PH12016000174A1 - An additive and a method for producing a cement composition - Google Patents

Abstract

This invention relates to an additive mixed with calcined Secondary Cementitious Materials (SCM), which when combined with clinker, forms a Portland cement mixture. Mixing the additive with the calcined SCM allows the Portland cement to contain more than 30 pcnt SCM, especially volcanic debris, while maintaining the same or resulting to improved compressive strength, flowability and setting time. This invention also relates to the method and device for producing a Portland cement which contains said additive and a significant proportion of SCM.

Description

Type 15: Portland blast-furnace slag cement

Type 1P: Portland-Pozzolan cement

Type (PM): Pozzolan-Modified Portland cement

Type S: Slag cement

Type 1(SM) Slag-modified Portland cement

Types 1S, 1P, 1(PM), and 1(SM) are general purpose cements that are further divided into sub-categories.

Pozzolan Modified Portland Cement, or Type 1(PM), is used in general construction. This type of cement is manufactured by combining

Portland cement or Portland blast-furnace slag cement and a fine pozzolan. This may be accomplished by either: (1) blending Portland cement with a pozzolan; or (2) blending Portland blast-furnace slag cement with a pozzolan; or (3) inter-grinding Portland cement clinker and a pozzolan; or (4) a combination of intergrinding and blending. The pozzolan content is less than 15% by mass of the finished cement.

Current practice may permit up to a 40 percent reduction of

Portland cement used in the concrete mix when replaced with a carefully designed combination of pozzolanic materials. Pozzolans can be used to control setting, increase durability, reduce cost and reduce pollution without significantly reducing the final compressive strength or other performance characteristics. The properties of hardened blended cements are strongly related to the development of the binder microstructure, ie. to the distribution, type, shape and dimensions of both reaction products and pores. The beneficial effects of pozzolan addition in terms of higher compressive strength performance and greater durability are mostly attributed to the pozzolanic reactionin which calcium hydroxide is consumed to produce additional C-S-H and C-A-H reaction products.

These pozzolanic reaction products fill in pores and result in a refining of thepore size distributionor pore structure. This results in a lowered permeability of the binder.

The contribution of the pozzolanic reaction to cement strength is usually developed at later curing stages, depending on the pozzolanic activity. In the large majority of blended cements, initial lower strengths can be observed compared to the parent Portland cement. However, especially in the case of pozzolans finer than the Portland cement, the decrease in early strength is usually less than what can be expected based on the dilution factor. This can be explained by the filler effect, in which small SCM grains fill in the space between the cement particles, resulting in a much denser binder. The acceleration of the Portland cement hydration reactions can also partially accommodate the loss of early strength.

The increased chemical resistance to the ingress and harmful action of aggressive solutions constitutes one of the main advantages of pozzolan blended cements. The improved durability of the pozzolan-blended binders enables to lengthen the service life of structures and reduces the costly and inconvenient need to replace damaged constructions. One of the principal reasons for increased durability is the lowered calcium hydroxide content available to take part in deleterious expansive reactions induced by e.g sulfate attack. Furthermore, the reduced binder permeability slows down the ingress of harmful ions such as chlorine or carbonate. The pozzolanic reaction can also reduce the risk of expansive alkali-silica reactions between the cement and aggregates by changing the binder pore solution. Lowering the solution alkalinity and increasing alumina concentrations strongly decreases or inhibits the dissolution of the aggregate aluminosilicates.

Cement additives or cement binder compositions used to increase pozzolanic activity are known.

PCT/jP2011/061868 discloses a cement composition that improves the fluidity of cement paste, mortar and concrete even in the case where comparatively large amounts of waste, such as coal, ash or soil generated by construction work, are used and the contents of Al and C3A in the cement clinker have increased.

PCT/US20101035560 shows a manufactured cementitious binder including a hydraulic binder in the range of about 40 to 75% by weight of the cementitious binder; metakaolin in an amount greater than 5% by weight of the cementitious binder; silica fume in an amount up to about 15% by weight of the cementitious binder; and cement kiln dust in an amount greater than about 10% by weight of the cementitious binder, the cement kiln dust including chlorine in an amount of at least 0.1 % by weight of the cement kiln dust, the cementitious binder providing a cementitious settable composition, when added with water and without a lightweight additive, that has a density lower than about 13 pounds per gallon and greater than about 11 pounds per gallon and a 24 hour compressive strength at 100F, as hardened, of at least 500psi. Said binder is used in a variety of applications including, subterranean applications such as drilling operations using casings and liners cemented in well bores for oil, gas, geothermal well bores, and the like.

PCT/JP2006/320449 discloses a cement additive that contains industrial waste, specifically calcium carbonate, gypsum and coal ash and/or blast-furnace slag powder, and has the effect of inhibiting formation of monosulfate in a hardened cementitious material having good durability (sulfate resistance).

PCT/GB2009/001610 demonstrates a cement binder composition based on MgO (at least one magnesium carbonate, either hydrated or . unhydrated, that absorbs CO2 when hardening. The MgO when mixed with water in the presence of the magnesium carbonate produces magnesium hydroxide that has a rosette-like morphology.

PCT/IB2009/005415 discloses a belite-calcium sulphoaluminate- ferrite (BCSAF) clinker or cement composition, which provides an increased 28-day and/or 90-day compressive strength in the mortar and concrete containing the same.

PCT/US2008/078640 presents a hydrothermally-cured cementitious formulation, which includes at least one calcium source, a reactant and a filler in a hydrated environment, wherein the reactant, in one form, is crystalline silica that has been modified for reactivity. Said reactant is a pozzolan comprising less than 25% weight, and the calcium source non-

reactive filler is in an amount of between about 20 wt.% to 80 wt. % of the dry formulation, has a particle size of less than 50 microns and a density of between about 90 to 130 kg/m3.

Portland cement is produced by grinding clinker consisting essentially of hydraulic calcium silicates along with some calcium aluminates and calcium aluminoferrites, and usually containing gypsum as an addition. No Portland cement manufacturing plants are alike. Every plant has significant differences in layout, equipment, or general appearance.

However, production of Portland cement using a primary kiln usually follows the following steps:

Step 1: Selected raw materials are crushed, milled, and proportioned in such a way that the resulting mixture has the desired chemical composition.

For example, 750 g limestone, 150 g silica, 50 g aluminate and 50 g iron are ground and mixed.

Step 2: After blending, the ground raw material is fed into a rotary kiln. The raw mix passes through the kiln at a rate controlled by the slope and rotational speed of the kiln. Burning fuel is forced into the lower (discharge) end of the kiln where temperatures of about 1450 °C (2640 °F) change the raw material chemically into cement clinker, which are grayish-black pellets, predominantly in the size of 13-mm (1/2-in.)- diameter nodules.

Step 3: The clinker is cooled rapidly.

Step 4: A small amount of gypsum (approximately 5%) is added to regulate the setting time of the cement.

Step 5: The clinker is ground so that most of it passes through a No. 325 mesh (45 micron) sieve.

Heating or calcination of clinkers and the related problems in controlling the temperature, as well as the environmental cost thereof are well-known, and the subject of the following inventions:

PCT/IB2006/002193 discloses a method and a device for the preheating of cement raw meal for the production of cement-clinker, in which the cement raw meal is conveyed towards the feed side of a cement clinker kiln in at least one heat exchanger-line in counter flow to hot gases.

The purpose of said method and device is to increase the output or production, while avoiding higher energy consumption.

PCT/IB2006/002194 shows a method for utilizing alternative fuels in the production of clinker or cement. Temperatures of about 20000C have to be achieved by burners employed for the heating of the rotary kiln in the production of clinker. This is only achieved by using high value fuels such as gaseous or liquid fuels, or coal dust burners. On the other hand,

the calcining is effected at substantially lower temperatures as compared to the clinker temperatures and, as a rule, is completely feasible at temperatures of about 850°C. Use of inferior alternative fuels is desired at this comparatively low temperature level, but complete combustion of lumpy alternative fuels is not ensured. This invention allows the complete combustion of alternative fuels in the production of clinker or cement.

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

The incompatibility of the pozzolan replacement materials with cement additive can result to significant reduction in flowability, strength and the initial and final setting of the concrete. Despite the cost and performance advantages of fly ash, slag, calcined clay, and natural pozzolans as additions to cement, there are practical limitations to the amount at which they can be used in the cementitious mixture. Using these materials at about 30 to 40 weight percent based on the weight of the

Portland cement, can result in the retarded setting time of the concrete up to several hours, or longer, depending upon the ambient temperature.

Solution to the Technical Problem

It is therefore the objective of the present invention to provide an additive for cement which allows more than 30% weight of pozzolan replacement materials or SCM, especially volcanic debris, which will result to a cement composition with an industry-acceptable or improved

IE compressive strength, flowability and setting time. It is likewise the objective of this invention to provide a method of manufacturing cement which contains said additive and a significant proportion of SCM.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be fully understood upon reading the detailed description taken in conjunction with the accompanying drawings wherein: : 10 Figure I is a schematic diagram showing the flow of the materials, specifically the SCM and additive, which are calcined through a rotary dryer, and thereafter mixed with clinker for the grinding process;

Figure Il is a schematic diagram of the drying system;

Figure III is a schematic diagram of the equipment comprising the calcination or drying system;

Figure IV is a figure of the dryer;

Figure V is a vertical cross-section of the dryer; and

Figure V1 is a circular cross-section of the dryer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to SCM and additives for cement.

Clinker is produced by mixing and grinding a specific mixture of raw materials containing Silicon Dioxide, Aluminum Trioxide and other materials. The four principal constituent components of Portland clinker are conventionally abbreviated to:

C3S (tricalcium silicate);

C2S (dicalcium silicate);

C3A (tricalcium aluminate);

C4AF (tetracalcium aluminoferrite)

These requirements are essential building blocks in creating cement products, finding alternative materials that can produce the same results is the key to create greener products using materials that are indigenous to any area.

Using volcanic debris as SCM is preferable as studies show that the silt of pyroclastic materials is pozzolanic. In various experiments conducted, the sample that contained 80% clay and 20% volcanic sand by weight performed very well in compression testing which gave strength of 300 psi. The chemical composition of the silt of volcanic debris, is compatible with the cement additive in improving the flowability, strength and the initial and final setting of cement or concrete even with volcanic debris comprising 30 to 40 weight percent based on the weight of the Portland cement.

Using ASTM C595-12 test specification, a widely produced cement mix with Portland clinker and less than 30 percent of calcium carbonate in a form limestone, resulted an initial setting time 116 min and final setting time of 270 min. and concurrently a 72-hour compressive strength of 2400 psi

A cement mix, wherein the amount of calcium carbonate was replaced by this invention resulted an initial setting time 135 min and final setting time of 210 minutes, with an 82 percent passing through 45 micron sieve, and concurrently a 72-hour compressive strength of 4054 psi.

Based on the foregoing results, this invention can be used as an alternative to commonly used SCM with the same or better results.

In this invention, the SCM is placed in the silo or loading bin (1) as shown in Figure II. Thereafter, the SCM is placed on a conveyor belt (Figure II [2]; see also Figure III [3]) to be fed at the rate of 58-60 tons/hour to a rotary dryer (Figure II [3]; see also Figure III [4]) measuring 3 meters in diameter and 20 meters in length, with maximum rotational speed of 5- 6 rpms. In the rotary dryer are nozzles (Figure V and Figure VI), which are used to spray the SCM with the additive, while the mixture is heated at 800°C to 1000°C for about 18 to 25 minutes. At the end of this calcination or drying process, the dried SCM and additive blend is expected to have a maximum moisture of 3% only. As the dried SCM and additive blend exits the calcination or drying process, it is transferred to a belt conveyor (Figure III [6]) and delivered to a proportioning bin or hopper (Figure 11[4]; see also Figure III[2]).

Thereafter, the dried SCM and additive blend, comprising more than 35% weight percentage of the Portland cement output, is mixed with clinker and gypsum (as shown in Figure I). This mixture is placed on a conveyor belt, which is fed to the grinding system so that most of it passes through a No. 325 mesh (45 micron) sieve. 18 —_—

An Additive and a Method for Producing a Cement Composition Using

Said Additive

FIELD OF THE INVENTION

This invention relates to a calcined additive that allows the substitution of Portland cement with secondary cementitious materials up to more than 30% in volume of proportion, without reducing the standard compressive strength, flowability and setting time for Portland cement, and a process for producing a cement composition using said calcined additive.

BACKGROUND ART

Mixtures of calcined lime and finely ground, reactive aluminosilicate materials were developed as inorganic binders in the ancient world. Use of volcanic materials such as volcanic ashes or tuffs for the same purpose by the ancient Greeks dates back to at least 500-400

BC. The Romans also used as inorganic binders volcanic pumices and tuffs found in neighbouring territories, the most famous ones found in Pozzuoli (Naples), hence the name “pozzolan.” The invention of other hydraulic lime cements and eventually Portland cement in the 18th and 19th century resulted in a gradual decline of the use of pozzolan-lime binders, which develop strength less rapidly. Over the course of the 20th century, the. use of pozzolans as additions or "Supplementary

Cementitious Material” (“SCM”) to Portland cement concrete mixtures has become common practice.

Both natural and artificial (man-made) materials show pozzolanic activity and are used as SCM. Artificial pozzolans can be produced deliberately, for instance by 1 thermal activation of kaolin-clays to obtain metakaolin, or can be obtained as waste or by-products from high- temperature process such as fly ashes from coal-fired electricity production. The most commonly used pozzolans today are industrial by- products such as fly ash, silica fume from silicon smelting, highly reactive metakaolin, and burned organic matter residues rich in silica.

Economic, technical and environmental concerns have made the so- called blended cements, i.e. cements that contain considerable amounts of

SCM (mostly around 20 weight percentage, but over 80 weight percentage in Portland blast-furnace slag cement) the most widely produced and used cement type by the beginning of the 21st century. The use of SCM in cement and concrete addresses these economic, technical and environmental concerns. Thus, the primary benefit of using SCM is the economic gain obtained by replacing a substantial part of the Portland cement by cheaper, pollution-free, natural pozzolans or industrial by- products. Secondly, the use of blended cement lowers the environmental cost associated with the greenhouse gases emitted during Portland cement production. A third advantage is the increased durability of the end product.

Portland cement is the most common type of cement in general use at this time. It is an essential element of concrete, mortar and non-specialty grouts. Portland cement consists of over 90% Portland cement clinker, “p to 5% gypsum and up to 5% other minor constituents. Portland cement clinker is a hydraulic material consisting mainly of dicalcium silicate (2Ca0,5i02), tricalcium silicate (3Ca0,Si0z2) , tricalcium aluminate (3Ca0,Al205) and calcium aluminoferrite (4CaO,Al:0sFe:0s) phases.

Gypsum (CaSOs2H:0) is added to Portland cement clinker to control its setting time, and the mixture is ground to give a fine powder. On reaction with water, the constituents of the cement hydrate forming a solid complex calcium silicate hydrate gel and other phases, as described in

PCT/GB2009/001610.

As further described in PCT/GB2009/001610, the manufacture of

Portland cement is 2 highly energy intensive process that involves heating high volumes of raw materials to around 1450°C. In addition to the COs generated from burning fossil fuels to reach these temperatures, the basic raw material used in making Portland cement is calcium carbonate (limestone, CaC0s), and this decomposes during processing to CaO, releasing additional geologically sequestered CO... As a result, the manufacture of Portland cement emits approximately one ton of CO: for every ton of cement produced, and is responsible for approximately 5% of all CO2 emissions.

Typical constituents of the Portland cement and Portland clinker with gypsum, using the Cement Chemists Notation (CCN) are shown below:

Cement CCN Mass %

Calcium oxide. CaO C 61-67%

Siicon dioxide. SiO, S 19-23%

Aluminum oxide. Al,O3 A | 2.5-6%

Ferric oxide, Fe,03 F | 0-6%

Sulfate 5 1.5-4.5%

Clinker CCN Mass %

Tricalcium silicate (CaO); - SiO; CsS 45-75%

Dicalcium silicate (CaO), - Si0, CS 7-32%

Tricalcium aluminate (CaQ)s - Al,O CA 0-13%

Tetracalcium aluminoferrite (CaO), -AlbOj Fe,0s CAF 0-18%

Gypsum CaSO, - 2 HO | | oo 2-10%

Different standards are used for the classification of Portland cement. The two major standards are the ASTM C150 used primarily in the United States of America and European EN 197. EN 197 cement types

CEM [, II, III, IV, and V do not correspond to the similarly named cement types in ASTM C150.

The five types of Portland cements under the ASTM C150 are as follows: }

Type 1, which is known as common or general-purpose cement, is commonly used for general construction especially when making precast and precast-prestressed concrete that is not to be in contact with soils or ground water. The typical compound compositions of this type are: 55%

CsS, 19% CaS, 10% CsA, 7% CAF, 2.8% MgO, 2.9% SOs, 1.0% ignition loss,

and 1.0% free CaO. A limitation on the composition of this type is that the

C3A shall not exceed 15%.

Type II gives off less heat during hydration. Its typical compound composition is: 51% css, 24% CaS, 6% CA, 11% CAF, 2.9% MgO, 2.5%

SOs, 0.8% ignition loss, and 1.0% free CaO. A limitation on the composition of this type is that the C3A shall not exceed 8%, which reduces its vulnerability to sulfates. This type is for general construction exposed to moderate sulfate attack and is meant for use when concrete is in contact with soils and ground water.

Type IIT has relatively high early strength. Its typical compound composition is: 57% C35, 19% CS, 10% CsA, 7% C:AF, 3.0% MgO, 3.1%

SOs, 0.9% Ignition loss, and 1.3% free CaO. This cement is ground finer than Type I. The gypsum level may also be increased a small amount. This gives the concrete using this type of cement a three-day compressive strength equal to the seven-day compressive strength of types I and II. Its seven-day compressive strength is almost equal to 28-day compressive strengths of types I and II. The only downside is that the six-month strength of type III is the same or slightly less than that of types I and II.

Therefore, the long-term strength is sacrificed a little. It is usually used for precast concrete manufacture, where high one-day strength allows fast turnover of molds. It may also be used in emergency construction and repairs and construction of machine bases and gate installations.

Type IV is generally known for its low heat of hydration. Its typical compound composition is: 28% CS, 49% C25, 4% CA, 12% C4AF, 1.8%

MgO, 1.9% SOs, 0.9% ignition loss, and 0.8% free CaO. The percentages of (2S and C.AF are relatively high, and CsS and CsA are relatively low. A limitation on this type is that the maximum percentage of C:A is seven, and the maximum percentage of CsS is thirty-five. This causes the heat given off by the hydration reaction to develop at a slower rate. However, as a consequence the strength of the concrete develops slowly. After one or two years the strength is higher than the other types after full curing. This cement is used for very large concrete structures, such as dams, which have a low surface to volume ratio.

Type Vis used where sulfate resistance is important. Its typical compound composition is: 38% CsS, 43% CaS, 4% (CA, 9% CAF, 1.9%

MgO, 1.8% SOs, 0.9% ignition loss, and 0.8% free CaO. This cement has a very low CsA composition which accounts for its high sulfate resistance.

The maximum content of CsA allowed is 5% for type V Portland cement.

Another limitation is that the CsAF + 2CsA composition cannot exceed 20%.

EN 197-1 defines the five classes of common cement that comprise

Portland cement as a main constituent. These classes are as follows:

EN 197-1:2000

Table 1- The 27 products In the family of common cements me ER

Hotatue of Me 27 products Main conslitueaty £

Man hpas Of Common come Furpelzen Fy ish: Ltresyne’ i Weoax . town Cravr | Baesttionaon | Sabo rout rer {Adal e o om x 3 x e 3 v “ T RN Es } [conn frowns corereJobws Tea | [7 TT TT TT TT Tee] pros opting. Jom Loon 1 Lo LL I Lo LoL ae pom Couns ey [nas [| [Tp es

Pottang-sica ure [CEM IA-0 = - 510 Co . . - . - 08

Seeliwil i. — — —

Poting gozzutana (CENIEAL eeepc 28

Zan Wn CEM WRF 65.7% - . F138 - - - - - a5

CenTag Tew | em oT bee vue [em bee ae crm fpananeop us Jopmuas | aed [1 1 bee [TL TE os

CEM IAM 80-04 - - - . - &. 41 - - . 4s

Cee [a es

Potiamdnmi sha oem ant Javan | FF TT Teal TF es en Ceuunt _[TeSTS [pp ms [es eons Jeowl TT 1 1 1 tem) | os

Foftand-amesiore (CEM WB | este [| I | + TT Tavs | 1 95 1} aon Cova Tson [rT Tem es

CrRnELC ee | TT TT [ae es

A omen” eee eee

CEM 1 |Biavtornave comma Tasaa | oees | T - T 7 7 TTT 1 os aermant ows | ose | eeey | | 1 pT TT es

Cone Jew eves |] [es oem {azo oer Leen | Teas cee LL Tes fe Jove |] sees ne er Lc LL Lee

CEM V [Composite CEM WA 40:54 Fo] . Kecovamnsve JE} mevormer—ir . _ TN as coment” conve [wa] See [7 | emi me [0 J os

On the other hand, Blended cements are used in all aspects of construction in the same manner as Portland cements. They are produced by uniformly inter-grinding or blending two or more types of fine materials. The primary materials usually include Portland cement, ground granulated blast-furnace slag, fly ash, silica fume, calcined clay, other pozzolans, hydrated lime, and pre-blended combinations of these materials. Blended hydraulic cements must conform to the requirements of ASTM C 595, the Specifications for Blended Hydraulic cements, or

ASTM C 618 05, Standard Specification for Coal Fly Ash and Raw or

Calcined Natural Pozzolans for Use as a Mineral Admixture in Concrete.

ASTM C 595 recognizes five primary classes of blended cements as follows:

Claims (6)

WE CLAIM:

1. An additive composed of Calcium Oxide (CaO), Calcium Dioxide (Ca02), Sodium Oxide (Na20), Magnesium Oxide (MgO), Zinc Oxide (ZnO), Titanium Oxide (TiO) and Aluminum Oxide (A203), which is mixed with calcined SCM;

2. An additive mixed with calcined SCM according to Claim 1, which uses thermally heated volcanic debris as the calcined SCM;

3. An additive mixed with calcined SCM according to Claim 1 or Claim 2, which is combined with clinker to form cement;

4. A cement composition according to claim 3, specifically forming Portland cement, and which has more than 35% of the additive mixed with calcined SCM according to Claim 1 or Claim 2;

5. A process for producing a cement composition according to Claim 3, comprising a step of spraying the SCM during its calcination with additive through nozzles in a rotary dryer; and

6. A device for producing a cement mixture according to Claim 5, having a rotary dryer containing at least one nozzle or injection pipe, used for injecting or spraying with chemicals the mixture passing through the dryer while the mixture is heated at a temperature of at least 800°C.