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Thursday, 15 December 2016

BASIC PROPERTIES OF CEMENT COMPOUNDS

We were discussing “Cements and its types” and " Raw materials for manufacturing of cements”, “Pyroprocessing in cement industry” and “Hydration of cement” in our previous posts. 

Today we are going to start here one very important topic i.e. Properties of cement compounds with this post. We will understand the various terminologies and engineering concepts used in cement technology with the help of this category.

Further we will go for discussion of selection of the process, process technology, burning technology, firing technology, clinker cooling and grinding, cement packing and dispatch, pollution control and much more facts about cement technology in our next post in this category of cement technology.

Properties of cement compounds

Cementing qualities

C3S:

It undergoes an initial and final set within a few hours after gauging. Mixes of C3S and water are less plastic than Portland cement clinker and more water is required to obtain a more workable paste. Addition of gypsum renders the mass more plastic.

C2S:

It exhibits no definite setting time and the gauged mass sets slowly over a period of some days. Addition of gypsum produces little effect.

C3A:

It gives a flash set on gauging with water. This is accompanied by evolution of so much heat as to lead to violent steaming. On further mixing, plastic, easily workable mass is obtained. In moist air the mass sets and hardens, giving fair strength, but on placing in water, the set material disintegrates and crumbles away.

Strengths

  1. C2S produces little strength at early stages, but gains steadily in strength at later stages until it approaches equality with C3S.
  2. C3S attains the greater part of its strength in 7 days.
  3. C3A produces some strength in one day, but shows no subsequent development. Its influence in the mix seems erratic and in some cases, it lowers the strength. Its presence increases the rate of hydration and strength development of C3S, However no expansion or disintegration is shown by cement as C3A is present in relatively small amounts (6 - 12 %)
  4. C4AF hydrates rapidly but its contribution to early strength is still uncertain. Though setting occurs in a few minutes, it does not show a flash set like C3A. There is a marked heat evolution but much less vigorous than C3A.

Strength developed by cement depends on the following factors

1.      Fineness of cement
2.      Grading of sand / aggregates
3.      Proportion of water used
4.      Degree of mixing
5.      Temperature and humidity of the atmosphere
6.      Curing conditions (presence water or air, temperature, steam etc. during setting). 

Compressive Strengths (Kg/sq. cm)

Compounds
7 days
28 days
180 days
365 days
C3S
322
466
512
584
C2S
24
42
193
325
C3A
118
124
0
0
C4AF
300
384
493
593

Compressive Strength of Cement Compounds (lb/in2)

Comp-ound
Gypsum added%
Mixing
water%
Total
water
used%
1
day
3
Days
7
days
28
days
3
months
6
months
1
year
2
years

C3S
0

5
35

35
50

50
1450

1770
2800

2780
5960

5830
7100

6760
7100

6330
9690

8700
10300

9800
11300

11300

C2S
0

5
30

30
50

50
0

0
60

90
140

220
910

1200
5160

3900
7560

7700
10230

9800
14350

13600

C3A
0

15
60

60
60

60
30

600
170

900
250

1000
600

1580
670

1280
890

1770
1090

1320
800

1320

C4AF
0

15
50

50
50

50
0

20
300

390
290

440
360

720
380

1110
580

1330
650

1420
720

1500

Compressive Strength Data (N/mm2)

Cement Type
1 day
3 days
7 days
28 days
91 days
OPC
9.3
22.5
32
42
50.5
Rapid Hardening Portland
14
27
36.6
46.3
52.5
Extra Hardening Portland
29.6
30.5
37.3
44.3
50
Ultra Hardening Portland
21
37.5
44.2
52.3
56
Sulphate Resisting Portland
-
22.1
29.5
41.3
-
Low Heat Portland
-
9.6
13.9
34.3
-
White Portland
-
26.5
36.2
46.5
-
Water Repellent Portland
-
20.5
28.7
38.4
-
Hyrophobic Portland
-
21.6
31.5
41.3
-
Portland Pozzolanic
7
12.4
23.2
41.4
51

Do you have any suggestions? Please write in comment box.

We will see other topic i.e. Cement manufacturing process andits selection: wet process and dry process in our next post in the category of Steel and cement technology.

I am very thankful to Mr. Subrata Bhaumik, Independent cement consultant, for providing such beautiful information and contents about cement technology.

Mr. Subrata Bhaumik has more than 50 (Fifty) Years (1965 - 2016) of Experience in Cement and other related Industry covering more than 100 assignments in cement plants with capacities ranging from 100 tpd to 10,000 tpd in India and abroad involving visit to 25 countries overseas in connection with work.

For more detailed information about the original Author of this content, please click the Author profile link below.

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