about 60% slag. It can be used for works where economic considerations are predominant.

8. High Alumina Cement

High alumina cement is obtained by melting a mixture of bauxite and lime and grinding with the clinker. It is a rapid hardening cement with initial and final setting time of about 3.5 and 5 hours, respectively.

You use this cement in places where concrete will be subjected to high temperature

9. White Cement

It is prepared from raw materials free from Iron oxide and is a type of ordinary portland cement, which is white. It is costlier and is used for interior and exterior decorative work 

10. Coloured Cement

It is produced by mixing 5- 10% mineral pigments with ordinary cement. They are used for decorative works.

11. Air Entraining Cement

Air entraining cement is produced by adding indigenous air-entraining agents such as resins, sodium etc when grinding clinkers.

With this cement you can decrease water content and still maintain the same workability.

12. Expansive Cement

Expansive cement expands slightly with time and does not shrink during and after the time of hardening. This cement is mainly used for grouting anchor bolts and prestressed concrete ducts.

13. Hydrophobic Cement

Hydrophobic cement is prepared by mixing water-repelling chemicals and has high workability and strength. It has the property of repelling water and is unaffected during monsoon or rains.

Hydrophobic cement is mainly used for the construction of water structures such as dams, water tanks, spillways, water retaining structures, etc.

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Compressive strength of concrete is how much load it can take without cracking. In general Construction the compressive strength of concrete varies from 15Pa to 30Pa and higher for commercial and industrial use.

Compressive strength of concrete depends on many factors such as water-cement ratio, cement strength, quality of concrete material, quality control during the production of concrete, etc.

How to find out compressive strength of concrete

We make concrete cubes and then apply compressive load on these cubes until it fails, that’s it. Depending on size of aggregates used we use either 15cm x 15cm x 15cm mould OR 10cm x 10cm x 10cm mould of these two 15cm cube is most commonly used.

Concrete mixture is poured into these moulds, compacted to remove any air. After 24 hrs moulds are removed and concrete cubes are dipped in water curing tank.

After 7 days or 28 days we test these concrete cubes on a compression testing machine. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of concrete.

Compressive Strength of Concrete at various ages

The strength of concrete increases with age. The table shows the strength of concrete at different ages in comparison with the strength at 28 days after casting

Compressive Strength of Different Grades of Concrete at 7 and 28 Days

Now that you know what compressive strength of concrete is and how to calculate it the next step is to learn how to design concrete mix yourself.

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Concrete at the very least contains 3 materials Cement, Sand and Crushed Stones. The ratio in which you add these determines how strong or weak concrete will be. If you are using concrete for not so demanding projects you may mix concrete in already known commonly used ratios. Below is a table listing all the Normal and Standard Mix Ratios. M means Mix and the number next to it means its Compressive strength in Mega Pascal(N/mm²). So M20 means Mix of concrete that has a strength of 20MPa.

Now you must be asking where’s the ratio for M30 and above. The simple answer is there is none. For concrete M30 and above you have to go to Concrete Lab and do some calculations and create concrete mix ratios yourself. These ratios that you designed yourself are known as Design Mixes. And the whole process is known as Concrete Mix Design.Before we move forward I am going to give you a free tool with which you can create Concrete Mix Designs without doing any calculations just enter your requirements and it will do the calculations for you and it will also generate human readable calculations within seconds

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Read this article to learn how to design Concrete Mix:Concrete Mix Design – M30 Grade of Concrete