FIELD OF THE INVENTION:
This invention relates to a chemically treated jute fibre reinforced cement sheet for use in corrugated roof tile applications.
This invention further relates to the development of jute fiber reinforced high strength modified cement sheet which can be used as an effective alternative of the commercially available asbestos sheet.
BACKGROUND OF THE INVENTION:
Asbestos cement sheet is the most important building material and its consumption is increasing in all countries. The disadvantage of asbestos sheet is its hazardous as well as brittle nature, with relatively low tensile strength and poor resistance to crack opening and propagation and negligible elongation at break.
Further, the cost of preparing such sheets is high depending on the reinforcing material to be used and the sheets are not eco-friendly.
OBJECTS OF THE INVENTION:
It is therefore an object of this invention to propose chemically treated jute fibre reinforced cement sheets which are prepared from easily available raw materials.
It is a further object of this invention to propose chemically treated jute fibre reinforced cement sheets, which are cost-effective.
Another object of this invention to propose chemically treated jute fibre reinforced cement sheets, which have appreciable strength and ductility.

Yet another object of this invention to propose chemically treated jute fibre reinforced cement sheets, which are eco-friendly.
These and other objects and advantages of the invention will be apparent from the ensuing description, when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS;
Fig.1. Degradation study of untreated and chemically treated jute fiber in cement paste
DETAILED DESCRIPTION OF THE INVENTION:
According to this invention is provided a chemically treated jute fibre reinforced cement sheet for use in corrugated roof tile applications.
In accordance with this invention untreated and treated chopped jute fibers of 2 to 15 mm length are used as reinforcing agent (0.5-2.0 weight percent with respect to cement weight) in cement composite. A uniform dispersion of fibers in cement-flyash matrix is achieved by following process.
When untreated jute fiber reinforced cement sheet (UJFRC) specimens are prepared, the chopped jute fibers were initially immersed in water. After 8 to 36 h the excess amount of water, which is not absorbed by jute, is decanted. The water saturated jute fibers are slowly poured into the mixer. A jute-cement-flyash slurry is prepared by adding 5-50% of total cement required and 30-70% of total water required to the water saturated jute fibers with constant stirring. Fly-ash and the rest of

cement are mixed with the jute-cement slurry. The remaining amount of water is then added and the mixture is stirred for 5 min. The fresh mixture thus obtained is cast immediately in molds. For chemically treated jute fiber reinforced modified cement sheet (CJFRMC) casting,
jute fibers are initially immersed in 0.25-1% alkali solution maintaining a liquor ratio 1:30. After 8 to 36 h, excess amount of liquor is drained out. 0.125-1.000% (v/v) water based polymer emulsion is prepared by 30-70% of total water required. A solution is prepared by dissolving 0.25-2.0% (weight %, with respect to cement weight) water reducing natural, admixture (e.g., tannin) in remaining amount of water. The polymer emulsion and admixture are mixed with treated jute fibers and CJFRMC specimens are prepared following the same jute-cement slurry process adopted for UJFRC fabrication. In the whole process, water cement ratio is calculated to be 0.30 to 0.70 and for both UJRFC and CJFRMC.
The polymer emulsion comprises a polymer such as carboxylated styrene butadiene polymer latex, a commercial product known as Sika Latex, KL001308 supplied by Sika India Pvt. Ltd. All the specimens are demolded after 24 h of casting and water cure. After curing the specimens are removed from water, surface dried and tested. Each test result represents the mean of at least five specimens.
Apparent bulk density
Bulk density of cement based composites is one of the most important properties. It measures the amount of material's mass present in unit volume. The bulk density of control cement-fly-ash sheet and jute fiber reinforced cement-fly-ash were measured according to ASTM. 948-81 (reapproved 2001). There are two different apparent bulk densities (wet bulk density and dry bulk density) were measured in this experiment.

Wet bulk density measurement
For measuring the wet bulk density of cement-fly-ash sheet, at first samples were immersed into water for 24 h. After removing the sample from water quickly surface dried by removing the moisture with towel and immediately measured the mass. Designate this saturated surface-dry mass as A. Secondly the mass of the samples were determined in the condition of suspended in water, designated as B. Now A-B measured the mass of water replaced by the sample. The density of water is 1 g/cc so mass of water replaced by sample is equal to volume of sample. Now the wet bulk density can be calculated as
Calculation:

Dry bulk density measurement
For the measurement of dry bulk density, samples were dried in Oven at the temperature 100°C to 110°C for 24h after measuring A. Removing the samples from the oven, allow it to cool in dry air (preferably in a desiccator) to room temperature and determine its mass. This designated as C.

Water absorption
Water absorption of control and jute reinforced cement cement-fly-ash sheet were measured by measuring the wet mass (A) and dry mass (C) of

the sample. The percent of water absorption was calculated in accordance with ASTM C 948-81 (reapproved 2001).

Apparent porosity
Apparent porosity of cement concrete samples is a most important parameter. It is measured by measuring the above masses in accordance with ASTM C 948-81 (reapproved 2001)

The flexural tests of the fabricated test specimens of dimensions 300 mm x 10 mm x 6 mm (length (1)x breadth (b) x thickness (d)) were carried out on the same testing system using a three point bending configuration, under a span of 200 mm according IS:4332 (2001). The tests were controlled at a rate of loading of 1.2 N/min. The load was increased until the specimen fails, and the maximum load applied to the specimen during the test was recorded. The flexural strength of the specimen was expressed as the modulus of rupture f,

Where, b is measured breadth (mm) of the specimen, d is measured depth (thickness) (mm) of the specimen at the point of failure, L is length (mm) of the span on which the specimen was supported, and p is maximum load in N applied to the specimen.

Properties of raw and modified natural fibers are show in Table 1 and 2. Cement-fly-ash sheet formulation using raw modified natural fibers are shown in Table 3, Properties of the developed specimens following the casting process according to the invention, with jute fiber reinforce are shown in Tables 4,5 and 6 and Figure 1.
Table 1: Physical and mechanical properties of jute fiber

Table 2: Physical and mechanical properties of chemically treated jute fiber

Table 3: The selected formulations of one (300 mm (length) x 300 mm (breadth) x 6 mm (depth)) cement-fly-ash sheet

*Sample dimension for flexural test: (300 mm x 10 mm x 6 mm)
Table 6: Post flexural behavior of cement-fly-ash sheet composite (28 days water cured)

Degradation study of jute fiber in cured cement matrix
This study was performed by making a jute cement paste. Long untreated and treated jute fibers were incorporated in cement paste (water cement ratio 0.4). After 24h the hardened and hydrated cement jute composite was then allowed to cure in water. The jute fibers were then isolated from cement composite after specific days, washed with water, acetone and then allowed to dry in oven for 24 h at 105°C. Tensile strength of isolated jute fiber was then measured using a tensile testing machine (UTM) and the result have been shown graphically in Fig 1; as a plot of aging time vs normalized tensile strength.

WE CLAIM:
1. A jute fibre reinforced cement sheet, comprising a cement-flyash reinforced with jute fibres.
2. A process for the preparation of a jute fibre reinforced cement sheet comprising the steps of providing chopping fibres in water, adding a first part of the total cement and water required, into the jute water
mixture with constant stirring to obtain a slurry, adding the flyash and the remaining portion of the cement to the slurry with stirring, to obtain a mixture, casting the mixture in moulds,
obtain the sheets, followed by demoulding the sheets and water-curing the same, to obtain the jute fibre reinforced cement sheets
3. The process as claimed in claim 1, wherein the jute fibres are treated or untreated jute fibres.
4. The process as claimed in the preceding claims wherein untreated chopped jute fibres are submerged in water for 8 to 36 hours prior to carrying out the process.
5. The process as claimed in the preceding claims, wherein treated jute fibres are obtained by chemical treatment.
6. The process as claimed in claim 5, wherein the chemically treated jute fibres are obtained by immersing jute fibres in alkali solution for 8 to 36 hours, following by draining out the excess alkali, adding a polymer emulsion and a natural admixture to the alkali treated jute fibres, to obtain the treated jute fibres.

7. The process as claimed in claim 5, wherein for the alkali treatment the jute fibres are immersed in alkali solution of a strength of 0.25 to 1%, maintaining a liquor ratio 1:30.
8. The process as claimed in claim 5, wherein said polymer emulsion is a 0.125 to 1.000% v/v water based polymer emulsion.
9. The process as claimed in claim 2, wherein said jute fibres are chopped to a length of 2 to 15 mm.
10.The process as claimed in claim 2, wherein 0.5 to 2.0 weight percent of jute fibres with respect to cement, is used.
11.The process as claimed in claim 2, wherein said polymer emulsion comprises a polymer such as carboxylated styrene butadiene polymer latex.