DESC:FIELD OF THE INVENTION
The present invention relates to a cement composition. More particularly, the invention relates to a high performance cement composition comprising ground granulated blast furnace slag.
BACKGROUND OF THE INVENTION
Due to rapid growth in infrastructure, real estate and industrial sectors, the demand for cement has sky rocketed. Particularly, there is an increased demand for high performance cement for application in critical structures, such as tunnels, bridges, dams, skyscrapers, airports, sea ports, etc. High performance cement, as the name suggests, exceeds the performance of ordinary Portland cement with respect to its desirable properties. High performance cement may encompass some or all of the following properties: - High compressive and flexural strength, low drying shrinkage, low heat of hydration, superior workability, low water demand, superior abrasion resistance, low permeability, resistance to chemical attack, high toughness and impact resistance.
High-performance cement compositions are made with carefully selected high-quality ingredients and optimized mixture designs. Ingredients used in high performance cements may include clinker, fly ash, ground granulated blast furnace slag, silica fume, calcined clay, metakaolin, calcined shale, superplasticizers, high-range water reducers, hydration control admixtures, retarders, accelerators, corrosion inhibitors, water reducers, shrinkage reducers, alkali silica reaction (ASR) inhibitors, and polymer/latex modifiers.
PCT publication number WO1996027564A1 discloses a cement admixture composition capable of causing combined effects of inhibiting drying shrinkage while providing enhanced workability. The admixture comprises a synthetic mixture of oxyalkylene ether adduct primarily consisting of napthalene sulphonate formaldehyde condensate or melamine suphonate formaldehyde condensate.
European Patent number EP1511699B1 discloses additives for hydraulically setting systems based on modified polycarboxylates and water soluble ethers of high polymeric polysaccharides that lead to improvement in rheological profile in hydraulically setting systems.
PCT publication number WO2010126457A3 discloses the production of High Performance Cement (HPC) where the clinker is ground through a special grinding technology by adding a modifier having complex chemical composition for improving mechanical-chemical properties of the cement particles, resulting production of high performance cements such as HPC 62.5 with improved properties of concrete such as early strength up to 300 kg/cm2 in 24 hours, and 500 kg/cm2 in 48 hours; high strength up to 1200 kg/cm2 in 28 days; extended life time due to high performance; early removal of formwork without any steam cure application; high abrasion resistance along with other improvements mentioned in the invention.
Clinker is one of the important ingredients in a high performance cement composition. Clinker consists of various calcium silicates including alite and belite. Tricalcium aluminate and calcium aluminoferrite are other common components. These components are often generated in situ by heating various clays and limestone. Portland cement clinker is made by heating a homogeneous mixture of raw materials in a rotary kiln at high temperature. The products of the chemical reaction aggregate together at their sintering temperature, about 1,450 °C. The major raw material for the clinker-making is usually limestone mixed with a second material containing clay as source of alumino-silicate. Normally, an impure limestone which contains clay or silicon dioxide (SiO2) is used.
Another important constituent in high performance cement is Gypsum, which is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4.2H2O. Gypsum plays a very important role in controlling the rate of hardening of the cement. During the cement manufacturing process, upon the cooling of clinker, a small amount of gypsum is introduced during the final grinding process. Gypsum is added to control the “setting of cement”.
When cement reacts with water, the silicates and aluminates of calcium gets converted to the hydrated colloidal gels and following reactions take place:
1. 2CaO.SiO2 + x H2O?2CaO.SiO2 .xH2O (hydrated colloidal gel of C3S)
2. 3CaO. Al2O3 + 6 H2O?3CaO. Al2O3 .6 H2O (hydrated colloidal gel of C3A)
3. 3CaO.SiO2?2CaO.SiO2 + Ca (OH)2
4. 3CaO. Al2O3 .6 H2O?3 Ca(OH)2 + 2 Al(OH)3
In the above reactions Calcium Hydroxide, Aluminium Hydroxide and Dicalcium silicate are obtained.
Calcium Hydroxide helps to bind the silicate participles together, while Aluminum Hydroxide helps to fill the space in the lattice. When Gypsum is added to the Cement it binds with Tricalcium aluminates to make a colloidal gel and the above reaction don’t take place. So it slows the process of fastening.
3CaO. Al2O3 + 3CaSO4+ 2H2O?3CaO. Al2O3 .3CaSO4.2H2O
If not added, the cement will set immediately after mixing of water leaving no time for concrete placing.
Yet another important constituent of a high performance cement composition is ground granulated blast furnace slag (GGBS or GGBFS) which is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder. The slag formation is the result of a complex series of physical and chemical reactions between the non-metallic charge (lime, dolomite, fluxes), the energy sources (coke, oxygen, etc.) and refractory bricks. Because of the high temperatures (about 1500 °C) in a blast furnace, slags are devoid of any organic substances.
The chemical composition of a slag varies considerably depending on the composition of the raw materials in the iron production process. Silicate and aluminate impurities from the ore and coke are combined in the blast furnace with a flux which lowers the viscosity of the slag. In the case of pig iron production the flux consists mostly of a mixture of limestoneand forsterite or in some cases dolomite. In the blast furnace the slag floats on top of the iron and is decanted for separation. Slow cooling of slag melts results in an unreactive crystalline material consisting of an assemblage of Ca-Al-Mg silicates. To obtain a good slag reactivity or hydraulicity, the slag melt needs to be rapidly cooled or quenched below 800 °C in order to prevent the crystallization of merwinite and melilite. To cool and fragment the slag a granulation process can be applied in which molten slag is subjected to jet streams of water or air under pressure. Alternatively, in the pelletization process the liquid slag is partially cooled with water and subsequently projected into the air by a rotating drum. In order to obtain a suitable reactivity, the obtained fragments are ground to reach the same fineness as Portland cement.
The main components of blast furnace slag are CaO (30-50%), SiO2 (28-38%), Al2O3 (8-24%), and MgO (1-18%). In general increasing the CaO content of the slag results in raised slag basicity and an increase in compressive strength. The MgO and Al2O3 content show the same trend up to respectively 10-12% and 14%, beyond which no further improvement can be obtained. Several compositional ratios or so-called hydraulic indices have been used to correlate slag composition with hydraulic activity; the latter being mostly expressed as the binder compressive strength.
The glass content of slags suitable for blending with Portland cement typically varies between 90-100% and depends on the cooling method and the temperature at which cooling is initiated. The glass structure of the quenched glass largely depends on the proportions of network-forming elements such as Si and Al over network-modifiers such as Ca, Mg and to a lesser extent Al. Increased amounts of network-modifiers lead to higher degrees of network depolymerization and reactivity.
Common crystalline constituents of blast-furnace slags are merwinite and melilite. Other minor components which can form during progressive crystallization are belite, monticellite, rankinite, wollastonite and forsterite. Minor amounts of reduced sulphur are commonly encountered as oldhamite. Because of the high temperatures (about 1500 °C) in a blast furnace, slags are devoid of any organic substances.
Ground granulated blast furnace slag have a color nearly white in appearance. Hence the use of GGBFS in concrete manufacture would give a light and brighter color to concrete unlike the dark grey color of ordinary cement concrete structures. This is an added advantage of GGBFS in terms of aesthetics.
The disposal of slags has been a major concern for steel makers since long. In recent years however efforts have been made, to utilize slags in different fields such as, cement making, construction and fertilizers. Generally, blast furnace slags are granulated and used in cement making due to their excellent cementitious properties.
United States Patent No 5,374,309 discloses a process for producing a cementitious material from molten ferrous slag containing CaO, MgO, and SiO2, comprising: mixing a source of CaO with said molten ferrous slag, so that a ratio of CaO to SiO2 in said molten slag in a range of about 1.06 to 1.25 is obtained and said molten slag has a Base Numberless than about 1.55, wherein said Base Number equals (CaO--MgO)/- SiO2; granulating by breaking up and quenching said molten slag; and grinding said granulated slag to a degree of fineness to obtain a hydration rate.
United States Patent No 5,976,243 discloses a process for producing cement clinker using granulated blast furnace slag, having a water content of 5 to 15%, by weight having granule sizes less than 0.25 inches and in an amount of 25 to 70%, by weight, based on the total weight of the slag and the cement clinker, in a blended cement without the need for separate special steps for drying the slag.
United States Patent Number 7,410,537 provides an improved process for the production of Portland slag cement using granulated blast furnace slag comprising attrition milled slag in the range of 50 to 95% by weight, ball-milled clinker in the range of 05 to 45% by weight and gypsum in the range of: 01 to 05% by weight mixed intimately for a period in the range of 15 to 30 minutes.
United States Patent Number 8,029,619 discloses a grouting composition having a Blaine specific surface area of 5000 cm2/g or more, containing 30 to 60% by mass of cement clinker, 40 to 70 % by mass of and blast-furnace slag and 0.5 to 3 parts by mass of gypsum in terms of SO3 based on 100 parts by mass of the total amount of cement clinker and blast-furnace slag and additionlly, 4 to 8 parts by mass of calcium-aluminate based rapid-hardening admixture, 0.05 to 0.2 parts by mass of setting retarder and 0.5 to 1.7 parts by mass of high-performance water-reducing agent, based on 100 parts by mass of the fine particle material.
United States publication 2006/0230986 discloses the composition of a slag cement comprising ground granulated blast furnace slag along with about 3-15% by weight ground limestone to GGBFS, having an improved compressive strength.
United States publication 2015/0299037 discloses the composition of a binder used for construction materials comprising a ground granulated blast furnace slag and at least one mono-, di- or trivalent metal salt selected from the group consisting of bismuth, copper, silver and tin salts in quantities of 0.02% and 10% by weight of the amount of slag, wherein the salt is capable of forming, during mixing with said slag, a metal sulfide for which the solubility product Kse, measured at 25°C, is less than 1010.
United States Patent Number 8.993,656 discloses compositions and methods of producing a cementitious material containing portland cement, cement clinker, fly ash, ground granulated blast furnace slag, limestone and natural pozzolans wherein polycarboxylate comb polymer containing a carbon backbone and pendant polyoxyalkylene groups with linkage groups comprising at least one ether group, are used as grinding additives for resisting degradation during grinding and retaining workability and strength enhancing properties of the hydratable cementitious materials.
Surface modifiers are used to modify the surface of particles present in the hydraulically setting systems such as OPC, PPC, PSC, etc. to improve workability and enhance physical as well as chemical properties. Therefore, suitable use of such modifiers play an important role as far as composition of high performance cement is concerned. A comb shaped polycarboxylate composed of anionic backbone (main chain) and holding polyoxyalkylene pendant groups where the main chain is linked via ester, ether, imide and/or amide groups with polyoxyalkylene side chains can be used as a surface modifier.
Cement is one of the important constituents of any concrete mix design which contributes to the overall performance of the concrete. Currently, in order to prepare high performance concrete, different kinds of expensive additives, such as reinforcing fibers, silica fume, water proofing compounds, various admixtures etc. are added along with ordinary Portland cement or blended cement. However, it is an object of the present invention to provide a cement composition that achieves comparable or better performing concretes without or with sparing use of the aforestated additives and hence provides hassle-free and reliable solution to the end users.
The strength of concrete is inversely proportional to the amount of water added or water-cement (w/c) ratio. In order to produce stronger concrete, less water is added, which makes the concrete mixture less workable and difficult to mix, necessitating the use of plasticizers, water reducers, superplasticizers or dispersants. It is also an object of the present invention to prepare a high performance cement composition having reduced water demand compared to ordinary Portland cement. It is a further object of the present invention to formulate a high performance cement composition affording a flow ability that is comparable to ordinary Portland cement.
Drying shrinkage is defined as the contracting of a hardened concrete mixture due to the loss of capillary water. This shrinkage causes an increase in tensile stress, which may lead to cracking, internal warping, and external deflection, before the concrete is subjected to any kind of loading. Hence, it is an object of the present invention to formulate a high performance cement composition that affords less drying shrinkage compared to ordinary Portland cement.
When concrete is permeable to water, it can cause corrosion in reinforcement in presence of dissolved oxygen, SO3-, Cl– etc. This formation of rust due to corrosion results in cracking and spalling of reinforced concrete. Hence, it is another object of the invention to formulate a high performance cement composition that exhibits superior impermeability to water ingress.
A higher heat of hydration causes higher temperature in concrete structure and that increases the risk of cracking. Incorporating secondary cementitious materials (SCMs) such as fly ash and GGBFS into a cement composition not only helps in reducing the total amount of heat released but also retards the rate of heat evolution as compared to OPC. Hence, it is an object of the present invention to formulate a high performance cement composition that affords slower and lower heat of hydration as compared to ordinary Portland cement.
It is essential that cement set neither too rapidly nor too slowly. In the first case there might be insufficient time to transport and place the concrete before it becomes too rigid. In the second case too long a setting period tends to slow up the work unduly, also it might postpone the actual use of the structure because of inadequate strength at the desired age. Hence, it is yet another object of the present invention to formulate a cement composition that affords optimum initial and final setting times.
As stated earlier, the structural design of modern infrastructure projects, such as dams, tunnels, bridges and skyscrapers necessitates the use of concrete with high compressive strength at an affordable cost. Hence, it is an object of the present invention to formulate a high performance cement composition that affords high compressive strength compared to ordinary Portland cement.
Flexural strength is a measure of the tensile strength of concrete beams or slabs. Flexural strength identifies the amount of stress and force an unreinforced concrete slab, beam or other structure can withstand such that it resists any bending failures. Flexural strength is also known as bend strength or modulus of rupture or fracture strength. Hence, it is another objective to the present invention to formulate a high performance cement composition that achieves comparable or better flexural strength compared to ordinary Portland cement.
The inventors of the present invention have developed a synergistic skim coat composition comprising Fillers, Ordinary Portland cement, Organic polymeric binder, and Organic polymer, wherein, fillers are by-product of cement manufacturing to overcome problems mentioned above.
SUMMARY OF THE PRESENT INVENTION
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, (a) Clinker, (b) Gypsum, (c) Ground granulated blast furnace slag (GGBFS); and (d) Cement modifier.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, Clinker present in the range from 40 to 60%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, Gypsum present in range from 1.8 to 5%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising GGBFS in an amount present in the range of 38 to 55%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, Cement modifier present in range of 0.1 to 1.5%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising Cement modifier, wherein one or more cement modifier selected from group comprising, a comb shaped polycarboxylate composed of anionic backbone (main chain) and holding polyoxyalkylene pendant groups where the main chain is linked via ester, ether, imide and/or amide groups with polyoxyalkylene side chains.
In accordance with an embodiment of the invention, there is provided a process for preparation of high performance cement composition; comprising steps of:
a. Grinding clinker, gypsum and fly ash;
b. Adding cement modifier to the mixture of step (a) to obtain the high performance cement composition of the present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
It is to be noted that, as used in the specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The expression of various quantities in terms of “%” or “% w/w” means the percentage by weight, relative to the weight of the total solution or composition unless otherwise specified. The term “water” used herein refers to demineralized water unless otherwise specified.
The term “clinker” used in reference is one of the important ingredients in a high performance cement composition. Clinker consists of various calcium silicates including alite and belite. Tricalcium aluminate and calcium aluminoferrite are other common components. These components are often generated in situ by heating various clays and limestone.
The term “gypsum” used in reference is soft sulfate mineral composed of calcium sulfate dehydrate, with the chemical formula CaSO4.2H2O. Gypsum plays a very important role in controlling the rate of hardening of the cement. Gypsum is added to control the “setting of cement”.

The term “GGBFS” used in reference is Ground granulated blast furnace slag having a color nearly white in appearance. GGBFS is used in concrete manufacture togive a light and brighter color to concrete unlike the dark grey color of ordinary cement concrete structures.

The term “cement modifier” used in reference are used to modify the surface of particles present in the hydraulically setting systems such as OPC, PPC, PSC, etc. to improve workability and enhance physical as well as chemical properties.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, (a) Clinker, (b) Gypsum, (c) Ground granulated blast furnace slag (GGBFS); and (d) Cement modifier.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, Clinker present in the range from 40 to 60%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, Gypsum present in range from 1.8 to 5%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising GGBFS in an amount present in the range of 38 to 55%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising, Cement modifier present in range of 0.1 to 1.5%.
In accordance with an embodiment of the invention, there is provided a high performance cement composition comprising Cement modifier, wherein one or more cement modifier selected from group comprising, a comb shaped polycarboxylate composed of anionic backbone (main chain) and holding polyoxyalkylene pendant groups where the main chain is linked via ester, ether, imide and/or amide groups with polyoxyalkylene side chains.
In accordance with an embodiment of the invention, cement modifiers are selected from the group consisting of a comb shaped polycarboxylate composed of anionic backbone (main chain) and holding polyoxyalkylene pendant groups where the main chain is linked via ester, ether, imide and/or amide groups with polyoxyalkylene side chains, dispersants and combinations thereof.
In accordance with an embodiment of the invention, there is provided a, there is provided a process for the preparation of the high performance cement composition; comprising the steps of:
a. Grinding clinker, gypsum and ground granulated blast furnace slag; and
b. Adding cement modifier to the mixture of step (a) to obtain the high performance cement composition of the present invention.
In accordance with another embodiment of the invention, the mixture of step (a) is ground to achieve a specific surface area (Blaine) in the range of 350 to 400.
Please note that the Test Samples (present invention) belong to high performance cement named as Dalmia INFRAGREEN.
The preferred compositional ranges of the constituent materials of present invention are tabulated below in Example 1.

Example 1
Constituents %
Clinker 40-60
Gypsum 1.8-5
GGBS (Ground granulated blast furnace slag) 38-55
Cement modifier 0.1-1.5

The following four examples (Example 2-5) tabulate the typical compositions of the high performance cement composition of the current invention.

Example 2
Constituents %
Clinker 50.75
Gypsum 2
GGBS (Ground granulated blast furnace slag) 47
Cement modifier 0.25
Example 3
Constituents %
Clinker 41
Gypsum 5
GGBS (Ground granulated blast furnace slag) 52.7
Cement modifier 1.3
Example 4
Constituents %
Clinker 53.5
Gypsum 2
GGBS (Ground granulated blast furnace slag) 44
Cement modifier 0.5
Example 5
Constituents %
Clinker 60
Gypsum 1.9
GGBS (Ground granulated blast furnace slag) 38
Cement modifier 0.1

Example 6
A comparison between regular slag based cement (PSC) and the present invention (high performance cement, already BIS approved) on the basis of physical characteristics are tabulated below (Table 1-4; Example 7-10). The results show an overall performance enhancement in the current invention. This high performance cement can be considered as a 53 grade cement in 7 days based on the compressive strength value as opposed to 28 days for a normal cement based on PSC or OPC

Composition used for Control Sample is given in the table below
Constituents Range (percentage)
Clinker 50.75
Gypsum 2
GGBS (Ground granulated blast furnace slag) 47.25
Example 7
Table 1: Consistency and Setting Time
Characteristics As per IS 455:2015 Test Sample Control Sample
CONSISTENCY Not Specified 22% 31.50%
SETTING TIME
a) INITIAL SETTING TIME Shall not be Less than 30 Minutes 165 minutes 180 minutes
b) FINAL SETTING TIME Shall not be More than 600 Minutes 225 minutes 240 minutes

Example 8
Table 2: Compressive Strength
Characteristics As per IS 455:2015 Test Sample Control Sample
COMPRESSIVE STRENGTH
a) 24h (average of three results) Not Specified 21.1 MPa 14.6 MPa
b) 72±1h (average of three results) Shall not be Less than 16 MPa 40.77 MPa 19.4 MPa
c) 168±2h (average of three results) Shall not be Less than 22 MPa 56.4 MPa 35.5 MPa
d) 672±4h (average of three results) Shall not be Less than 33 MPa 70.3 MPa 47.3 MPa

Example 9
Table 3: Flexural Strength
Characteristics As per IS 455:2015 Test Sample Control Sample
FLEXURAL STRENGTH
a) 24h (average of three results) The cement shall show a progressive increase in Strength from the strength at 72 hours 4.8 MPa 5.0 MPa
b) 72±1h (average of three results) 7.5 MPa 7.1 MPa
c) 168±2h (average of three results) 8.4 MPa 7.8 MPa
d) 672±4h (average of three results) 9.1 MPa 8.8 MPa

Example 10
Table 4: Drying Shrinkage
Characteristics As per IS 455:2015 Test Sample Control Sample
DRYING SHRINKAGE
a) 1 Day Not Specified 0.004% 0.004%
b) 3 Days 0.012% 0.016%
c) 7 Days 0.031% 0.024%
d) 28 Days 0.054% 0.056%
Example 11
In accordance with another aspect of the present invention, there is provided a high performance structural concrete mix design (M70 grade with initial slump, approx 550m) to compare, evaluate and establish the superior properties (compressive strength and particularly in 3 and 7 days) imparted by using high performance cement over ordinary Portland cement. Please note that there is also a substantial decrease in the cement and cementitious materials along with reduction in water content and admixture dosage in the concrete mix design using the high performance cement (Dalmia INFRAGREEN).
The concrete mix design is comprised of the following.

,CLAIMS:We claim:
1. A high performance cement composition comprising ,
(a) Clinker;
(b) Gypsum;
(c) Ground granulated blast furnace slag (GGBFS); and
(d) Cement modifier.
2. The high performance cement composition as claimed in claim 1 comprising, Clinker present in the range from 40 to 60%.

3. The high performance cement composition as claimed in claim 1 comprising, Gypsum present in range from 1.8 to 5%.

4. The high performance cement composition as claimed in claim 1 comprising, GGBFS in an amount present in the range of 38 to 55%.

5. The high performance cement composition as claimed in claim 1 comprising, Cement modifier present in range of 0.1 to 1.5%.

6. The high performance cement composition as claimed in claim 1 comprising, wherein one or more cement modifier selected from group comprising, a comb shaped polycarboxylate composed of anionic backbone (main chain) and holding polyoxyalkylene pendant groups where the main chain is linked via ester, ether, imide and/or amide groups with polyoxyalkylene side chains.
7. A process for preparation of high performance cement composition; comprising steps of:
a. Grinding clinker, gypsum and fly ash;
b. Adding cement modifier to the mixture of step (a) to obtain the high performance cement composition of the present invention.