Cements and concretes which contain them

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new cement compositions as well as concretes which utilize these cements.
2. Description of the Prior Art
The cements employed at this present time are hydraulic cements which have a base of hydrated compounds of calcium silicate and aluminates of calcium. Amongst these cements, those poorest in lime are the aluminous cements of the "ciment fondu" type and the superaluminous cements such as SECAR 250, SUPER-SECAR, ALCOA CA-25, ASAHI AC.1, etc.. All of these cements nevertheless still assay more than 20% of CaO. Unfortunately in numerous cases lime is a baneful constituent (lowering of the refractory character, solubility in an acid medium, violent dehydration during a fire, and . . . ). Thus it is desirable to have available cements which are free of these disadvantages.
U. S. Pat. No. 3,802,894 describes hydraulic-setting refractory compositions which comprise by weight
(a) 5-8 parts of at least one aluminous hydraulic cement,
(b) 2.5-4 parts of at least one powdery refractory material selected from clay, kaolin, micronized silica, micronized magnesia, micronized chromite and micronized forsterite,
(c) 0.01 to 0.30 parts of at least one dispersing agent selected from the phosphates of alkali metals, the carbonates of alkali metals, the humates of alkali metals, and
(d) 86-92 parts of at least one refractory aggregate. The constituent (b) must have a particle size less than 50 microns, preferably less than 1 micron. The constituents (a), (b) and (c) constitute a cement or binder for the aggregate (d).
U.S. Pat. No. 3,060,043 describes a refractory composition having improved mechanical strength and resistance to abrasion, which comprises by weight 55-90% of a refractory aggregate (chromium ore, calcined alumina, etc.), 9-40% of a cement having a base of calcium aluminate, and 1 to 5% of volatilized silica of a particle size less than 44 microns, with more than half the silica particles being smaller than 10 microns.
The object of the invention is to provide new cements having remarkable properties, as well as concretes which contain these cements as a binders.
SUMMARY OF THE INVENTION
The cements of the present invention consist of a mixture of (1) 10 to 30% by weight of an alkaline earth mineral substance selected from steelworks slags having a base of calcium mono- or di-aluminate or of calcium silico-aluminates, aluminous cements of calcium mono-aluminate and calcium di-aluminate types silico-aluminous cements, calcium or barium silicate, and alkaline-earth oxides previously calcined at very high temperature from the group comprising magnesia, dolomite, calcium oxide and baryta; (2) 14 to 56% of a constituent having a particle size lying between 100 A and 0.1 micron selected from silica, chromium oxide, zirconia, titanium dioxide and alumina; and (3) 14 to 56% of an inert filler having a particle size lying between 1 and 100 microns, the sum of the constituents (2) and (3) representing from 70 to 90% of the weight of the cement.
The invention likewise involves concrete mixtures which consist by weight of 10 to 30% of a cement in accordance with the invention as a binder, and 70 to 90% of an aggregate.
The invention is based upon the discovery that cements and concretes having exceptional properties can be prepared by incorporating into their compositions two mineral constituents, one in the range of grain size from 1 to 100 microns and the other in the range of grain size from 100A to 0.1 micron, these two constituents being capable of being easily dispersed in water, if necessary with the addition of a dispersing agent, without reacting with the water to form gels or various sols.
It seems in fact that the exceptional properties of the products of the invention result from the fact that the constituent of grain size from 100 A to 0.1 micron acts to fill a considerable portion of the voids existing between the particles of the constituent of grain size from 1 to 100 microns.
At the present time cements are preferred in which the constituent (1) is a steelworks slag of calcium aluminate, an aluminous cement of the types defined or calcined magnesia, and the constituent (2) is vitreous silica or chromium oxide. Likewise preferably the constituent (3) has a particle size between 1 and 10 microns. Likewise preferred are cements consisting of a mixture of 25 to 30% by weight of aluminous cement, 35 to 40% by weight of vitreous silica, and 35 to 40% by weight of inert filler.
The constituent (1) must have been calcined (preferably fused or sintered) at very high temperature in order to be sufficiently inert and to react only progressively with water and in any case solely when the cement or the concrete formed from this cement has been put into position, preferably by vibration. The cement of the present invention may be put into position by vibration after mixing with less than 20% of water, preferably less than 15% of water with respect to the weight of the cement. When an aluminous cement is employed of calcium mono-aluminate or calcium di-aluminate type as constituent (1), aluminous cements may be employed which are available in the trade such as "fused cement", SECAR 250, ALCOA CA.25, ASAHI AC.1. When an aluminous steelworks slag is employed as constituent (1), it may be a recovery slag containing ferruginous or titaniferous impurities. The size of particles in constituent (1) is not very critical. It is, however, preferred to employ a constituent (1) having a particle size not exceeding 100 microns, and better still of not more than 50 microns.
The constituent (2) must have a particle size lying between 100 A and 0.1 micron. This constituent (2) may be vitreous silica such as the vitreous silica obtained as a by-product in certain industrial processes such as in the reduction of zirconium silicate into zirconia or in the production of ferro-silicon (the dust from electric furnaces contains suitable silica). The constituent (2) may also be silica, chromium oxide, titanium oxide or even aluminum oxide obtained by known techniques of precipitation, drying and calcination. These oxides might also be obtained by known techniques of dissociation or hydrolysis of certain metallic compounds (such as halides) in a hot flame, in a plasma or by simple firing in a furnace. Oxides of a particle size less than 0.1 micron are also called colloidal oxides. The method of preparation of the constituent (2) does not in fact appear to be critical. What matters is that this constituent have a particle size within the range from 100 A to 0.1 micron, can be easily dispersed in water (where necessary with the help of a dispersing agent) and does not form with water any gel or sol. Whilst an aluminous cement or a conventional Portland cement is mixed with water contents of 25 to 30%, the cements of the invention are normally mixed with a water content of less than 20%, preferably less than 15%, which after setting enables cements to be obtained which are of high density and low porosity.
The constituent (3) may be any mineral matter insensitive to hydration, capable of being obtained in the natural state or by grinding, with an average grain size of 1 to 100 microns. Preferably an inert filler will be employed with particles of a size from 1 to 10 microns because a coarser (10 to 100 microns) inert filler (3) yields less advantageous results, in particular in the production of concretes (less advantageous mechanical properties and higher water content for working up). Suitable inert fillers are, for example, oxides such as silica, alumina (alternatively calcined), magnesia, zirconia, titanium dioxide, natural minerals such as bauxite (alternatively calcined), quartzite, dolomite, magnesite, chromite, zircon, granite, basalt, or pure quartzitic sands. One may also employ calcined clay or synthetic minerals such as silicon carbide, silicon nitride, silicon oxynitride, etc. In no case must there be employed as filler, clays, bentonites or other earths which can have a colloidal action upon contact with water.
The aggregate of the concretes of the invention may consist of hard and dense rocks (for example, basalts, quartzites, granites, pebbles, etc...), electrically fused or sintered oxides (corundum, for example), premanufactured or synthetic matter (for example, calcined clay, calcined bauxite, etc.), as well as carbonaceous matter (coke, coal, anthracite, for example). The grain size of the aggregate is not very critical and will generally lie within the range normally employed in conventional concretes (less than 30 mm, preferably not more than 10 mm, the majority of the components forming the aggregate being more than 0.2 mm).
The cements and concretes of the invention may be worked up with a proportion of water distinctly less than that necessary with conventional concretes. The reduction in water content for one and the same workability is at least of the order of 25% and may reach in certain cases 50% and over.
The concretes of the invention exhibit high density, an open porosity in the raw state of less than 15%, preferably less than 10%, and a compressive strength in the raw state higher than 400 kg/cm.sup.2, preferably higher than 700 kg/cm.sup.2 and better still higher than 1000 kg/cm.sup.2. After complete dehydration of the cement at a temperature from 800.degree. to 1000.degree. C. (firing), the open porosity of the concretes remains less than 15%, preferably less than 10%, and the compressive strength remains higher than 400 kg/cm.sup.2, preferably higher than 700 kg/cm.sup.2, and better still higher than 1000 kg/cm.sup.2.
The concretes of the invention exhibit in addition after hardening, excellent resistance to fierce heating in the event of fire. Setting of the concretes is rapid. Removal of forms from the concretes obtained is possible after 24 hours. About 80% of complete setting is reached 48 hours after working up.
Apart from the essential constituents indicated above, the cements and concretes of the invention may contain one or more mineral or organic dispersant additives in order to facilitate dispersion of the various constituents and the wetting of them, in a manner in itself known. A very effective dispersant additive is sodium tripolyphosphate in the ratio from 0.01 to 0.05% by weight with respect to the weight of the concrete. The concretes of the invention are useful in both civil engineering and refractory applications, for example, for the achievement of highway surfacings which are resistant to erosion and to frost, containers for radioactive waste, light-weight reinforced concrete structures, prefabricated parts, undersea works and fire-resistant structures.

The following non-restrictive examples are given with a view to illustrating the present invention.
EXAMPLE 1
A cement is prepared in accordance with the invention, which is useful for the preparation of civil engineering concretes, by carefully mixing the following constituents:
______________________________________aluminous slag of aparticle size from 5 to 50 microns 25% by weightvitreous silica of aparticle size from 100 A to 0.1.mu. 38% by weightFontainebleau sand of aparticle size of 5.mu. 37% by weight______________________________________
The chemical compositions according to the fired product of the different constituents are the following in % by weight:
______________________________________ Aluminous Vitreous Fontaine- slag silica bleau sand______________________________________SiO.sub.2 0.10 94.70 98.75Al.sub.2 O.sub.3 57.90 3.65 1.25Fe.sub.2 O.sub.3 0.05 0.15 tracesTiO.sub.2 2.60 traces tracesCaO 35.5 traces 0MgO 1.13 traces 0Na.sub.2 O 0.01 0.15 tracesK.sub.2 O 0.01 0.05 tracesZrO.sub.2 -- 1.30 --SO.sub.3 2.70 -- -- 100.00 100.00 100.00______________________________________
The CaO content in the final cement is 8.87%.
In Examples 3 and 4 this cement will be called "inv.1".
EXAMPLE 2
A cement is prepared in accordance with the invention, which is useful for the preparation of refractory concretes, by carefully mixing the following constituents:
- aluminous cement of a particle size of 5 to 50 microns . . . 28% by weight
- vitreous silica of a particle size from 100 A to 0.1.mu. . . . 36% by weight
- calcined alumina, ground to a particle size of 5.mu. . . . 36% by weight
The chemical composition according to the fired product of the different constituents is the following, in % by weight:
______________________________________ Aluminous Vitreous Calcined cement silica Al.sub.2 O.sub.3______________________________________SiO.sub.2 0.25 94.70 0.05Al.sub.2 O.sub.3 71.50 3.65 99.50Fe.sub.2 O.sub.3 0.06 0.15 tracesTiO.sub.2 traces traces tracesCaO 27.74 traces tracesMgO 0.10 traces 0Na.sub.2 O 0.35 0.15 0.45K.sub.2 O traces 0.05 tracesZrO.sub.2 -- 1.30 -- 100.00 100.00 100.00______________________________________
The CaO content of the final cement is 7.76%.
In Example 5 this cement will be called "INV.2".
EXAMPLE 3
a concrete is prepared in accordance with the invention, which is useful for civil engineering purposes by mixing carefully in the usual fashion the constituents indicated in the table below, which likewise gives by way of comparison the composition of a conventional concrete. The properties of the concretes obtained are likewise indicated.
______________________________________ Conventional Concrete withComposition in % by weight concrete INV.1 cement______________________________________Finely crystalline granite, grainsize 4/2mm 46.5 46.5Granite, ungraded 2mm 18.6 18.6Sand, grain size 0.15/0.05 mm 15 15Portland cement 400 HTS 20 --INV.1 cement -- 20Water, % added with respect tothe composition of dry concrete 9.6 3.5Dispersing agent (sodium -- 0.1tripolyphosphate)PropertiesDensity in the rough, dry 2.21 2.49Open porosity, % 11.1 4.1Compressive strength after 20days, Kg/cm.sup.2 400 1200Content of CaO capable of beinghydrated, % 13 1.73______________________________________
EXAMPLE 4
A concrete is prepared in accordance with the invention, which is useful for civil engineering purposes by mixing carefully in the usual fashion the constituents indicated in the table below, which likewise gives by way of comparison the composition of a conventional concrete. The properties of the concretes obtained are likewise indicated.
______________________________________ Convent- Concrete ional withComposition in % by weight concrete INV.1 cement______________________________________Black corundum, grain size 5/10 mm 23 23Black corundum, grain size 2/4 mm 23 23Black corundum, grain size 0.2/2 mm 20 20Black corundum, grain size 0./0.2 mm 20 20Portland cement 400 HTS 14 --INV.1 cement -- 14'Water, % added with respect tothe compositon of dry concrete 5 2.5PropertiesDensity in the rough, dry 3.10 3.46Open porosity, % 16.80 7.1Compressive strength after 20 days,kg/cm.sup.2 445 1050Content of CaO capable of beinghydrated, % 9.1 1.23______________________________________
EXAMPLE 5
A refractory concrete is prepared in accordance with the invention by mixing carefully in the usual fashion the constituents indicated in the table below, which likewise gives by way of comparison the composition of a conventional concrete. The properties of the concretes obtained are likewise indicated.
______________________________________ Convent- Concrete ional withComposition by weight concrete INV.2 cement______________________________________Calcined bauxite, grain size 4/2 mm 30 30Calcined bauxite, ungraded 2 mm 50 50Calcined bauxite, grain size 0/0.2 mm 10 11SECAR 250 cement 15 --INV.2 cement -- 14Water, % added with respect to thecomposition of dry concrete 12.5 5PropertiesDensity in the rough, dry 2.50 3.00Open porosity % 19 11Compressive strength after 3 days,kg/cm.sup.2 600 1050After firing at 1200.degree. CDensity in the rough 2.35 2.90Open porosity % 24 12Compressive strength, kg/cm.sup.2 300 1100Content of CaO capable of beinghydrated, % 4.15 1.09______________________________________
EXAMPLE VI
A cement is prepared in accordance with the invention, which is useful for the preparation of a concrete, by mixing carefully the following constituents:
- 14% by weight of an aluminous slag ground to a particle size less than 20 microns,
- 43% by weight of a vitreous silica of a particle size from 0.1 micron to 100 A, and
- 43% by weight of calcined alumina of a particle size from 1 to 10 microns.
This cement may be put into a form by vibration with 13 to 15% of water with respect to the weight of the cement. This cement will be called INV.III cement.
The chemical compositions according to the fired product of the different constituents are the following, in % by weight:
______________________________________ Aluminous Vitreous Calcined slag silica alumina______________________________________SiO.sub.2 0.10 94.70 0.05Al.sub.2 O.sub.3 57.90 3.65 99.5Fe.sub.2 O.sub.3 0.05 0.15 tracesTiO.sub.2 2.60 traces tracesCaO 35.5 traces tracesMgO 1.13 traces 0Na.sub.2 O 0.01 0.15 0.45K.sub.2 O 0.01 0.05 tracesZrO.sub.2 -- 1.30 --SO.sub.3 2.70 -- --TOTAL 100.00 100.00 100.00______________________________________
With this cement a concrete is prepared which is of high density, low porosity and good compressive strength by mixing carefully in the usual fashion the constituents indicated below in the proportions by weight as mentioned:
______________________________________23% of black corundum of grain size 5/10 mm,23% of black corundum of grain size 2/5 mm,20% of black corundum of grain size 0.2/2 mm,20% of black corundum of grain size 0.05/0.2 mm,14% of INV.III cement100______________________________________ -Water, % added with respect to the composition of the dry concrete: 2.9.
______________________________________PropertiesDensity in the rough dry state: 3.42Open porosity: 4.2%Compressive strength: 1500 kg/cm.sup.2 after 8 daysAfter firing at 800.degree. C:Apparent density: 3.40Open porosity: 5.6%Compressive strength: 1400 kg/cm.sup.2After firing at 1200.degree. C:Apparent density: 3.40Open porosity: 5.4%Compressive strength: 1450 kg/cm.sup.2______________________________________
EXAMPLE VII
A cement is prepared in accordance with the invention, which is useful for the preparation of a concrete, by mixing carefully the following constituents:
- 28% by weight of MgO calcined at 1650.degree. C., of a grain size less than 50 microns,
- 36% by weight of a vitreous silica of a particle size from 0.1 micron to 100 A,
- 36% by weight of a calcined alumina of a particle size from 1 to 10 microns.
This cement may be put into a form by vibration with 13 to 15% of water with respect to the dry weight of cement. This cement will be called INV.IV cement.
The chemical compositions according to the fired product of the different constituents are the following, in % by weight:
______________________________________ Calcined Calcined MgO Vitreous silica alumina______________________________________SiO.sub.2 1.80 94.70 0.5Al.sub.2 O.sub.3 0.40 3.65 99.50Fe.sub.2 O.sub.3 0.70 0.15 tracesTiO.sub.2 0.05 traces tracesCaO 1.25 traces tracesMgO 95.60 traces 0Na.sub.2 O 0.07 0.15 0.45K.sub.2 O 0.03 0.05 tracesZrO.sub.2 -- 1.30 --Total 100.00 100.00 100.00______________________________________
With this cement a concrete is prepared which is of high density, low porosity and good compressive strength by mixing carefully in the usual fashion the constituents indicated below in the proportions by weight as mentioned:
______________________________________23% of black corundum of grain size 5/10 mm,23% of black corundum of grain size 2/5 mm,20% of black corundum of grain size 0.2/2 mm,20% of black corundum of grain size 0.05/0.2 mm,14% of INV.IV cement100______________________________________ -Water, % added with respect to the composition of the dry concrete: 3.1.
______________________________________PropertiesDensity in the rough, dry: 3.35Open porosity: 8.80%Compressive strength: 770 kg/cm.sup.2 after 8 daysAfter firing at 800.degree. CApparent density: 3.35Open porosity: 10%Compressive strength: 700 kg/cm.sup.2.After firing at 1200.degree. CApparent density: 3.35Open porosity: 9.5%Compressive strength: 900 kg/cm.sup.2______________________________________
EXAMPLE VIII
A cement is prepared in accordance with the invention, which is useful for the preparation of a concrete, by mixing carefully the following constituents:
- 24% by weight of an aluminous cement of a particle size from 5 to 50 microns,
- 47% by weight of chromium oxide of a particle size from 500 A to 2500 A,
- 29% by weight of calcined alumina ground to a particle size from 1 to 10 microns.
This cement may put into a form by vibration with 11 to 14% of water with respect to the weight of cement.
This cement will be called INV.V cement.
The chemical compositions according to the fired product of the different constituents are the following, in % by weight
______________________________________ Aluminous Chromium Calcined cement oxide alumina______________________________________SiO.sub.2 0.25 0.22 0.05Al.sub.2 O.sub.3 71.50 0.18 99.5Cr.sub.2 O.sub.3 0 98.90 0Fe.sub.2 O.sub.3 0.06 0.30 tracesTiO.sub.2 traces 0.10 tracesCaO 27.74 0.14 tracesMgO 0.10 0.16 0Na.sub.2 O 0.35 traces 0.45K.sub.2 O traces traces tracesTotal 100.00 100.00 100.00______________________________________
With this cement a concrete is prepared which is of high density, low porosity and good cold compressive strength by mixing carefully in the usual fashion the constituents indicated in the table below in the proportions by weight indicated:
______________________________________23% of black corundum of grain size 5/10 mm,23% of black corundum of grain size 2/5 mm,20% of black corundum of grain size 0.2/2 mm,15% of black corundum of grain size 0.05/0.2 mm,19% of INV.V cement100______________________________________ - Water % added with respect to the composition of the dry concrete: 3.3.
______________________________________PropertiesDensity in the rough, dry: 3.55Open porosity: 6%Compressive strength: 800 kg/cm.sup.2After firing at 800.degree. CApparent density: 3.53Open porosity: 6.9%Compressive strength: 750 kg/cm.sup.2After firing at 1200.degree. CApparent density: 3.49Open porosity: 11.0%Compressive strength: 1050 kg/cm.sup.2______________________________________
EXAMPLE IX
A concrete is prepared in accordance with the invention, having the following composition by weight:
______________________________________23% of black corundum of grain size 5/10 mm23% of black corundum of grain size 2/5 mm20% of black corundum of grain size 2/0.2 mm aggre-20% of black corundum of grain size 0.2/0.01 mm gate 6% of calcined Al.sub.2 O.sub.3 of a particle size from 5 to 20 microns 6% of vitreous silica of a particle size binder from 100 A to 0.1 micron cement 2% of Portland cement100______________________________________
The chemical analysis of the constituents is the following:
______________________________________Black Calcined Vitreous Portlandcorundum Al.sub.2 O.sub.3 silica cement______________________________________SiO.sub.2 0.50 0.05 94.70 22.0Al.sub.2 O.sub.3 6.5 99.5 3.65 4.5Fe.sub.2 O.sub.3 0.1 traces 0.15 1.5TiO.sub.2 2.7 traces traces 0.2CaO traces traces traces 70.8MgO 0.2 traces traces 0.8Na.sub.2 O traces 0.45 0.15 0.1K.sub.2 O traces traces 0.05 0.1ZrO.sub.2 -- -- 1.30 --Total 100.00 100.00 100.00 100.00______________________________________
The composition so defined may be put into a form by vibration with 3.8% of water.
After setting for 15 days and stoving at 110.degree. C, the following properties were obtained:
______________________________________Properties:Apparent density: 3.31Open porosity: 9.3%Compressive strength: 510 kg/cm.sup.2After firing at 800.degree. C:Apparent density: 3.28Open porosity: 12.6%Compressive strength: 695 kg/cm.sup.2After firing at 1200.degree. C:Apparent density: 3.27Open porosity: 13.1%Compressive strength: 740 kg/cm.sup.2______________________________________
By way of comparison, if the vitreous silica as defined is replaced by a micronized silica of a particle size from 1 micron to 10 microns, the amount of water necessary for putting into a form by vibration is 6%.
After setting for 15 days and stoving at 100.degree. C., the following properties are obtained:
______________________________________Properties:Apparent density: 3.17Open porosity: 16.5%Compressive strength: 80 kg/cm.sup.2After firing at 1200.degree. C:Apparent density: 3.23Open porosity: 15.2%Compressive strength: 260 kg/cm.sup.2______________________________________
The results show well the critical importance of the use of a constituent (2) exhibiting a particle size within the range defined.
EXAMPLE X
A concrete is prepared in accordance with the invention, having the following composition by weight:
______________________________________41% of calcined anthracite of grain size 2/4 mm16% of calcined anthracite, ungraded 2 mm aggregate13% of calcined anthracite of grain size 0.5/ 0.1 mm11% of Fontainebleau sand of a particle size of 5 microns11% of vitreous silica, of a particle size from binder 100 A to 0.1 microns cement 8% of aluminous slag of a particle size from 5 to 50 microns100______________________________________
The characteristics of the calcined anthracite are the following:
______________________________________Carbon content >94%Ash content: 5.1%Apparent density: 1.68Open porosity: 4.42%______________________________________
The chemical analysis of the other constituents is the following:
______________________________________ FontainebleauAluminous slag Vitreous silica sand______________________________________SiO.sub.2 0.10 94.70 98.75Al.sub.2 O.sub.3 57.90 3.65 1.25Fe.sub.2 O.sub.3 0.05 0.15 tracesTiO.sub.2 2.60 traces tracesCaO 35.5 traces 0MgO 1.13 traces 0Na.sub.2 O 0.01 0.15 tracesK.sub.2 O 0.01 0.05 tracesZrO.sub.2 -- 1.30 --SO.sub.3 2.70 -- --Total 100.00 100.00 100.00______________________________________
The composition so defined may be put into a form by vibration with 5.8% of water.
After setting for 8 days and stoving at 110.degree. C., the following properties were obtained:
______________________________________Apparent density: 1.77Open porosity: 7.3%Compressive strength: 620 kg/cm.sup.2Permeability: <0.2 npAfter firing at 800.degree. C:Apparent density: 1.75Open porosity: 9.0%Compressive strength: 650 kg/cm.sup.2Permeability: <0.2 npAfter firing at 1200.degree. C:Apparent density: 1.75Open porosity: 10.5%Compressive strength: 780 kg/cm.sup.2Permeability: >0.2 np______________________________________
It goes without saying that the embodiments described are only examples and that it would be possible to modify them, especially by substitution of equivalent techniques, without thereby departing from the scope of the invention.

Number	Date	Country	Kind
76 22344	Jul 1976	FRX
77 14717	May 1977	FRX

Cements and concretes which contain them

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