LC3 (Limestone Calcined Clay Cement):
LC3 is a ternary cement, blended or interground mixture of Portland cement clinker, calcined clay and limestone with addition of gypsum (natural or chemical), of Portland cement clinker .
Or
An intimate and uniform blending of ordinary Portland cement, finely ground limestone and fine calcined clay with addition of ground gypsum, if required.
History:
LC3 has been developed in an international collaboration between the University of Las Villas, Cuba and EcolePolytechniqueFédérale de Lausanne, Switzlerand, which was funded by the Swiss government.
Researchers from IIT Delhi, IIT Madras and IIT Bombay are working together with the personnel of TARA to understand and develop LC3 for the Indian cement Industry.
In India as on 04/08/2021 ‘DRAFT INDIAN STANDARD IN WIDE CIRCULATION’ has been submitted to BIS Core team for comments by “Technical Committee : Cement And Concrete, CED 02”, the last date for sharing the comments has been given upto 16 September 2021.
Ratio of Components are shown as following (when use OPC)
Or
Ratio of Components areshown as following (when use Clinker)
Manufacturing Process:
Material Proportion to be used in Limestone Calcined Clay Cement
Material Proportion | (Percent by Weight) | |
(1) | (2) | (3) |
a | Portland cement clinker | 50 – 80 (in case clinker is used) |
b | Calcined clay | 10 – 35 |
c | Limestone | 5 – 20 |
Limestone calcined clay cement shall be manufactured by
· Intimately inter-grinding Portland cement clinker, limestone and calcined clay.
or
· Intimately and uniformly blending ordinary Portland cement, finely ground limestone and finely ground calcined clay.
When limestone calcined clay cement is obtained by grinding limestone and calcined clay with Portland cement clinker, no material shall be added after burning, other than gypsum (natural mineral or chemical, see Note), water and not more than a total of 1.0percent of air-entraining agents or other agents including colouring agents, which have proved not to be harmful. The limitation of all such additions shall also apply to manufacture of limestone calcined clay cement by blending process. Furthermore, when the grinding of the clinker is carried out along with limestone and calcined clay, care shall be taken to ensure that a uniform fineness is achieved for all constituents of the cement, that is clinker, calcined clay and limestone.
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Raw Materials (Components):
Limestone:(15%):
· The limestone used in the manufacturing of LC3 shall contain at least 75% of carbonates, including limestone and dolomite. The total of calcium oxide and magnesium oxide content in the limestone shall not be less than 35 percent.
· Suitable limestone can be identified by measuring the weight-loss between 700 °C and 800 °C and by XRD,The mass loss of the limestone shall be not less than 28 percent of the mass of the limestone when measured as per Annexure-C of IS 17844.
Clinker or Portland Cement:
· The Portland cement clinker used in the manufacturing of the cement shall confirm to IS 16353. When the cement is produced by blending of the individual components, the fineness of the ground clinker shall not be less than 225 m2/kg.
· If clinker is not available in nearby sites then Portland cement (OPC) may be used and the Portland cement for blending for manufacture of cement as per this standard shall confirm to IS 269.
Calcined Clay:
The raw clay used in the manufacture of the calcined clay should contain at least 40% kaolinite when determined as per Annex-B & activated through thermal calcination, have been found to be suitable, and it is explained inIS-1344 for kaolinite types of clay
· The loss of mass on ignition of the raw clay, as determined according to the procedure described in Annex-B, shall not be less than 5.6 percent of the weight of the clay.
· The clay shall be calcined by maintaining it at high temperatures for a duration long enough to achieve temperatures above 750 ˚C throughout the mass of the clay. During calcination, the temperature of the clay shall, in no case, be higher than 950 ˚C. When tested in accordance with IS 1727, the lime reactivity of the calcined clay shall not be less than 8 MPa.
· The clays can be calcined at 700 °C to 800 °C to remove its chemically attached hydroxyl groups, making it amorphous and reactive.
· The mass loss on ignition of the clay after calcination, when measured according to the procedure described in Annex B, shall not be more than 1.5 percent of the mass of the clay.
· Suitable clays can be easily identified by measuring the weight-loss in the clay between 300 °C and 800 °C using Thermo Gravimetric Analysis (TGA) or a muffle furnace since the kaolinite phase loses 14% of its weight in this temperature range.
· This can be verified using X-Ray Diffraction (XRD), where the kaolinite and other peaks are visible.
Gypsum:
· Limestone calcined Clay cement required addition of gypsum so as to produce cement capable of complying with this standard, means addition should be on that proportion in which the cement can achieve the physical requirement as per above table 01.
· The homogeneity of the mixture shall be guaranteed within ±3 percent for each of the declared limestone and calcined clay addition in the same consignment.
Physical Characteristic/ Requirement:
Limestone Calcined Clay Cement shall have the physical requirements given in following Table 01.
SINo. | Characteristic | Requirement | Method of Test, Reference |
i) | Fineness,m2/kg,Min | 400 | IS4031 (Part2) |
ii) | Soundness: a) ByLe-Chateliermethod,mm,Max
b) Byautoclavetest method, percent,Max |
10
0.8 | IS4031 (Part3) 1. In the event of cements failing to comply with one or both the requirements of soundness specified in the above table, further tests in respect of failure shall be made as described in IS4031 (Part 3), from another portion of the same sample after aeration. The aeration shall be done by spreading out the sample to a depth of 75 mm at a relative humidity of 50 to 80 percent for a total period of 7 days. The expansion of cements so aerated shall not be more than 5 mm and 0.6 percent when tested by Le-Chatelier method and autoclave test, respectively. |
iii) | Settingtime: a) Initial,min,Min b) Final,min,Max |
30
600 | IS4031(Part5) 1. If cement exhibits false set, the ratio of final penetration measurement after 5 min of completion of mixing period to the initial penetration measured exactly after 20 s of completion of mixing period, expressed as percent, shall not be less than 50. In the event of cement exhibiting false set, the initial and final setting time of cement when tested by the method described in IS 4031 (Part 5) after breaking the false set, shall confirm to the value given in the above table. |
iv) | Compressivestrength,MPa): a) 72±1h,Min b) 168±2h,Min c) 672±4h,Min |
23 33 43 | IS4031(Part6) 1. For measurement of the compressive and transverse strength of the cement, the specimens shall be cured under conditions specified in IS 4031 (Part 6).
|
v) | Dryingshrinkage,percent,Max | 0.15 | IS4031 (Part10) |
vi) | Transversestrength(Optional) |
| IS4031(Part8) 1. For measurement of the compressive and transverse strength of the cement, the specimens shall be cured under conditions specified in IS 4031 (Part 6). 2. By agreement between the purchaser and the manufacturer, transverse strength test of plastic mortar in accordance with the method described in IS 4031 (Part 8) may be specified. The permissible values of the transverse strength shall be mutually agreed to between the purchaser and the supplier at the time of placing the order. 3. Notwithstanding the compressive andtransverse strength requirements specified as per the above table, the cement shall show a progressive increase in strength from the strength at 72 h. |
Chemical Requirements
Chemical Requirements for Limestone Calcined Clay Cement is shown in following
Table-02.
SI No. | Characteristic | Requirement |
1 | Insoluble residue, percent by mass, Max | where x is the declared percentage of calcined clay in the given Portland calcinedclay limestone cement |
2 | Magnesia, percent by mass, Max | 6 |
3 | Total sulphur content calculated as | 3.5 |
4 | Loss on ignition, percent by mass, Max | 12 |
5 | Chloride content, percent by mass, Max | 0.1 |
6 | Alkali content | Alkali aggregate reactions have been noticed in aggregates in some parts of the country. On large and important jobs where the concrete is likely to be exposed to humid atmosphere or wetting action, it is advisable that the aggregate be tested for alkali aggregate reaction. In the case of reactive aggregates, the use of cement with alkali content below 0.8 percent expressed as sodium oxide (Na2O + 0.658 K2O) is recommended. Where, however, such cements are not available, use of alternative means may be resorted to for which a reference may be made to appropriate provisions on durability in the concrete codes. If so desired by the purchaser, the manufacturer shall carry out test for alkali content. |
Economic Feasibility
Production of LC3 is very much economical where good quality fly ash is not available, as calcined clay may replace the fly ash.
Environmental sustainable growth:
LC3 supports a sustainable growth by following factors
a. Reducing the CO2 Emission approx. 30% Lower than OPC, 11% Lower than PPC.
b. Energy consumption is also reduced compared to OPC & PPC.
To be Noted:
The fineness of the clay should be controlled since finer clays can increase water-demand of the cement. The presence of limestone reduces the water-demand of the cement.
- LC3 is understood to have a finer pore-structure than OPC
- A high chloride binding capacity.
- It is therefore durable against corrosion, sulphate attack and other deterioration mechanisms, making it suitable in aggressive conditions.
References:
1. BIS: https://www.services.bis.gov.in:8071/php/BIS/WCDraft/wcfiles/17844.pdf
2. LC3 Technology: https://lc3.ch/
3. IIT Research papers: https://web.iitd.ac.in/~bishnoi/lcc/LCCProjectSummary.pdf
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