**1.STIPULATIONS**** ****FOR**** ****PROPORTIONING**

a) Grade designation : M25 RCC

b) Type of cement :53 grade Ordinary Portland Cement conforming IS 12269

c) Maximum nominal size of coarse aggregate : 20 mm

d) Minimum amount of cement : 300 kg/m³ as per IS 456:2000

e) Maximum water-cement ratio : 0.50 as per Table 5 of IS 456:2000

f) Workability : 100 – 125 mm slump

g) Exposure condition : Moderate (For Reinforced Concrete)

h) Method of concrete placing : Pumping

j) Degree of supervision : Good

k) Type of aggregate : Crushed Angular Aggregates

l) Chemical admixture type : Super Plasticizer Normet

**2.TEST**** ****DATA**** ****FOR**** ****MATERIALS**

a) Cement used : Sagar 53 grade Ordinary Portland cement conforming IS 12269.

b) Specific gravity of cement :3. 15

c) Chemical admixture : Super Plasticizer conforming to IS 9103.

d) Specific gravity of

1) Coarse aggregate 20 mm : 2.799

2) Coarse aggregate 10 mm: 2.789

3) Combined Specific Gravity of aggregate

( 20 mm-45% & 10 mm -55% )=2.792.

4) Fine aggregate : 2.517

e) Water absorption:

1) Coarse aggregate 20 mm : 0.41 %

2) Coarse aggregate 10 mm : 0.59 %

3) Fine aggregate : 1.87 %

f) Aggregate Impact Value : 20.52 %

g) Combined Flakiness & Elongation Index : 27.57 %

h) Sieve analysis:

1) Coarse aggregate: Conforming to all in aggregates of Table 2 of IS 383

2) Fine aggregate : Conforming to Grading Zone III of Table 4 of IS 383

**3**** ****TARGET**** ****STRENGTH**** ****FOR**** ****MIX**** ****PROPORTIONING**

**f’ck**** =fck ****+**** ****1.65**** ****s**

where

f’ck = average target compressive strength of concrete at 28 days,

fck = characteristics compressive strength of concrete at 28 days, and

s = standard deviation.

From table 1 of IS 10262 assumed Standard Deviation, s = 4 N/N/mm². Therefore, target strength of concrete = 25 + 1.65 x 4 = 31.6 N/mm².

**But as per MORT&H 5th revision Table 1700.5 required target mean compressive strength = 25 + 11 = 36.00 N/mm² where 11 is the current margin.**

**4**** ****SELECTION**** ****OF**** ****WATER•CEMENT**** ****RATIO**

Based on the trial , adopted water cement ratio 0.38

From the Table 5 of IS 456 maximum Water Cement Ratio is 0.50

0.38 < 0.50 Hence ok.

**As per MORT&H 5th revision Maximum Water Cement Ratio water cement ratio for moderate exposure is 0.45 , hence it is ok**

** ****5.**** ****SELECTION**** ****OF**** ****WATER**** ****CONTENT**

From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 liter for 25 to 50 mm slump range but for an increase by about 3 percent for every additional 25 mm slump so here estimated water content for **125 mm slump** = 186+(9/100) x 186 = 202 liter.

**Water requirement if we are considering cement 360 kg & w/c ratio o.38 for concrete mix design ; calculated water will be 136.8 so net reduction in water while using super plasticizer = 100 – (136.8/202 x 100) = 32.28 %.**

Now we had got reduction percentage of water , calculate of the required water = 202 – (202 x 32.28) % = 202 – 65.20 = 136.80 **(For 75 mm slump increase 3% , for 100 mm increase 6% & increase 9 % for 125 mm slump)**** **

**6.**** ****CALCULATION**** ****OF**** ****CEMENT**** ****CONTENT**

Adopted w/c Ratio = 0.38 then Cement Content = 136.80/0.38 = 360 kg/m³ ,from Table 5 of IS 456, minimum cement content for ‘moderate’ exposure conditions is 300 kg/m³ but taken 360 kg/m³ > 300 kg/m³ hence ok.

**As per MORT&H 5th revision for moderate exposure with reference to Table number 1700-2 maximum water cement ratio 0.45 & minimum cement 340 kg/m³ is specified but we had taken 360 kg/m³ , hence ok**

**7. ****CALCULATION ****OF**** ****COARSE**** ****AGGREGATE**** ****AND**** ****FINE**** ****AGGREGATE PROPORTION**

From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone III) for water-cement ratio of 0.50 =0.64 **(a)**

In the present case water-cement ratio is 0.38 therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content.

As the water cement ratio is lower by 0.12 , the proportion of volume of coarse aggregate is increased by= (0.12/0.05) = 2.4 times of 0.01 ,so 0.01 x 2.4= 0.024 **(b)**

Net required water cement ratio= **a+b** = 0.64 + 0.024 =0.66(at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio) therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.38 = 0.66

NOTE – In case the coarse aggregate is not angular one, then also volume of coarse aggregate may be required to be increased suitably based on experience & Site conditions.

If we are doing concrete with pump , reduce upto 10% these value ,therefore volume of coarse aggregate =0.66 x 0.9 =0.59.

Actual reduced volume of fine aggregate content = 1 – 0.59 = 0.41.

**8.**** ****MIX**** ****CALCULATIONS**

Determination of mix calculation will be as under:

a)Volume of concrete = 1 m³

b)Volume of cement = [Mass of cement] / {[Specific Gravity of Cement] x 1000} = 360/{3.15 x 1000} = 0.115 m³

c)Volume of water = [Mass of water] / {[Specific Gravity of water] x 1000}

= 136.80/{1 x 1000} = 0.136 m³

d) Base on trial we had kept admixture 0.45 percentage by weight of cement

Volume of admixture = [Mass of admixture ] / {[Specific Gravity of admixture ] x 1000}

= 1.62 /{1.090 x 1000} = 0.00149 m³

e)Volume of all in aggregate = [a-(b+c+d)]

= [1-(0.115+0.134+0.00149)] = 0.750 m³

f)Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of coarse Aggregate x 1000

= 0.750 x 0.59 x 2.792 x 1000 = 1235.46 kg/m³

g)Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000

= 0.750 x 0.41 x 2.517 x 1000 = 773.98 kg/m³

**9.**** ****MIX**** ****PROPORTIONS**

Cement = 360 kg/m³

Water = 136.80 l/m³

Fine aggregate = 834 kg/m³

Coarse aggregate 20 mm = 1235.46 x 45 %= 555.96 kg/m³

Coarse aggregate 12 mm = 1235.46 x 55%= 679.50 kg/m³

Chemical admixture = 1.62 kg/m³

Water-cement ratio = 0.38

1.Aggregate 20 mm = 555.96/ (1+(0.41/100)} = 554.0 kg

2. Aggregate 10 mm = 679.50/ (1+(0.59/100)} = 676.0 kg

3.Sand = 834.0/ (1+(1.87/100)} = 819.0 kg

4.Water = 2568 -360 – 819 -554 – 676 = 160.0 kg

**NOTE**

1.Do the trial in dry position as in practical in batching plant you can cot use aggregate in SSD condition.

2.Batch for trial is given in dry position.

3.Do the number of rials with variation of ± 10 percent of water-cement ratio & different cement content

4.Do the surface moisture correction whenever required.

VERY MUCH INFORMATIVE AND USEFUL

Very nice. For easy and quick reference