M25 ACI CONCRETE MIX DESIGN EXAMPLE

A-1) Design stipulations

Characteristics compressive strength 28 days              : 25N/mm²

maximum size of aggregates                                            : 20 mm

workability, slump                                                              :50 to 75mm

Type of exposure                                                                : moderate

Aggregates surface condition                                           : aggregates are in surface dry 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

Dry rodded density of coarse aggregates                       :1464 kg/m³

Fineness modulus of fine aggregates                            :3.1

Table for densities of materials used

materials	Specific gravity	X 1000	Specific weight(kg/m3)
Water	1	1000	1000
Cement	3.155	1000	3155
Ssd fine aggregates	2.47	1000	2470
Ssd course aggregates	2.54	1000	2540
Dry rodded course aggregates			1464
admixture	1.07	1000	1070

A-3) Selection of water/cement ratio

 Maximum water cement ratio for M25 mix = 0.61 ( From from ACI 211.1-91 table A1.5.3.4)

Hence selected W/C ratio is = 0.46 (based on trials)

A-4)Estimation of mixing water and air content

a)      Weight of water for 20 mm aggregates and slump 60-70 mm = 198 litre (From ACI 211.1_91 TABLE A 1.5.3.3)

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

Net water volume(A) =198X0.85=158.4litre =168.3 m (0.168 m³)

a)      Volume of air in 1 m³ of mix is 2.00% of 1 m³ ((From ACI 211.1_91 TABLE A 1.5.3.3)

for non-air-entrained, Nominal Maximum size = 20mm)

 Air volume(B)= 0.020 m³

A-6) estimation of weight of cement

Weight of cement=weight of water/water cement ratio

Weight of cement=168.3/0.46 =365.87 kg/m³

volume of cement used (C)=weight of cement/specific weight of cement

(C)=365.86/3155 =0.1159 m³

A-7) calculating volume of dry rodded aggregates used

Volume of dry rodded aggregates used =0.6

(From table 6.3.6 of ACI 211.1-91 for fineness modulus 3.00 and 20mm maximum aggregates size)

Dry rodded weight of aggregates used =0.6m³ x 1464 kg/m³ = 878.4 kg  

 SSD volume of coarse aggregate(D)= 878.4/2540 = 0.3458 m³

A-8) estimation of weight of admixture

weight of admixture @0.5% of weight of cement=1.83kg

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

                                     =1.83/1070 = 0.001709 m³

A-9) estimation of weight of fine aggregates

Sum of all known volumes =(A+B+C+D+E)

                         =0.168+0.020+0.1159+0.3458+0.001709 =0.6514 m³

SSD volume of fine aggregate = 1 –0.6514 =0.3485 m³

SSD mass of fine aggregate = 0.3485 x2470 =861.01kg

A-10) proportion ratio

Cement : fine aggregates : coarse aggregates           1 :2.35 :2.40

A-11) Table of ingredients

Ingredients	Surface dried weights
Cement	365.87 kg
coarse aggregates	878.4kg
Fine aggregates	861.01 kg
water	168.3 litre
admixture	1.83kg
W/C ratio	0.46