Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A DURABLE LOW CARBON CEMENT(DLCC) AND A PROCESS TO PRODUCE THE SAME.


2 APPLICANT (S)

Name : JSW CEMENT LIMITED.

Nationality : An Indian Company incorporated under the Companies Act, 1956.

Address : JSW CENTRE,
BANDRA KURLA COMPLEX,
BANDRA(EAST),
MUMBAI-400051,
MAHARASHTRA,INDIA.




3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a Durable Low Carbon Cement (DLCC) having compositioncomprising ground granulated blast furnace slag(GGBS), anhydrous gypsum and about 5% alkali activatoras portland cement clinker, and a process to produce the same.
The DLCCproduced is more finely ground1 than Ordinary Portland Cement to enhance the degree of hydrationof the binder. GGBS in DLCCvaries from 80-85% with10-15% anhydrous gypsum which is obtained by calcination of high purity gypsum at temperature ranges from 200°C to 700°C through stepwise heating-cooling cycles.The inventive step in this innovation is the stepwise calcination of mineral gypsum which converts the mineral gypsum to a highly reactive mineral and thus contributing to the hydration reaction during cement hydration. More particularly, the present invention is directed to providevery low consumption of clinker (upto5%), activation of gypsum at relatively low temperature (compared to high clinkerization temperature range from 1400-1500°C) which accelerates the hydration reaction with glassy slags. Here naturally occurring anhydrite (CaSO4) or industrial by-product anhydrite may also be used with modification of stepwise calcination process which includes time and temperature of treatment, cooling process and grinding size.

BACKGROUND OF THE INVENTION
Cement is a hydraulic binder, forming a paste with water, which sets and hardens due to hydration reactions. The main constituent of Portland cement is clinker (often termed as Portland cement clinker) which is produced from calcination of limestone (CaCO3), silica (SiO2), alumina(Al2O3) and iron oxide(Fe2O3) at very high temperature (>1400°C). The conventional ordinary Portland cement (OPC) is produced by the clinker with certain amount of mineral gypsum (3-5%).
Portland cement production is a highly energy consuming and air-polluting sector within the industrial world. It is due to the huge emission of greenhouse gases like CO2 to the atmosphere. About 900-1000kg of CO2 per ton of clinker is released of which 60% is related to calcination of limestone (CaCO3), while the rest accounts for the fuel combustion2. Coal is mainly used as a fossil fuel in clinkerization process of cement production. It is believed that globally at least 5-7 % of CO2 is released to the atmosphere is due to the production of OPC.
High temperature calcination in the rotary kiln to produce per ton of clinker requires high energy of 3.8GJ by combustion of different types of fossil fuels, biomass fuel and waste. Each ton of cement produced require 60-130 kg coal or its additional energy for cement production (crushing and grinding) is about 100kWh/ ton cement. The combustion of fossil fuel also generates a huge amount CO2. Needless to say that CO2 is not only responsible for air pollution but also climate change, global warming and ecological imbalance. These problems may lead to various natural calamities like flood, tsunami etc.
Hence it is necessary for the cement industry to reducethe carbon footprint to the atmosphere. As for example; cutting down the use of clinker in cement production can reduce the CO2 emission. This can be achieved by using more supplementary cementitious materials (SCM) such as blast furnace slags, fly ash, silica fume etc. Hence blended cements are introduced to the cement industry where SCM’s are blended in a certain ratio with OPC. SCM’s show pozzolanic activity or hydraulic activity when mixed with OPC and develop strength of concrete. Blended cements like portland slag cement (PSC), portlandpozzolana cement (PPC), composite cement (PCC), limestone calcined clay cement (LC3) are used where clinker consumption can be minimized and hence carbon footprint can also be reduced.
Granulated blast furnace slag (GGBS) is a by-product of steel industry which is produced by quickly quenching (cooling) the molten slag and followed by finely grounded to granules. The fineness is similar to OPC. The granular slag may vary from a popcorn like structure to small,sand size grains resembling a dense amorphous glass, depending upon the chemical composition, cooling rate and temperature of quenching. The rapid quenching allows for higher concentration of glassy state and restricts the molten slag for growing the crystals of different silicates and aluminates. The glassy slag contains the major oxides (CaO, SiO2, Al2O3, Fe2O3) as does OPC, but with considerably different proportions of lime and silica. Like OPC, it has excellent hydraulic properties and, with a suitable activator (such as calcium hydroxide) will set in similar way. As per IS 12089, the glass content of GGBS should be more than 85 %. Higher the glass content higher is the hydrolytic reactivity of GGBS particles. GGBShas the characteristic property of improved sulphate and chloride resistance. GGBS tend to be hydrated and hardened in presence of activator (clinker) and gypsum.
Durable Low Carbon Cement (DLCC) is a special category of blended cement which doesn’t necessarily requires calcination of limestone. Hence this type of cement accounts for a very low CO2 emission to the atmosphere. Since GGBS is used in a very large quantity (= 80%) which accounts for very low CO2 emission (0.14ton per ton of GGBS); hence about 0.05-0.06 ton CO2 is released in producing per ton of slag cement. Utilization of GGBS for infrastructure building is a great approach for waste utilization and sustainable world.
Durable Low Carbon Cement (DLCC) is a latent hydraulic cement which have the compositions broadly intermediate between those of pozzolanic materials and portland cement. Pozzolanic materials are high in SiO2 and Al2O3 and low in CaO to produce C-S-H gel at normal temperature and thereby act as hydraulic cements. In DLCC; GGBS shows the latent hydraulic property i.e. when it mixed with portland cement clinker; it is activated by Ca(OH)2released from clinker and further produces C-S-H gel.
Ca(OH)2 ( from clinker) + SiO2 (glassy phase of GGBS)? C-S-H Gel

The anhydrous CaSO4plays an important role which releases Ca2+and SO42- ion to the mixture. The Ca2+ion further activates the GGBS and produce more C-S-H gel. On the other handthe increased concentration of SO42- ion contributes to the stable ettringite (AFt) formation by reducing C3A content. In Portland cement ettringite is formed by the primary initial reaction of C3A and water in presence of gypsum. In DLCC- that anhydrous CaSO4act as a powerful reactor which accelerates the reaction of glassy GGBS. This is due to the precipitation of ettringite which provides a sink for the Ca2+andAl(OH)4-ions released from GGBS.3

STATE OF PRIOR ARTS:
DLCChas a tremendous potential to be a low carbon foot print alternate of conventional clinker based cements. From last few decades several slag and sulphate based cement materials has been disclosed in various peer reviewed research articles and in patents. Herein few relevant existing literatures have been discussed briefly as following.
Chinese patent CN1046 discloses development of slag based cement from mineral powder, sulphate, alkali excitant, macromolecular salt as enhancer. They use it to prepare concrete with polyaluminium chloride and concrete compressive strength can be improved by 20- 50 %.
Chinese patent CN102910852B discloses a coagulant for slag cement which comprises the following components in parts by weight: A (60-90 parts of lithium slag) and B (10-40 parts of high aluminium admixture). The coagulant for the slag based cement can be used for shortening the initial and final setting time, thus accelerating the early strength development and being better widely applied.
Chinese patent CN102875040B discloses development of slag based cement based on phosphorous slag which comprises the following components in parts by weight 30-50 parts of electric furnace phosphorous slag,25-50 parts of slag, 10-20 parts of plaster, 1-10 parts of auxiliary material and 1-10 parts of alkaline composition, wherein the auxiliary materials are admixtures of active CaO, active Al2O3 and active SiO2, and the alkaline composition is at least one of cement clinker and calcium hydroxide.
Hence as a summery, all the above mentioned reports have represented slag based cement with more than three ingredients in the system which makes the system more complicated.

OBJECTIVES OF INVENTION
The objectives of the present invention are as follows-
• Development of Durable Low Carbon Cement (DLCC) which is low clinker slag based cement composition involving activated anhydrite gypsum and activated ground granulated blast furnace slag with some amount of alkali activator.
• Development of cement with minimum consumption of portland cement clinker. Hence the production will leave minor carbon footprint.
• Development of a binder which consumes low thermal energy with equivalent physical and chemical properties just like OPC/PSC.
• Development of a suitable process to activate mineral gypsum and ground granulated blast furnace slag such that these two activated materials develop good binding properties when combined with minimal alkali activator.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a Durable Low Carbon Cement (DLCC) comprising of
activated ground granulated blast furnace slag (GGBS) > 80%;
activated mineral gypsum in the range of 10-15wt%; and
alkali activator upto 5 wt% including clinker;
synergistically co-acting for accelerated hydraulic reactivity of activated GGBS for accelerated cement hydration with glassy slags.

A further aspect of the present invention is directed to said Durable Low Carbon Cement (DLCC) wherein said activated ground granulated blast furnace slag (GGBS) is in the range of 80 to 85% and said activated mineral gypsum comprise anhydrous gypsum including calcined mineral gypsum with or without naturally occurring anhydrite (CaSO4) or industrial by-product anhydrite favouring cement hydration.
A still further aspect of the present invention is directed to said Durable Low Carbon Cement (DLCC) wherein the hydraulic reactivity of the activated GGBS is synergistically enhanced by the co-acting levels of clinker and anhydrous gypsum.

A still further aspect of the present invention is directed to said Durable Low Carbon Cement (DLCC) having selectively blaine number in the range of 350 to 450; leading to 28 days compressive strength in the range of 50-80 Mpa, and
concrete (M-40 Grade) made with said DLCC shows satisfactory results in various types of durability tests such as:
Water permeability test : Depth of water penetration is preferably in the range 4 to 9 mm
Rapid Chloride Permeability Test (RCPT): Charge passed is preferably in the range of 900 to 1000 coulomb which indicates very low chloride ion penetration of DLCC based concrete.
Rapid chloride migration test :the chloride migration coefficient is preferably in the range of 1.0 x 10-12 m2/s to 2.0 x 10-12 m2/s. after 28 days.

A still further aspect of the present invention is directed to said Durable Low Carbon Cement (DLCC) comprising polycarboxylateether based organic mix.
Another aspect of the present invention is directed to said Durable Low Carbon Cement(DLCC) adapted to ensure improved binding properties and reduced carbon dioxide emission said cement being finely ground to blaine number 400 to 450 to enhance the degree of hydration of the binder.
Yet another aspect of the present invention is directed to said Durable Low Carbon Cement wherein said anhydrous gypsum is obtained by calcination of high purity gypsum at temperature ranges from 200°C to 700°C through stepwise heating-cooling cycles which converts the mineral gypsum to a highly reactive mineral and thus contributing to the hydration reaction during cement hydration.
A further aspect of the present invention is directed to said Durable Low Carbon Cement wherein the initial loss on ignition value of gypsum is less than 20% and activated anhydrite gypsum has a loss on ignition value not exceeding 1.0%.
A still further aspect of the present invention is directed to said Durable Low Carbon Cement wherein the cement produced from the said composition is having a specific surface area atleast 350 cm2/g.
A still further aspect of the present invention is directed to said Durable Low Carbon Cement wherein fineness of GGBS used is kept more than 400 m2/kg to increase the slag reactivity with other components.
A still further aspect of the present invention is directed to said Durable Low Carbon Cement wherein incorporation of liquid polycarboxylateether (PCE) based organic admixture 0.6 -0.7% with respect to said cement enhances the slump retention (till 2.5 hrs) and increases strength to 75.8 Mpa.
A further aspect of the present invention is directed to a process to produce durable low carbon cement(DLCC) as described above comprising selectively processing raw material mix including mechanically activated GGBS, activated anhydrous mineral gypsum and/or activated chemically treated gypsum and clinker as an alkali activator in desired proportion.
A still further aspect of the present invention is directed to said process comprising providing selectively
mechanically activated ground granulated blast furnace slag(GGBS) of desired fineness in the range of 80-85wt%;
anhydrous gypsum in the range of 10-15wt% as a highly reactive mineral obtained by stepwise calcination of high purity gypsum;
Ordinary Portland Cementclinkerupto 5wt%;
mixing said ingredients and grinding to desired fineness to obtain said cement having blaine number 400 to 450 to enhance the degree of hydration of the binder.

A still further aspect of the present invention is directed to said process wherein for activating the anhydrite gypsum through stepwise heating and controlled cooling is performed in at least two heating-cooling cycles.
A still further aspect of the present invention is directed to said process wherein to activate the ground granulated blast furnace slag through mechanical means include grinding and dosing of polymeric admixtures including polycarboxylateether(PCE) to make the ground granulated blast furnace slag highly reactive.
A still further aspect of the present invention is directed to Calcined activated mineral gypsum for use in producing durable Low Carbon Cement having accelerated cement hydration with glassy slags comprising:

Phase
Gypsum hydrate preferably <30.5 %
Anhydrite preferably >1.3%
Gypsum hemihydrate preferably <68.2%
Lime (CaO) preferably 0.0%
A still further aspect of the present invention is directed to saidprocess for manufacturing the calcined activated mineral gypsum comprising:
subjecting the mineral gypsum through said heating-cooling cycles comprises the temperature of heating ranges from 200°C to 600°C and the rate of cooling is controlled through forced and compressed air such that the average cooling rate is atleast 50°C/minute in the range of 50 to 60°C.

The above and other aspects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying drawings and examples.

BRIEF DESCRIPTION OF ACCOMPANIED DRAWINGS
Fig 1: DLCC preparation process flowchart.
Fig 2: Digital image of DLCC powder sample, mortar cube and concrete cube made of DLCC.
Fig 3: shows Heat of hydration study results.
Fig 4: shows Cumulative heat of hydration vs time plot.
Fig 5: shows XRD Spectra of raw MG (G-1).
Fig 6: shows XRD Spectra of Anhydrous Gypsum (G-2) calcined at 600°C.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS AND EXAMPLES
The present invention is directed to provide low clinker slag based cement formulation comprising of (a) Mechanically activated GGBS (80- 85 %), (b) calcined and activated mineral gypsum and/or chemically treated cum activated gypsum (10-15%) and clinker (5%) as activating agent. Calcination of mineral gypsum is carried out at various stages with different temperature starting from 120° to 600°C. Gypsum calcination converts it to Anhydrite form which is confirmed by XRD analysis (see Fig no:6).
Different physical parameters like normal consistency,setting time, blaine fineness, soundness (Le-Chatelier and autoclave method) has been tested while developing DLCC. Cement mortar cubes are casted and compressive strength of mortar cubes have been tested after 1,3,7 and 28 days of water curing. The developed formulations show 28 days compressive strength in the range of 50- 80 MPa. It is observed that the strength depends upon different factors like percentage composition of each ingredient, Blaine fineness of cement, calcination temperature of gypsum and type of gypsum used in the formulation.
The fineness of GGBS used is kept more than 400 m2/kg to increase the slag reactivity with other components
Incorporation of organic admixture (polycarboxylateether based) in the cement further improves the strength.
The developed cement has been further used for concrete trial (M-40 grade). We have obtained 28 days strength of 57.6 Mpa. Incorporation of liquid PCE based admixture (0.6 -0.7% with respect to cement) enhances the slump retention (till 2.5 hrs) and increases strength to 75.8 Mpa.
Hence the present invention of high slag cement represents a simple formulation where slag can be activated by the synergistic effect of clinker and anhydrite gypsum. Here the calcination temperature of gypsum is one parameter which can influence the strength of cement.
Accompanying Fig 1 shows DLCC preparation process flowchart and Fig 2 shows Digital image of DLCC powder sample, mortar cube and concrete cube made of DLCC.

The present invention thus disclosesa Durable Low Carbon Cement with high proportion of activated GGBS (>80%) in the formulation. Unlike other clinker based cements; this type of cement uses very low clinker content (5%). The hydraulic reactivity of the activated GGBS used is greatly enhanced by the synergistic effect of clinker and anhydrous gypsum. Unlike other slag based cements with various additives incorporated for increasing strength and durability; our system has a simple formulation where a single additive can be incorporated which further enhances the strength of cement mortar cube. The additive used is Polycarboxylate ether (PCE) in a fine powder form.
Example:
Various compositions of cement under sample number DLCC 1 to 6 have been trialled under present invention as presented in following Table 1 and Physical parameters and compressive strength of the same samples are presented in Table 2.

Table 1: Example of various compositions of cement with Blainefineness andcompressive strength (28days)

Cement composition
Gypsum % Gypsum Calcination temperature(°C)
GGBS %
OPC Clinker %
Additive%
Blaine fineness ( m2/kg)
Compressive Strength @ 28days (MPa)
DLCC1 10 600 85 5 0 416 69.1
DLCC2 12 600 83 5 0 430 75.2
DLCC3 12 600 83 5 0 376 56.35
DLCC4 12 600 83 5 0.06 434 76.75
DLCC5 12 120 83 5 0 431 59.4
DLCC6 15 600 80 5 0 449 75.8

Table 2: Physical parameters and compressive strength of different cement compositions
Physical parameters:

Tests
DLCC 1
DLCC 2
DLCC 3
DLCC 4
DLCC 5
DLCC 6
Normal Consistency (%)
28.00
28.25
26.75
25.0
29.25
28.75
Initial setting Time (min)
220
210
180
190
210
205
Final Setting time (min)
310
300
250
305
310
315
Fineness (Blaine ,m2/kg)
416
430
376
434
431
449
Le-Chatelierexpansion (mm)
1.0
1.0
1.0
1.0
1.0
1.0
Autoclave expansion (%)
0.189
0.192
0.184
0.186
0.190
0.181
Compressive Strength(MPa) ; 1 day
9.54
9 .74
7.89
10.45
12.35
9.64
Compressive Strength(MPa) ; 3 days
16.8
17.5
13.65
19.9
17.55
18.05
Compressive Strength(MPa) ; 7 days
35.45
37.2
26.8
38.75
37.15
37.55
Compressive Strength(MPa) ; 28 days
69.1 75.25 56.35
76.75
59.4
75.8

It has been observed that the increase in percentage of anhydrous gypsum in the composition can be useful to increase the 28days compressive strength. As for example if we compare the two compositions DLCC1 and DLCC2 with 10% and 12% respectively; DLCC2 shows higher strength of 75.25 Mpa against 69.1 Mpa of DLCC1. Secondly, increase in Blaine fineness has a positive effect in strength development which is seen in DLCC 2 (Blaine 430) against DLCC 3 (Blaine < 400).
In DLCC5; we have used gypsum which is heated upto 120°C. XRD study shows that it has only 1.8% of anhydrite and the remaining phase is gypsum hemihydrate. The 1,3 and 7 days strength for this composition looks satisfactorybut the 28 days strength found to be inferior (59.4 MPa) than the other combinations where gypsum is heated upto 600°C.
So it is observed that the gypsum calcination temperature (up to 600°C)with higher percentage of anhydrite formed has a significant role in development of long term (28 days) compressive strength of the cement.

Heat of Hydration study:
The heat of hydration of cement paste were performed in Isothermal calorimeter. The instrument accurately and reliably measures the heat of hydration (ASTM C1702) and predict the setting behaviour of various cement pastes. The heat of hydration and its rate of different system was tested till 7 days for OPC, PSC and DLCC samples.
Fig 3 shows theresults of Heat of hydration study of various cement samples.
In case of OPC (and PSC also) a typical secondary peak (sulphate depletion) corresponding tothe conversion of ettringite (AFt) to monosulphate(AFm) has been observed. However, this type of peak is absent in DLCC. So it is possible that ettringite may be a stable phase here at the end of hydration itself. In the DLCC formulation the concentration of anhydrous gypsum is kept higher (> 10%) which is responsible for delay in the hydration of C3A phase. Also the high concentration of sulphate (from anhydrous gypsum) is responsible to keep the ettringite as a stable hydration product. Next the high concentration of GGBS (> 80 %) in DLCC results very low formation of C3A phase and hence a very high gypsum to C3A ratio.
As a result – very low amount of C3A available to react with etrringite phase and water to convert it to monosulphoaluminate (AFm). Hence ettringite remains as a stable phase in DLCC unlike in OPC where a sulphate depletion peak is observed in hydration study. In OPC; the increase in C3A content is responsible for initial hydration of clinkers which helps in early strength of development cement.
The higher concentration of GGBS is DLCC is also responsible for lower heat of hydration and lower temperature rise against the OPC as shown in the Fig. 4 that showsCumulative heat of hydration vs time plot for various samples trialled.
In comparison with OPC with approximately 240- 300 J/g (after 7 days), DLCC develop considerably less heat of hydration of approximately 110 -130 J/g (after 7 days).

X-ray diffraction Study of Gypsum:
Anhydrousgypsum is obtained by calcination of high purity mineral gypsum(MG) to convert to anhydrite; calcination temperature may range from 500°C to 600°C. MG powder is finely grounded and subjected to different temperature and X-ray diffraction study was performed.
Fig 5 showsXRD Spectra of raw MG (G-1).
Fig 6 showsXRD Spectra of Anhydrous Gypsum (G-2) calcined at 600°C.

Phase analysis:
Phase G-1
G-2
Gypsum hydrate 30.5 % 0.0%
Anhydrite 1.3% 99.1%
Gypsum hemihydrate 68.2% 0.6%
Lime (CaO) 0.0% 0.3%

It has been observed that at high temperature (upto 600°C); the major phase is anhydrite (99.1%) as shown in Fig.6. The raw MG is treated to different temperatures like 120° C, 200°C and X-ray diffraction has been studied where the percent anhydrite form is less (1.8 and 1.9% only).
The anhydrite phase shows hydrolytic activity to higher extent which depends on its crystal structure and structural defects. Breaking the Ca2+ ion coordination in CaSO4crystalline grating is necessary to accelerate the setting process of DLCC. This is achieved by fine grinding4.
Concrete Trials
The applicability and performance of the developed DLCC has been further validated by preparation of concrete and testing. One of the best DLCC composition from Table 1 has been used to prepare concrete mix (M-40 grade). Here 470 Kg/ m3 of cement has been used in concrete mix and other components like water, coarse and fine aggregates are incorporated as per standard M-40 design. Water has been fixed to keep a uniform homogeneous mix The workability of the concrete is tested by monitoring slump retention. 80mm slump is observed in 30 minutes. Concrete cubes are casted for 1,3, 7 and 28 days. Concrete cubes are demoulded after 24h ambient temperature curing and then placed for water curing at ambient temperature. The compressive strength after 1,3 ,7 and 28 days of the concrete cubes are 5.95 ,12.45, 25.94 and 57.6 MPa respectively. Hence the developed DLCC based concrete shows expected strength and compatibility with conventional concrete testing. The concrete mix design is also tested with Polycarboxylate ether based superplasticizers/Admixtures. It is observed that admixtures havea positive effect with DLCC based concrete in terms of flow, workability and strength. We achieved a slump retention of 175 mm in 2 hrs 30mins. The strength values are 16.44, 29.8, 46.9 and 75.8 MPa after 1,3,7 and 28 days of curing respectively. So it is also confirmed that DLCC based concrete has a good compatibility with conventional concrete admixtures.
Reference :
(1)Jawed, I., Skalny, J., Young, J. F., Hydration of Portland cement, in Structure andperformance of cement (Barnes, P. ed.), Applied Science Publishers, London and NewYork, 1983, pp. 237-317

(2) European Commission. Reference Document on Best AvailableTechniques in Cement, Lime and Magnesium Oxide ManufacturingIndustries. http://eippcb.jrc.ec.europa.eu/reference/BREF/clm_bref_0510.pdf (accessed July 8, 2012).

(3) Cement chemistry 2nd edition: Tayler p- 285
(4) V. Leskevicience, I. Sarlauskaite : Influence of gypsum dehydration temperature and alkali additives on the properties of anhydrite cement

, Claims:We Claim:
1. A Durable Low Carbon Cement (DLCC) comprising of

activated ground granulated blast furnace slag (GGBS) > 80%;
activated mineral gypsum in the range of 10-15wt%; and
alkali activator upto 5 wt% including clinker.
synergistically co-acting for accelerated hydraulic reactivity of activated GGBS for accelerated cement hydration with glassy slags.

2. The Durable Low Carbon Cement (DLCC) as claimed in claim 1 wherein said activated ground granulated blast furnace slag (GGBS) is in the range of 80 to 85% and said activated mineral gypsum comprise anhydrous gypsum including calcined mineral gypsum with or without naturally occurring anhydrite (CaSO4) or industrial by-product anhydrite favouring cement hydration.
3. The Durable Low Carbon Cement (DLCC) as claimed in anyone of claims 1 or 2 wherein the hydraulic reactivity of the activated GGBS is synergistically enhanced by the co-acting levels of clinker and anhydrous gypsum.
4. The Durable Low Carbon Cement (DLCC) as claimed in anyone of claims 1 to 3 having selectively blaine number in the range of 350 to 450; leading to 28 day compressive strength in the range of 50-80 Mpa, and
concrete (M-40 Grade) made with said DLCC shows satisfactory results in various types of durability tests such as:
Water permeability test : Depth of water penetration is preferably in the range 4 to 9 mm
Rapid Chloride Permeability Test (RCPT): Charge passed is preferably in the range of 900 to 1000 coulomb which indicates very low chloride ion penetration of DLCC based concrete.
Rapid chloride migration test: the chloride migration coefficient is preferably in the range of 1.0 x 10-12 m2/s to 2.0 x 10-12 m2/s. after 28 days.
5. The Durable Low Carbon Cement (DLCC) as claimed in anyone of claims 1 to 4 comprising polycarboxylateether based organic mix.
6. The Durable Low Carbon Cement(DLCC) as claimed in anyone of claims 1 to 5 adapted to ensure improved binding properties and reduced carbon dioxide emission said cement being finely ground to blaine number 400 to 450 to enhance the degree of hydration of the binder.
7. The Durable Low Carbon Cement as claimed in anyone of claims 1 to 6 wherein said anhydrous gypsum is obtained by calcination of high purity gypsum at temperature ranges from 200°C to 600°C through stepwise heating-cooling cycles which converts the mineral gypsum to a highly reactive mineral and thus contributing to the hydration reaction during cement hydration.
8. The Durable Low Carbon Cement as claimed in anyone of claims 1 to 7 wherein the initial loss on ignition value of gypsum is less than 20% and activated anhydrite gypsum has a loss on ignition value not exceeding 1.0%.
9. The Durable Low Carbon Cement as claimed in anyone of claims 1 to 8 wherein the cement produced from the said composition is having a specific surface area atleast 350 cm2/g.
10. The Durable Low Carbon Cement as claimed in anyone of claims 1 to 9 wherein fineness of GGBS used is kept more than 400 m2/kg to increase the slag reactivity with other components.
11. The Durable Low Carbon Cement as claimed in anyone of claims 1 to 10 wherein incorporation of liquid polycarboxylateether(PCE) based organic admixture 0.6 -0.7% with respect to said cementenhances the slump retention (till 2.5 hrs) and increases strength to 75.8 Mpa.
12. A process to produce durable low carbon cement(DLCC)as claimed in anyone of claims 1 to 11 comprising selectively processing raw material mix including mechanically activated GGBS, activated anhydrous mineral gypsum and/or activated chemically treated gypsum and clinker as an alkali activator in desired proportion.
13. The process as claimed in claim 12 comprising providing selectively
mechanically activated ground granulated blast furnace slag(GGBS) of desired fineness in the range of 80-85wt%;
anhydrous gypsum in the range of 10-15wt% as a highly reactive mineral obtained by stepwise calcination of high purity gypsum;
Ordinary Portland Cementclinkerupto 5wt%;
mixing said ingredients and grinding to desired fineness to obtain said cement having blaine number 400 to 450 to enhance the degree of hydration of the binder.
14. The processas claimed in claim 12 or 13 wherein for activating the anhydrite gypsum through stepwise heating and controlled cooling is performed in atleast two heating-cooling cycles.
15. The processas claimed in anyone of claims 12 to 14 wherein to activate the ground granulated blast furnace slag through mechanical means include grinding and dosing of polymeric admixtures including polycarboxylateether(PCE) to make the ground granulated blast furnace slag highly reactive.
16. Calcined activated mineral gypsum for use in producing durable Low Carbon Cement having accelerated cement hydration with glassy slags comprising:

Phase
Gypsum hydrate preferably <30.5 %
Anhydrite preferably >1.3%
Gypsum hemihydrate preferably <68.2%
Lime (CaO) preferably 0.0%

17. A process for manufacturing the calcined activated mineral gypsum as claimed in claim 16 comprising:
subjecting the mineral gypsum through said heating-cooling cycles comprises the temperature of heating ranges from 200°C to 600°C and the rate of cooling is controlled through forced and compressed air such that the average cooling rate is atleast 50°C/minute in the range of 50 to 60 °C.

Dated this the 7th day of February, 2024
Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199