FERLAZZO NATALE (IT)
FORZATTI PIO (IT)
FERLAZZO NATALE (IT)
| WO2006056205A1 | 2006-06-01 |
| US4476187A | 1984-10-09 | |||
| GB2294259A | 1996-04-24 | |||
| EP0562969A1 | 1993-09-29 |
CLAIMS
1. A process for the preparation of manufactured articles containing cement and clay comprising the steps of: a) impregnating the clay with water and kneading the latter until making it fluid; b) adding cement and flow improving agent to the fluid clay to give a plastic "paste" ; c) extruding the plastic "paste" to give a semifinished product having the desired shape; d) drying the semifinished product for a period of time ranging between 1 and 28 days; characterized in that: e) the dried semifinished product of step d) is calcined at temperatures ranging between 400° C and 1000° C to give the finished manufactured article.
2. The process according to the claim 1, wherein the calcination temperature is in the range between 400° C and 600° C.
3. The process according to the claim 1 or 2, wherein the weight ratio of clay to cement is in the range between 9:1 and 0.5:1, preferably between 9:1 and 2:1. 4. The process according to any claim 1 to 3 comprising, between the step a) and the step b) , a curing step al) of the clay impregnated with water for a period of time ranging between 1 day and 1 month, preferably 1 month. 5. The process according to any claim 1 to 4, wherein said clay has a particle size ranging between 0.1 microns and 200 microns, preferably between 1 and 150 microns.
6. The process according to any claim 1 to 5, wherein said clay comprises 30-70% SiO 2 , 10-40% Al 2 O 3 , 0-5%
TiO 2 , 0.5-10% Fe 2 O 3 , 0-30% CaCO 3 , 0.5-10% MgO, 0.1-5% K 2 O, 0.1-5% Na 2 O.
7. The process according to any claim 1 to 6, wherein the calcium concentration is brought to a value above 1% by means of the addition of a calcium compound such as CaCO 3 and/or calcium hydroxide, Ca(OH) 2 .
8. The process according to any claim 1 to 7, wherein said cement has a particle size distribution ranging between 0.1 microns and 200 microns, preferably between 1 and 100 microns.
9. The process according to any claim 1 to 8, wherein said cement is pozzolanic and/or I 52,5 R Portland cement and/or I 42,5 R Portland cement.
10. The process according to any claim 1 to 9, wherein said cement is Portland cement comprising tricalcium silicate ranging between 40 and 60%, bicalcium silicate between 10 and 20%, tricalcium aluminate . between 0 and 15% tetracalcium aluminoferrite between 5 and 20%, calcium sulphate between 0 and 20%.
11. The process according to any claim 1 to 10, wherein said cement comprises 15-25% SiO 2 , 5-12% Al 2 O 3 , 0.5-5% Fe 2 O 3 , 50-70% CaO, 0.1-3% MgO, 0.2-2% K 2 O and Na 2 O, 0-5% SO 3 . 12. The process according to any claim 1 to 11, wherein said flow improving agent is selected from the group consisting of ligninsulphonate, naphthalene sulphoiiate, and melamine-formaldehyde sulphonate.
13. The process according to any claim 1 to 12 , wherein said flow improving agent concentration is in the range between 0.1% and 15% of the "paste", preferably between 0.5% and 10%, more preferably between 1% and 7%.
14. The process according to any claim 1 to 13 , wherein the amount of water added to the clay in order to make it fluid is in the range between 10% and 50% of the total paste, preferably between 20% and 40%.
15. Manufactured article which can be obtained according to the process of any claim 1 to 14. 16. The manufactured article according to claim 15, having a calcium concentration of more than 1%. 17. The manufactured article according to claim 15 or 16, having a pressure load ranging between 15 and 40 MPas. |
DESCRIPTION
"Preparation of clay/cement-based manufactured articles by- means of extrusion"
In the literature, many compounds based on cement and silico-aluminates such as kaolin, montmorillonite, bentonite, and clay have been used for the extrusion. The blends of cement and kaolin turn out to be poorly plastic, thus being hardly extrudable. The clay blends with a structure of montmorillonite and cement, as reported in the publication in the name of M. Temini in Applied Clay Science 13 (1998) pp. 245-253, do not prove to be suitable to the extrusion, because the extruded manufactured articles tend to scale off on contact with moisture and water. The problem underlying the present invention is to provide a method to extrude blends of clay and cement which allows achieving manufactured articles which keep their shape after the extrusion, do not scale off on contact with water and exhibit good mechanical characteristics following curing and calcination.
Such problem is solved by means of a method as described in the annexed claims .
Upon carrying out the preparation of the clay/cement-based manufactured articles according to the preparative process of the present invention, it has been
surprisingly found that extruded manufactured articles are obtained which keep their shape following the extrusion, do. not scale off upon contact with water and exhibit good mechanical characteristics after curing and calcination. Furthermore, the manufactured articles prepared, extruded and cured according to the present invention turn out to be moisture resistant, at temperatures up to 90° C, without sensibly modifying their physical characteristics such as their shape, and their mechanical characteristics such as pressure load and flexural load strength. Another characteristic of the manufactured articles as being prepared, extruded and cured according to the present invention is their low cost. DETAILED DESCRIPTION OF THE INVENTION
The ground clay is added with water and either used immediately, or left to cure for a period of time ranging between 1 day and one month, preferably for 1 month, and preferably in a closed container and at room temperature. After curing, the clay is loaded in a plug mill and water is added under stirring to make the clay more fluid. In the event a wet clay is used, it is necessary to take into account the water contained therein, to be subtracted in the computation of the total water amount to be used.
The cement and the flow improving agent are added under stirring to the clay, which is made fluid by means of water addition, thus obtaining a slurry which is extruded into the desired shape by means of a special die. The extruded article manufactured is kept in moisture and temperature-controlled conditions for a period of time sufficient to reach the curing, being the setting of the cement partially or wholly completed.
Once the curing in closed containers for a period of time ranging between i and 28 days has been carried out, the manufactured articles are calcined at a temperature ranging between 400° C and 1000° C, preferably between 400° C and 600° C. The manufactured articles thus obtained exhibit good mechanical characteristics with flexural loads ranging between 15 and 40 MPas, they keep their shape, and do not scale off upon contact with water. This is a surprising result, since the calcination is carried out at temperatures lower than the typical calcination temperatures used in the art, which are in the range between 1100° C and 1300° C. Thereby, not only clay/cement-based manufactured articles are obtained which exhibit with good mechanical properties, but products to be used in the building field can be obtained at markedly lower prices compared to the existing materials. Therefore, the manufactured articles of the
invention offer valuable alternatives to the brick which is currently present on the market.
The weight ratio of clay to cement which is employed in the process of the invention is in the range between 9:1 and 0.5:1, preferably between 9 : 1 and 2:1.
The used clay has a particle size distribution ranging between 0.1 microns and 200 microns, preferably between 1 and 150 microns, so as to make the degree of filling of the clay-cement blend high. The clay chemical composition of comprises: 30-70% SiO 2 , 10-40% Al 2 O 3 , 0-5%
TiO 2 , 0.5-10% Fe 2 O 3 , 0-30% CaCO 3 , 0.5-10% MgO, 0.1-5% K 2 O,
0.1-5% Na 2 O.
Using clays with a calcium content ranging between 0 and 5%, the addition of a calcium-containing compound such as calcium carbonate, CaCO 3 and/or calcium hydroxide, Ca(OH) 2 , in order to increase the calcium content, allows achieving a manufactured article provided with higher mechanical strength. The best results have been noticed with clays in which the calcium concentration has been brought to a value above 1% by means of the addition of calcium carbonate and/or calcium oxide.
The concentration of the water added to the clay in order to make it fluid and plastic is in the range between 10% and 50% of the total paste, preferably
between 20% and 40%.
The cements which are used are pozzolanic and/or Portland cements having different inherent characteristics, such as I 52.5 R, 42.5 R and/or Portland cements containing tricalcium silicate ranging between 40 and 60%, bicalcium silicate between 10 and 20%, tricalcium aluminate between 0 and 15%, tetracalcium aluminoferrite between 5 and 20%, calcium sulphate between 0 and 20%. Advantageously, the cement which is employed in the present invention comprises: 15-25% Siθ 2 , 5-12% Al 2 O 3 , 0.5-5% Fe 2 O 3 , 50-70% CaO, 0.1-3% MgO, 0.2-2% K 2 O and Na 2 O, 0-5% SO 3 .
The particle size distribution of the cements is in the range between 0.1 microns and 200 microns, preferably between 1 and 100 microns.
The flow improving agents which are used are selected from the group consisting of: ligninsulphonates , naphthalene sulphonates, melamine-formaldehyde sulphonate, acrylic polycondensates . The concentration of the flow improving agents is in the range between 0.1 and 15% by weight of the total paste, preferably between 0.5% and 10%, more preferably between 1% and 7%.
Without limiting the scope of the present, invention, some examples of the inventive process are set forth herein below.
Example 1
In a Brabender S 300 C mixer provided with Sigma blades with 600 cc capacity, 251.6 grams clay is loaded, having the following composition: 45.55% SiO 2 , 15.75% Ai 2 O 3 , 0.51% TiO 2 , 5.23% Fe 2 O 3 , 21.35% CaCO 3 , 2.90% MgO, 2.33% K 2 O, 1.37% Na 2 O. 73.1 grams water is added under stirring. The paste thus obtained is left to rest for one day in a closed container at room temperature. After this period of time, the paste is loaded in a N 350 Brabender plug mill (a plug mill provided with cam stirrers with 350 cc capacity) and, under stirring, 2.6 grams water is added, then 100.6 grams I 52.5 R Portland cement is added. Again under stirring, after 5 minutes, 21.1 grams Iperflux MS (melamine-formaldehyde sulphonate at 35% active ingredient) by the Axim company is added and stirred for further 5 minutes. The paste thus obtained is extruded my means of the Plasti-Corder - PL 2000" Brabender apparatus provided with loader, worm screw and die suitable to the extrusion of honeycombed manufactured articles. After 4 hours following the extrusion, the extruded manufactured article soaked in water does not disaggregate, but keeps its shape. The extruded manufactured article is cured in a closed container at room temperature for 11 days, then in a Vδtsch climatic test chamber mod. VC 4018 for 4 days at 35° C and 90%
moisture. The calcination is carried out by increasing the temperature from 120° C/h to 450° C and keeping it at 450° C for . twelve hours. The calcined manufactured article underwent mechanical strength measurements. The flexural load of a sample with 4x10x80 mm dimensions (height, width, length) (according to the ASTM - D790 standard) subjected to a stress with an INSTRON-type electromechanical strain instrument (bending on three points) turned out to be 27.7 MPas. Example 2
In a Brabender S 300 C mixer provided with Sigma blades with 600 cc capacity, 278.8 grams clay is loaded having the following composition: 53.16% SiO 2 , 11.01% Al 2 O 3 , 0.55% TiO 2 , 4.57% Fe 2 O 3 , 22.2% CaCO 3 , 1.45% MgO, 1.49% K 2 O, 0.05% Na 2 O. 77.1 grams water is added under stirring. The paste thus obtained is left to rest in a closed container at room temperature. After one-month curing, the paste is put in a N 350 Brabender plug mill (cam kneader with 350 cc capacity) , and 5 grams water is added under stirring, then 91.5 grams I 42.5 R Portland cement is added. Again under stirring, after 6 minutes, 15.4 grams Superflux naphthalenesulphonate by the Axim company at 35% active ingredient is added and stirred for further 6 minutes. The paste thus obtained is extruded by means of the Brabender "data processing Plasti-Corder -
PL 2000" apparatus equipped with loader, worm screw and die suitable to the extrusion of honeycombed manufactured articles. After 5 hours following the extrusion, the extruded manufactured article soaked in water does not disaggregate, but keeps its shape. The extruded manufactured article is cured in a closed container at room temperature for 20 days, then in a Vδtsch climatic test chamber mod. VC 4018 for 4 days at 35° C and 90% moisture. The calcination is carried out by increasing the temperature from 120° C/h to 500° C and kept at 500° C for two hours. The manufactured article after the calcination has been subjected to mechanical strength measurements: the flexural load of a sample with 4x10x80 mm dimensions (height, width, length) (according to the ASTM - D790 standard) , subjected to a stress with an INSTRON-type electromechanical strain instrument (bending on three points) turned out to be 32.5 MPas. Example 3 In the Brabender S 300 C mixer provided with Sigma blades with 600 cc capacity, 264.2 grams clay is loaded, having the following composition: 60.7% SiO 2 , 25.4% Al 2 O 3 , 1.5% TiO 2 , 1.0% Fe 2 O 3 , 0.1% CaO, 0.4% MgO, 2.5% K 2 O, 0.4% Na 2 O. 79.4 grams water is added under stirring. The paste thus obtained is put in a Brabender N 350 plug mill (cam kneader with 350 cc capacity) and 88.1 grams I 52.5 R
Portland cement is added under stirring. Again under stirring, after 5 minutes, 22.2 grams ligninsulphonate by the Axim company at 35% active ingredient is added and stirred for further 5 minutes. The paste thus obtained is extruded by means of the Brabender "data processing Plasti-Corder - PL 2000" apparatus equipped with loader, worm screw and die suitable to the extrusion of honeycombed manufactured articles. After 3 hours following the extrusion, the extruded manufactured article soaked in water does not disaggregate, but keeps its shape. The extruded manufactured article is cured in a closed container at room temperature for 28 days. The calcination is carried out by increasing the temperature from 120° C/h to 550° C, and maintained for two hours. The manufactured article after the calcination period of time underwent mechanical strength measurements . The flexural load of a sample with 4x10x80 mm dimensions (height, width, length) (according to the ASTM - D790 standard) subjected to a stress with an INSTRON-type electromechanical strain instrument (bending on three points) turned out to be 21.4 MPas. Example 4
In the Brabender S 300 C mixer provided with Sigma blades with 600 cc capacity, 200.8 grams clay is loaded, having the following composition: 60.7% SiO 2 , 25.4% Al 2 O 3 ,
1.5% TiO 2 , 1.0% Fe 2 O 3 , 0.1% CaO, 0.4% MgO, 2.5% K 2 O, 0.4% Na 2 O and mixed to 63.4 grams calcium carbonate, CaCO 3 . 79.4 grams water is added under stirring. The paste thus obtained is left to rest for one day in a closed container at room temperature, then it is put in a Brabender N 350 plug mill (cam kneader with 350 cc capacity) and, under stirring, 88.1 grams I 52.5 R Portland cement is added. Again under stirring, after 5 minutes, 21.2 grams Iperflux MS (melamine-formaldehyde sulphonate at 35% active ingredient) by the Axim company is added and stirred for further 5 minutes. The paste thus obtained is extruded by means of the Brabender "data processing Plasti-Corder - PL 2000" apparatus equipped with loader, worm screw and die suitable to the extrusion of honeycombed manufactured articles. After 4 hours following the extrusion, the extruded manufactured article soaked in water does not disaggregate, but keeps its shape. The extruded manufactured article is cured in a closed container at room temperature for 28 days. The calcination is carried out by increasing the temperature from 120° C/h to 500° C and kept for two hours. The manufactured article after the calcinations period of time underwent mechanical strength measurements. The flexural load of a sample with 4x10x80 mm dimensions (height, width, length) (according to the standard ASTM -
D790) subjected to a stress with an INSTRON-type electromechanical strain instrument (bending on three points) turned out to be 33.5 MPas.
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