CONCRETE MIX DESIGN AND QUANTITY CALCULATION

Concrete Mix design and Quantity Calculation

Concrete is a composite mixture of Cement Sand & Aggregate. We use concrete in structure because of its load bearing ability. Here the term Concrete Mix design introduced. It is the process where we find the mixing ratio of concrete ingredient to achieve desire strength. Here strength is compressive in nature.

As per IS-456:2000 different grade of concrete and desire compressive strength are mention bellow.

SL NO	GRADES OF CONCRETE	RATIO OF CONCRETE (CEMENT : SAND :AGGREGATE)	CHARACTERISTIC COMPRESSIVE STRENGTH OF 150MM CUBE AFTER 28DAYS OF CURING
1	M5	1:5:10	5 N/ mm2
2	M7.5	1:4:8	7.5 N/ mm2
3	M10	1:3:6	10 N/ mm2
4	M15	1:2:4	15 N/ mm2
5	M20	1:1.5:3	20 N/ mm2
6	M25	1:1:2	25 N/ mm2
7	M30	1:0.75:1.5	30 N/ mm2
8	M35	1:0.5:1	35 N/ mm2
9	M40	1:0.25:0.5	40 N/ mm2

Here “M” stands for Mix and the “number” stands for Characteristic Compressive strength of the concrete in N/mm2 of 150 mm cube (150mmx150mmx150mm) after 28 days.

Now we calculate the quantity of Cement, Sand & Aggregate in general ways for 1cum volume of Concrete.

Let, Ratio of graded concrete given- C: S: A

Wet volume of concrete given 1cum, but we continue our calculation to multiply dry volume factor to given wet volume. For concrete we consider dry volume factor 1.54-1.57.

So, now our volume is 1cum x 1.54 = 1.54cum

For Cement –                    1.54 x C/(C+S+A) cum

For Sand -                            1.54 x S/(C+S+A) cum

For Aggregate -                  1.54 x A/(C+S+A) cum

For example, we calculate the quantity of Cement, Sand & Aggregate in M15 grade concrete.

Ratio of M15 - C: S: A = 1:2:4

For Cement –                    1.54 x 1/(1+2+4) cum

=1.54 x 1/7 cum

= 0.22 cum

We know Volume of 1bag cement is 0.035 cum.

Now required cement in Bags = 0.22/0.035 = 6.28, Say 6 Bags

For Sand –                           1.54 x 2/(1+2+4) cum

=1.54 x 2/7 cum

= 0.44 cum

For Aggregate –                1.54 x 2/(1+2+4) cum

=1.54 x 4/7 cum

= 0.88 cum

Quantities of Cement, Sand & Aggregate of different grade of Concrete at a glance

SL NO	GRADE OF CONCRETE	UNIT	MATERIALS	QUANTITY OF MATERIALS	UNIT
1	M5 (1:5:10)	cum	1.       Cement            2.       Sand            3.       Stone Chips (6-                20mm)	1.       0.096             2.       0.48             3.       0.96	cum
2	M7.5 (1:4:8)	cum	1.       Cement           2.       Sand           3.       Stone Chips (6-               20mm)	1.       0.12            2.       0.48            3.       0.96	cum
3	M10(1:3:6)	cum	1.       Cement           2.       Sand           3.       Stone Chips (6-               20mm)	1.       0.156            2.       0.47            3.       0.94	cum
4	M15(1:2:4)	cum	1.       Cement           2.       Sand           3.       Stone Chips (6-               20mm)	1.       0.22            2.       0.44            3.       0.88	cum
5	M20(1:1.5:3)	cum	1.       Cement           2.       Sand           3.       Stone Chips (6-              20mm)	1.       0.286            2.       0.43            3.       0.86	cum
6	M25(1:1:2)	cum	1.       Cement          2.       Sand          3.       Stone Chips (6-                20mm)	1.       0.385            2.       0.385            3.       0.77	cum