Claims:We Claim:
1. A method of manufacture of cementitious material from steel slag
comprising:
steps of re-melting, reduction and metal separation from iron containing steel slag to modify and render it suitable for cementitious material involving
providing batched steel slag;
melting the steel slag in a furnace at a temperature between 1600- 1650OC;
adding reducing agents to molten steel slag for reduction and thereafter separating the iron from the reduced steel slag; and
obtaining from said iron separated steel slag the cementitious material.

2. The method as claimed in claim 1, wherein said step of obtaining from said iron separated steel slag the cementitious material includes water granulation with or without any required modification such as to obtain desired cementitious material like granulated blast furnace slag matching Indian standard IS:12089 – 1987.

3. The method as claimed in anyone of claims 1 or 2, wherein the steel slag is selected from basic oxygen furnace slag or electric arc furnace slag.

4. The method as claimed in any of the claims 1 to 3, wherein the reducing agent is selected from the source of carbon or aluminium without any impurities.

5. The method as claimed in any of the claims 1 to 4, wherein prior to said water granulation the iron separated steel slag preferably the basic oxygen furnace slag the same is modified involving a modifying agent, a source of silica, without any impurities.

6. The method as claimed in any of the claims 1 to 5, wherein the mass percentage of the reducing agent is 5% to 8.4%.

7. The method as claimed in any of the claims 1 to 6, wherein the mass percentage of the modifying agent is 15% to 20%, preferably about 18%.

8. The method as claimed in any of the claims 1 to 7, wherein the amorphousness of the cementitious material is maintained to achieve like granulated blast furnace slag that complies with the Indian standard IS:12089 – 1987.

9. The method as claimed in any of the claims 1 to 8, wherein the amorphousness of the cementitious material is maintained in the range of from 85% to 100%.

10. A cementitious material comprising iron separated steel slag based cementitious material having compressive strength in the range of 48 MPa to 53.5 MPa and the heat of hydration in the range of 286 J/g to 303 J/g of the heat of hydration.

11. The cementitious material as claimed in claim 10 which is comparable with granulated blast furnace slag that complies with the Indian standard IS:12089 – 1987 and includes 5% to 8.4% of reducing agent, 18% of the modifying agent, and the balance is steel slag.

12. The cementitious material as claimed in any of the claims 10 to 11, comprising said iron separated steel slag based cementitious material and Portland clinker in a mass ratio of not more than 3:2 as cement.

Dated this the 23rd day of January, 2021
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199

, 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 METHOD OF MANUFACTURE OF CEMENTITIOUS MATERIAL FROM STEEL SLAG.



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 generally to the field of cementing material technology. More specifically, the present invention relates to providing a cementitious material compositionwith enhanced amorphousness to achieve cementitious properties and method of its making by bulk utilization of BOF and EAF steel slag.

BACKGROUND OF THE INVENTION

The Global crude steel production reached 1,869.9 million tons for the year 2019 with China’s share about 53.9% (996.3 million tons) followed by India 111.2 million tons up by 8.3% in 2018 (World Steel Association 2020).As Indian steel production capacity will rise to 300 million tons by 2030 from the current capacity of about 140 million tons, the production of BOF slag would rise to 12 million tons (Indian Minerals Yearbook 2015, Ministry of Steel, 2018, Steel guru, 2019).In 2018, about 8.82 million tons of basic oxygen furnace (BOF) slag was generated in India while only 1.57 million tons were utilized in Sinter Plant, Blast furnace, Traffic & construction activities achieving utilization of 17.84 % (Annual report 2018-2019). In the case of electric arc furnace (EAF) slag, roughly about 7 million tons per year of EAF slag is produced in India whereas, it is about 103 million tons per year worldwide (Steel Statistical Yearbook 2018, Bureau and Mines, 2018).

Efforts have been made to utilize these steel slags as a cementitious material.Wang, Q., Yan, P., and S. Han. 2011. “The influence of steel slag on the hydration of cement during the hydration process of complex binder”. Science China Technological Sciences, 54 (2), 388–394, utilized the steel slag in a cementitious binder. This study concluded that steel slag application with cement provides later strength after hydration. However, early hydration of slag cement was decreased and the dormant phase of cement hydration increased with the adding percentage of steel slag. Also, the expansion effect of free lime and magnesia onthe application of cement was not studied. Xue Y., Wu S., Hou H., and Zha J. 2006. “Experimental investigation of basic oxygen furnace slag used as aggregate in asphalt mixture”. Journal of Hazardous Material, 138, 261–268,wherein the BOF slag was utilized as aggregate. However, a small part could be utilized due to the presence of free lime and magnesia. The free lime and magnesia absorb moisture and carbon dioxide from the air and form hydroxides and carbonates respectively which is the reason for volume expansion/swelling resulting inthe formation of cracks. This leads to the need to explore other ways of steel slag utilizationAgrawal, S.K., Vanguri, S., Chaturvedi, S.K., Kumar, A., and Reddy, A.S. 2017. “Performance evaluation of granulated bf slag -steel slag based Portland slag cement.” 15th NCB International Seminar on Cement, Concrete and Building Materials, New Delhi, India, 413, 1-11, wherein BOF slag was applied for partial replacement of granulated blast furnace slag (GBS) in Portland slag cement (PSC). However, only 7.5% of BOF slag can be recycled as a fractional substitution to GBS in PSC due to the expansion of steel slag on application with a higher percentage.

Similarly, the application of EAF slag as a construction material has been also reported. Pasetto, M., and N. Baldo. 2011. “Mix design and performance analysis of asphalt concretes with electric arc furnace slag.” Construction Building Materials 25:3458–3468, wherein EAF slag was applied as aggregates in road pavements. However,high metallic concentration in EAF slag hinders the application of it.

To overcome the expansion ofthe direct application,researchers also tried to utilize steel slag inthe clinkerization process. Singh R, Gorai AK, Segaran RG, 2013. Characterization of LD slag of Bokaro steel plant and its feasibility study of manufacturing commercial ‘fly ash–LD slag’ bricks. International Journal of Environmental TechnologyManagment 16:129–145, whereinBOF slag was used toreplace iron ore in raw feed during clinker manufacture. However,only 2% of BOF slag can be used as a raw mix component for the correction of iron content in the raw mix.

In addition to the mentioned studies, several referenced havealso been made for the development of cementitious products from steel slags.European patent EP1741683A2 discloses a major component of cement is cement clinker made from a mixture of raw materials calcium oxide, silica, aluminium, and iron oxide by mixing, milling, and firing. According to the invention, the raw material mixture comprises a lime component and converter slag and/or electro-steelworks slag. As a result, both natural resources can be spared and the carbon dioxide emissions are reduced when burning the cement clinker. The basic oxygen furnace (BOF) slag was utilized in the proportion of 5-8% with 25-35% of blast furnace slag in the preparation of the cement clinker.

European patent EP0780347B1 discloses the utilization of electric arc furnace dust as a partial replacement or additive for cement. The present invention provides set retardation and enhanced properties including corrosion inhibiting to the concrete end product.

European patent EP3315471A1 discloses the BOF slag was activated to utilize it as a composite material for the cement industry. The BOF slag was modified at a high temperature to achieve the activation of the belitic phase in the BOF slag. However, this activated steel slag was crystalline in nature and had limited applications.

US patent (US20130269573A1) wherein it provided an ultra-rapid hardening hydraulic binder including reduced steel slag powder and a method of preparing the same. The reduced slag powder is prepared by rapidly cooling molten electric arc furnace reduced slagto room temperature not to have free-calcium oxide by scattering the molten electric arc furnace reduced slag into the air using high-pressure gas by dropping the molten electric arc furnace reduced slag through a tundish.

Chinese patent (CN101466650A) wherein, the invention provides a process for conversion of basic oxygen furnace slag into construction materials like a hydraulic binder and other applications. The fluorspar was added to the molten slag to increase its fluidity and then the slag was allowed to cool. However, The reduction process for theseparation of metallic and nonmetallic iron was not performed in this method. Also, modified BOF slag with fluorspar could not achieve the desired amorphousness due to lack of silica and slow cooling.

Korean patent application no. 10-2010-0111768, wherein method of an ultra rapid-hardening hydraulic binder preparation from reduced steel slag powder is provided.The method comprises the process of scattering electric arc furnace to high pressure in a steel mill; quick freezing at room temperature; pulverizing the reduction slag into a fixed fineness, and mixing gypsum with the pulverized reduction slag was prepared through and a manufacturing method thereof are provided to enhance rapid hardening property and replace normal Portland cement. However, the slag was cooled at room temperature which leads to crystalization of the slag, which is the major drawback of this invention.

Despite progress made by previous studies as shown in the above prior arts, further efforts are required for bulk utilization of steel slags. In prior mentioned arts the methods forsteel slag reduction and modification and then water granulation for enhanced amorphousness to achieve cementitious properties are not available. Also, the bulk utilization of BOF and EAF slag is not available as most of the studies and inventions are focused on the co-utilization of these slags in very less proportion.

As per IS: 12089-2008. Specification for granulated slag for the manufacture of portland slag cement. Bureau of Indian Standards, New Delhi, India and ASTM (American Society of Testing and Materials). 2017. Standard Specification for Slag Cement for Use in Concrete and Mortars. C989, West Conshohocken, Pennsylvania, USA: ASTM, the glass content or amorphousness in slag should be more than 85% for its gainful utilization in cement. However, the glass content inthe originalBOF and EAF slag is only varying from 40% to 49%, which also restrict their application in cement.The utilization of steel slags for the metallic recovery and modification to more amorphous, GBS like material can provide a sustainable solution for its bulk utilization. The development of the metallurgical reduction method and the generation of more reactive amorphous slags is the main objective of this invention.

OBJECTS OF THE INVENTION

The main object of the present invention is directed to provide a method for the reduction and modification of steel slags to produce Granulated blast furnace slag (GBS) like cementitious material.

Yet another object of the present invention is to provide a method for the bulk use of steel slag to reduce the content of Portland cement clinker.

It is a further object of the present invention to provide a method to reduce and remove the iron from the steel slag.

It is another object of the present invention to use Granulated blast furnace slag (GBS) like cementitious material to make cement for increasing the compressive strength of the concrete.
It is another object of the present invention to beneficially use waste industrial material like steel slag in the production of cement/mortar/concrete.
It is an object of the present invention to reduce the cost of cement products.

It is a further object of the present invention to lower the heat of hydration of the cement.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a method of manufacture of cementitious material from steel slag comprising steps of remelting, reduction and metal separation from iron containing steel slag to modify and render it suitable for cementitious material involving:providing batched steel slag;melting the steel slag in a furnace at a temperature between 1600- 1650 °C;adding the reducing agents to the molten steel slag for reduction;and thereafter separating the iron from the reduced steel slag.; and obtaining from said iron separated steel slag the cementitious material.

A further aspect of the present invention is directed to said methodwherein said step of obtaining from said iron separated steel slag the cementitious material includes water granulation with or without any required modification such as to obtain desired cementitious material like granulated blast furnace slag matching Indian standard IS:12089 – 1987.

There is further provided said method wherein the steel slag is selected from basic oxygen furnace slag or electric arc furnace slag.

There is further provided said method wherein the reducing agent is selected from the source of carbon or aluminium without any impurities.

There is further provided said method wherein prior to said water granulation the iron separated steel slag, preferably the basic oxygen furnace slag, the same is modified involving that the modifying agent, a source of silica without any impurities.

In accordance with the method of the present invention, the mass percentage of the reducing agent is 5% to 8.4%.

In accordance with the method of the present invention, the mass percentage of the modifying agent is 15% to 20% preferably about 18%.

In accordance with the present invention,the amorphousness of the cementitious material is maintained to achieve like granulated blast furnace slag that complies with the Indian standard IS:12089 – 1987.

In accordance with the present invention, the amorphousness of the cementitious material is maintained in the range of from 85% to 100%.

A further aspect of the present invention is directed to provide cementitious material comprising the iron separated steel slag based cementitious material having compressive strength in the range of 48 MPa to 53.5 MPa and the heat of hydration in the range of 286 J/g to 303 J/g of the heat of hydration.

A still further aspect of the present invention is directed to provide the cementitious material which is comparable with granulated blast furnace slag that complies with the Indian standard IS:12089 – 1987 and includes 5% to 8.4% of reducing agent, 18% of modifying agent and the balance is the steel slag.

A still further aspect of the present invention is directed to the cementitious material comprising said iron separated steel slag based cementitious material and Portland clinker in a mass ratio not more than 3:2 as cement.

A still further aspect of the present invention is directed to the cement has a compressive strength in the range of 48 MPa to 53.5 MPa and heat of hydration in the range of 286 J/g to 303 J/g of the heat of hydration.

The above and other objects and advantages of the present invention are described hereunder in greater detail with reference to the following accompanying non-limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 illustrates the flow chart of a steel slag reduction and modification method to form cementitious material;

FIG. 2 illustrates the image of cementitious material formed by BOF slag;

FIG. 3 illustrates the microscopic image of (a) granulated blast furnace slag (GBS), (b) cementitious material (reduced, modified and air-cooled BOF slag), (c) cementitious material (BOF slag), (d) cementitious material (reduced and air-cooled EAF slag), (e) cementitious material (EAF slag)

Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity to help to improve understanding of embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS

The accompanying figure together with the detailed description below forms part of the specification and serves to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.

The present invention is now discussed in more detail referring to the drawings that accompany the present application. In the accompanying drawings, like and/or corresponding elements are referred to by like reference numbers.

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts.

Before describing in detail embodiments that are in accordance with the invention, it should be observed that the embodiments reside primarily to the full metallurgical reduction of the steel slag and conversion to more reactive form, much similar to Granulated blast furnace slag (GBS). More specifically, the present invention relates to the utilization of steel slag as a starting material. The slag was re-melted, reduced, chemically modified and water granulated which resulted in a cementitious material.

The present invention discloses a steel slag reduction and modification method to form cementitious material. Method 100 as illustrated in FIG.1 comprises the following steps. In step 102, steel slag is batched. The steel slag is selected from the group consisting of basic oxygen furnace (BOF) slag or electric arc furnace (EAF) slag. The BOF slag contained about 50% ß-belite. However, it reacts very slowly.The presence of periclase was also a concern for the BOF slag. In EAF slag, the typical mineral phases were detected, mainly Gehlenite- Akermanite and Wustite.

In step 104, the steel slag is melted in a furnace at a temperature between 1600- 1650 °C. The steel slag was melted in the Tammann furnace.

In step 106, the reducing agents are added to the steel slag.The melting and reduction of steel slag are done to recover the hot metals. The reducing agent is selected from the group consisting of a source of carbon or aluminium without any impurities. The mass percentage of the reducing agent is 5% to 8.4%.

In step 108, the iron is separated from the reduced steel slag.The hot metal that is iron was separated.

In step 110, the modifying agent is added to the iron separated steel slag. The modifying agent is the source of silica without any impurities and is added preferably to the basic oxygen furnace slag. The mass percentage of the modifying agent is 18%. Preferably, the characterization of steel slag is performed to add the modifying agent in the steel slag.

Lastly in step 112, water granulation is performed for the modified or iron separated steel slag to prepare a cementitious material. This process generates the granulated slags with cementitious properties like granulated blast furnace slag (GBS). The water cooling after re-melting was done in order to stabilise amorphousness and to prevent free lime and periclase formation during the cooling of the melted steel slags.

The cementitious material includes 5% to 8.4% of reducing agent, 18% of modifying agent and the balance is the steel slag. The amorphousness of the cementitious material is like granulated blast furnace slag that complies with the Indian standard IS:12089 – 1987. The amorphousness of the cementitious material varies from 85% to 100%.The cementitious material is mixed with Portland clinker in a mass ratio of 3:2 to form cement. The cementitious material includes 5% to 8.4% of reducing agent, 18% of modifying agent and the balance is the reduced and modified steel slag.The resulting reduced and modified steel slag was blended with Portland clinker and tested for cementitious properties. Hence prepared cementitious binder has performed better than the cement prepared with blending of GBSand Portland cement in ratioof 3:2 in terms of strength properties. The cement prepared with steel slags has a compressive strength in the range of 48 MPa to 53.5 MPa and heat of hydration in the range of 286 J/g to 303 J/g of the heat of hydration.

Hence the steel slags could be effectively utilized in the manufacturing of cement. This will not only save natural resources but also help in reducing landfilling issues and encouraging cleaner production. The sustainable use of slags will also contribute towards environment friendly, economical, and energy-efficient construction.It works as an efficient metal recovery process.It provides the cement industry with alternative cementitious material.It also provides protection for natural resources and reserves. The products are cost-effective as well as eco-friendly as waste materials from the steel industry were valorised.

In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or composition that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article or composition. An element proceeded by "comprises...a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or composition that comprises the element.

In the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless specifically stated otherwise.

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. Commonly used dictionary-defined terms are additionally interpreted as having meanings consistent with related technical documents and currently disclosed content and are not interpreted as ideal or very formal meanings unless defined.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

In addition, unless otherwise specified, % means weight%.

The advantages and features of the present invention and methods for achieving them will be clarified with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and are conventional in the art to which the present invention pertains. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid obscuring the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains.

The present invention is described further hereinafter by reference to a series of accompanying examples.

Experiments that were actually performed are now described by way of the following examples.

Examples

Example 1: Chemical evaluation of steel slag
The analyses of BOF slag and EAF slag were done by XRF, gravimetric (SO3), titration (S2-, Cl-, free lime), photometry (Cr-VI, F-), and infrared spectroscopy (CO2 and H2O). Table 1 illustrates the chemical analysis of steel slags.

Table 1: Chemical composition of the steel slag (in wt.-%)
BOF Slag EAF Slag
CaO 42.2 23.2
CaOfree, titra. 6.1 ?0.20
MgO 8.2 6.3
SiO2 12.1 15.9
Al2O3 4.1 10.6
TiO2 0.67 0.91
Na2O ?d.l. ?d.l.
K2O 0.03 0.05
Fetotal 16.7 28.1
Femet* 1.85 8.63
FeO * 11.9 20.4
Fe2O3 * 8.74 6.75
P2 O5 1.79 0.82
Stotal 0.12 0.03
SO3, gravi. 0.11 0.081
S2-titra 0.02 0.02
Cr 0.075 0.063
Cr-VI, photo[mg/kg] ?0.0 ?0.0
Cl-titra. ?0.001 0.043
Mn 1.433 0.658
V 0.053 0.034
CO2 , IR 1.2 0.23
H2O, IR 2.7 ?0.03
C/S 3.49 1.46
* Separate analyses of Fe total, Fe met., FeO and Fe2O3 calculation

The BOF slag contained about 50%ß-belite. However, it reacts very slowly.The presence of periclase was also a concern for the BOF slag. In EAF slag, the typical mineral phases were detected, mainly Gehlenite- Akermanite and Wustite.The composition of Fetotal in steel slags was found high which is the sole reason for remelting, reduction, and metal separation from the slag. While due to low silica content in the original BOF slag, the modification was done with the addition of silica.

Example 2: Steel slag reduction and modification method
A steel slag reduction and modification method to form cementitious material comprising of following steps. Firstly, steel slag wasbatched. Secondly, steel slag was melted in a furnace at a temperature between 1600- 1650 °C. Thirdly, the reducing agents were added to the steel slag. Fourthly, the iron was separated from the reduced steel slag. Fifthly, the modifying agent was added to the iron separated steel slag. Lastly, the water granulation or air coolingwas performed for the modified or iron separated steel slag to prepare a cementitious material.

The treatment conditions for BOF and EAF slag are given in Table 2.

Table2: Treatment conditions for BOF slag and EAF slag
Temp. Reduction agent Modification Cooling
? Type Addition Type Addition
- Wt.-% - Wt.%
EAF 1650 C, Al 6.2, 2.2 - - Water granulation/Air Cooling
BOF 1650 C, Al 2.5, 2.5 SiO2 18 Water granulation/Air Cooling

Example 3: Chemical analysis of reduced and modified BOFand EAF slags

Table 3 represents the chemical analysis of the reduced and modified BOF and EAFslags. The analysis reflected the recovery of 98.3% of Fe from the original slags.While in the case of BOF slag silica content was increased from 12.1 wt.% to 31.5 wt.% due to the addition of quartz in the slag. The modified and water granulated slags were found fulfilling the requirement of Portland slag cement manufacturing in accordance with IS 12089: 1987. Table 3 reveals the mineralogical analysis of BOF and EAF slag also revealed the amorphous nature of the modified slag.The glass content in the case of EAF slag was found 100% by volume while BOF slag was found with 86.4% of the glass content by volume.

Table 3:Chemical composition of the modified BOF and EAF slag (in wt.-%)
BOF Slag EAF Slag
Insoluable residue 0.24 0.29
CaO 44.5 36.3
MgO 10.2 9.74
SiO2 31.5 24.7
Al2O3 9.37 21.6
TiO2 0.78 1.47
Na2O 0.00 0.00
K2O 0.01 0.01
Fetotal 0.28 2.67
Femet* ? 0.1 0.03
FeO * ? 1.0 3.46
Fe2O3 * 0.40 0.12
Stotal 0.14 0.19
SO3, gravi. 0.15 0.12
S2-titra 0.10 0.26
Cr [mg/kg] 91 116
Cl-titra. 0.009 0.011
Mn 1.32 0.74
V[mg/kg] 211 156
CO2 , IR 0.15 0.11
H2O, IR 0.11 ?0.03
C/S 1.41 1.47
* Separate analyses of Fe total, Fe met., FeO and Fe2O3 calculation

Example 4: Comparison of cementitious material with granulated blast furnace slag (GBS)and Effect of water granulation and air cooling on the amorphousness of cementitious material

FIG. 2 represents the image of cementitious material of the present invention. The image represents the glassiness of the cementitious material formed by using BOF slag.

FIG. 3 illustrates the fraction 40-63 µm of the crushed cementitious material being used for glass content analysis by microscope. The coloured zones indicate crystalline while colourless represent the amorphous areas. The microscopic image of air-cooled BOF slag and EAF slag show more coloured area which represents the crystalline nature of the air-cooled slags. While in the case of GBS and water granulated steel slags most of the area becomes colourless due to the amorphous nature of the material.

Example 5: Comparision of cement made from cementitious material formed by reduced and modifiedslags with GBS

Cement was made from modified, iron separated steel slags and GBS separately and was tested and compared for properties. The modified, iron separated steel slags and GBS were blended with Portland clinker in the ratio of 3:2then tested for compressive strength and heat of hydration test.

The strength properties and heat of hydration of the cement prepared with cementitious material of the present invention were compared with the strength properties and heat of hydration of cement with GBS as shown inTable 4.

Table 4:Comparision of propertiesof different types of cements containing modified steel slags and GBS
EAF Slag Cement BOF Slag Cement GBS Cement
Steel Slag 60 60 0 Wt.-%
GBS - - 60 Wt.-%
OPC Clinker 40 40 40 Wt.-%
w/c (Water to cement ratio) 0.505 0.505 0.485 -
Spread 209 207 206 mm
1 day Compressive Strength 15.5 11.8 5.8 MPa
3 daysCompressive Strength 31.2 25.1 19.6 MPa
7 days Compressive Strength 43.8 36.6 33.2 MPa
28 days Compressive Strength (IS 383) 48.0 53.5 49.3 MPa
Heat of Hydration
7 days (w/c = 0.50) 303 286 260 J/g

The strong impact of the EAF slag and BOF slag was also recognizable in the heat of hydration analysis. The EAF and BOF slag based cement developed more heat of hydration than GBS cement.The water demand increment was also found negotiable with a water to cement (w/c) ratio of 0.505. The cement has a compressive strength in the range of 48 MPa to 53.5 MPa and the heat of hydration in the range of 286 J/g to 303 J/g of the heat of hydration.The BOF slag cement developed 8.5% more compressive strength and 10% more heat of hydration than GBS cement. However, the EAF slag cementdeveloped 2.63% less compressive strength as compared to GBS cement.The EAF slag cement has 16.5% more heat of hydration than GBS cement.