LU85619A1 - FIBER REINFORCED CEMENT SHEET MATERIAL - Google Patents

Description

at

The present invention relates to a fiber-reinforced cement sheet material which may be flat or of profiled cross section, for example, corrugated. Such a material is suitable for use as building panels, for example, for roofing. The flat material is particularly suitable for use as roofing slates.

Cement sheet materials reinforced with asbestos fibers r 10 have been known for many years and constitute a lightweight roofing material which is resistant to both weather and fire. It is now necessary to replace asbestos as a component of these materials, but the product obtained as a result of this replacement must be substantially the equivalent of existing asbestos-cement materials with regard to all of their desirable properties. Materials should also be capable of being produced using existing asbestos-cement manufacturing equipment to avoid the investment involved in major replacement or modification. of this equipment.

The use of glass fibers as a substitute for asbestos fibers in equipment of this type has been the subject of intensive research over the past 10 to 15 years.

The problems which arose at the outset and which are discussed, for example, in the specification of British Patent No. 1,543,951 of the Applicant, ® have been resolved to the extent that it is now possible to formulate cement slurries containing glass fibers which can be processed in asbestos cement production machines, for example, by taking the measures described in the

L

2 specification of the aforementioned patent No. 1,543,951. This ability is not necessarily accompanied by the manufacture of a product having properties suitable for a particular application.

5 Sheets or panels intended for use in construction must generally have an average modulus of rupture (resistance to bending) of at least 16 'N.mm and a density of at least 1.3 g .cm For roofing slates - 10 of roofing, the requirements are more stringent. The roofing slates based on asbestos-cement roofing currently available and also called "compressed asbestos-cement slates" have a smooth surface to which is generally applied an acrylic coating of the desired color, these slates in front have, according to ~ current British standards, a minimum mean rupture modulus of 22.5 N.mm. A minimum density - 3 mum of 1.8 g.cm is recommended to avoid porosity which can cause frost damage to roofing slates.

The simple replacement of the asbestos content of asbestos-cement sheet materials by glass fibers in the form of chopped strands does not make it possible to manufacture materials of equivalent appearance, since chopped strands tend to be visible in or out of the surface, thus giving rise to a surface finish which is either unacceptable when the usual amount of coating has been applied, or requires such a high amount of decorative material to obtain a coating ζ acceptable, resulting in an unacceptable cost increase. In addition, this simple replacement of asbestos by glass fibers in the form of chopped strands does not make it possible to obtain equivalent resistance.

’'J

3 nits with economical amounts of glass fibers due to an uneven distribution of glass fibers in the cement and the attack to which these fibers are exposed by the alkalis contained in the cement. In the specification of British Patent No. 1,543,951 of the Applicant, there has been described a method of manufacturing a composite material based on fiber-reinforced cement and free of asbestos from an aqueous slurry of cement containing -? 10 comprising both chopped strands of glass fibers and individual filaments of a non-crystalline inorganic material, which can be obtained from strands of glass fibers with continuous filaments which separate or transform into filaments on contact aqueous porridge. If glass fibers in this form of individual filaments get? bare from chopped strands transformed into filaments are used as the sole fibrous reinforcement, a smooth surface finish can be obtained. However, the resistance problems are aggravated by the fact that the individual filaments are exposed to attack by the alkalis contained in the cement and that it is also difficult to obtain an adequate bond between the fibers and the matrix.

In order to improve the strength of glass fiber reinforced cement products, different modes of incorporating reactive silica in various forms have been proposed. For example, British Patent Specification No. 1,402,555 (NRDC) relates to a glass fiber reinforced pozzolanic cement product comprising a cement matrix containing ς at least 10% by weight of a pozzolan (which is a silicate glassy material capable of reacting with calcium hydroxide and thereby turning into a hard and resistant material), as well as fibers

L

4 i of a glass of silica / zirconia resistant to alkalis and containing at least 6 mol% of ZrC ^. The aforementioned specification mentions that a very desirable increase in the resistance of composite materials can be obtained by means of a controlled thermal treatment which accelerates the obtaining of a breaking strength and stable properties, treatment which can consist of: immersion in water at a temperature, for example, 60 to 80 ° C for at least two days. One of the preferred pozzola nes described is the pulverized fuel ash used in amounts of 15% to 40% by weight. In the specification of British Patent No. 1,421,556 ("TAC Construction Materials Limited"), the manufacture of cement plate products reinforced with a mixture of glass fibers in long and short wicks resistant to alkali, for example, is described. , chopped strands of glass fibers and ground mineral fibers, with cellulose fibers and silica, for example, in the form of diatomite, in an amount sufficient to react with the lime released during hydration of the cement. The plate products are autoclaved to facilitate the reaction. European patent application No. 68.742 ("Cape Boards & Panels

Limited ") relates to shaped articles such as sheets and sheets for roofing and roofing, and describes a manufacturing process in which an aqueous slurry is used containing, on a dry weight basis, 50% to 90% of cement, 5% to 40% of highly reactive pozzolanic silica S and 5% to 15% of cellulose fibers. A reaction takes place between the cement and the silica following an air hardening. The above mentioned specification mentions 35 that you can use mixtures of silica pozzo-

L

5 highly reactive lanigues, for example, volatilized diatomite and silica, while glass fibers can be incorporated in addition to cellulose fibers. In specification 5 of British Patent No. 2,048,330B ("Rockwool

International A / S "), a process for the preparation of a cementitious plate reinforced with fibers is described from an aqueous slurry of cement and fibers chosen from the group comprising: mineral fibers: 10 synthetic lines , natural organic fibers, as well as mixtures of these fibers, a process in which a fine particle material (specifically filter dust obtained as a by-product in the manufacture of silicon or silicon alloys by an electrothermal process and consisting essentially of volatilized silica) having an average granularity lower than that of the cement particles is incorporated into the slurry in order to reduce the losses of fine cement particles and to neutralize the alkaline products contained in the mixture, thus inhibiting the alkaline degradation mineral fibers. It is stipulated that the quantity of fine particles should preferably not exceed 15%, calculated on the weight of the cement, being 25 do However, high concentrations of fine particles reduce the rate at which excess water is removed from the slurry. Finally, in the specification of the British patent No. 1,565,823 of the Applicant, the use of reactive silica in the form of pulverized fuel ash ΐ or of silica flour in fine particles such as V or the diatomite is described. "ELKEM" silica which is a silica

volatilized, materials which have been found to exert a synergistic effect in the case of the compositions of particular granularity described in P

L

i 6 this specification for application to alkali resistant glass fibers for the purpose of cement reinforcement. It has been found that proportions of reactive silica from 10% to 40% can further improve the durability of the calibrated strands of glass fiber incorporated into the cement. Reactive silica is believed to help bond the glass fibers in the cement matrix, as well as the reaction with the alkalis contained in the latter.

Recent research by the Applicant indicates that the various forms of reactive silica exert different effects on the initial strength and the long-term strength of composite materials. This is particularly the case when glass fibers in the form of individual filaments are used as reinforcement. The research carried out by the Applicant has demonstrated that if strands of dispersible glass fibers transformed into filaments were used as the sole fibrous reinforcement material, it was essential to use a mixture of two different reactive silicas, namely ashes. of pulverized fuel and volatilized silica, in specific intervals, in order to be able to manufacture a flat sheet material suitable for use as building panels on existing asbestos-cement production machines, with both good initial resistance and good long-term durability which can even be accompanied by an increase in resistance beyond s, the initial value. The use of volatile silica in the absence of pulverized fuel ash gives good initial strength but, when subjected to simulated / L-7 aging tests, the material shows a marked reduction in strength. The use of pulverized fuel ash alone without volatilized silica results in poor initial strength and overall strength of the matrix.

Consequently, according to the invention, there is provided a sheet material consisting of a fiber-reinforced cement composition comprising, in percentages by weight of solids: 10 Ordinary Portland cement 50 to 71%

Fuel ash pulverized 14 to 40% Volatilized silica (containing at least 86% by weight of S1O2) 5 to 12% Strands of chopped glass fibers and 15 transformed into filaments 2 to 7% material in which these components constitute at least 90 % by weight of the solid constituents of the composition and in which, when the cement composition comprises less than 8% by weight of volatilized silica, the latter is of a quality containing more than 86% by weight of S1O2 while, when the cement composition comprises only 5% by weight of volatilized silica, this is of a quality containing at least 94% by weight of S1O2, the sheet material having a minimum mean modulus of rupture of —2 —3 16 N.mm and a minimum density of 1.3 g.cm

The combination of pulverized fuel ash and volatile silica in the proportions defined above gives rise to a product having satisfactory initial strength and long-term durability which is accompanied by an increase in strength beyond of the initial value after hardening. The use of glass fibers transformed into filaments makes it possible to obtain a smooth surface as is required when

L

J

8 coating must be applied, avoiding that strands ends protrude from the surface as could happen if we used strands "chopped in one piece.

As used herein, the term "volatilized silica" refers to the material (otherwise called "microsilica" or "fumed silica") which is obtained on an industrial scale as a by-product during the manufacture of silicon or silicon / metal alloys by an electrometallurgical process. Its chemical composition may vary slightly depending on the characteristics of the process and the main product, but it normally contains at least 86% by weight of S1O2 and 0.1 to 0.7% of SiC. Lower purity grades are not appropriate for one. use in the present-7 te invention, since the amount which is then required, poses problems during dehydra-. cement sheet material. Purer grades of volatile silica, relatively free of carbon, containing at least 94% S1O2 and about 0.1% SiC may be available. It has been found that these purer qualities have better surface activity and that they can therefore be used in quantities lower than those of normal qualities, according to the present invention. If the proportion of volatilized silica used in the sheet material of the present invention is less than 8% by weight, the volatilized silica must therefore be of a quality containing more than 86% by weight of S1O2, while that when we use; the minimum proportion of 5% of volatilized silica, - this must contain at least 94% by weight of S1O2.

The preferred percentage of strands of chopped glass fibers transformed into filaments in the

VS

* 9 sheet material is 3 to 4%. Although the percentage can be as low as 2%, problems can arise in this case when handling the raw (i.e. not hardened) sheet. With percentages between 4% - and 7%, difficulties can be encountered in ensuring uniform dispersion of the glass fibers in the cement matrix.

The rest of the composition may comprise up to 4% by weight of cellulose pulp which is incorporated as an auxiliary treatment agent to facilitate drying. It is also possible to incorporate up to 5% by weight of a plasticizer, for example, figulin clay, bentonite or talc, in order to improve the plasticity of the material before hardening. Small amounts of conventional flocculating and dispersing agents can also be used.

Preferably, the strands transformed into filaments consist of an alkali-resistant glass composition containing at least 6 mol% of ZrO 2> For example, the strands of glass fibers can be of the type described and claimed in the specification of the British Patent No. 1,290,528 to the Applicant, these strands being sold by "Fiberglass Limited" under the trademark "Cem-FIL", while their composition may be practically as follows, in molar%:

Si02 69% 30 Zr02 9%

Na20 15.5% s CaO 6.5% The invention also provides a flat sheet material suitable for use as 35 roofing slates and consisting of a

L

J

10 composition of fiber-reinforced cement comprising, in percentages by weight of solids:

Ordinary Portland cement 50 to 70% T Fuel ash pulverized 20 to 40% 5 Volatilized silica (containing at least "86% by weight of S1O2) 8 to 12%

Strands of chopped glass fibers and transformed into filaments 2 to 5% these components constituting at least 98% by weight 10 of the solid constituents of the composition, while the rest, if any, consists of compatible constituents, the sheet material having a module —2 minimum mean breaking strength of 20 N.mm and a minimum density -3 of 1.8 g.cm, while it has a smooth surface for receiving a coating.

Tests carried out on roofing slates made from this material have demonstrated that they have resistance to repeated freezing and thawing, as well as to weathering in general, much better than that of asbestos slates. conventional cement.

The invention also resides in a process for manufacturing a fiber-reinforced cement sheet material, this process comprising the steps which consist in mixing an aqueous slurry whose solids content comprises: ordinary Portland cement 50 to 71 % pulverized fuel ash 14 to 40% volatilized silica (containing at least 30 86% by weight of S1O2) 5 to 12%? strands of dispersed chopped glass fibers 2 to 7% process in which these components constitute at least 90% by weight of the solids content of this slurry and, when the latter comprises less

/ L

J

11 of 8% by weight of volatilized silica, this is of a quality containing more than 86% by weight of SiO 2, while, when the slurry comprises 5% by weight: only volatilized silica, this is d 'a grade containing at least 94% by weight of SiO 2, the mixture being carried out so as to disperse the strands of chopped glass fibers into individual filaments, deposit a layer of this slurry on a perforated surface, superimpose several layers of this type 10 on top of each other to form a sheet of cementitious material, then allow the sheet to harden.

In order to avoid mechanical deterioration of the glass fibers during processing, the mixing of the slurry can be carried out by first mixing the cement, pulverized fuel ash and silica with water in a mixer at high shear stress, then by adding the strands of chopped glass fibers which are dispersible under low shear mixing conditions. Alternatively, the mixture of the slurry can be carried out by first mixing the cement and the pulverized fuel ash, as well as optionally a certain amount of the silica with water in a high shear mixer. , then adding the silica or the remainder thereof with chopped glass fiber strands and dispersible under low shear mixing conditions.

The deposition of the layers and the formation of the sheet can be carried out on an asbestos-cement production machine of the "Bell" or "Hatschek" type.

The sheet can be shaped to a desired cross-sectional profile before curing, for example, so as to define contiguous or spaced corrugations therein. For example, the sheet can be shaped by applying a vacuum profiling head of a known type, or by placing it on a forming plate, the upper surface of which has the desired cross-sectional profile, and in layers. - ~ sant the sheet sag in contact with this surface. In the latter case, a second forming plate can be placed over the sheet to complete the profiling.

The sheet can be cured at a temperature in the range of 60 ° C to 90 ° C, preferably 70 ° C to 80 ° C for 24 hours, before storing at room temperature for at least at least 7 days to complete the hardening.

This initial hardening at elevated temperature helps to ensure the long-term durability of the finished product, while the presence of pulverized fuel ash and volatilized silica allows the glass fibers transformed into filaments to resist hardening. in sufficient quantity to ensure adequate reinforcement.

The sheet may be pressed to remove water therefrom before curing, for example, by placing a stack of these sheets with interleaves in a press and subjecting the stack to pressure to expel water therefrom.

For the manufacture of roofing slates, the shapes of these roofing slates are preferably punched out of the sheet before pressing and hardening of the latter, while that the slates are Γ separated from each other after hardening.

Now, specific embodiments of the invention will be described in more detail by way of example.

fi / (__ 13

A sheet material according to the invention suitable for the manufacture of roofing slates can be produced using machines: for producing conventional asbestos-cement or of the Bell type as described in the patent application published British N ° 2.059.867A, of the type! Well-known Hatschek. In these two types of machines, several layers (specifically eight) are super! laid to form a cement sheet reinforced ’* 10 with glass fibers 4 to 5 mm thick after pressing. In the case of the Bell machine, a boil- ί; aqueous cement cement containing glass fibers | is transferred, via a scraper roller system, i to a moving belt or belt where it is i ’15 dehydrated by suction to a water content of about 25%. The laminate thus formed is transferred | moving tape on a rotating drum. When sufficient layers have been overlaid on the drum to form a sheet of the desired thickness, the sheet is detached from the drum. In the case of the Hatschek machine, the laminate is deposited on a rotary sieve, then transferred to a strip and, from the latter, to a drum. The sheet is again detached from the drum as soon as a sufficient number of layers have been superimposed to achieve the desired thickness.

The subsequent treatment is practically the same in each case. A cutting device is used to cut the shape of several ardoi-30 rectangular flat roofing sheets with their fixing holes on the sheet. These ar-vends can have standardized dimensions, for example, 600 x 300 mm, or 500 x 250 mm. The film is placed on an intermediate steel plate and transferred to a stack of similar sheets.

L

14

After the accumulation of a sufficient number of cut sheets in the stack, the latter is passed through a press where the sheets are further dehydrated by pressure to a final water content of about 20%. The interlayers are then removed and the sheets are hardened at 80 ° C for 24 hours, then finally stored at room temperature for 7 days. The individual roofing slates can then be detached from one another and are ready to receive any coating.

Specific examples I and II below relate to the manufacture of roofing slates as described above using a Bell machine.

Example I

An aqueous slurry was formulated having the following composition, expressed in parts by weight of solids: 20 ordinary Portland cement 61% pulverized fuel ash 25% volatile silica (86% by weight of

Si02) 9% strand of alkali-resistant glass fibers, chopped and processed into filaments, sold under the trade name "Cem-FIL" by "Fiberglass Limited" 3%

Cellulose pulp 2% 30 Flocculating agents, conventional dispersing agents, etc. can also be incorporated in small quantities (less than 0.1%) in a known manner.

The glass fiber strands which were substantially 3 mm in length and made up of filaments having a diameter of almost 20 µl were coated with a sizing composition for dispersing. strands or their transformation into filaments in contact with slurry. Examples of such finishes are "described in the specification of the patent of the United States of America that No. 3,948,673. The composition of glass fibers was as follows, in mole%:

SiC> 2 69% 10 Zr02 9%

Na20 15.5%

CaO 6.5%

After curing as described above at 80 ° C for 24 hours and storage for 7 days at room temperature, the slates were tested to assess their flexural strength at the same time in the longitudinal direction and the transverse direction with respect to the direction of travel of the moving band of the Bell China machine; they have also been tested for impact resistance. Other slate samples were subjected to accelerated aging by total immersion in water at 70 ° C for 16 days, thus simulating natural exposure to the weather for approximately 30 years, after which they did so. new test object. The results obtained are given in the table below.

K

- s “i“ 16

Table 1

Longitu- Trans- Medium dinal versai 5

Proimmediate- proportionality limit (N.mm_2) 22.9 12.6 ment v Breakup module.

hardens- (N.mm) 25.8 15.1 20.5 10 ment Impact resistance _2 (Nmm.mm; - - 3.2

Pro-limit after aging portion (N.mm 28.7 16.0 15 ment Rup- modulus 0 (N.min) ‘29.7 17.3 23.5 slight _ ...

'' Resistance to * shocks _2 (Nmm.mm) - - 2.4 20--

Slate density: 1.95 g.cm-3

It will be noted that the mean modulus of rupture -2 is greater than 20 N.mm and that it increases after aging.

25 Example II

Roofing slates were made in the manner described above from an aqueous cement slurry having the following composition, expressed as% by weight of solids: j- ordinary Portland cement 61% - fuel ash pulverized 24.5% L Volatized silica (86% by weight of Si02) 9% 35 strands of chopped glass fibers and

L

i 17 transformed into filaments (as in Example I) 3.5%

Cellulose pulp 2% dispersing agents, flocculating agents, etc. <0.1%

The slates thus produced were subjected to tests as described in Example I; the results obtained are given in the table below.

10 Table 2

Longitu- Trans- Medium dinal versai

Limit of 15 Immediate- proportionality, (N.mm_2) 24.6 15.9 ment N Rup- aPres ture modulus.

hardens- (N.mm j 25.8 16.5 21.2 ment Impact resistance ~ (Nmm.mm) - - 2.9 - —2

Slate density: 1.90 g.cm

Example III

Roofing slates were made as described in Examples I and II from an aqueous slurry having the following solids content, expressed by weight: ordinary Portland cement 70% 30 fuel ash pulverized 14% volatilized silica (86% by weight of SiO 2) 11% L strands of chopped glass fibers and transformed into filaments (as in Example I) 3.5% / * 18 * auxiliary processing agents (pulp of cellulose, dispersing agent, flocculating agent) 1.5%

Comparative example IV

5 By way of comparison, an additional set of slates was made from a slurry prepared as described in Example III, but replacing the pulverized fuel ashes with limestone flour (CaCO ^).

10 Comparative example V

As a further comparison, roofing slates were made from a slurry, the solids content of which was as follows (by weight): 15 ordinary Portland cement 69% pulverized fuel ash 6% volatile silica (86 % by weight of Si02) 20% strands of chopped glass fibers and 20 transformed into filaments (as in Example I) 3% auxiliary processing agents (cellulose pulp, dispersing agent, flocculating agent) 2% 25 The results tests carried out on the roofing slates of example III and comparative examples IV and V are given in the table below.

U '' i 19

Table 3

Density Limit âe Modulus Resis- Modulus of rupture rate: tionality rupture at specific '5 shocks · „- —III - III-' ... '' I .1 .. I II .1 '' III Immediately after hardening 1.7 12.3 15.1 3.8 8.9> 10

After aging; accelerated 1.7 16.0 17.0 2.7 10.1 IV Immediately after hardening 1.7 12.6 15.4 4.0 9.1 ö After aging- 2q accelerated smoothing 1.7 11, 1 11.4 1.0 6.7 V Immediately after hardening! o c | 1.5 8.7 11.8 “8.0 7.9

It will be seen that the replacement of the pulverized fuel ash with limestone flour in Example IV gave rise to a markedly reduced resistance after aging, while the results of Example V in which a a much larger amount of silica and an insufficient amount of pulverized fuel ash causes poor resistance even immediately after curing.

U

f 'ï 20

Example VI

This example relates to the manufacture of a flat sheet of cement reinforced with glass fibers, using a Hatschek machine, for use as a construction panel for which a * -2 modulus of rupture minimum mean of 16 N.mm and a minimum density of 1.3 g.cm 3 can be specified.

The aqueüse slurry had the following composition, in parts by weight: 10 ordinary Portland cement 60.5% pulverized fuel ash 24.5% volatilized silica (86% by weight of S1O2 8.0% chopped glass fiber strands 15 dispersible 3.5% processing aids (cellulose pulp, dispersing agent, flocculating agent) 3.5%

The glass fiber strands were as described above in detail in Example I.

Sheets were formed in the usual manner on the Hatschek machine. Some of these sheets have been profiled (i.e., corrugated) using a conventional profiling head, and then deposited on a forming plate of corresponding configuration for curing. Other sheets were pressed to dehydrate them to a water content of 20% before hardening. In each case, the sheets were then cured at 80 ° C for 24 hours, then stored for 7 days at room temperature. Cut samples of the sheets were tested as described above to assess their flexural strength, both in the longitudinal and transverse directions with respect to the movement of the screen.

U

i »21 cylindrical and Hatschek machine band.

It has also been tested for impact resistance.

The results obtained are given in the table below.

5 Table 4 V | ; “” ”_3

Profiled sheet not pressed. Dry density: 1.4 g.cm

Longitu- Trans- Medium dinal versai

Proportionality limit 13.8 12.6 13.2

Breaking modulus 22.4 16.7 19.6 Impact resistance - - 3.7 _ - - Z3

Pressed flat sheet. Dry density: 1.7 g.cm 15

Longitu- Trans- Medium dinal versai

Proportionality limit 18.7 16.9 17.8

Breaking modulus 31.8 19.8 25.8 20 Impact resistance - - 3.5

Further laboratory tests were carried out to study the range of possible compositions for the sheet material intended for the manufacture of roofing slates. In these laboratory tests, it is difficult, with normal equipment, to produce a product as thin as on full-scale machines and it is not possible to produce the slate from a series of necks. ches or to obtain a product of the same density. The results obtained are useful in a comparative sense, although the absolute values obtained cannot be converted directly into values which could be obtained using similar formulations in a full-scale operation on a Bell machine or

L

# 't 22

Hatschek. The laboratory tests were carried out by forming a square slate 30 cm side and 8 mm thick, then removing the water by the simultaneous application of pressure and suction. The slate was then allowed to harden at 60 ° C for 24 hours and the resistances were measured as in the previous examples. The results obtained are shown in table 5 below, which also indicates the composition of each slate, the length of the glass filaments used, as well as a breaking modulus figure corrected for the lower density of the slate, as opposed to that expected for a slate made from the same composition in a full-scale operation. In all of these samples, volatilized silica was used having an S1O2 content of at least 86% by weight.

U, t 23

& Q) MD

! i) O + J Q) p, -H

ό σ'Ο) co (DPU> G COCDhOlHMtTlhlß'i CD Vj Ρ Ή Q) P 'il H Ό r'ChrHI ^ -OOCTiCnChCn 3 PUPP, -Ι Γ-Η' Ό Qj'Q) O to Q 3ûürl SP to - 03 (D 10

ϋ l. · ϋ io ^ OmroLnr-cri'3'CN

2 £ cNro ^ rvinn ^^ mn (¾ +> (d ü

I (U

| 5¾ i f1 Pcrimincor- ~ vDcopin 1 "Q. & y] Ό Q) p 3 n ^ ONwvDamvJ'f j S i IH -P! 1 r— \ (N" —I i—! I — 1 rH ι — 1 i —Lr — 1:, i 01 Ù O'D)

^ hJ · '"! · ^ 1 mcnm - ^ - ^ rofMr'CnO

Pj * P * H

E .. r ^^ coiHinminro- ^ oi

! P] »Säe PPP-PPPPPP

in! w! μ l'flj coojojoiiD ^ hnmin n, GP 0Dr ^ r ^ m \ DVDVDVDV £> in

! - vy (U ·! —1 Vlkk.t.Vk.wVVV

H ÛW - · I Il Il — I I — I Γ-H I — I I — I I — li — Il — I

X! c CÖ 110 £ I in p - ω o * h

.3 <u £ 8.43¾ ^ ¾. “1“ 1 “1 ^ ^“ 1 “1“ 1 “l R

alo ^ S ^ pH oiHPPPPPP Ptf)

UHrö'ötn (öröu (U

I ^ Π3 -P

where? 8 -h ë iiiiiiiiii m oit) Pc vDUDmmmnnooixjn ω ÜJ (ü

PQJ | -j uOLninOOOinmunO

p fl) γογογλγλγογογλγογνΙγο

In>

Q) -H

ΰ minoinin • H fO NQ) àP "" ". w K. w

H P [fl OPPLOChCTlPPPO

W g H HP H P P P

Q) I ω I P -H

Cl) g XI P

y P -h 'm m in 1/1

TS U P> [fl dP

> · S .. SdJ ιη ^^ ω ^ σιΐ ^ ίΝ ^ ο

Ö * 8 J§ E 8 CNOPPCNCMCMC ^ rOM

• Ü I

C -w

P B <ϋ c P c fl) P -H dP

Çp'p 0 \ mmMNhh (Mr-r- ’γΊιΡ ^ Ρ

U A) O P

1 c g 0

(0 P

SZ 1 — I dP Q

^ p "- iNro '^' invDr ^ com" - / 1 - ^ - 1 24 '.

')

Of the ten samples tested, samples 1 and 10 are only comparative samples outside the scope of the invention, since they do not contain volatilized silica or pulverized fuel ash, respectively. Sample 4 also departs from the scope of the invention because its volatilized silica content is too low for use as a material with an S1O2 content of only 86% by weight. The resistances obtained could be increased by increasing the curing temperature and they could be increased with certainty in a full-scale operation due to the better distribution of the glass fibers resulting from the formation of individual layers on the Bell and Hatschek machines .

Table 5 shows that in the absence of volatilized silica (sample 1), the overall resistance of the matrix is poor compared to that of samples containing more than 8% of volatilized silica. Sample 10 shows that in the absence of pulverized fuel ash, the initial strength is low compared to that of samples containing equivalent amounts of volatilized silica; when subjected to artificial aging, products made from such a composition exhibit an additional reduction in strength. The resistance of sample 4 could be significantly increased by using volatilized silica having an SiO 2 content of 94% in accordance with the invention. In order to demonstrate the importance of using volatilized silica having an S1O2 content of 94% instead of 86% when the proportion of volatilized silica is relatively low in the material, a preparation was made. series of laboratory samples, which differ only in the type and proportion of volatilized silica, and have been tested for the purpose of assessing the proportionality limit and the modulus of failure; the results obtained are shown in the tables below.

Two qualities of volatilized silicas containing 86% of S1O2 and a third containing 94% of S1O2 were used, identified in the tables by qualities 1, 10 2 and 3.

Table 6A

Limit Modulus of pro- portion - breaking 15 nality 8 | % volatilized silica (86% SiO ^) (Quality 1) 12.6 15.3 6 | % "" "" 11.1 13.4 5 | % "" "" 10.4 12.4 20

Table 6B

8 | % volatilized silica (86% SK ^) (Quality 1) 10.6 13.2 8 | % "" "(Quality 2) 10.8 13.6 25 6 |%" "" "10.3 12.5 51%" "" "8.6 11.4

Table 6C

30 8§% volatilized silica (86% S1O2) (Quality 1) 10.6 12.2 8 | % volatilized silica (94% SK ^) (Quality 3) 9.6 12.5% "" "" 9.4 12.0 <5 | % "" "" 9.5 12.0

L

4 26 *

It will be seen that a reduction in the silica content of 8 | % to 5¾% is accompanied by a substantial loss of strength when using volatilized silica having an SiO 2 content of 86%, 5 however that volatilized silica with a SiO 2 content of 94% does not give rise to any loss of appreciable resistance.

%

Claims (18)

1. Sheet material consisting of a fiber-reinforced cement composition, characterized in that this composition comprises, in percentages by weight of solids: 5 ordinary Portland cement 50 to 71% pulverized fuel ash 14 to 40% v volatilized silica (containing at least 86% by weight of Si02) 5 to 12% strands of chopped glass fibers and 10 transformed into filaments 2 to 7% material in which these components constitute at least 90% by weight of the solid constituents of the composition and in which, when the cement composition comprises less than 8% by weight of volatilized silica, this is of a quality containing more than 86% by weight of SiO 2, while, when the * cement composition comprises only 5% by weight of volatilized silica, this is of a quality containing at least 94% by weight of SiO 2, the sheet material 20 having a minimum mean modulus of rupture -2, -3 of 16N.mm and a minimum density of 1.3 g.cm 2. Sheet material according to claim 1, characterized in that the percentage by weight of strands of chopped glass fibers and transformed into filaments is 3 to 4%. 3. Sheet material according to claim 1 or 2, characterized in that the rest of the composition comprises up to 4% by weight of cellulose pulp. " 30 4. Sheet material according to any one of claims 1 to 3, characterized in that the strands of chopped glass fibers transformed into filaments consist of an alkali resistant glass composition containing at least 6% 35 molars of Zr02 · / 28 * * 5. Sheet material according to claim 4, characterized in that the composition of the strands of glass fibers is practically as follows, in molar%: ^ 5 Si02 69% - Zr02 9% Na20 15.5% CaO. 6.5%. 6. Flat sheet material suitable for use as roofing slates, consisting of a fiber reinforced cement composition, characterized in that the composition comprises, in weight percent solids: ordinary Portland cement 50 to 70 % 15 pulverized fuel ash 20 to 40% volatilized silica (containing at least 86% by weight of Si02) 8 to 12%% chopped strands of glass fibers and; transformed into filaments 2 to 5% i 'I 20 these components constituting at least 98% by weight of the solid constituents of the composition, while the optional residue consists of compatible constituents, the sheet material having a minimum mean modulus _2 of 20 N.mm and a minimum density of -3 25 1.8 g.cm, while it has a smooth surface for receiving a coating. 7. A method of manufacturing a fiber-reinforced cement sheet material, characterized by the steps of mixing an aqueous slurry whose solids content comprises: ordinary Portland cement 50 to 71% S pulverized fuel ash 14 to 40% -, volatilized silica (containing at least 86% by weight of Si02) 5 to 12% 35 strands of chopped glass fibers dispersible 2 to 7% L * * 29 process in which these components constitute at least 90% by weight of the solid content of the slurry and, when the latter comprises less than 8% by weight of volatilized silica, the latter is of a quality containing more than 86% by weight of SiO 2, while, when the slurry comprises only 5% by weight of volatilized silica, this is of a quality containing at least 94% by weight of SiO 2, the mixing being carried out so as to disperse the to-10 rons of chopped glass fibers into individual filaments , place a layer of this porridge on a s perforated surface, superimpose several layers of this type on top of each other to form a sheet of cementitious material, then allow the sheet to harden. 8. Method according to claim 7, charac terized in that the mixing of the slurry is carried out by first mixing the cement, the ashes of pulverized fuel and the silica with water in a high-effort mixer of shear, then adding the strands of chopped glass fibers which are dispersible under low shear mixing conditions. 9. Method according to claim 7, characterized in that the mixture of the slurry is effec-25 _ killed by first mixing the cement and the pulverized fuel ash, as well as possibly a certain amount of silica with water in a high shear mixer, then adding the silica or the rest of the latter 30 with chopped glass fiber strands and dispersed under low shear mixing conditions- 1 - i lie. Γ 10. Method according to any one of claims 7 to 9, characterized in that the deposition of the 35 layers and the formation of the sheet are carried out (* 30) on an asbestos-cement production machine of the "Bell" type. "or" Hatschek ". 11. Method according to any one of claims 7 to 10, characterized in that the sheet 5 is shaped to a desired cross-section profile before hardening. 12. Method according to claim 11, characterized in that the sheet is shaped by applying a vacuum profiling head of a known type. 13. The method of claim 11, charac terized in that the sheet is shaped by placing it on a forming plate whose upper surface has the desired cross section profile, and allowing the sheet to collapse in contact with this. area. 14. Method according to claim 13, characterized in that a second forming plate having the aforementioned profile is placed over the sheet. 15. Method according to any one of re-vendications 7 to 14, characterized in that the sheet is hardened at a temperature ranging from 60 ° C to 90 ° C for 24 hours before storing it at room temperature for 7 days to complete curing. 16. The method of claim 15, characterized in that the sheet is cured at a temperature in the range of 70 ° C to 80 ° C. 17. A method according to any one of re-vendications 7 to 16, characterized in that the sheet - · is pressed to remove the water before hardening i ing. 18. The method of claim 17 for the manufacture of roofing slates, characterized in that the shapes of the roofing slates. # t 31 roof greens are cut out from the sheet before pressing and hardening, while slates are separated from each other after hardening. <*