## Concrete Mix Design – M70 Grade of Concrete (OPC 53 Grade)

Concrete mix design – M70 grade of concrete provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

**A. Design Stipulation:**

Characteristic comprehensive Strength @ 28 days = 70 N/mm^{2}

Maximum size of aggregate = 20 mm

Degree of workability = Collapsible

Degree of quality control = Good

Type of exposure = Severe

Minimum cement content as per is 456-2000

**B. Test data for concrete ingredients**

Specific gravity of cement = 3.15

Specific gravity of fly ash = 2.24

Specific gravity of microsilica = 2.21

Setting time of cement initial = 165 min, final = 270min

Cement compressive strength =

39.0 N/mm^{2} @ 3 days

51.0 N/mm^{2} @ 7 days

64.2 N/mm^{2} @ 28 days

Specific gravity of coarse aggregates (ca) and fine aggregates (fa)

20 mm 2.729

10 mm 2.747

R/sand 2.751

C/sand 2.697

Water absorption

20 mm 1.540, 10mm 1.780, R/sand 3.780, C/sand 4.490

Characteristic strength @ 28 days 70 N/mm^{2}

Target mean strength : Depend upon degree of quality control “good” and considering (std. Dev.As 5 N/mm^{2})

Characteristic strength given by the relation 70 +(1.65 *5 ) = 78.25 N/mm^{2}

**C. Quantities of ingredients (By Absolute Volume Method )**

Actual cement used = 486 kg/cum

Actual fly ash used = 90 kg/cum

Actual microsilica used = 24 kg/cum

W/C fixed = 0.26

Absolute volume of cement = 0.154

Absolute volume of air = 0.02

Absolute vol of water. = 0.156

Absolute vol of fly ash. = 0.040

Absolute vol of microsilica = 0.011

Total volume of CA and FA used = 1.00-(0.155+0.044+0.022+0.02 +0.154)

= 0.619 Cum

**D. Aggregate percent used.**

20 Mm = 24, 10 mm = 36, r/sand = 20, c/sand = 20

(2.729*0.24) + (2.747*0.36) +(2.751* 0.20 )+(2.697*0.20) *0.619*1000

405+612+340+334=1691

Aggt: cement = 2.82 : 1

**Mix proportion = 0.26:1:0.57:0.56:1.02:0.67 **

**E. Abstract:**

20 mm = 405 kg/cum

10 mm = 612 kg/cum

r/sand = 340 kg /cum

c/sand = 334 kg/cum

water = 154 kg/cum

Admixture 0.50 % BY WT OF (C+F+MS) ASTP-1 OF BASF

**Cube Compressive Strength (N/mm ^{2})**

3 days = 49.13

7 Days = 59.57

28 Days = 81.49

Note: Mix design is same for Crane bucket and Pump concrete only admixture dosage will fine tuned by 0.05 to 0.10%

*We are thankful to Deshmukh D S for submitting this very useful mix design information to us.*