AU2004277443B2

AU2004277443B2 - Cement sheet product and production method thereof

Info

Publication number: AU2004277443B2
Application number: AU2004277443A
Authority: AU
Inventors: Valdir Aparecido Zampieri; Gael Cadoret; Charlotte Famy; Paul Houang
Original assignee: Saint Gobain Materiaux de Construction SAS
Current assignee: Saint Gobain Materiaux de Construction SAS
Priority date: 2003-10-02
Filing date: 2004-10-01
Publication date: 2010-07-15
Anticipated expiration: 2024-10-01
Also published as: WO2005033043A2; BRPI0414960A; EP1678101A2; BRPI0414960B1; WO2005033043A3; EP1678101B1; AU2004277443A1

Description

- 1 CEMENTITIOUS PRODUCT IN BOARD FORM AND MANUFACTURING PROCESS The present invention relates to the field of the 5 manufacture of products based on cement (generally Portland cement) or other hydraulic binder reinforced with fibers. It relates more particularly to the manufacture of products in sheet or board form, that can be used as building elements, especially as 10 weatherboards, cladding elements or partition elements. These products are usually manufactured using a wet papermaking technique that utilizes the presence of the fibers in the mixture. This technique consists in 15 forming a sheet that can be likened to a paper, by filtration using a fluid aqueous suspension obtained by essentially mixing cement, fibers and water; the sheet, or if necessary a superposition of sheets, then being drained of water by suction and/or pressure. The 20 fibers, generally cellulose fibers, become attached to the filter, forming an additional screen or filter mesh, the mesh cells of which have a size suitable for retaining the particles, even fine particles, of cement or of other binder or additive, together with a 25 considerable amount of water that contributes to the cohesion of the thick layer being formed on the screen. In one particular technique, the filter consists of a drum covered with a filter cloth installed in a tank 30 containing the suspension; since the drum rotates in the tank, the hydrostatic pressure forces some of the water to pass through the cloth, whereas the solids, that is to say especially the cellulose fibers, the cement particles and the particles of other additives, 35 build up on the screen of the drum as a thin layer whose thickness increases with the rotation of the drum. This is known as the Hatschek technique.

- 2 This technique is used to manufacture various types of product, such as roofing panels, weatherboards, cladding elements, etc., these various types of product each having to meet particular requirements. Thus, the roofing 5 products must principally have good mechanical strength properties, whereas the weatherboards, cladding elements or partition elements that are intended to be nailed generally have/slightly lower mechanical strength properties while at the same time having stricter 10 dimensional stability characteristics (shrinkage values) (especially to avoid the appearance of cracks at the nails) The use of an autoclaving step at high temperature (above is 1500C) and high pressure (saturation pressure of the order of a few bar) on products coming from the Hatschek process generally makes it possible to limit the shrinkage characteristics (little longitudinal change with change in moisture content).Although good roofing products, that are 20 less strict in terms of dimensional stability performance levels, can be obtained without using this autoclaving operation, it has not hitherto been possible to obtain good products that can be used as weatherboards or cladding elements or partition elements by the Hatschek 25 technique without carrying out an autoclaving step or without using formulations that are complex, demanding in terms of maintenance, or expensive. It is desired therefore to develop a novel product that 30 can be obtained by the Hatschek process for a lower cost and without autoclaving, this product having satisfactory mechanical properties and/or dimensional stability performance levels, particularly those that are appropriate for its use as weatherboard, cladding element 35 or partition element. Also described herein is a product, being in particular in 2303O56_ (GHMatters) - 3 the form of a board, able to be obtained by the Hatschek process and without autoclaving, and being able to be used as weatherboard, cladding element or partition element, said product comprising at least one hydraulic binder, 5 such as cement, at least one filler, such as calcium carbonate, and at least synthetic fibers, such as polyvinyl alcohol or polyolef in fibers. Preferably, such a product comprises at least cement with contents between 18% and 55%, at least calcium carbonate with contents 10 between 30% and 70%, and at least synthetic fibres, such as polyvinyl alcohol or polyolefin fibres. The term "synthetic fibers", as opposed to natural fibers such as cellulose fibers, is understood to mean fibers 15 obtained by synthesis (involving a man-controlled chemical reaction), especially organic fibers, in particular those coming from petroleum derivatives, these fibers generally being meltable and being formed from at least one polymer, particularly a thermoplastic polymer, such as a polyvinyl 20 alcohol or a polyolefin. Preferably, these fibers are polyvinyl alcohol (PVA) fibers or advantageously polypropylene (PP) fibers or possibly polyethylene (PE) fibers. 25 The product according to the invention is able to be obtained by the Hatschek process, that is to say from a sheet material obtained in particular by filtration, on a screen or filter, of an aqueous suspension (this suspension comprising, in the present invention, the 30 constituents defined above, that is to say at least one hydraulic binder, one filler and synthetic fibers as defined above) , thicknesses of said sheet material thus obtained being, where appropriate, superposed until the desired final thickness is obtained, in order to obtain a 35 board. The board may furthermore be drained of water by suction and/or pressed (especially in order to adjust the density and/or to print a decorative pattern), for example 2303856_1 (GHMa1ters) by a size roll (on which are generally superposed the sheets of material brought by the felt and wound onto this roll) or a static mechanical press, and/or undergo a curing step, generally in an oven at low temperature (for 5 example around 600C) and/or in the open air. The product according to the invention advantageously has the desired properties without requiring the use of an autoclaving step. 10 The product according to the invention, obtained in this way generally in the form of a board resulting from one or more sheets formed by filtration of an aqueous suspension according to the above description, is therefore formed from a fiber-reinforced cementitious matrix, this matrix 15 including the constituents mentioned in the definition of the invention, this matrix or this product optionally being able to be provided with other elements, particularly those attached to the board obtained according to the above process, such as decorations (coat 20 of paint, printing, etc.), fittings, etc. In accordance with the definition of the invention, the product according to the invention comprises at least one hydraulic binder, such as cement; this is in general 25 Portland cement. The content of said binder or cement in the suspension used to obtain the product as explained above is preferably between 18 and 45%, by weight relative to the total weight of dry matter (hereafter, the weight contents or values in the suspension being always given by 30 weight of dry matter relative to the total weight of dry matter) The product according to the invention also includes at least one filler, advantageously an inert or weakly 35 reactive mineral filler, such as calcium carbonate. Preferably, this filler is present in amounts ranging between 18 and 70% by weight in the suspension. 230385_1 (GHMatters) - 5 The product according to the invention also includes synthetic fibers, such as those mentioned above. Advantageously, these fibers are present in an amount of between 2 and 10% by weight in the suspension and may be 5 in a relatively dispersed or bonded form. Preferably, these fibers are chosen so as to have a diameter of 5-16 m (generally 10-15 m) and are short fibers (having a length of less than a few centimetres) , and in particular are chosen so as to have a length from 3 to 15 mm (for 10 example from 3 to 8 mm or even 4 to 7 mm, in the case of PVA fibers, and from 5 to 15 mm, or even 6 to 12 mm in the case of PP fibers) . Also preferably, these fibers are chosen so as to have a tensile strength (or tenacity) of at least 400 MPa (in particular, at least 500 MPa in the 15 case of PP fibers and at least 800 MPa, or even 900 MPa, in the case of PVA fibers), a Young's modulus of at least 4 GPa (in particular, at least 6 GPa in the case of PP fibers and at least 20 GPa in the case of PVA fibers) and an elongation of between 6 and 40% (in particular, between 20 6 and 12% or even between 7 and 11%, in the case of PVA fibers and between 15 and 25%, or even between 17 and 20%, in the case of PP fibers), these values being measured according to the DIN 53816 standard. 25 In general, the product according to the invention also includes, in combination with the abovementioned fibers, at least plant-based fibers, especially cellulose fibers, in particular bleached Or unbleached fibers, preferably refined to an SR (Schopper-Riegler) number of about 40 to 30 70, or even 55 to 65, particularly fibers from pine, but also from sisal or other plants, the total fiber content (including the synthetic fibers and the optional cellulose fibers) not exceeding 10% by weight in the suspension. 35 Part of the cement may also be replaced with at least one reactive material capable of reacting with the cement, especially with the formation of calcium silicate, in 2303856_1 (GHMatters) - 5a particular replaced with at least one 23038561 (GHMatters) - 6 pozzolan or material capable of undergoing a pozzolanic reaction. This pozzolan (or material capable of undergoing a pozzolanic reaction) is preferably chosen from aluminosilicates, calcium aluminosilicates and 5 amorphous silica and is particularly preferably metakaolin, which is a dehydroxylated form of aluminum silicate, or fly ash from thermal power stations, which is a material of the aluminosilicate type or calcium aluminosilicate type (type F or C according to the ASTM 10 C618 standard), or another reactive material of the type comprising rice husk ash, which is based on an amorphous form of silica or a blast furnace slag obtained from the manufacture of pig iron, which slag is a material of the calcium aluminosilicate type, or 15 else natural pozzolans such as volcanic rock or ash, tufa, trass, fossil silica or kieselguhr. Preferably, this pozzolan, used in powder form, has a particle size characterized by a mean diameter (D 50 ) of 20 greater than 1 pim and less than or equal to 50 pm, advantageously about 10 to 30 pm. This powder generally also has a specific surface area of about 10 to 50 m 2 /g (measured by the BET method). 25 Advantageously, the total content of cement (or binder) and of any pozzolan (or material capable of undergoing a pozzolanic reaction) does not exceed 75% by weight, preferably does not exceed 65% by weight and particularly preferably does not exceed 60% by weight 30 in the suspension, the weight ratio of said cement to said pozzolan preferably being greater than or equal to 2. The embodiment that combines the cement with the pozzolan (among the constituents defined according to the invention) is conducive to obtaining a final 35 product with improved mechanical properties, while still being able to have relatively satisfactory dimensional stability performance levels. In parallel, both good results in terms of dimensional stability and very satisfactory results in terms of mechanical - 7 properties are obtained, independently of the presence or otherwise of pozzolan, when a limited cement content (of between 18 and 55% and preferably between 20 and 50%) is combined with a rather high calcium carbonate (or filler) 5 content (of between 30 and 70% and preferably between 35 and 65%), as illustrated later. The product according to the invention may also include additives, such as kaolin and/or flocculants and/or other 10 adjuvants of the aqueous suspension, etc. Also described herein is a suspension comprising: - from 20 to 50%, advantageously from 25 to 45%, by weight of hydraulic binder (or cement); is - from 35 to 65%, advantageously from 38 to 62%, by weight of inert or weakly reactive mineral filler (or calcium carbonate) - from 2 to 10%, advantageously from 3 to 8%, by weight of fibers, at least some of which are synthetic fibers; 20 -from 0 to 30%, advantageously from 0 to 25%, by weight of pozzolan (or material capable of undergoing a pozzolanic reaction) - from 0 to 10%, especially from 0 to 5%, by weight of additives; 25 the content of binder (or cement) and of pozzolan preferably being less than 60% and the cement/pozzolan ratio being greater than or equal to 2. Preferably the content of synthetic fibers is at least 1% 30 by weight in the suspension or at least 25% by weight relative to the total weight of fibers (the optional other fibers being advantageously cellulose fibers) and particularly preferably the content of synthetic fibers represents from 1 to 5%, or even from 1.5 to 4%, by weight 35 in the suspension. The product according to the invention is advantageously 2303856_1 (GHMatters) - 8 in the form of a weatherboard, a cladding element or a partition element (or is intended to be used as such). In accordance with the invention, there is provided a 5 product, in particular a board, obtained by the Hatschek process and without autoclaving, able for use as a weatherboard, cladding element or partition element, this product comprising: the following by weight: 10 2% to 10% fibres, including some synthetic fibres; 0% to 30% pozzolan, or a material capable of undergoing a pozzolanic reaction; 18% to 45% cement; and 15 38% to 70% calcium carbonate. In accordance with the invention, there is also provided a process for manufacturing a product as described above by filtration of an aqueous suspension comprising at least 20 one hydraulic binder, a filler and fibers and optionally by superposition of the thicknesses of the sheet material thus formed until the final desired thickness is obtained, in order to obtain a board. 25 Also described herein is a process for manufacturing the product described above, wherein a sheet material is prepared by filtration, on a screen or filter, of an aqueous suspension as defined above, thicknesses of said sheet material are superposed, where appropriate, until 30 the desired final thickness is obtained, in order to give a board, and optionally the board is subjected to a suction draining and/or mechanical pressing (in a size roll and/or press) step and/or a curing step, generally carried out at a few tens of degrees (for example 600) in 35 an oven for a few hours (for example 8 hours) and/or in the open air. 2303856_1 (GHMatters) - 8a Optionally, the board may undergo other treatments, for example it may be formed and/or printed and/or decorated, for example molded, especially when it is still in a malleable form (for example during the pressing operation), 5 in particular in order to obtain a corrugated or non planar board, a board with the appearance of wood, etc. The following examples illustrate two formulations of products according to the principles disclosed herein and 10 the mechanical and dimensional stability properties of said products. Example 1 15 In this example, the matrix was produced from the following composition by weight of dry matter: -34.7%- of standardized (CEM I 52.5) Portland cement; -60%- of calcium carbonate; -2.3%- of PVA fibers supplied by Lanzhou; and 20 -3%- of bleached pine cellulose fibers refined to 230385_1 (GHMattes) -9 600 Schopper-Riegler. Example 2 5 In this example, the matrix was produced from the following composition by weight of dry matter: - 39.7% of standardized (CEM I 52.5) Portland cement; - 40% of calcium carbonate; 10 - 2.3% of PVA fibers supplied by Kuraray; - 3% of bleached pine cellulose fibers refined to 600 Schopper-Riegler; and - 15% of fly ash sold by Pozo Fly Comercio de Cinzas Lima Ltda. 15 Manufacture of the specimens The fiber cement boards were manufactured by the Hatschek process. 20 In particular, a dilute aqueous suspension (the dilution being for example around 50 to 200 g of dry matter per liter of water, as is usual in the Hatschek technique) of the compositions indicated above was 25 prepared, 0.04% of anionic polyacrylamide flocculant relative to the weight of dry matter of the above constituents being added. The boards manufactured had a length of about 2.5 to 30 3.6 m, a width of 1.2 to 1.5 m and a thickness of approximately 8 mm. They were formed from several monolayers (generally between 7 and 9 monolayers) that were superposed in the fresh state, having been obtained using the dilute fibrous cement suspension 35 described above in the abovementioned Hatschek line, these monolayers being superposed in order to form a board, and said board being pressed by the size roll so as to remove a certain amount of water and to increase the adhesion of the monolayers to one another.

- 10 Cure The pressed boards were cured in an oven at 60 0 C and 5 100% relative humidity for 8 hours. The boards were then stored for 28 days in order to complete their cure. At the end of cure, the boards were cut up and characterized as follows. 10 Characterization: The characterization of the boards was carried out on the basis of the procedures specified in the ISO 8336 standard. 15 - Determination of the three-point bending strength or MOR (modulus of rupture): The bending strengths were determined, on the one hand, 20 on test pieces immersed for 24 hours in water at 20 0 C (saturated MOR) and, on the other hand, on test pieces dried in a laboratory atmosphere at 20 0 C and 60% relative humidity (dry MOR). The final bending strength value is an average from ten test pieces. The bending 25 strength is regarded as sufficient for use as weatherboard, cladding element or partition element when the saturated MOR value is greater than 7 MPa and when the dry MOR value is greater than 10 MPa. 30 - Shrinkage or moisture movement: The length of the test piece was measured after it had been immersed in water for 48 hours and after it had been dried at 105 0 C in an environmental chamber. The 35 length of the test piece dried at 105 0 C was measured when the mass of the test piece was constant to within 0.1%. The final shrinkage value is a mean value from three test pieces. The shrinkage value is regarded as particularly satisfactory for use as weatherboard, - 11 cladding element or partition element when it is less than or equal to 0.2%. The results of the evaluations are given in Table 1 below. 5 Table 1 Fly Dry Cement CaCo3 PVA Cellulose saturated Shrinkage Ex. ash MOR (%) (%) (%) (%)(MPa) MOR (MPa) 1 34.7 60 2.3 3 0 14.7 9.2 0.18 2 39.7 40 2.3 3 15 15.4 10.3 0.20 The boards prepared from formulations 1 and 2 have 10 shrinkage values that are very satisfactory for their use as weatherboards, cladding elements or partition elements, as well as good mechanical properties, also satisfactory for their use as weatherboards, cladding elements or partition elements. 15 The product according to the invention may be used as weatherboard, cladding element or partition element, etc. and may be flat or corrugated, etc. 20 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, 25 i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 2303856_1 (GHMatter) - 12 It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the 5 common general knowledge in the art, in Australia or any other country. 2303856_1 (GHM8tterS)

Claims

1. A product, in particular a board, obtained by the Hatschek process and without autoclaving, able for use 5 as a weatherboard, cladding element or partition element, this product comprising: the following by weight: 2% to 10% fibres, including some synthetic fibres; 10 0% to 30% pozzolan, or a material capable of undergoing a pozzolanic reaction; 18% to 45% cement; and 38% to 70% calcium carbonate. 15

2. The product as claimed in claim 1, wherein it furthermore includes at least one pozzolan or material capable of undergoing a pozzolanic reaction, preferably chosen from aluminosilicates, calcium aluminosilicates and amorphous silica. 20

3. The product as claimed in either of claims 1 and 2, wherein it furthermore includes plant-based fibers, such as cellulose fibers. 25

4. The product as claimed in any one of the preceding claims, wherein the content of synthetic fibers is at least 1% by weight relative to the total weight of dry matter or at least 25% by weight relative to the total weight of fibers. 30

5. The product as claimed in any one of the preceding claims, wherein it is in the form of a weatherboard or a cladding element or a partition element. 35

6. A process for manufacturing a product according to any one of the preceding claims by filtration of an aqueous suspension comprising at least one hydraulic 23038561 (GHMatters) - 14 binder, a filler and fibers and optionally by superposition of the thicknesses of the sheet material thus formed until the final desired thickness is obtained, in order to obtain a board. 5

7. The process as claimed in claim 6, wherein the board is drained and/or pressed and/or subjected to a curing step. 10

8. A cement based product, substantially as herein described with reference to the accompanying drawings.

9. A process for manufacturing a cement based product, substantially as herein described with reference is to the accompanying drawings. 2303a50_1 (GHMatlers)