M25 IS CONCRETE MIX DESIGN EXAMPLE

A-1) Design stipulations

Characteristics compressive strength 28 days              : 25N/mm²

Target mean strength                                                       :f^’_ck = f_ck +1.65 s ( s =4 from is 10262                      table 1)

                                                                                               f^’_ck = 25+1.65 x 4 = 31.6N/mm²

maximum size of aggregates                                            : 20 mm

workability, slump                                                              : 50 to 75mm

Type of exposure                                                                : moderate

Aggregate surface condition                                            : all aggregates are in surface dried   

                                                                                                 Condition                                                     

A-2) Test data for materials

Type of cement                                                                  :ACC 43 grade (OPC)

Specific gravity of cement                                                  :3.15

Specific gravity of admixture                                             :1.07

Specific gravity of coarse aggregates                               :2.54

Specific gravity of fine aggregates                                    :2.47

Table for densities of materials used

materials	Specific gravity	X 1000	Specific weight(kg/m3)
Water	1	1000	1000
Cement	3.155	1000	3155
Surface dried fine aggregates	2.47	1000	2470
Surface dried coarse aggregates	2.54	1000	2540
admixture	1.07	1000	1170

A-3) Selection of water/cement ratio

From is 456-2000 table 5 maximum W/C ratio =0.5

Based on trials adopted w/c ratio=42 hence ok

Hence selected W/C ratio is = 0.42

A-4)Estimation of mixing water

a)      Weight of water for 20 mm aggregates and slump 25-50 mm = 186 litre.

b)      Weight of water for 50-75 mm slump (increased by 3% for additional 25 mm slump as per is 10262 clause 4.2) = 191.58 litre.

Note: on adding  super plasticizer @ 0.5% water content reduces by 15%

Net water volume  =191.58X0.85=litre =162.84 litre

A-6) estimation of weight of cement

Wt. of cement=wt. of water/water cement ratio

Wt. of cement=162.84/0.42=387.31kg/m³

Min. content as per is 456 for moderate exposure =360kg

A-7) estimation of weight of admixture

weight of admixture @0.5% of weight of cement=0.5x 387.31/100 =1.93kg

volume of admixture(E)=wt. of admixture/specific weight

                                     =1.93/1070 = 0.00378 m³

A-8) calculating proportion of coarse and fine aggregates

(From is-10262 table 3)

Volume of coarse aggregates corresponding to 20mm size and fine aggregates zone 1=o.60

Volume of fine aggregates =(1-0.60)= 0.40

A-9) mix calculations

a)      Volume of concrete    =1m³

b)      volume of cement      =  (mass of cement/specific gravity)x(1/1000)

                                       = (387.71/3.155)x(1/1000) =0.1228m³

c)       volume of water          =(mass of water/specific gravity)x(1/1000)

                                              = (162.84/1.00)x(1/1000) =0.1628 m³

d)      volume of admixture = (mass of admixture/specific gravity)x(1/1000)

                                       =(1.938/1.07)x(1/1000)   =0.00181 m³

e)      Volume of all in aggregates=  {a-(b+c+d)}

1-(0. 1228+0.1628+0.00181) =0.7126

f)        Weight o coarse aggregates  = 0.7126x0.60x specific gravity of coarse aggregates x 1000

                                                    =0.7126x0.60x2.54 x 1000 =1086kg

g)       Weight of fine aggregates    = 0.7126 x0.40x 2.47 x 1000 = 704.04kg

A-10) proportion ratio

Cement: coarse aggregates : fine aggregates = 1 : 1.815 : 2.80

A-11) Table of ingredients

Ingredients	Surface dried weights
cement	387.71kg
Coarse aggregates	1086 kg
Fine aggregates	704.04 kg
water	162.84 litre.
Admixture	1.94 kg
Water cement ratio	0.42