Low heat cement is a type of cement that was developed in US during 1930 for use in large construction of Gravity dams.
Low Heat Cement is a type of Portland cement releasing low heat upon hydration. The C3A content is about 5 % while C2S content is about 46 %.
It is categorized as type IV cement in ASTM C 150 standards.
What is Low Heat Cement?
Definition: Low heat cement is a specially prepared portland cement, which produces low heat of hydration as setting and hardening of cement takes place.
It is low heat of hydration cement. Hence, called low heat cement. Low heat refers to low heat of hydration,
Working of Low Heat Cement
Low heat cement produces less heat or dame amount of heat at a low rate during its hydration. This low heat evaluation is achieved by lessening of contents of C3S and C3A, which are compounds releasing maximum amount of heat of hydration daring the process and increasing C2S.
The reduction in temperature retards chemical reaction of hardening and further restrict the rate of evolution of heat. Therefore, the evolution of heat extends over longer period of time.
So the main feature of low heat cement is slow rate of gain of strength.
Low Heat Cement Composition
Low heat cement is type-IV cement according to ASTM C 150 standards.
The maximum compound composition for type-IV cement is tabulated below:
| Compound Composition in Low Heat Cement | Maximum Content |
|---|---|
| C3S | 28 % |
| C2S | 49 % |
| C3A | 4 % |
| C4AF | 12 % |
| Blaine Fineness | 380 m2/kg |
Manufacture of Low Heat Cement
Low heat cement is a type of hydraulic binding material. In manufacturing process of low heat cement, OPC clinkers are mixed and ground together with appropriate amount of gypsum and other admixtures. Manufacturing process is same as the OPC entirely
Properties of Low Heat Cement
Low heat cement properties as per IS Code 12600:1989 standards are Tabulated below:
Physical Properties of Low Heat Cement
| Physical Properties | Requirements |
| Fineness Specific Surface Area | 320 m2/kg |
| Soundness Le Chatelier Autoclave test | 10 mm 0.8 % |
| Setting Time Initial Setting Time Final Setting Time | 60 minutes 600 minutes |
| Compressive Strength (minimum) @ 3 Days @ 7 Days @ 281 Days | 10 MPa 16 MPa 35 MPa |
| Heat of Hydration 7 Days 28 Days | 272 kJ/kg 314 kJ/kg |
Chemical Properties of Low Heat Cement
| Chemical Properties | Requirements |
| Ratio of % age of alumina to that of iron oxide | Not less than 0.66 |
| Insoluble residue, % by mass | Not less than 4 % |
| Magnesia, % by mass | Not less than 6 % |
| Total sulphur content calculated as sulphuric anhydride (SO3), % by mass | Not less than 2.5 and 3.0 when tricalcium aluminate % by mass is 5 or less and greater than 5 respectively |
| Total loss on ignition | Not less than 5 % |
Specification of Low Heat Cement
Low heat cement has low heat of hydration. Here, both ASTM C 150-05 and BS 1370: 1979 limits the heat of hydration to 250 J/g (60 cal/g) at 7 days and 290 J/g (70 cal/g) at 28 days.
Lime content is controlled by limiting the lime saturation factor to 0.66 to 1.08 as per BS 1370: 1979.
The strength of low heat cement is developed slower than OPC as C3S and C3A content are lower comparatively, but the ultimate strength is unaffected.
Fineness of low heat cement should not be less than 320 m2/kg to ensure satisfactory rate of gain of strength.
Advantages of Low Heat Cement
Advantages of low heat cement are listed below:
- It produces relatively low heat of cement which leads to low rate of shrinkage cracks.
- In mass concreting where excessive heat of hydration is evolved by hydration of cement, LHC can be used to control the temperature.
The packaging of low heat cement is done in bags. The criteria for the type of bags to be used can be found
HERE.
Disadvantages of Low Heat Cement
Disadvantages of low heat cement are listed below:
- It is not suitable for construction in regions having low temperatures
- Because of its high price, it is not used in residential or general purpose construction
- It cannot be used for cold weather concreting
- It gives low initial strength (but, its final strength is same as that of OPC)
- It is expensive as compared to OPC
Application of Low Heat Cement
In case of mass concreting structures, such as dams, where the large amount of heat is released by the exothermic reaction of hydration of cement. Formation of large cracks is observed in such cases, which lead to development of low heat cement. It produces low heat of hydration during construction of such large concrete bodies.
Storage criteria of low heat cement are the same as that of OPC. You can find the precautions to
be taken during storage and the proper way to store cement bags at the site here – Storage of
Cement Bags.
Low Heat Cement Uses
Use of low heat cement are as follows:
- It is used for mass concrete structure
- For Construction of Dams where where temperature rise by heat of hydration can become excessive
- For Large raft foundation construction it is useful
Key Take Away
Definition: Low heat cement is a specially prepared type of portland cement, which
produces low heat of hydration as the setting and hardening of cement takes place.
Hydration and Hardening of LHC: It is produced by lessening C3S and C3A content and
increasing C2S content in OPC. This ensures that the heat evolved during hydration is less
or the same but at a lower rate.
It may retard the rate of hardening in turn though, which is counteracted by grinding the
cement to the fineness of 320 m2/kg. The strength development is slower than OPC but
the ultimate strength remains the same.
It is Type-IV cement according to ASTM C 150 standards. Its properties and
characteristics are specified in IS 12600:1989.
Physical Properties of Low Heat Cement
| Physical Properties | Requirements |
|---|---|
| Fineness Specific Surface Area | 320 m2/kg |
| Soundness Le Chatelier Autoclave test | 10 mm 0.8 % |
| Setting Time Initial Setting Time Final Setting Time | 60 minutes 600 minutes |
| Compressive Strength (minimum) @ 3 Days @ 7 Days @ 281 Days | 10 MPa 16 MPa 35 MPa |
| Heat of Hydration 7 Days 28 Days | 272 kJ/kg 314 kJ/kg |
Chemical Properties of Low Heat Cement
| Chemical Properties | Requirements |
|---|---|
| Ratio of % age of alumina to that of iron oxide | Not less than 0.66 |
| Insoluble residue, % by mass | Not less than 4 % |
| Magnesia, % by mass | Not less than 6 % |
| Total sulphur content calculated as sulphuric anhydride (SO3), % by mass | Not less than 2.5 and 3.0 when tricalcium aluminate % by mass is 5 or less and greater than 5 respectively |
| Total loss on ignition | Not less than 5 % |
Application/Use: Due to its low rate of the heat of hydration LHC is used for mass
cotreating structures such as Dams, Large raft footings, Tunnels, etc.
FAQ
What type of cement is good for low heat?
As per ASTM C 150, Type-IV cement is good for low heat. According to IS 12600:1989, low
heat cement conferring to criteria mentioned is suitable for low heat.
| Heat of Hydration | LHC | OPC |
|---|---|---|
| 7 Days | 272 kJ/kg | 372 kJ/kg |
| 28 Days | 314 kJ/kg | 418 kJ/kg |
Is code for low heat cement?
IS 12600:1989
What is the initial setting time of low heat cement?
60 minutes (1 hour)
Why low heat cement used in dams?
Because the temperature rise by heat of hydration can become excessive in dams, low heat cement is used for dam construction.