AU2017401054C1 - Light-weight & high strength non-asbestos corrugated fiber cement roofing sheets manufactured by autoclave method - Google Patents

Abstract

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date W O 2019/069315 Al 11 April 2019 (11.04.2019) W IPOIPCT (51) International Patent Classification: C04B 28/04 (2006.01) (21) International Application Number: PCT/IN2017/050541 (22) International Filing Date: 20 November 2017 (20.11.2017) (25) Filing Language: English (26) Publication Language: English (30) Priority Data: 201741035233 05 October 2017 (05.10.2017) IN (71) Applicant: HIL LIMITED (FORMERLY HYDER ABAD INDUSTRIES LIMITED) [IN/IN]; SLN Tenni nus, 7th Floor, Near Botanical Garden, Gachibowli, Hyder abad 500032 (IN). (72) Inventor: SATYANARAYANA, D.; Head R & D, Hil Limited (fonnerly Hyderabad Industries Limited), Erragad da, Sanatalnagar, Hyderabad 500018 (IN). (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BE, BN, BR, BW BY, BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, Fl, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IR, IS, JO, JP, KE, KG, KH, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (84) Designated States (unless otherwise indicated, for every kind of regional protection available) ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Published: - with international search report (Art. 21(3)) - with amended claims (Art. 19(1)) (54) Title: LIGHT-WEIGHT & HIGH STRENGTH NON-ASBESTOS CORRUGATED FIBER CEMENT ROOFING SHEETS MANUFACTURED BY AUTOCLAVE METHOD (57) Abstract: Light weight & high strength non-asbestos corrugated fiber cement roofing sheets by autoclave method. A light weight and high strength non-asbestos conugated fiber cement roofing sheets comprising, Portland cement, pozzolonic material, fibrous rein forcing material, bentonite clay and additives wherein said fibrous reinforcing material is a combination of plurality of fibers having 8 to 20% of cellulose fiber, 0 to 3% of modified PET fibers and 0 to 6% other fibers optionally containing 0 to 3% rock wool/modified rock wool, organic fiber like jute, bamboo and mineral fibers selected from wollastonite modified or unmodified, sepiolite and mineral fiber.

Description

IN/PA-210

1 TITLE:

Light weight & high strength non-asbestos corrugated fiber cement roofing

sheets manufactured by autoclave method.

FIELD OF THE INVENTION:

The present invention relates to light weight & high strength non-asbestos

corrugated fiber cement roofing sheets manufactured by autoclave method.

BACKGROUND OF THE INVENTION:

In the past asbestos-cement compositions have been formed into products such

as flat sheets, corrugated sheets, boards, panels and the like. These sheets

generally contained Portland cement in the amount of 43 to 55%, siliceous

material and / or filler in the amount of about 30 to 35% and asbestos fibres in

the amount of about 10 to 12%. The products had many desirable qualities,

including high strength, exterior durability and easy application. Asbestos is a

naturally occurring mining product. But day by day the availability of quality fibers

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2

is reduced tremendously. Hence it is essential to develop corrugated sheeting

product with alternative fibers with similar strength of asbestos based and cost

effective.

Conventionally, the wood pulp and synthetic fibers such as Poly vinyl alcohol and

modified poly propylene fibers has been used as an alternate to asbestos due to

its unique characteristic of good dispersion in cementicious / water slurry

because of its hydrophilic nature. These sheets generally contained Portland

cement in the amount of 70 to 80%, siliceous material and / or filler in the amount

of about 10 to 20% and synthetic fibers like poly vinyl alcohol, modified poly

propylene and wood pulp in an amount of about 4 to 8%.

The above combination of fiber and fillers the end product can't be subjected for

hydrothermal curing (autoclave) only Air cured/ water cured method to be

adopted.

Indian Patent application 6305/CHE/2015 describes the manufacturing of non

asbestos corrugated sheet by auto clave method. In this invention, Asbestos

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fibers were replaced with cotton pulp, modified or unmodified wollastonite and

modified PET fiber. The part quantity of cement was replaced with GGBS slag

and fly ash. In addition to this microsilica and additives are used.

US 4377415 relates to a cement-wollastonite product consisting essentially of Portland

cement binder in an amount of between about 40% and 90% by weight, and

wollastonite in an amount of between about 10% and 60% by weight. The product may

contain fibers in an amount of between about 1% and 15% by weight. If the product

contains fibers other than asbestos and is to be formed on a Hatschek or other type of

wet forming machine, it may contain clay in an amount of between about 2% and 15%

by weight, and poly(ethylene oxide) homopolymer in an amount of between about

0.03% and 0.5% by weight. The product may also contain silica and/or filler in an

amount of between about 10% and 40% by weight for replacing part of the wollastonite.

The filler may be waste fiber-cement product or inert filler material.

US8293003B1 teaches us a cement product incorporating nanocrystalline cellulose and

cellulose fiber throughout the product and a method of making the product.

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US5122550 relates to a non-asbestos friction material composition suitable for use as a

friction element includes: a binder; a reinforcing material; and a structural integrity

imparting amount of cellulose ester fibrils.

US6284815B1 teaches us a non-asbestos friction material is disclosed, which

comprises a non-asbestos fibrous reinforcement, a thermosetting resin binder, and a

filler as the main components, wherein the fibrous reinforcement is a combination of

plural kinds of non-asbestos fibers and contains sepiolite fibers, cellulose fibers, and an

acryl pulp as the fibrous reinforcement. The friction material of the present invention is

excellent in fade characteristics, stability of effectiveness, etc., and low in cost.

US Patent 8182606B2 describes the manufacturing of low density fiber cement

building materials by using low density additives such as hollow ceramic

microspheres, volcanic ash (density : 2-25 lbs/cu.ft) and other low density

additives either alone or in combination.

Australian patent 2008348271A1 illustrates the manufacturing of structural fiber

cement building materials with density less than 1.25 g/cc & thickness less than

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19 mm by using microspheres, calsil, polymeric beads, expanded

vermiculite/perlite/shale and their combinations.

Indian Patent 279236 describes the manufacturing of light weight cementicious

cellulose fiber reinforced building material without using any low density

additives. In this invention flat fiber cement boards are manufactured by using

bauxite and wood pulp by autoclave method.

In present invention to get the light weight and high strength of non-asbestos

corrugated sheets an attempt has been made by increasing the pulp quantity and

using high aspect ratio modified wollastonite.

An attempt has been made replace part or full quantity of PET fibers with

alternative fibers like mineral fiber, sepiolite, Jute fiber, bamboo fiber etc.

A part quantity of Cellulose fiber (cotton pulp) has been replaced with modified

rock wool fiber.

GGBS slag has been replaced with fly ash to reduce density and make the sheet

lighter.

Similarly micro silica has been replaced with high surface area fly ash for cost

reduction and addressing the processing problems by maintaining cone and sieve

filtrate solids.

We have made use of bentonite to improve interlaminar bonding and replaced a

part quantity of fly ash with fine ground silica and rice husk ash.

We have made use of anionic poly acrylamide flocculent by effective utilization of

fine particle in the form of floccs.

A product replacing asbestos fibres and PVA fibers, silica and partly replacing

cement with suitable materials makes it unique Green product in many ways. The

present invention provides the method to manufacture of Light weight and high

strength Non asbestos fiber cement corrugated sheet comprising of the processing

reinforced fibers such as herein described

SUMMARY OF THE INVENTION:

The present invention relates to Light weight & high strength non- asbestos

corrugated fiber cement roofing sheets manufactured by autoclave method.

The present invention proposes to replace asbestos fibers, wood pulp, PVA,

modified Poly propylene fibers, micro silica and part replacement of cement to

make it light weight and high strength Non Asbestos fiber cement corrugated

roofing sheets.

There is also proposed to use more quantity of Cellulose fibers and high aspect

ratio Wollastonite/modified wollastonite to replace asbestos fibers, Modified poly

propylene and PVA fibers.

Also proposed is to use sepiolite, mineral fibers, jute fiber and bamboo fiber to

replace part quantity or full quantity of modified PET fibers.

There is also proposed to use modified rock wool fiber to part replacement of cotton

rag pulp.

Also proposed is to make non-asbestos corrugated sheets with light weight by

replacing GGBS with fly ash.

Further proposed is to improve the bonding between the layer at green stage by

incorporation of bentonite in the formulations.

Also proposed is to maintain cone and sieve filtrate solids to address the process

problems by replacing micro silica with high surface area fly ash, rice husk ash and

fine ground silica.

The invention also seeks to achieve the effective utilization of fine particle in the

form of floccs by adding anionic poly acrylamide flocculent and to reduce drying

shrinkage of corrugated sheets produced by hydrothermal (Autoclaving) curing.

Specifically, the invention relates to a non-asbestos corrugated fiber cement

roofing sheet comprising:

i) 20 to 60% by wt. of Ordinary Portland cement,

ii) 20-60% by wt. of pozzolanic material

iii) 8-20% by wt. of cellulose fibers as reinforcing material

iv) 1-5% by wt. of bentonite clay

v) 0.1-3% by wt.of modified PET fibers

vi) 0.2- 6 % by wt. of modified/unmodified wollastonite

vii) 0.01-2% by wt. of additives and

viii) Optionally 0.1 to 6% by wt. of other fibers selected from rock wool,

jute fibers, bamboo fibers, sepiolite, ceramic fibers, Glass fibers, mineral fibers, mineral wool and ceramic wool are used either alone or in combination along with cellulose fibers to replace (partial or full) modified wollastonite, and modified PET fibers wherein the density of the sheet is less than 1200Kg/m 3

. The invention also relates to a method of manufacturing building product with

improved strength and other properties to the product manufacturing non-Asbestos

fiber cement roofing sheet by autoclave method.

Accordingly, there is also provided a process for manufacturing a non-asbestos

corrugated fiber cement roofing sheet according to any one of claims 1-12, the

method comprising the steps of:

a) preparing a slurry

b) subjecting the slurry to a step of forming thin films by Hatschek process

c) applying the thin films on accumulator rolls to obtain a flat sheet

d) cutting the flat sheet from the accumulator rolls

e) profiling the cut flat sheet

f) pre-curing and de-stacking the profiled sheet

g) curing the pre-cut and de-stacked profiled sheet in an autoclave

9A

According to this disclosure there is provided light weight & high strength non

asbestos fiber cement corrugated roofing sheets comprising:

Portland cement, pozzolonic material, fibrous reinforcing material, bentonite clay

and additives wherein said fibrous reinforcing material is a combination of plurality

of fibers having 8 to 20% of cellulose fiber, 0 to 3% of modified PET fibers, and 0

to 6% other fibers optionally containing fibers mineral selected from wollastonite

modified or unmodified, sepiolite and mineral fiber.

Also disclosed is a process for manufacturing light weight and high strength non

asbestos corrugated fiber cement roofing sheets comprising; preparing a slurry;

subjecting the said slurry to the step of forming thin films, applying the said thin

films on accumulator rolls, pre curing and curing in autoclave to produce the

product.

INIPA-210

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DETAILED DESCRIPTION OF THE INVENTION:

The present invention relates to Non asbestos cement roofing fiber product by

autoclave method which does not contains asbestos, PVA and virgin wood pulp,

GGBS, and micro silica powder but which contains other fibers either alone in

the combination of Cellulose, Modified PET Fibers, wollastonite/modified

wollastonite, sepiolite, mineral fiber, jute fiber, bamboo fiber along with cement

and siliceous material such as fly ash, fine ground silica and rice husk ash so as

to permit satisfactory production thereof on a machine in which a slurry is formed

on a screen and subsequently vacuum-filtered through a screen and or felt.

In the following paragraphs, wherein the term cellulose pulp is referred, it the

cellulose pulp, which is obtained by mechanical pulping of waste jeans cotton

rags or other natural cotton in loose or cloth form. Modified PET Fibers are

having high molecular weight with good water dispersion and compatible with

cement. Wollastonite is natural occurring mineral fiber having very good aspect

ratio to attain strength and durability by reducing moisture movement. The wollastonite is optionally modified with using additives such as Vinyl silane, Amino silane, glycidoxy silane and Vinyl acetoxy silane either alone or in combination. The sheet of the present disclosure may achieve the strength similar to asbestos based fiber cement sheets with light weight. Sepiolite is naturally occurring soft white clay mineral. Fibers texture of sepiolite makes it suitable for reinforcement. Jute and bamboo fiber are obtained from natural plants which are processed to suitable for fiber cement application. Mineral fibers is naturally occurring mining product.

Similarly wherein the fly ash is referred, it means the fly ash generated during the

combustion of pulverized coal in the thermal power plant. Rice husk ash is an ash

produced by controlled burning of grounded rice husk which contains amorphous

silica.

Bentonite is also naturally occurring clay mineral which have very good swelling

properties used to achieve the bonding between the layers.

In the following paragraphs, when inventor refers Non-asbestos fiber cement

sheets, that is the new and invented non-asbestos fiber cement sheets which are environment friendly products as is described herein.

The process of the invention and its advantage will now be explained in greater

detail with reference to the known method of manufacture of such sheets for clear

and better understanding of the invention.

STEP 1- PREPARATION OF SLURRY

There is described herein an improved process for manufacture of Non Asbestos

Cement Roofing Fiber cement sheets comprising of the processing reinforced

fibers is provided.

The said reinforcing fibers essentially included Cellulose Pulp having fiber opening

Deg.SR 12 - 50 used in an amount of 8-20%, modified PET fibers 0 to 3% and

wollastonite/modified wollastonite is having the aspect ratio 5 to 40 in an amount

of 0.25 to 10%, sepiolite 0-5%, mineral fibers 0-5%, jute fibers 0-5%, bamboo fibers

-5%, modified rock wool fiber 0-5%, Portland cement in an amount of 20 to 55%,

Siliceous material in the binder essentially pulverized fly ash having surface area

of 2000-4000 cm2/gm used in an amount of 15 - 55%,

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fine fly ash having surface area of above 4000 cm 2/gmused in an amount of 20

%, rice husk ash having surface area of greater than 5000 cm 2/gm used in an

amount of 0-20%, fine ground silica used in an amount of 0 to 25% and bentonite

used in an amount of 1-5% and fillers, flocculent and additives in an amount of

0.01 to 2% by weight of the total mixing comprising or the reinforcing fibers,

cement, fillers and additives.

While making slurry, care was taken to ensure there was homogeneous mixing of

siliceous material, additives and cement with reinforcing fibers.

Mixing/holding system ensured that solids are not separated from the aqueous

solution, i.e. solids do not settle so that the lamination having uniform distribution

of the binder and the reinforcing fibers is obtained in the process.

STEP 2: APPLICATION OF SLURRY

The recipe thus obtained in respect of the above formulations were

independently run on pilot plant and plant sheet forming machine such as

HATSCHECK MACHINE where thin films are picked up and superimposed on

INIPA-210

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accumulator roll. The composite is cut upon after building up to desired thickness

and laid flat and or conveyed for corrugation and stacking before pre curing. Over

a period of time and at predetermined temperature, the initial curing in the

composite make it strong and acquire enough strength for demoulding.

STEP 3: CURING THE ARRANGED PRODUCT.

Demoulded corrugated sheets are then arranged on a trolley and cured under

Autoclave maintaining the steam pressure for 90 to 130psi and duration of 5 to

hours. After curing is over, cured material in the trolleys is pulled out and

stacked in ambient condition for further inspection and dispatch.

EXAMPLES

Using the above said slurry and process of manufacturing the claimed light

weight & high strength Non Asbestos Fiber Cement corrugated Roofing sheet,

the various trials were conducted in order to replace the Asbestos fibers, PVA

fibers, GGBS, micro silica and part replacement of cement with fly ash. Some

typical examples and test results are as follows:

Table 1 Plant trials

% of raw materials used

Conventional Indian Preentinveiion Raw-Material Asbestos patent corrugated application Example Example Example Example 63051CIE 1 2 3 4 sheets 2015 Ordinary P43-55 20 to 55 20-60 20-0 20-60 20-60 cement Pulverized fly ash SSA: 20004000 30-35 15 to 50 15-55 15-55 - cm'lgm Fine fly a SSA :above400 - - - 25-50 25-50 rn/~gm Asbesto fibers 10-12 - - - -

Ground granulted 21020 - -

blast furace slag Jeans cotton rag 3 to 15 8-20 8-20 8.20 8-20 PET Fibers 0,25 to 6 02-3 0.2-3 0.2-3 02-3

INIPA-210

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Modified/unmodified wollastonite - 0.25 to 6 0.2-6 - 0.2-6 Aspect ratio: 5-10 Modified/unmodified wollastonite - - 0.2-6 - 0.2-6 Aspect ratio: Above 10 Micro silica 0.25 to 5 - Bentonite - - 1 to 5 1 to 5 1 to 5 i to 5 Additives 0.25 to 5 0.25 to 5 0.01 to 2 0.01 to 2 0.01 to 2 0.01 to 2 Total 100 100 100 100 100 100

Properties - Pilot plant trial Size Lengthxwidthxthickness 1270 x 575 x 6 mm Density 1.39 1.13 1.05 1.12 1.16 1.2 Load bearing 267 271 250 265 280 293 capacity Water absorption % 33.0 42.8 44.37 47.56 40.75 43.4

Properties - Plant trial Size Lengthxwidthxthickness 2500 x 1050 x 6 mm Density 1.41 - 1.07 1.09 1.05 1.07 Load bearing capacity IS 5913 550 - 408 430 525 600 Span: 1000 mm Load bearing capacity IS 14871 NA - 380 410 475 520 Span: 1100 mm

By using fine fly ash and high aspect ratio modified/unmodified wollastonite in example 4 achieved the superior properties compared to conventional asbestos and non asbestos fiber cement corrugated roofing sheets. The invented product meeting all the

INIPA-210

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requirements of IS 14871:2000 Indian standard and International standard of ISO 9933: 1995. Type Tests performance: 1) Water impermeability: No water droplets observed after 24 hours underneath of the corrugated sheet. 2) Frost Resistance: The corrugated sheets are subjected freeze thaw cycles cooling to -20°C within 1 to 2 hours and holding for 1 hours. Thawing in water to ambient temperature within I to 2 hours and holding for 1 hour. After 50 cycles, there is no cracks, delamination and color change observed. 3) Heat & Rain: The corrugated sheets are subjected to wetting 2.51/min/m2 for 2 hour 50 minutes and heating to 70°C for 2hour 50 minutes with an interval of 10 minutes each. The cycle is repeated for 25 times and examined for longitudinal and transverse cracks, visual defects, color change and delamination. The exposed sheets are passed the tests. 4) Warm Water: The specimens are exposed to warm water having temperature 60 0C for 56 days and exposed sheets are meeting standard requirement. 5) Soak & dry: The tests are carried out as per EN 494 : 2004 (Immersionin water for 18 hours at ambient temperature and dry at oven for 60°C and relative humidity < 20% for 6 hours for every cycle). After 50 cycles sheets kept at ambient temperature for 7 days and tests are carried out which is meeting standard requirement. 6) Carbonization test: The carbonization each cycle is 24 hours which is consist of following: 9 hrs immersion in water at ambient, 1 hr dry in ventilated oven at 60 0C, Shrs purging C02 at ambient temperature, 8 hours dry in ventilated oven at 600C and cooling to ambient temperature within 1 hour time. The specimens are subjected to expose for 50 cycles. No visual defect cracks are observed.

Table 2. Pilot plant trials

"Aof raw mutri~su..d R - Hatcil Rpfprpnrp fl~*i ExamlI Lxanpi. Exampb Exwan* Ezamp 5 6 7 8 o1

204 20450 2Q40* 20-0 20-61) 2D-60

Pu~atadfly wh SSA: 2000-4000 15-55 15-35 15-i 1 S-" 15-55 15456

Jensc!ttn M 4-12 8- .0- 20 8 -20 84%0

04 1- 0- 04 046 04 dwabstonUi

B'swn" ItI1o5 1t*5 I W5 1 to5 lboS 10 Moc~wW -OkW Oato5 Iibe Sepiolif iber ms C'o5

Mriar - - 01tr .JwWJwihoofiber - .1- 01 Rice husk ath ~2

Admito Mri-o 0.01 to 2 0.01 to2 0.01toD2 0.01 to2 0.01102 S 100 1 100 100 100 100 100 Ppfts- PUCK PUMtisi Sin: L*WhWk d~hzthkWMI7 x5x 9 iW Dwrruy 1.0 B.C 1.13 1.15 1-19 .i-0 Low baulrag w2 262 23 277 3w0 213

WtrewpA 4eA 47-9 421- 43.9 47.5 4.

Rock wool fibers are used in example 5 for part replacing jeans cotton rag pulp. Rice

husk ash and ground fine silica are used as a part replacement for pulverized fly

ash in Example 6 and 7 respectively. Sepiolite, mineral fiber, jute/bamboo fibers are

used as part or full replacement of modified PET fibers in examples 8,9 and 10

respectively.

It has been determined by way of compression of the invented light weight & high

strength non-asbestos fiber cement corrugated roofing sheets produced by

autoclave method in this invention are having better load bearing capacity than that

of conventional asbestos and non-asbestos fiber cement corrugated roofing sheets.

The reference in this specification to any prior publication (or information derived

from it), or to any matter which is known, is not, and should not be taken as an

acknowledgment or admission or any form of suggestion that that prior publication

(or information derived from it) or known matter forms part of the common general

knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context

requires otherwise, the word "comprise", and variations such as "comprises" and

"comprising", will be understood to imply the inclusion of a stated integer or step or

group of integers or steps but not the exclusion of any other integer or step or group

of integers or steps.

Claims (16)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A non-asbestos corrugated fiber cement roofing sheet comprising:

i) 20 to 60% by wt. of Ordinary Portland cement,

ii) 20-60% by wt. of pozzolanic material

iii) 8-20% by wt. of cellulose fibers as reinforcing material

iv) 1-5% by wt. of bentonite clay

v) 0.1-3% by wt.of modified PET fibers

vi) 0.2- 6 % by wt. of modified/unmodified wollastonite

vii) 0.01-2% by wt. of additives and

viii) Optionally 0.1 to 6% by wt. of other fibers selected from rock wool, jute fibers,

bamboo fibers, sepiolite, ceramic fibers, Glass fibers, mineral fibers, mineral

wool and ceramic wool are used either alone or in combination along with

cellulose fibers to replace (partial or full) modified wollastonite, and modified

PET fibers

wherein the density of the sheet is less than 1200Kg/m 3 .

2. The sheet as claimed in claim 1 wherein ordinary Portland cement is present in the

range of 35-50% by wt, pozzolanic material is present in the range of 35-50% by wt.,

cellulose fibers is present in the range of 10-16% by wt, bentonite clay is present in the

range of 1.5-3% by wt., modified PET fibers is present in the range of 0.2-1 % by wt.,

modified/unmodified wollastonite is present in the range of 2-6% by wt,

3. The sheet as claimed in claim 1 or 2, wherein wollastonite is modified with Vinyl

silane, Amino silane, glycidoxy silane and Vinyl acetoxy silane either alone or in

combination, in an amount of 0.1 to 3% of wollastonite weight, said silanes helping in

bridging between organic and inorganic materials.

4. The sheet as claimed in any one of claims 1-3, wherein the pozzolanic material is

selected from pulverized fly ash, fine fly ash, rice husk ash, fumed silica, volcanic ash, and

ground granulated blast furnace slag.

5. The sheet as claimed in any one of claims 1-4, wherein siliceous material is used to

partially replace the pozzolanic material.

6. The sheet of claim 5, wherein the pozzolanic material is fly ash, and the siliceous

material is used in an amount of 5 to 25% by wt.

7. The sheet of claim 5 or 6, wherein the siliceous material is ground fine silica.

8. The sheet as claimed in any one of claims 1-7, wherein the cellulose fiber is selected

from jeans cotton rag, waste cotton, virgin cotton, and a combination thereof.

9. The sheet as claimed in any one of claims 1-8, wherein wood pulp is used with the

cellulose fiber.

10. The sheet as claimed in any one of claims 1-9, wherein the modified/unmodified

wollastonite has the aspect ratio 5 to 50.

11. The sheet as claimed in any one of claims 1-10, wherein the additives comprise pan

gel, plasticizers, superplasticizers, flocculating agents, defoamers, water reducing

admixtures of silicones or acrylic base.

12. The sheet as claimed in any one of claims 1-11, when used for manufacture of non

asbestos flat sheets/boards.

13. A process for manufacturing a non-asbestos corrugated fiber cement roofing sheet

according to any one of claims 1-12, the method comprising the steps of:

a) preparing a slurry

b) subjecting the slurry to a step of forming thin films by Hatschek process

c) applying the thin films on accumulator rolls to obtain a flat sheet

d) cutting the flat sheet from the accumulator rolls

e) profiling the cut flat sheet

f) pre-curing and de-stacking the profiled sheet

g) curing the pre-cut and de-stacked profiled sheet in an autoclave.

14. The process as claimed in claim 13, wherein the slurry is a homogeneous mixture of

Siliceous material, Portland cement, reinforcing fibers, bentonite, and additives.

15. The process as claimed in claim 13 or 14, wherein curing is carried out under

autoclave maintaining a steam pressure of 90 to 130 psi for 5 to 15 hours.

16. A process as claimed in any one of claims 13 to 15, wherein the reinforcing material

comprises cellulose pulp processed to opening Deg.SR 12-50 and has Length weighted

average fiber length of 0.7 to 2.9 mm.