CA1131664A - High sulphate slag cement and the method for manufacturing this cement - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A high sulphate slag cement having a Blaine specific surface ratio of 4500 - 5500 cm2/g, consists of water-granulated blast furnace slag (in a quantity 80 - 85%) and which contains the following ingredients in the amounts indicated;
CaO (40 - 50%) Al2O3 (14 - 20%) SiO2 (30 - 35%) MgO (5 -8%) The high sulphate slag cement also contains the following ingredients;
CaSO4 (13 - 17%) Portland cement (1.5 - 2.5%) organic carbonic acid or its alkali metal salts (0.1 - 0.5%) water-soluble highly polymerized compounds (0.03 -0.6%) sodium sulphate (0.6 - 2%) The high sulphate slag cement is manufactured by mixing, crushing and pulverizing the ingredients noted above in the ranges indicated.

Description

~L3~64 TITLE OF THE INVENTION
~Ijgh Sulphate Slag Cement and Method for Manufacturing This Cement ~ACKGROUND OF THE INVENTION
. . . _ It is a matter of common knowledge that water-granulated blast furnace slag has a tendency to harden because of the effects of hydration. Utilizing this property, this type of slag is mixed with Portland cement clinkers and pulverized to make low cost blast furnace slag and steel-making slag cement. However, in such cases, water-granulated slag by itself required relatively long periods of time to harden and does not acquire sufficient strength so that such slag tends to be used as an e~tender for Portland cement and the slag contents of such cements tend to be around 30% or less.
In addition to the type of slag cements referred to above, there is another well-known type of high sulphate slag cement known as Sealithor variety, but it is not possible to make such cement in quantity in Japan since suitable water-granulated blast furnace slag cannot be obtained, coagulation and hardening of such cements require relatively long periods of time and the surfaces of such cements, when hardened tend to develop weak areas so that such cements are, in actual practice, not widely usedO

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DErAILED DESCRIPTIO~' OF THE I~E~TIO.~
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This invention relates to slag cement and its manufacture, or stated more specifically special high sulphate slag cements and methods used in their manufac-ture.
This invention consis~s of a new type of highsulphate blast furnace slag which hardens rapidly and does not develop weak surface areas, and the methods used to make such a type of cement.
High sulphate slag cements known up to the present time, as represented by the Se~lithor variety, not only require water-granulated slags not readily available in Japan but do not begin to coagulate for approximately five hours and the coagulation stage does not end for approximately ten hours. Hardening requires relatiYely long periods of time and hardening of the surface areas - is unsatisfactory with weak areas frequently developing.
The invention which is the subject of this patent application consists of a high sulphate slag cement for practical use. This cement begins to coagulate in 1 - 3 hours~ Coagulation ends after 4 - 6 hours of time have elapsed. Weak surface areas do not develop so that forms with sharp angles can be cast.
The cement which is the subject of this paten~ -applicatio~ is a powdered mixture with a Blaine specificsurface ratio of 4500 - 5500 cm2/g and consisting of water-granulated slag in the amount of 80 - 85% (such slag, containing CaO (40 - 50~)~ A12O3 (14 - 20~), SiO2 (30 : 35%), ~IgO (5 - 8%)) or, preferably 82 - 85%, plus CaSO4 (13 - 17%), Portland cement (1.5 - 2.5%), organic 113~
arboxylic acid or alkali metal salts (0.1 - 0.5%, water-soluble high~r molecular weight compounds (0.03 - O. 6%) and sodium sulphate (O. 6 - 2%) ~
The method of manufacturing this cement consists of pulverizing and mixing blast furnace slag or blast furnace slag to which A1203 and/or CaO have been evenly added, mixed and which has then been reheated so that the slag particles recoalesce and then, which has been regranulatecl using water, in amount of 80 - 85% of the total (preferably 82 - 85%), with addition~l 1~ ingredients such as CaS04 (13 - 17%), Portland cement (1.5 -

2.5%), organic carboxylic acid or alkali metal salts (0.1 -0.5%), water-soluble higher molecular weight compounds (0.03 -0~6%) and sodium sulphate (0~6 ~ 2%) to produce a powdered mixture with a Blaine specific surface ratio of 4500 - 5500 cm2/g.
In the manufacture of the high sulphate slag cement which is the subject of this patent application, the chemical structure of the slag is important. It is necessary to utilize slag which has high basicity and which contains CaO (40 - 50%), A1203 (14 - 20%), SiO2 (30 - 35%) and MgO (5 - 8%). Howe~er, at the 2~ present time, slag which is readily available in Japan typically has such ingredients as CaO (40 - ~3%), A1203 (14 -16%) ~ SiO2 (30 ~ 35%) ~ MgO (5 - 8%), TiO2 (0.5U/o)~ S (1.0%) and FeO (0~2%)~ Thus, as a slag for making the slag cement which is the subject of this patent application, it barely satisfies the lower limit for required basicity. When basicity is low, the time required for hardening increases and strength decreases. Therefore, it is desirable to increase the 28 basicity of such water-granulated blast furnace slag.

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Howe~er, this cannot be accomplished merely by adding A12O3 and CaO and pulverizing them with the slag since this will have a negative effect on hardening time and S t rength.
S ~ather, the manufacturing process which is the subject of this patent utilizes a new method of obtain-ing slag of suitable characteristics, namely adding A12O3 and/or CaO, mixing them with the slag particles, then heating and refusing the particles and regranulating the resulting slag by using water.
When slag of insufficient basicity is to be used to make the slag cement which is the subject of this patent, the use of the process described above, i.e., addition of A12 and/or CaO - mixing - heating to cause recoalescence of the slag particles - regranulation using water becomes a necessary part of the overall manufacturing process. Likewise, if slag of sufficient basicity is available, this portion of the overall p~ocess becomes unnecessary.
The amount of slag used to make the slag cement which is th~ subject of this patent is 80 - 85~ of total weight, preferably 82 - 85%. The ingredient CaSO4, i.e., gypsum, can ~be anhydride plaster of Paris or aqueous.
Lime from anti-pollution devices aimed a~ removing SOx from stack gas can be used. The amowlt of CaS04 used (calculated as anhydride) is 13 - 17%. If CaS04. 2H20 is used, the volume becomes 16 - 22~. The amount of Portland cement used is 1. 5 - 2.5~ 5preferably 2.5%).
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Examples of "organic-6~h4*~ acids or alkali metal salts" would be sodium tartrate, ci~ric acid, ~ ~ 3~
odium citrage, etc. The amount used is 0.1 - 0.5%. These organic carboxylic acids or alkali metal slats works to speed coagulation and hardening.
Examples of "water soluble higher molecular weight compounds" are methyl-cellulose, sodium stearate in the metallic soap category or sodium lauryl benzenesulfonate. The amount used is 0. 03% ~ 0 ~ 6%~ In the case of the metallic soaps and methy-cellulose, the amount used is 0.1 - 0. 6%~ For sodium lauryl benzenesulfonate, the amount is 0. 03 ~ 0~ 06%~ Overuse of sodium lauryl benzenesulfonate has the effect of slowing coagulation and hardening, but raises strength so that the amount used depends on the use of the final product.
Regarding the organic carboxylic acids and their alkali metal salts, and the higher molecular weight compounds mentioned above, one of each can be used or several types of each can be used in combination.
The amount of sodium sulphate used is 0. 6 ~ 2%~
The high sulphate which is the subject of this patent application has a Blaine specific surface ratio of 4500 - 5500 cm2/g is desirable. If the ratio is lower than ~500, the time require~ for hardening rises. In contrast, if the ratio is raised above 5500 3 the costs outweigh the benefits.
As a way of understanding the high sulphate slag cement manufacturing method described above, either water granulated blast furnace slag, or such slag to which A1203 and/or CaO has been added and mi~ed in, then heated so that the particles of slag have recoalesced and then have been 2~ regranulated, should be mixed with gypsum, i~f'~,.,`

~ortland cement, organic carboxylic acid or its alkali metal salts, the stipulated water-soluble higher molecular weight compounds and sodium sulphate, in the proportions stated above and should be pulverized until the specific Blaine specific surface ratio is obtained or, rather the various ingredients, singly or in various combinations should be pulverized in the specified proportions and mixed together to obtain a mixture with the specified Blain specific surface ratio.
The high sulphate slag cement described in this patent application, when compared to the well-known Sealithor cement, is noticeably better for its faster coagulation and hardening. The technical reasons for this are not sufficiently clear at the present time, but the invention has offered the possible explanations below although the invention and its related claims are in no way bound by these possible explanations.
In way of poss~ble explanation, it is thought that when the high sulphate slag cement which is the subject of this patent is mixed with a suitable amount of water, the dissociation of the organic carboxylic acids and alkali metal salts causes, directly or indirectly, the stimulation of a slag dissolving action based on Na20 and K20 The carboxylic acid also works to dissolve the gypsum. This causes the formation of Ca(OH)2 which in turn causes the formation of a highly alkaline solution. The liquidation of the CaO and A1203 contained in the slag and the increased concentration of the CaSO4 in solution cause an increase in the probability of 28 molecular collision in the liquid phase which in turn hastensthe ~ 3~
eaction. This prevents the formation of a silica gel, containing SiO2, which salts out, is dense and will not allow water to penetrate. Rather, a silica gel of rather coarse porous texture is formed which improves the penetration of water and aids the formation of ettringite (3CaO.A1203.CaS04.32H20)and calcium silicate hydrates. As the reaction progresses, the level concentration of the liquid phase CaO.A1203.S04 drops, and the formation of an alumina hydrate ~A1203.3H20) takes place. This hydrate and the Si~2 gel form particles of a crystalline 10 nature on the surace of the slag particles. The ions cause the gel particles to align themselves in a net-like form which fills in the gaps in the ettringite and knit together. This series of reactions are speeded up based on the rapid hydroysis of the solute caused by the catalystic action of the additives, because saturation at the liquid phase ceases. This causes, it is theorized, the more rapid beginning of coagulation and its more rapid completion.
Further, like the additive metallic soaps, methyl-cellulose and the sodium lauryl benzenesulfonate, the higher molecular weight compounds dissolve and form a film on the surface of the hardening cement which cuts off its exposure to the surround~gair~ thus preventing the formation of weak areas in the surace and stimulating the dispersionof the cement particles and causing a camping effect so that the density and strength of the cement are heightened.
As curing takes place, the structures of the hydrates 27 becomes fixed and coalesce, giving the cement stability ~ ~ 3~ 6~ ~
and the ability to resist water. Specific examples will be used below to provide a more specific explanation of the invention. These specific examples are intended for the purposes of explanation only and are intended in no way to limit the generality and validity of the claims as set forth in this patent. In addition, it should be noted that where percentages are referred to in this patent unless otherwise stipulated, they indicate percentage by weight.
Example ~1:
Slag was obtained from Shin-Nihon Seitetsu's Hirohata mill. The composition was CaO (41.8%), A1203 (14~), SiO2(34%), MgO (7%), MnO (0.5~), TiO2 (1.0%), S (l.Q%), FeO (0.2~). This blast furnace slag, with an calcination loss of 0.5% and chemical structure basicity of 1.85, was pulverized to a Blaine specific surface ratio of 5000 cm2/g using a pulverizer (carbon steel stainless alloy rod and ball) belonging to Chuo Kakoki K.K. (Toyo~a-shi, Aichi Pref.). This pulverized slag came to 83% of :-the total by weight. To this was added calcina~ed gypsum (used for stack gas SOx removal) in the amount of 18%
tl3.8% converted to the anhydrous form).
The CaS04.2H20 contained had a purity ratin~ of 96.4 - 97.~%. (This CaS04 solu~ion had an overall chemi-cal composition as follows: CaO (32.3 - 33~), S03 (44.8 -45 5~)~ H20 (20.7 - 20.9~), Fe~03 (0.05 - 0.12%)9 S (0.05 -0.92%), C02 (0.41 - 0.82~, Cl ~0.03 - 0.05%), H2S04 (0.07~), water soluble alkalis (0.07 - 0.23%), MgO ~0.01~), A1203 (0.01~). In addition, ~he following substances were added: Portland cement (2~), citric acid (0.2~

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metallic soap (0.1%), sodium sulphate (0.6%), methyl-cellulose (0.1~). The ingredients were well mixed together and a high sulphate slag cement was then made. Water was added and mixed with ~he cement to obtain a W/C ratio of 25~ which was then poured into a mold. The surrounding air temperatu~e was 10 - 20C and the relative humidity was 78~.
Coagulation be~an in approximately 1.5 hours and ended after a total elapsed time of 4.5 hours.
A film formed on the surface of the concrete form and devitrofication occurred~ The form was removed from the mold 24 hours later. Weak areas in its surfaces could not be detected. The upper surface was milk-white in ap~earance. The bottom surface had a blue-green hue.
The form was placed in water for 27 days and when measured on the 28th day, no signs of swelling or shrinkage were noted. Compression strength ~es~ing produced the follow-in~ ~esults:
Day 3 - 378 kg/cm2 Day 14 - 502 kg/cm2 Example ~2: -Slag of *he type used in Example ~1 (83%), calci-nated gypsum (18%) and Portland cemen~ (2~ were mixed togetheT and then calcium stearate (0.45~), methyl-cellulose (O.1~), sodium tartrate (0.21~), sodium sulphate (0.6~) 25 and potassium citrate ~K3C6H507.H20, 0. 2%) were added and all ingredients were mixed together. Then water (w/c 28%) was added and the resulting cement was mixed and poured into a mold. The surrounding temperature was 10 - 20~ (and relative h~nidity was 78~). Coagula-tion began after 2 hours and ended after 5 hours. A

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film formed on the surface o~ the form and devitrofica-tion occurred. The form was removed from the mold after 24 hours. The bottom surface was green. The upper surface was greenish blue. The form was placed in water for 14 days. The bluish hue deepened and thè surface become shiny. Neither swelling or shrinking in size could be detected and after drying the form by exposure to the surrounding air, no changes in appearance or physical size took place.
Example #3.
To slag (similar to that used above), CaSO4.2H2O
and Portland cement were added calcium stearate (0.3~), methyl-cellulose (0.3~, potassium citrate (0.21%) and sodium sulphate (0.6%). These ingredients were blended together and wate~ was added (w/c 26%) and mixed with the ingredients. Then the cement was poured into a mold.
The temperature was lO - 20C and the humidity was 78%.
Coagulation began one hour and Fifty minutes had elapsed and ended after five hours elapsed time. A film formed on the surface. No bridging wa~er was present and devitro-fication occurred. The form was removed from the mold af~er 24 hours. The surface was milk-whi~e in color, the bottom was spotted blue. No weak areas could be detect-ed in the surface.
25 Example J4.
Slag similar to that used in Example ~l, CaSO~.2H2O
and cement were blended together. To this mixture was added methyl-cellulose ~0. 3%), calcium steara~e (0.2%), c sodium sulphate ~0.7~), potassium citrate ~0. 2%~, and ~ k~ yl ben æe~sLllf~r1 Qt~
f~ 30 sodium b~i~u~ ul~h~te (0.01%). All ingredients were ~ ~ 3~
blended together and then mixed wi~h water (w/c 25~).
The resulting cement was poured into a mold. The surround-ing temperature was 20C, humidity was 7B%. Coagulation began after two hours and forty minutes and ended after five hours and twenty minutes. A film formed on the sur-face of the form and a small amount of bridging water was detected. After 24 hours, the form was removed from the mold. No weak areas were detected on the surface of the form. The corners were sharp and the surface was white, the bottom pale blue. After air-drying, the pale blue color faded, but hardening was good. After air drying for seven days and submergence in water for 28 days, no swelling, shrinking or cracking had occurred and corners remained sharp.
15In addition to the four examples described above, an additional seven samples of similar chemical composi-tion were made and similar results were obtained. For j~ leu~/ benze~s~ o~Qf~
one sample, the amount of sodium ~ was greatly increased and the percen~age of water was also 29 significantly increased. Hardening took longer, but sufficient strength was obtain~d.
To increase the basicity of *he blast furnace slag CaO and Al2O3 used were added to slag o ~he type used in Example #1. The slag particles were heated and recoalesced, then regranulated by using water. In this manner, a slag was obtained that had a chemical composi-tion as follows: CaO (45~01%), A12O3 (18.28~), SiO2 (29.87%~, MgO t6 10%)~ MnO (0.25%), TiO2 C0.4~), S (0.7%), Fe2O3 (0.1%), (ignition loss was not measured) and a 30 basicity of 2.32. This slag (83%) was mixed with Portland ~ ~ 3~

eement ~2~)9 CaSO~.2H2O (19%, calculated as CaSO4, 14.6~), methyl-cellulose (0.15~), calcium stearate 10.2%), sodium sulphate (0.6%), and potassium citrate (0.1~) in a stainless steel drum and pulverized to obtain a Blaine specific surface Tatio of 5000 cm2/g. Then a suitable amount of water was mixed in and the resulting cement was poured into a mold. Hardening took place at 10 - 20C and relative humidity of 78%. When the form was Temoved from the mold 24 hours later, no weak surface areas could be detect-ed. The color was deep blue. After 27 days in water, in the 28th day no swellin~. shrinking or crackin8 could be detected.
strength was measured at 600 kg/cm .

Claims (8)

WHAT IS CLAIMED IS:

1. A high sulphate slag cement with a Blaine specific surface ratio of 4,500 to 5,500 cm2/g consisting of:
a. approximately 80-85% blast furnace water slag by weight which in turn contains 40-50% CaO, 14-20%
Al2O3, 30-35% SiO2, and 5-8% MgO;
b. 13 17% CaSO4 calculated as anhydrite;
c. 1.5-2.5% Portland cement;
d. 0.1-0.5% of at least one compound selected from the group of organic carboxylic acids or acid salts consisting of tartaric acid, sodium tartrate, potassium tartrate, citric acid, sodium citrate, potassium citrate;
e. 0.03-0.6% of at least one water-soluble higher molecular weight compound selected from the group consisting of methyl-cellulose, sodium stearate and sodium lauryl benzenesulfonate; and f. 0.6-2% sodium sulfate.

2. The slag cement of Claim 1, wherein the CaSO4 is gypsum.

3. The slag cement of Claim 1, wherein the CaSO4 is aqueous lime.

4. The slag cement of Claim 1, wherein the CaSO4 is anhydrite.

5. The slag cement of Claim 1, wherein said 0.1-0.5% of at least one compound selected from the group of organic carboxylic acids and acid salts comprises an aggregate amount equalling 0.1-0.5% of two compounds selected from the group of organic carboxylic acids or acid salts consisting of tartaric acid, sodium tartrate, potassium tartrate, citric acid, sodium citrate, potassium citrate.

6. The slag cement of Claim 1, wherein said 0.03-0.6% of at least one water-soluble higher molecular weight compound consists of an aggregate of two water-soluble higher molecular weight compounds selected from the group consisting of methyl-cellulose, sodium stearate and sodium lauryl benzenesulfonate.

7. The slag cement of Claim 1, wherein said slag contains 2-2.5% Portland cement.

8. A method for making the slag cement of Claim 1, comprising the steps of blending and mixing 80-85% water slag which in turn has a composition by weight of CaO (40-50%), Al1O3 (14-20%), SiO2 (30-35%) and MgO (5-8%), together with 13-17% CaSO4, 1.5-2.5% Portland cement and 0.1-0.5% of at least one compound selected from the group consisting of tartaric acid, sodium sulphate, potassium tartrate citric acid, sodium citrate, potassium citrate; together with 0.03-0.6% of at least one compound selected from the group consisting of methylcellulose, potassium stearate, sodium lauryl benzenesulfonate; and together with (0.6-2%) sodium tartrate to form a mixture; and reducing said mixture to powder form.