Mix design of M30 grade concrete

Projects requirements 

1 Mix design of : M30 grade concrete
2 Type of cement used PPC cement ( supplied only with strength of 33 grade as per clause no 7.4.1 page no 2 of IS 1489 ). conforming to IS 1489 Part 1. -2015. 3. Maximum nominal size of aggregate: 20 mm. 4. Exposure condition : Moderate exposure condition
5 Workability : mm 50 mm (slump)
6 Method of concrete placing  Chute (Non Pumpable )
7 Degree of supervision : Good
8 Type of aggregate : Crushed angular aggregate
9 Maximum cement content : 450 kg per cum    10 Chemical admixture type : Super-plasticizer (Polycarboxylate ether based)

Basis for design calculations 

Material properties  
1 Specific gravity of cement : 2.86
2 Specific gravity of coarse aggregate (at SSD conditions ) : 2.68
3 Specific gravity of Fine sand ( at SSD condition)  : 2.63
4
 Water absorption of coarse aggregate  : 0.68 percent 
5 Water absorption of fine aggregate  : 1.12 percent 
6 Moisture content of coarse and fine aggregate : NIL   7 Specific gravity of Chemical admixture : 1.08

Aggregate properties 

  1. Sieve analysis of coarse aggregate Conforming to Table 7 page no 6 of IS 383 2016  i). 90 to 100 percent passed from 20 mm IS Sieve ii)25 to 55 percent passed from 10 mm IS sieve iii). 0 to 10 percent passed from IS sieve.
  2. Sieve analysis of Fine aggregate conforming to Grading Zone II of Table 9 page 7 of IS 383 2016  i). 90 to 100 percent passed from 4.75 mm IS Sieve ii). 75 to 100 percent passed from 2.36 mm IS sieve no iii). 55 to 90 percent passed from 1.18 mm IS Sieve. iv). 35 to 59 percent passed from 600 micron IS Sieve v). 8 to 30 percent passed from 300 micron IS Sieve vi). 0 to 10 percent passed from 150 micron IS Sieve

Target Strength for Mix Proportioning as per clause number 4.2 Page no 02 of IS 10262 : 2019 

As per IS 10262 : 2019 Table 1 and Table 2 of page no 3  F’ck = fck + 1.65 X Standard deviation 
OR
F’ck = fck + factor based on grade of concrete , whichever is higher 
For M30 grade concrete Factor based on grade of concrete = 6.50
Standard Deviation = 5.00 F’ck= 30 + 1.65 X 5 = 38.25 N/mm2
F’ck = 30 + 6.5 = 36.50 N/mm2. Hence higher value of F’ck = 38.25 N/mm2 is to be used for design calculations

 
Approximate Air content 

As per clause number 6.2.3 Table no 6 ,page no 7 of IS 10262 : 2019 
For 20 mm nominal maximum size of aggregate, 0.5 percent of entrapped air of total volume of concrete. If site data is available then actual values of air content can also be adopted.

Calculations of cement content 

Water content (As per Table 4 , page no 5 of IS 10262 ) for 20 mm nominal maximum size of saturated surface dry aggregate is 186 kg per cum ( for 50 mm slump without using superplasticiser ) .

Super plasticisers

As per clause number 6.2.4 , page no 7 of IS 10262: 2019, Polycarbonate ether based super plasticisers reduce water content by 30 percent or above at appropriate dosages. Water content with using appropriate dosages of super plasticisers =186 X 0.7 =130 kg/cum

water – cement ratio (w/c ratio)

From figure 1 Page no 4 of IS 10262 : 2019 free water cement ratio required for the target strength of 38.25 N/mm2 is 0.42 for PPC (curve 2) which is less than the maximum value of 0.45 prescribed for mild exposure for reinforced concrete as per Table 5 of IS 456 :2000 hence OK

Revised w/c ratio=00.42

Hence ( Cement ) content = 130/0.42 = 310 kg /cum. which is less than given in Table 5 (min cement content 320 kg/cum) , Page 20 of IS 456 2000 and less than as per clause of 8.2.4.2 , page 19 of IS 456 2000. hence adopt 320 kg/cum

Hence revised Cement quantities per cum 

Cement = 320 kg/cum 
which is less than maximum cement content of 450 kg/cum. Hence OK  
Volume of cement = ( Mass of cement /( Specific gravity of cement X1000) = 320/(2.86X1000) = 0.112 cum 

Revised Water quantities per cum

Water = 320 X 0.42 = 134 kg /cum
Volume of water = ( Mass of water /( Specific gravity of water X1000) = 134/(1X1000) = 0.134 cum

Admixture quantities per cum


Weight of admixture ( assumed 0.5 percent super plasticisers used.. should be adjusted for desired workablity ) = 320 X 0.005 = 1.6 kg/cum
Volume of admixture ( assumed 0.5 percent super plasticisers used )= (1.6) / (1.08 X1000) = 0.0015 cum

Volume of entrapped air 

Volume of entrapped air = 0.005 cum

Volume of coarse and fine aggregate 

Hence Volume of coarse aggregate and fine aggregate = 1 – (0.112-0.134–0.0015-0.005) = 0.747 cum

Proportion of volume of coarse aggregate and fine aggregate 

As per clause number 6.2.7 , Table 10 page number 10 of IS 10262 : 2019 . For Zone II 20 mm nominal maximum size aggregate, Volume of coarse aggregate and fine aggregate = 0.66 per unit volume . Hence volume of fine aggregate = 1 – 0.66 = 0.34 per unit volume of total aggregate . ( for pumpable mixes 10 % coarse aggregate should be decreased and the same percentage of fine aggregate is to be increased)

Coarse aggregate quantities per cum 

Volume of coarse aggregate = 0.747 X 0.66 = 0.493 cum 
Weight of coarse aggregate = 0.49 X 2.68 X 1000 = 1321.00 kg/cum

Fine aggregate quantities per cum 


Volume of fine aggregate = 0.747 X 0.34 = 0.254 cum 
Weight of Fine aggregate = 0.254 X 2.63 X 1000 = 668.00 kg/ cum 

First trial 

Cement  : 320 kg/cum
Water  : 134 kg / cum
Fine aggregate  :668 kg/ cum
Coarse aggregate  :1321 kg/cum

W/c  : 00.42  Super-plasticizer (Polycarboxylate ether based) : 1.6 kg /CUM

Rates per cum For Gairsain Uttarakhand

cement Ambuja PPC : 320 kg/ cum = 6.4 X 450.00 = 2880.00
Water  : 147 kg / cum = Free of cost = 0.00
Fine aggregate  :668 kg/ cum= 0.254 Cum X 2700.00 = 686.00
Coarse aggregate  :1321 kg/cum = 0.493 cum X 2700.00 = 1331.00
Super-plasticizer (Polycarboxylate ether based) : 1.6 kg /CUM @ Rs 125.00 per kg = 200.00

  1. Cost of M30 Grade concrete with admixture (Approx) = Rs. 5097.00
  2. M30 grade Concrete without admixture approx rate per cum = Rs. 5752.00
  3. Hence cost of concrete with using admixture is cheaper (Rs. 655 per cum)

Note : 1. Two more trials having variation of + or – 10 percent of water – cementitious material ratio shall be carried out and a graph between these water cementitious materials ratios and their corresponding strengths shall be plotted to work out the mix proportions for the given target strength for field trials . Considering the durability requirements too. 2. Aggregate shall be used in saturated surface dry conditions if otherwise , when computing the requirements of mixing water , allowances shall be made for the free surface moisture contributed by the fine and coarse aggregate. And if the aggregate is dry the amount of mixing water shall be increased by an amount equal to the moisture likely to be absorbed by the aggregate