Rawmix Design calculations on basis of hydraulic modulus
Here you have to decide and fix the hydraulic modulus of clinker as per your quality requirement. Based on the hydraulic modulus, this method helps to predict how many parts of first raw material can be mixed with one part of second raw material to yield the required hydraulic modulus in clinker.
This method is applicable for two raw material components.
Tips
1. Select the required hydraulic modulus to get required quality in clinker/cement.
2. Analyse the chemical composition of raw materials.
3. Apply the formula.
The formula
Where Z = parts of first raw material required (to mix with one part of second raw material)
HM = required hydraulic modulus of clinker
S2,A2 & F2 = percentages of silica, alumina and iron of second raw material
S1,A1 & F1 = percentages of silica, alumina and iron of first raw material
C1 = percentage of calcium oxide of first material
C2 =percentage of calcium oxide of second material
Lets take an example.
In a cement factory, you have two materials namely high grade limestone and blast furnace slag. At what composition if the two materials can be mixed to get a clinker with a hydraulic modulus of 2.4.
(the composition of high grade limestone and blast furnace slag was given below)
Compounds
|
High grade limestone
(all values are in percentage)
|
Blast furnace slag
(all values are in percentage)
|
CaO
|
47.8
|
31.2
|
SiO2
|
2.5
|
34.1
|
Al2O3
|
4.2
|
6.9
|
Fe2O3
|
2.8
|
2.5
|
LOI
|
37.7
|
23.8
|
Alkalies
|
1.1
|
0.5
|
MgO
|
0.9
|
-
|
Others
|
2.0
|
1.0
|
Total
|
100
|
100
|
So, Required hydraulic modulus of clinker = 2.4
Material I is high grade limestone
Material II is blast furnace slag
So as per formula,
So 2.928 parts of high grade limestone (material I) to be mixed with one part of blast furnace slag (material II) to yield a clinker of hydraulic modulus of 2.4
To convert the above ratios into percentage:
High grade limestone: blast furnace slag = 2.928:1
So,total parts = 2.928+1 = 3.928
Percentage of high grade limestone required
= (2.928/3.928) X 100
=74.54%
Percentage of blast furnace slag required
= (1/3.928) X 100 = 25.46%
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