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

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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.

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