WO2017085565A2

WO2017085565A2 - Portland cement free activation of ground granulated blast furnace slag

Info

Publication number: WO2017085565A2
Application number: PCT/IB2016/001897
Authority: WO
Inventors: Ramkumar Natarajan; Satheesh Kumar Kartheesan THIYAGARAJAN
Original assignee: Eko Tech4Trans Pvt. Ltd.
Priority date: 2015-11-18
Filing date: 2016-11-16
Publication date: 2017-05-26
Also published as: CA2912184A1; WO2017085565A3

Abstract

A Portland cement-free cementitious binder composition, said composition comprising: ground granulated blast furnace slag and/or pulverized fly ash; an alkali metal oxide; an alkali metal phosphate; an alkali metal fluoride; nano alkali metal carbonate; and an alkali metal sulfate. Preferably, the slag is present in an amount ranging from 80 to 90% by weight of the composition.

Description

PORTLAND CEMENT FREE ACTIVATION OF GROUND GRANULATED BLAST

FURNACE SLAG FIELD OF INVENTION

The present invention relates to a new cement composition which is more environmentally friendly than traditional Portland cement, more specifically, the novel cement comprises a high proportion of ground granulated blast furnace slag. BACKGROUND OF THE INVENTION

Blast furnace slag is the non-metallic by-product of iron production, generally consisting of silicon, calcium, aluminum, magnesium and oxygen. When iron is manufactured using a blast furnace, two products collect in the hearth - molten iron and slag. The slag floats on top of the iron and is skimmed off to be fed to a granulator. In the granulator the molten slag is rapid quenched with water. The resulting granules are essentially glassy, non-metallic silicates and alumino silicates of calcium. The glass content of the slag generally determines its cementitious character or suitability for use in hydraulic cement— the higher the glass content the greater the cementitious properties.

Significant quantities of this blast furnace by-product are produced annually. Disposal of blast furnace slag had been problematic until subsidiary uses for the slag were developed. For instance, ground granulated blast furnace slag (GGBFS) may be added to cement clinker and calcium sulfate and inter- ground to create a modified Portland slag cement.

Manufacturing Portland cement through a dry method is a very energy intensive process. After quarrying the principal raw materials such as limestone, clay, and other materials, the rock is crushed. This is done is multiple steps. The first step reduces the rock to a maximum size of about 6 inches. Subsequent crushing steps reduce the rocks to a size of about 3 inches or smaller. At that point the rocks are combined with other ingredients such as iron ore or fly ash and ground further and mixed and added to a cement kiln. The cement kiln heats the mixture to a temperature ranging from about 2,700 to about 3000 degrees Fahrenheit. The finely ground raw material or slurry is fed into the elevated end of the kiln. At the other end of the kiln are the flames produced by the burning of powdered coal, oil, alternative fuels, or other combustible material. The high temperature calcines the chemically combined water and carbon dioxide from the raw materials which comes out at the higher end of the kiln and forms new compounds such as tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite) which forms the clinker that comes out at the lower end of the kiln. This clinker is in the form of marble sized balls. Clinker coming out of the kiln is cooled, ground and mixed small amounts of gypsum and limestone. EP 0 553 131 discloses method of converting latent hydraulic ground granulated amorphous blast-furnace slag to a hydraulic binder which will act directly when water is added, by improved activation of a slag activated with an activator comprising magnesium oxide and phosphate. The description states that improved activation is obtained by mixing the slag and the activator with a combination of additional activators which include alkali and calcium, wherein alkali is present in an amount of less than 4 percent by weight, based on the amount of binder present, and calcium is present in the form of a Portland cement and optionally calcium oxide.

US Patent No. 5,411 ,092 teaches a method for cementing a well, comprising: combining constituents comprising water, blast furnace slag having a particle size within the range of 2,000 to 15,000 cm² /g, and an activator comprising trisodium phosphate, to form a cement slurry; displacing the cement slurry into the well; and allowing the cement slurry to set. The description states that the activator can include a citrate ion-containing compound such as sodium citrate, calcium citrate and potassium citrate.

US patent application No. 2014/0264140 teaches a product comprising: a geopolymer composite binder comprising: one or more Class F fly ash materials; one or more gelation enhancers, and one or more hardening enhancers which includes ground granulated blast furnace slag in an amount ranging from about 5 to about 92 wt. %.

US patent No. 5,026,215 teaches a method of grouting formations with a cementitious material comprising microfme ground slag is useful for stabilizing and strengthening soil and rock formations as well as underground structures associated with buildings, tunnels and dams. A composition is provided which comprises water, a dispersant, slag and an accelerator to activate the slag.

US patent No.4,018,616 discloses a water glass composition comprising a water-soluble or water-dispersible silicate binder and an inorganic phosphate curing agent, wherein said inorganic phosphate curing agent is composed of an inorganic solid fine powder comprising as the main ingredient a silicon polyphosphate or its metal salt and said curing agent. Slag is mentioned as one of the potential filler additive.

US patent application No. 2014/0343194 teaches stabilized aqueous suspensions include aluminous cement and/or calcium sulfoaluminous cement and binding compositions including the aqueous suspension in combination with organic binders, which are stable at room temperature and at high temperature as well as methods for preparing the same are described.

US patent No. 8,703,659 discloses a sealant composition for servicing a wellbore comprising at least one gel system, a loss prevention material and water, wherein the at least one gel system comprises a crosslinking agent such as polyethylene amine, wherein the loss prevention material comprises a particulate material which comprises silica flour. It is stated that in addition to the gel system comprising the pumpable, corrosion resistant, hardcnable epoxy described, certain hydraulic cements such as Portland cement may be desirable as components of this sealant composition.

US Patent No. 4,761 , 183 discloses a grouting composition comprising a very small particle size slag, an equal or greater weight of water and the optional components cement, alkali silicate, anionic dispersant, a source of orthophosphate ions, sodium hydroxide and sodium carbonate. US patent No. 8,722,772 teaches a hydraulically setting sealing composition based on a) a hydraulically setting compound from the group comprising high-alumina cement, ordinary portland cement, blast furnace slag, b) protective-colloid stabilized polymer of one or more ethylenically unsaturated monomers in form of an aqueous polymer dispersion or a water-redispersible polymer powder, and c) one or more fillers.

US patent No. 5,673,753 teaches a drilling mud for in situ conversion to cement by addition of blast furnace slag. The description states that the purpose of the invention is achieved through the in situ solidification of water-base drilling fluids through the addition of blast furnace slag, set-time control additives, and rheology modifying additives. The blast furnace slag is said to be added in an amount equivalent from about 50 to 400 pounds of slag per standard (42-gallon) barrel of drilling fluid. It is also stated that the composition is particularly useful for the solidification of drilling fluids containing polyhydric alcohols.

WO 201 5/082585 discloses a binder composition for improved mortars and coatings, comprising first standard mineral constituent and a second constituent based on pulverulent calcium hydroxide, wherein said second constituent based on pulverulent calcium hydroxide has a specific surface calculated according to the BET method which is lower than 12 m²/g. The description states that among the cements that can be selected ground blast furnace slag and fly ash can be used. One of the issues with the addition of slag to Portland cement is that increasing the amount of slag addition increases the setting time of the final cement. The early strength gain of the cement considerably decreases thus making the cement unusable. Currently, the addition of slag to Portland cement has been limited to a maximum of 50% depending on the fineness and glass content of the slag. Consequently, there is still a need to increase the percentage of slag loading without compromising on the early and final strength of the final cement and, more advantageously, to remove altogether the presence of Portland cement in the cementitious binder composition. Some of the problems of prior art cements include: slow setting and decreased early strength when slag percentage is increased; the use of high pH and harsh alkalis like sodium hydroxide and sodium silicate; and the mandatory use of Portland cement and high amount of calcium sulfate. The inventors have discovered that cement made according to a preferred embodiment of the present invention promotes the reaction between lime and phosphate and hence provides a more durable cement than previously used or known cements.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a method of producing blast furnace slag cement that does not involve any addition of Portland cement and hence requires very less energy to make and does not release green house gases during its production.

According to a second aspect of the present invention, there is provided an activator composition for combining with hydraulically-active materials comprising ground granulated blast furnace slag (GGBFS) and/or pulverised fuel ash (PFA) to form a cementitious binder, methods for using such activator compositions and methods of forming cementitious binders.

According to a preferred embodiment of the present invention, there is provided a cementitious binder composition comprising at least 80 % by weight of a hydraulically-active material comprising ground granulated blast furnace slag (GGBFS) and/or fly ash having a surface area ranging between 2500-12000 cm²/g, preferably of approximately 4000 cm²/g; at least 0.5 % by weight of lime; at least 0.5% of nano calcium carbonate having a particle size of 5- 10 micron meter; at least 0.5% by weight of alkali metal fluoride; at least 0.5% by weight of an alkali metal sulfate; optionally, 0.1 % by weight of a hydrocolloid as water retention agent; and at least 0.1 % by weight of acid and/or alkali metal phosphate as part of cement composition for the hydraulically-active material. The cementitious binder composition according to an aspect of the present invention does not comprise any Portland cement and is, therefore, more environmentally friendly. The resulting cement does not involve clinkering. According to an aspect of the present invention, there is provided a concrete, mortar, grout, screed or render formed by mixing the cementitious binder composition according to the present invention with aggregate particles, water and a superplasticiser. The particles of slag must preferably be within the specified ranges or if too coarse, the particles will have fewer chemical reactions with other components of the binder and therefore lead to a cement with reduced strength.

According to another aspect of the present invention, there is provided the use of an alkali metal poly phosphate such as sodium hexa meta phosphate as activator which was heretofore not known to the inventors. The cement according to preferred embodiments of the present invention provides for a strength gain comparable to Portland cement compositions.

According to another aspect of the present invention, there is provided the use of an increased percentage in the use of slag as well as higher strength because of the use of mechanically activated GGBFS or fly ash.

According to a preferred embodiment of the present invention, a curing agent can be added to the cement composition in order to provide a cement which does not need to undergo the complex process of curing. The curing agent used in a preferred embodiment of present invention can be a hydrocolloid such as sodium polyacrylate.

DETAILED DESCRIPTION OF THE INVENTION

It is known in the prior art to combine GGBFS, lime and other harsh alkalis like sodium hydroxide or sodium silicate to form a cementitious binder. In the prior art, a high proportion of lime has been used and a cement prepared using such a binder has low initial strength and a slow setting time. Previously phosphate has been used as retarder for slag cements containing a high amount of calcium sulfate to prevent the flash setting of the cements. The inventors have unexpectedly and surprisingly found that in combining ground granulated blast furnace slag (GGBFS) with lime, nano alkali metal carbonate, a source of alkali metal fluoride, a source of alkali metal phosphate as accelerator and alkali metal sulfate one could obtain a cement having comparable characteristics with Portland cement. The inventors have now determined that concretes with improved durability can be prepared using a cementitious binder comprising a high proportion of GGBFS and/or PFA and a low proportion of combination of CaO, or lime, alkali metal phosphate, alkali metal fluoride, nano calcium carbonate, and alkali metal sulfate as described herein. Preferably, ground granulated blast furnace slag can be used in an amount ranging from 80 to

90% by weight in the cement composition. Preferably, the alkali metal oxide is present in an amount ranging from 0.1 to 10 %. Preferably, the alkali metal oxide is lime. According to a preferred embodiment, the nano alkali metal carbonate is nano calcium carbonate and is present in an amount ranging from 0.1 to 10%. Preferably, alkali metal fluoride such as sodium fluoride is present in an amount ranging from 0.1 to 5%. Preferably, acid phosphate is present in an amount ranging from 0.1 to 5%. Preferably, alkali metal phosphate such as sodium hexa meta phosphate is present in an amount ranging from 0.1 to 10%. Preferably, alkali metal sulfate such as sodium sulfate is present in an amount ranging from 0.1 to 10%. Preferably, hydroco!loids are present in an amount ranging from 0. 1 to 0.5%. Preferred hydrocolloids are selected from the group consisting of poly acrylates, alginates, starch, and polyacronitrile. Most preferred is sodium polyacrylate.

Example 1

Concrete containing cement according to an embodiment of the present invention was made having the following components:

Slag - 864 g

Lime - 50 g

SHMP - 50g

Sodium Sulfate - 30 g

Sodium Fluoride - 5 g

Sodium Polyacrylate - 1 g

Sand - 2000 g

Aggregates - 2875 g

Water - 500 ml

All the powder components were mixed first and water is added and mixed in a mixer. Then sand and aggregates were added and the resulting mixture was mixed for another 10 minutes.

For the compressive strength testing, 100 mm concrete cubes were cast using the above mix for testing of compressive strength. The compressive strength was tested at 1 , 3, 7 and 28 days. The results are provided in the respective tables below.

Table 1 - Testing data of the compressive strength of the concrete made in Example 1

Example 2

Slag - 864 g

Lime - 50 g

SHMP - 30g

Sodium Sulfate - 30 g

Sodium Fluoride - 5 g

Sodium Poly acrylate - 1 g

Nano Calcium Carbonate - 20 g

Sand - 2000 g

Aggregates - 2875 g

Water - 500 ml Table 2 - Testing data of the compressive strength of the concrete made in Example 2

Example 3

Slag - 874 g

Lime - 50 g

SHMP - 20g

Sodium Sulfate - 30 g

Sodium Fluoride - 5 g

Sodium Poly acrylate - 1 g

Nano Calcium Carbonate - 20 g

Sand - 2000 g

Aggregates - 2875 g

Water - 500 ml

Table 3 - Testing data of the compressive strength of the concrete made in Example 3

Examples 4 through 11

Preparation of concrete made with cement according to examples 4 to 1 1 was made as follows. All the powder components (referring to Table 4 for components and quantities) were mixed first in the above mentioned ratio and the cement was made. Concrete was then made using the ratio of 1 : 2 : 2.87 for Cement : Sand : Aggregate.

The water ement ratio was maintained as 0.5 in each example.

All the components cement, sand, aggregate and water were mixed for about 10 minutes and 100 mm cubes were casted. All of the cube samples were water cured except for the composition of Example 6 where an internal curing agent, sodium polyacrylate, was added to the mixture.

Table 4 - Effect of Various additives on Compressive strength of Slag Cement

SHMP- Sodium hexa meta phosphate

LP- Lime Powder (CaO)

SS- Sodium Sulfate

SF - Sodium Fluoride

PS - Potasium Silicate

NCC - Nano Calcium Carbonate

SPA- Sodium Poly acrylate

Observations

By looking at examples 10 and 1 1 , a net hardening reaction was observed which was caused by the reaction of lime and sodium hexa meta phosphate.

By referring to examples 7 and 10, one notices that the addition of sodium sulphate has an impact in increasing the strength across all test points ( 1 day, 3 days, 7 days and 28 days).

By comparing examples 4 and 5, one can establish the positive impact of the addition of nano calcium carbonate in the increase of the concrete strength across all test points. Example 6 provides an indication that the addition of 0.1 % of hydrocolloids allows to make a cement which does not require curing.

Examples 8 and 9 illustrate that the addition of potassium silicate alone or in the presence of a phosphate additive such as SHMP decreases the strength of the cured composition.

Concrete made with pozzolona portland cement undergoing the same test have compression data as follows: 1 day : 8.1 Mpa; 3 days : 14.6 Mpa; 7 days : 21.1 Mpa; and 28 days : 31.6 Mpa.

The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations unless otherwise specifically indicated. Those skilled in the art will recognize that many variations are possible within the scope of the invention as defined in the following claims, and their equivalents, in which all terms are to be understood in their broadest possible sense unless otherwise specifically indicated. While the examples shown and described in detail herein are capable of attaining the above-described aspects of the invention, the person skilled in the art will understand that these are but preferred embodiments of the present invention and the invention is not to be limited to those embodiments.

Claims

1. A Portland cement-free cementitious binder composition, said composition comprising: ground granulated blast furnace slag and/or pulverized fly ash; an alkali metal oxide; an alkali metal phosphate; an alkali metal fluoride; nano alkali metal carbonate; and an alkali metal sulfate.

2. The cementitious binder composition according to claim 1, wherein the slag is present in an amount ranging from 80 to 90% by weight of the composition.

3. The cementitious binder composition according to claim 1 or 2, wherein the alkali metal oxide is present in the range from 0.1 to 10 %.

4. The cementitious binder composition according to any one of claims 1 to 3, wherein the alkali metal oxide is lime.

5. The cementitious binder composition according to any one of claims 1 to 4, wherein the nano alkali metal is nano calcium carbonate present in an amount ranging from 0.1 to 10%.

6. The cementitious binder composition according to any one of claims 1 to 5, wherein the alkali metal fluoride is present in an amount ranging from 0.1 to 5%.

7. The cementitious binder composition according to any one of claims 1 to 6, wherein the alkali metal fluoride is sodium fluoride.

8. The cementitious binder composition according to any one of claims 1 to 7, wherein the acid phosphate is present in an amount ranging from 0.1 to 5%.

9. The cementitious binder composition according to any one of claims 1 to 8, wherein the alkali metal phosphate is present in an amount ranging from 0.1 to 10%.

10. The cementitious binder composition according to any one of claims 1 to 9, wherein the alkali metal phosphate is sodium hexa meta phosphate.

1 1. The cementitious binder composition according to any one of claims 1 to 10, wherein the alkali metal sulfate is present in an amount ranging from 0.1 to 10%.

12. The cementitious binder composition according to any one of claims 1 to 1 1 , wherein the alkali metal sulfate is sodium sulfate.

13. The cementitious binder composition according to any one of claims 1 to 12, wherein the hydrocolloids are present in an amount ranging from 0.1 to 0.5%.

14. The cementitious binder composition according to any one of claims 1 to 13, wherein the hydrocolloid is selected from the group consisting of: poly acrylates, alginates, starch, and polyacronitrile.

15. The cementitious binder composition according to claim 14, wherein the hydrocolloid is sodium polyacrylate.

16. The cementitious binder composition according to any one of claims 1 to 15, wherein the ground granulated blast furnace slag (GGBFS) has a surface area ranging from between 2500 and 12000 cm²/g.

17. The cementitious binder composition according to any one of claims 1 to 16, wherein the ground granulated blast furnace slag (GGBFS) has a surface area of approximately 4000 cm²/g.

18. A Portland cement-free cementitious binder comprising at least 80 % by weight of a hydraulically-active material comprising ground granulated blast furnace slag (GGBFS) and/or fly ash has a surface area ranging between 2500- 12000 cm /g; at least 0.5 % by weight of lime; at least 0.5% by weight of nano calcium carbonate having a particle size of 5- 10 micron meter; at least 0.5% by weight of an alkali metal fluoride; at least 0.5% by weight of an alkali metal sulfate; and at least 0.1% by weight of an acid and/or alkali metal phosphate.

19. The Portland cement-free cementitious binder according to claim 18, further comprising 0.1% by weight of a hydrocolloid as water retention agent.

20. The Portland cement-free cementitious binder according to claim 18 or 19, wherein the ground granulated blast furnace slag (GGBFS) has a surface area of approximately 4000 cm /g.

21. The Portland cement-free cementitious binder according to any one of claims 18 to 20, wherein the alkali metal phosphate is sodium hexa meta phosphate.

22. The Portland cement-free cementitious binder according to any one of claim 18 to 21 , wherein the ground granulated blast furnace slag (GGBFS) is present in an amount ranging from 84.5 % to 86.5% by weight of the total binder.

23. A Portland cement-free cementitious binder composition, said composition comprising: 80% by weight of ground granulated blast furnace slag; 10%) by weight of an alkali metal oxide; and 10% by weight of an alkali metal phosphate.