What is low heat cement?
Low heat cement is one of the types of Portland cement. It is specially made cement that generates low heat of hydration during the time of the setting process of construction. Low heat is in the context of low heat of hydration. Low heat cement is developed in 1930 in the US for the construction of large gravity dams.
It is mainly used cement for the mass concrete construction such as dams, roads, factory floors, etc. where more heat generation due to hydration raises the temperature where low heat cement plays the role to balance it.
Low heat cement is all about releasing a low amount of heat during the hydration process. This kind of composition can be achieved by reducing the contents of C3S and C3A in making components of the cement. these compounds release the maximum amount of heat of hydration during its process and increase the amount of C2S.
Also Read: Composition of Cement Clinker
Reduction in temperature slower the chemical process of hardening and further restricts the generation rate of heat. So because of this main feature of low heat cement, it will be called a slow rate of gaining strength.
The Low heat cement composition
This is a special type of Portland cement which is much the same as normal Portland cement, but some changes in the chemical compositions are made. It contains a low percentage of tricalcium aluminate(C3A) and a higher percentage of dicalcium silicate(C2S). Low heat cement is type-VI cement as per ASCM C 150 standards.
The compounds of composition most probable are below in the tabulated form:
|
C3A |
28% |
|
C3S |
49% |
|
C2S |
4% |
|
C4AF |
12% |
| Blaine fineness |
380 m2/kg |
Final setting time of low heat cement
The final setting time is the time when the water is added to cement to the time when a 1mm needle makes an impression but a 5mm needle does not make any impression on the surface.
The final setting time of low heat cement may differ from normal Portland cement because of its hydration. Normally It has been seen that the final setting time of low heat cement is 600 min up to 720 min max( means max 12 hours).
Also Read: Complete Guide on White Cement
Low heat cement properties
Physical and chemical properties according to its IS code12600:1989 standard are below:
Physical properties
|
Properties |
Requirement |
| Specific surface area | 320 m2/kg |
| Initial setting time | 60 minutes (minimum) |
| Final setting time | 600 min- 720 min (12 hr max) |
| Compressive strength at 7 days (min) | 16 MPa |
| Compressive strength at 28 days (min) | 35 MPa |
| The heat of hydration at 7 days | 272 kJ/kg |
| The heat of hydration at 28 days | 314 kJ/kg |
Chemical properties
|
Properties |
Requirements |
|
The ratio of % of alumina to its iron oxide |
not less than 0.66 |
| Insoluble residue, by % of the mass | Not less than 4% |
| Magnesia | Not less than 6% |
| Total sulfur content | Not less than 2.5 to 3.0 |
| Total loss at ignition | Not less than 5% |
Uses of low heat cement
Uses of low heat cement are:
- It is used for the huge construction of mass cement structures.
- Used in construction dams where temperature rise due to hydration can be more than normal.
- For the construction of large footing of dams, rafts slabs & foundation, wind turbine plinths, etc.
- It is used in the construction of roads and workroom surface of factories like chemical plants and sulphuric acid factories etc.
Advantages of low heat cement
Advantages of low heat cement are as follows:
- As per it produces relatively low heat of cement which leads to low rate cracks due to shrinkage.
- In mass concrete structures like dams, roads, etc. which involve a high rate of heat due to hydration their low heat cement will be an advantage to balance the temperature.
- Improvement in durability performance.
- It will be a good performer in case of high final strength, resistance against sulfur corrosion, good long-lasting properties, rupture resistance, and anti-seepage.
- Very impressive with increased workability and pouring capacity in the case of hydraulic engineering concrete and marine concrete work, etc.
- In the case of concrete pipes great performance against sulfate resistance.
Disadvantages of low heat cement
Disadvantages of low heat cement are as follows:
- In the case of initial strength, it’s lower than normal OPC but the final strength is the same as OPC.
- Low heat cement is not good to use in the case of an area where the temperature is relatively low.
- It is costlier than normal Portland cement.
- As it has a higher cost it is not cost-effective to use in residential or small budget constructions.
Difference between rapid hardening cement and low heat cement
|
Rapid hardening cement |
Low heat cement |
| The initial setting time of rapid hardening cement is 30 minutes | The initial setting time of low heat cement is 60 minutes. |
| This cement itself emits more heat during the process of hydration. | The name of cement itself says that it emits low heat during the hydration process. |
| It is used for the fast construction where the formwork, etc. needs to remove earlier to use another place. | It is used where needed to control or balance the temperature due to rise in that because of hydration process like dams, roads, etc. |
| Rapid hardening cement is used in cold weather concreting because the evolution of heat rapidly in the hydration process protects concrete from freezing in weather. | Low heat cement can not be used in cold weather concreting as it generates low heat in the hydration process which leads to freezing of concreting in that weather. |
| It gains high strength from the earlier days. | It gains high strength after specific days not as early as rapid hardening cement. |
Questions and Answers
Why low heat cement is used in dams?
Low heat cement is used in dams as it helps to balance the rise of temperature due to the hydration process of cement.
Initial and final setting time of low heat cement
The initial setting time of low heat cement is a minimum of 1 hour and the final setting time is a maximum of 600 minutes.
Which IS code is used for low heat cement?
IS code for low heat cement is IS 12600:1989
What type of mix design is used in low heat cement?
Type IV cement by ASTM C150
Who invented low heat cement?
Wiliam Aspdin is the inventor of modern Portland cement. As Low heat cement is the type of normal Portland cement.
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