Indian Patents. 226352:SHORT POLYESTER FIBRES AS SECONDARY REINFORCEMENT IN CEMENTITIOUS MATERIALS

Title of Invention	SHORT POLYESTER FIBRES AS SECONDARY REINFORCEMENT IN CEMENTITIOUS MATERIALS
Abstract	Short polyester fibers for secondary reinforcement in cementitious matrix which increases 5 - 30% compressive strength of the cement matrix and 5 - 30 % flexural strength of the cement matrix and reduces 10 - 60% water penetration in the cement matrix are disclosed herein.

Full Text	COMPLATE AFTER PROVISIONAL. LEFT ON 28 JUL 2004 FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13) 1. TITLE OF THE INVENTION: Short polyester fibres as secondary reinforcement i n cementitious Materials. 2 APPLICANT (a) NAME : Reliance Industries Limited (b)NATIONALITY: Indian company incorporated under the Companies Act 1956 (c) ADDRESS : Reliance Technology Centre, B-4 MIDC Industrial Area, Patalganga- 410220, Dist- Raigad, Maharashtra, India. 3. INVENTORS i (a) Name : Nadkarni Vikas Madhusudan (b) Nationality: Indian (c) Address A18 Garden Estate, Off D P Road, Aundh, Pune -41 1007, Maharashtra, India. (a) Name Deshpande Amit Avinash (b)Nationality : Indian (c) Address : 203, Kanuma Apartments, Hendrepada, Kulgaon, Badlapur (west), Pin 421 503, Dist: Thane, Maharashtra, India (a) Name : Gajelli Chandramouli Gangaram (b) Nationality : Indian (c)Address : F/401, Padmashali CHS, R. P. Nagar, Mahim (East), Mumbai - 400 019. Maharashtra, India (a) Name : Patil Kirti Gajanan (b) Nationality : Indian (c) Address : C/6/4/1:4 Sector 18, New Panvel (E), Dist Raigad - 410 206 Maharashtra, India (a) Name : Rekhi Sushant Suresh (b) Nationality : Indian (c) Address : B- 404, Vrindavan Society, Tirth Dham Complex, Near Lai Chowky, Andharwadi-Road, Kalyan (West) - 42130 Maharashtra, India (a) Name : Joshi Ajit Hemant (b) Nationality : Indian (c) Address : 2, Diamond House, D. L. Vaidya Road, Dadar - Mumbai 400 028 Maharashtra India 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed. 2 8 JUL 2004 Field of Invention: The invention relates to short polyester fibres particularly suited for reinforcing cementitious matrix. Particularly, the present invention relates to short polyester fibres as secondary reinforcement in cementitious matrix, wherein the fibres have a modified surface characteristic for excellent dispersibility and a unique geometrical shape for better anchoring in the cementitious matrix. Background and Prior art: Concrete is the most frequently used human-made material in the world. It is durable, inexpensive, readily molded into complicated shapes and has adequate compressive strength and stiffness. However, concrete has low tensile strength, low ductility and low energy absorption. Due to lack of its tensile strength, concrete is often reinforced with steel bars in structural applications. Such applications under abusive environmental conditions often result in corrosion of steel bars, subsequently contributing to the decay of reinforced concrete structures. An intrinsic cause of the poor tensile behaviour of concrete is its low toughness and the presence of defects. An effective way to improve the toughness of concrete is by adding small fraction of short fibres to concrete during mixing. In the fracture process of fibre reinforced concrete (FRC), fibres bridging the cracks in the matrix provide resistance to crack propagation and crack opening before being pulled out or stressed to rupture. 2 Concrete undergoes a volume change as it dries with casting. Deformation due to drying shrinkage when restrained, is one of the major reasons of cracking in concrete. Positive effects of fibre reinforcement in controlling concrete drying shrinkage and shrinkage cracking have been reported. In the prior art there is a mention of the use of Polyolefin fibres, PVA fibres, Carbon fibres, Para aramid fibres, Glass fibres or even the bi-component fibres as secondary reinforcement in concrete. US 6582511 reports a non-alkaline resistant glass and in particular E-glass as reinforcement for concrete to reduce the occurrence of plastic shrinkage cracks. This is directed toward short-term crack abatement of concrete. The glass fibers are generally brittle and therefore prone to damage or strand seperation during the conventional concrete mixing process. The handling of glass fibers is also particularly hazardous. US 5855663 disclose carbon fibres for reinforcement of cement particularly suitable for a direct spray method. The carbon fibres conventionally have a weak bonding with the concrete matrix, the mentioned art tries to improve the bonding of Carbon fibre with the concrete matrix by using a particular sizing agent. The Carbon fibers are expensive and are not cost effective in the use. US 4968561 disclose a synthetic fibre, in particular a PVA fibre, showing good reinforcing property when added to a hydraulic substance such as cement. The mentioned art discloses a coarser 3 denier exceeding 1000 Dr., flat cross section PVA monofilament which can be used as an admixture to the cementitious matrix. JP10279335 discloses a multifilament fibre preferably para-aramid fibre or parapheylenebenzoxazole fibre to improve the fibre reinforcing effect for aerated lightweight concrete (ALC). The fibres such as PVA, Carbon fibres, Para aramid fibres and glass fibres reported in the abovementioned prior art are expensive, further the glass fibres used are hazardous in the end use application. US 5753368 discloses fibres with enhanced bonding strength using a coating material selected from certain glycol ethers, having atleast three carbon atoms in an oxyalkylene group and glycerol ethers. The coated fibre is preferably polypropylene. US 3(345961 reports an impact resistant concrete admixture comprising inorganic hydraulic cement and selected aggregate together with a plurality of finite fibres distributed substantially throughout the admixture. The said fibres are selected from a group consisting of nylon, polypropylene, polyethylene and polyvinylidene chloride. US 5399195 disclose a method for producing cement material with reduced development of self-induced cracking. The said synthetic fibres consist essentially of polyolefin, a polyolefin derivative, polyester or a mixture thereof. The fibres are added as filament 4 bundles with 10 to 10000 filaments per bundle. Further the filaments in each bundle are held together by wetting agent. US 5985449 discloses crimped thermoplastic fibres for reinforcing concrete. The fibres have a crimp frequency of 20 per inch and are formed in bundles wherein the outer wrapping is a crepe paper wrapping wound spirally. US 6569526 discloses reinforcing matrix materials having a quadrilateral cross-sectional profile. The fibre body consists of at least one synthetic polymer selected from the group of polyethylene, polypropylene, polyoxymethylene, poly(vinylidine fluoride), poly(methyl pentene), poly(ethylene- chlorotrifluoroethylene), polyvinyl fluoride), poly(ethylene oxide), polyethylene terephthalate), poly(butylene terephthalate), polyamiide, polybutene. More preferably Polypropylene US 6592790 discloses mechanically flattened fibres with elongated bodies, the said fibres selected from polyolefins, nylon, polyester, cellulose, rayons, acrylics, polyvinyl alcohol or mixtures thereof. US 6503625 disclose high performance fibres made by mechanical flattening processes and methods for reinforcing matrix materials against cracks. The said fibres comprise one or more synthetic polymers e.g. polypropylene, polyethylene, styrene etc., metals such as steel etc. or mixtures thereof. KR 9405536 disclose concrete reinforcement using organic monofilament fibres made from cutting sheets of synthetic resin 5 films. The synthetic resin films comprise of either polyolefin, nylon, polyester. In the above mentioned prior art the Polyolefin fibres used are Polypropylene, Polyethylene which are low-density fibres hence float on the water surface, suggesting a dispersibility problem. Also these fibres are hydrophobic in nature and in most cases having ribbon cross-section, this indicates lower adhesion strength with hydrophilic cementitious matrix. This low density of Polyolefin fibre suggests dispersion problems in the aqueous concrete mix. Further the pull out resistance in ribbon like fibre is an issue of concern. To improve the state of the art and taking cost into consideration the present work was initiated to develop a polyester fibre as a secondary-reinforcing agent for concrete. The main object of the invention is to provide short polyester fibres with unique nonround multilobal geometry for better anchoring in cementitious matirx. Another object of the invention is to provide the short polyester fibres with surface modification to improve dispersability in cement matrix and stability in alkaline condition of cement matrix and thus making it useful for secondary reinforcement in cement matrix. Another object of the invention is to provide the short polyester fibres as secondary reinforcement in cement matrix by which 6 curing shrinkage cracks are reduced and thus reduced crack propogation. Another object of the invention is to provide the short polyester fibres with unique non round mulitilobal geometry when used in cementitious matrix for secondary reinforcement may increase time required for complete break of concrete matrix. Another object of the invention is to provide low cost short polyester fibres for secondary reinforcement in cementitious matrix produced by continuous polymerization. Summary of the Invention: The present invention discloses short polyester fibres for secondary reinforcement in cement matrix having characterized fineness of the fibres in the range of 1 to 20 denier, aspect ratio of fibres in the range of 85 to 500, tenacity of the fibres in the range of 2 to 6 g/denier or unique non-round multilobal geometrical shape of the fibres or combinations thereof. The fibres of the invention have the trilobal geometrical shape. The fibres of the invention are further coated with a coating comprising anionic surfactants or noninonic surfactants or combinations thereof for excellent dispensability and stability in alkaline condition. 7 The anionic surfactants are selected from sodium or potassium salts of phosphate esters of long chain alkyl groups such as decyl, tridecyl, cetyl, stearyl etc and/or sulphonated salts of derived from sulphosuccinic acids. The nonionic surfactants are selected from alkoxylated polypropylene glycol, alkoxylated long chain acids, alkoxylated long chain alcohols, alkoxylated alkyl phenol ethers, alkoxylated natural oils and fats. The coating composition comprises 1-10% of anionic surfactants or non ionic surfactant or combinations thereof in the form of emulsions and/or aqueous solutions. The coating used in the invention is in the range of 0.1 to 1.5 % by weight of total weight of the fibres. Preferably, the coating used in the invention is in the range of 0.2% to o.6% by weight of the total weight of the fibres. According to the invention, the fibres are produced by a continuous polymerization route in which polymer melt from last polymerization reactor, termed finisher, fed directly through a melt distribution manifold to the spinning machine to obtain fibers followed by coating the fibers with anionic surfactants or nonionic surfactants or combinations thereof. Number average molecular weight of the fibers is in the range of 16000-24000. 8 The polyester herein is intended to include any polyester but preferably polyethylene terephthalate or copolymers thereof. Detailed description: The present invention discloses short polyester fibres, suited for secondary reinforcement in cementitious matrix. Particularly, the present invention relates to short polyester fibres with excellent dispersibility, alongwith a unique geometrical shape that helps in better anchoring of the fibres in the cementitious matrix. Further the cross sections of the unique geometrical shape of the fibres is multi-lobal and thus have broader surface area to improve the pull out resistance. Further, these fibres are substantially stable in the alkaline conditions of the cementitious matrix and can be used employing the conventional mixing equipment used for cementitious matrix. The modified multi-lobal cross-section of the short polyester fibres of the invention also provides a substantial more surface area compared to conventional circular cross-section fiber. Thus for given fiber loading the multilobal cross-section fiber gives a substantially more surface area coverage in the cementitious matrix compared to circular cross -section or vice versa for a given surface area coverage, a substantially less mulitlobal fiber loading is required. The short polyester fibres monofilaments have a multi lobal cross-section for broader surface area to improve pull out resistance of the fibres, with the fineness in the range of 1 - 20 denier. Further, 9 the Aspect ratio of the polyester fibre monofilaments is in the range of 85 to 500 while the tenacity range of 2 to 6 gm/denier. Further, short Polyester fibres used in the present invention are spun from a polymer produced on a continuos polymerization plant. The process produces fibres of high molecular weight thus producing fibres of higher modulus and strength. Further, the effective cost of the product also goes down due to its production by continuous polymerization. A process for preparing the short polyester fibres comprising esterifiication or trans-esterification of monomers, melt condensation of esterified monomer to obtain oligomer, further polycondensation of oligomer to obtain polyester. In most industrial processes, the melt-phase reaction or continuous polymerization is performed in three to six or some times even more continuous reactors in series. The final stage reactor is generally termed as finisher. Once the desired IV of the molten polymer is achieved, the same is pumped from finisher through manifolds to the extruder for spinning into desired denier spun tow. The spun tow is drawn heat set and cut into desired lengths for getting fibers of desired denier and cut length. The polyester herein is intended to include any polyester but preferably polyethylene terephthalate or copolymers thereof. Further the short polyester fibres of the invention are coated with coating comprising anionic surfactants or nonionic surfactants or 10 combinations thereof by the conventional coating techniques like kiss roll, dipping, spraying, metering or lip roll. The coating composition comprises 1-10% of anionic surfactants or non ionic surfactant or combinations thereof in the form of emulsions and/or aqueous solutions. The coating used in the invention is in the range of 0.1 to 1.5 % by weight of total weight of the fibres. Preferably, the coating used in the invention is in the range of 0.2% to o.6% by weight of the total weight of the fibres. The coating used on the short polyester fibres, is based on combination of anionic/nonionic surfactants, which improve the dispersibility of fibres in the cementitious matrix compared to the standard textile coating used on the fibres. The coating with anionic surfactants or nonionic surfactants or combinations thereof gives more hydrophilicity to the fibre surface thus improving the adhesion of fibre with the cementitious matrix, suggesting better interfacial stress transfer. The short polyester fibres of the invention are coated with the coating composition comprising anionic surfactant or non-ionic surfactant in the form of emulsion or solution and further coated fibres were tested for their dispersability. A method to rate the fibres for dispersion in water is developed in-house, which comprises dispersing measured amount of fibers in a specific quantity of water followed by stirring the mixture using a magnetic stirrer for 30 sec and observing openability of fibers in water in 30 sec. The rating of 1 is poor when the fibers clump together and do 11 not open, while the rating of 5 is best when all the individual fibers open up and disperse evenly through out the water. Comparative dispersion rating of coated short polyester fibres of the invention with the fibres coated with conventional textile coating, fibres without coating and polypropylene was observed and shown in Table A. Table A : Comparative dispersion rating Type of fibres used Dispersion Rating With out surface coating 2 Polypropylene fibre 3 (Fibre Floats) Coating 1 (conventional textile coating) 4 Coating 2 (coating of the invention) 5 Further improvement observed with coated short polyester fibre is the sinking time, which determines the uniformity of the surface coating on the fibre surface. Lower the sinking time better is the uniformity of the coating on the fibre surface. The lower sinking time indicates the faster wettability of fiber surface by water, thus indicating increased hydrophilicity, and this suggests better dispersion in hydrophilic cementitious material. Comparative sinking time data is given in Table B Table B: comparative sinking time data Sinking Time in seconds (Average of 10 readings) Finish Identity of the fibres Fibre Cut length Minimu m Average Maximu m %CV Without surface 12 mm 15 22.0 30.2 22.99 12 coating Coating 1 12 mm 2.77 3.01 3.25 4.41 Coating 2 12 mm 2.08 2.15 2.22 2.45 Note: PP fibre does not sink Coating 1 : conventional textile coating Coating 2 : coating of the invention In the present invention an enhancement in concrete properties is achieved with addition of the short polyester fibres of the invention at the dosing level of 0.05% to 2% by weight of cementitious material. The drying shrinkage strain studies of the short polyester fibres of the invention showed a marked reduction in drying shrinkage strain, depending on the cement grade and the drying condition. This implies reduced generation of shrinkage related microcracks, which would in turn reduce the seepage of water and aggressive chemicals into concrete, thus increasing the durability and service life of concrete structure The water penetration actually goes down after using short polyester fibres of the invention in cement matrix indicating the reduction in cracks in the cementitious matrix. By adding of the short polyester fibres as a secondary reinforcement it is observed that there is increase in compressive strength and flexural strength of the cementitious matrix indicating 13 good interfacial stress transfer between the secondary reinforcement fibres and the matrix. The aging effect shows no deterioration in properties of concrete after adding the fibres of the invention. The impact property of the aged concrete suitably reinforced with the claimed short polyester fibre shows a substantial improvement. Thus rendering improved toughness in the concrete with the addition of the short polyester fiber. Thus the short polyester fibres of the invention improve compressive strength, flexural strength and impact resistance and reducing water penetration and drying shrinkage strain of the cement matrix. Therefore the short polyester fibres of the invention are used for secondary reinforcement in the cement matrix. Advantages of the invention: 1. Provides cross-section that would have broader surface area to improve the pull out resistance. 2. Improves dispersion by modifying surface characteristics with application of surface coating on the fibre. 3. Modifies the surface with application of surface coating to have a hydrophilic surface thereby improving adhesion between cementitious matrix and fibre, thus suggesting better interfacial stress transfer. 4. Significantly reduces cost, as the product is made on a continuous polymerization platform. 5. Improves in performance characteristics of cementitious material by using the fibres. 14 The invention is illustrated below by Examples of the property improvement of concrete with the addition of claimed fibres Example 1 The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 1. Concrete used was conventional OPC mixed concrete and fiber used was of 10 denier and of cut length 12 mm. Control sample (without short polyester fibres of the invention) and cement matrix with fibres were studied for the compressive strength. The results of compressive strength are tabulated in table 2. The control as well as cement matrix with fibre were also studied for water penetration by standard method and results are tabulated in Table 3. The flexural strength of the control and cement matrix with fibres was studied and tabulated in Table 4. Table 1: Cement composition with the short polyester fiber loading to the tune of 0.25 wt % on the weight of cement (Per CUBIC METER). Ingredients Quantity Used Control With Fibre Cement 350 kg 350 kg Fibre - 0.9 Kg 20 mm Aggregate 740 kg 740 kg 10 mm Aggregate 350 kg 350 kg 0-5 mm unwashed sand 229.1 kg 229.1 kg 15 0 - 5 mm washed sand 430 kg 430 kg Dune Sand 234 kg 234 kg Admixture 6.5 Liters 6.5 Liters Free Water 131 Liters 131 Liters Tabel 2 : Compressive strength (N/mm2) for control and cement matrix with fibres. (Standard Used: BS 1881 Part 116 : 1983) Age of Test Control With Fibre % Improvement Remark 7 days 50.3 61.8 22.8 Significant increase inearlystrengthseen incementmatrix withfibres 28 days 63.7 73.0 14.7 SignificantIncrease inCompressivestrengthseen incementmatrix withfibres 16 Table 3: Water penetration in mm for control and cement matrix with fibres. Age of Test Control With Fibre % Improvement Remark SignificantReduction inwater 28 days 26.3 10.7 59.5 penetrationseen incement matrixwith fibres Table 4: Flexural Strength in N/mm2 for control and cement matrix with fibres. (Standard Used: BS 1881 Part 118: 1983) Age of Test Without Fibre With Fibre % Improvement Remark SignificantIncrease inFlexural 28 days 6.5 8.3 22.0 Strengthseen incementmatrix withfibres 17 Example 2: The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 5. The short polyester fiber used was of 10 denier and of cut length 6 mm. Control sample (without short polyester fibres of the invention) and cement matrix with fibres were studied for the compressive strength. The results of compressive strength are tabulated in table 6. The control as well as cement matrix with fibre were also studied for the flexural strength and the results are tabulated in Table 7. Table 5 : Cement composition with the short polyester fiber loading to the tune of 0.25 wt % on the weight of cement (Per CUBIC METER). Ingredients Quantity Used Control With fibres Cement 330 kg 390 kg Microsilica 35 kg 35 kg Fibre - 0.9 Kg 20 mm Aggregate 740 kg 740 kg 10 mm Aggregate 350 kg 350 kg 0-5 mm unwashed sand 195 kg 195 kg 0-5 mm washed sand 430 kg 430 kg Dune Sand 234 kg 234 kg Admixture 6.5 Liters 6.5 Liters 18 Free Water 134 Liters 134 Liters Table 6: Compressive strength (N/mm2) for control and cement matrix with fibres. (Standard Used: BS 1881 Part 116: 1983) Age of Test Control With Fibre % Improvement Remark 7 days 67.7 70.8 4.7 Increase in strength is observed incement matrix withfibres 28 days 70.8 81.5 6.3 Increase in strength is observed incement matrix withfibres Table 7: Flexural Strength in N/mm2 for control and cement matrix with fibres. (Standard Used: BS 1881 Part 118: 1983) Age of Test Control With Fibre % Improvement Remark 28 days 8.9 10.1 12.7 Significant Increase in Flexural 19 Strength in cement matrix with fibres Example 3: The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 8. The short polyester fiber used was of 10 denier and of cut length 12 mm. Control sample (without short polyester fibres of the invention) and cement matrix with fibres were studied for compressive strength. The results of compressive strength are tabulated in table 9. The control as well as cement matrix with fibres v/ere also studied for the drying shrinkage upto 23 days after initial curing period of 7 days and the results obtained are tabulated in Table 10. The abrasion resistance of control and cement matrix with fibres are tabulated in Table 11. Table 8 : Cement composition with the short polyester fibre loading to the tune of 0.25 wt % on the weight of cement (Per CUBIC METER). Ingredients Quantity Used for M20 Concrete matrix Quantity Used for M40 Concrete matrix Without fiber (Control) With Fiber Withoutfiber (Control) With Fiber Cement 350 kg 350 kg 350 kg 350 kg 20 Fiber - 0.9 Kg Nil 0.9 Kg Sand (Zone II) 807 kg 807 kg 794 kg 794 kg CoarseAggregate(12 mm) 398 kg 398 kg 392 kg 392 kg CoarseAggregate(20 mm) 722 kg 722 kg 710 kg 710kg Water 172 kg 172 kg 164 kg 164 kg Superplasti cizer 0.75% byweight ofcement 0.75% byweight ofcement 1 % byweight of cement 1 % byweight ofcement Table 9: Compressive strength (N/mm2) of control M20 sample and cement matrix of M20 with fibres (Testing Standard: IS 516) Age of Test Without Fibre With Fibre % Improvement Remark 7 days 27.3 30.4 11.35 Increase in strength is observed in M20 cement matrix with fibres 28 days 33.9 38.0 12.09 Increase instrength isobserved inM 20 cement 21 matrix with fibres Drying shrinkage strain was observed up to 23 days after initial curing period of 7 days. For this study cement composition tabulated in Table 8 was used with two different grades of cement which are OPC grade and PPC grade. Table 10: Drying Shrinkage results with fibre loading of 0.25% on wt. of cement Cement type CuringConditions % Reduction in Shrinkage after fibre addition (After 23 days) over the control sample without fiber M20 concrete with OPC grade cement Air Dried 20 - 25 % Inside Water Reduced shrinkage marginally M20 concrete with PPC grade cement Air Dried 80% Inside water 80% The above results indicate that compared to control cement matrix, the cement matrix with the short polyester fibers showed reduced drying shrinkage strain. This implies a reduced generation of shrinkage related micro-cracks, which would in turn reduce the 22 seepage of water and aggressive chemicals into concrete, thus increasing the durability and service life of concrete. The abrasion resistance was carried out on both the above-mentioned M20 grade concrete (Table 8) and also on M40 grade concrete (Table 8). The testing of abrasion was carried out on both the control sample (Without fiber) and the samples with fiber. The fiber loading is to the tune of 0.25% on the weight of fiber. The abrasion Resistance is calculated as follows: % wearwithoutfibre - % wearwithfibre % Increase = %wearwithoutfibre Table 11: Increase in Abrasion Resistance of the cement matrix with fibres over the control sample (Without fiber) (Standard Used: BS 812) Concrete Grade % Increase in Abrasion Resistance of concrete with fiber over control concrete without fiber . M20 Grade 18.8% M40 Grade 23.7% Example 4: The impact resistance of concrete was measured by drop weight test. This test method is designed to obtain the relative performances of control and fiber reinforced concrete. 23 A 150 mm diameter and 64 mm thick concrete disc is subjected to repeated impact loads (blows) by dropping a 4.54 kg hammer from a height of 460 mm. The load is transferred from the hammer to the specimen through a 64 mm steel ball placed at the center of the disc. The number of blows that cause first visible crack is recorded as the first crack strength. The loading is continued until the disc fails completely. The results of these tests exhibit high variability. The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 12. The short polyester fiber used was of 10 denier and of cut length 12 mm. Control sample (without short polyester fibres) and cement matrix with fibres were studied for Impact resistance. Impact resistance was studied for control and cement matrix with fiber after normal curing of 28 days. The durability test was performed by aging the samples in a 50 °C lime saturated water for a period of 35 days after normal curing of 28 days. Table 12: Cement matrix composition of control and cement matrix with fibres Ingredients Quantity Used Control With fibres Cement 350 kg 350 kg Fibres - 4.7 kg Sand (Zone II) 807 kg 794 kg Coarse Aggregate (12 398 kg • . ' 392 kg 24 mm) Coarse Aggregate (20 mm) 722 kg 710 kg Water 172 kg 164 kg Superplasticizer 0.75% by weight of cement 1.0% by weight of cement Table 13: Impact Testing on Disc Specimen (Normal Curing): Specimen No Control With fiber loading of 4.7 Kg/m3 1st Crack Through out crack 1st Crack Throughout crack 1 34 38 16 43 2 36 42 28 39 3 62 67 71 86 The above results indicate that with the fibre loading, the number of blows for complete failure increases substantially after the first crack is seen, suggesting improvement in toughness. Table 14: Impact Testing on Disc Specimen (After Aging): Specimen No Control With fiber loading of 4.7 Kg/m3 1st Crack Through out crack 1st Crack Throughout crack 1 166 169 508 511 2 172 174 701 709 25 3 239 241 667 675 According to the results obtained after ageing, cement matrix with the fibre acted as a very good stress transfer medium through out the concrete matrix and dissipated energy pretty evenly. The number of blows for the first crack had gone up substantially higher. Thus indicated a good adhesion between the matrix and the fibre. Example 5: The short polyester fiber is tested for alkaline resistance. For this study we have selected the polyester fiber made from polyethylene terephthalate with the number average molecular weight in the range of 16,000 to 18,000 and was of 10 denier. The test is carried in more harsh conditions compared to ICBO AC 32, which is termed as Test 1. The test conditions are tabulated in Table 15. Table 15 : Test conditions for standard ICBO AC 32 and Test employed in-house for Alkaline resistance Test Condition ICBO AC 32 criteria Test1 Alkaline Medium Calcium Hydroxide Calcium Hydroxide, saturated Range of pH 11.0 to 13.0 13.5 Temperature Room Temperature 50 °C for two days40 °C thereafter for onemonth The criteria for acceptance as per ICBO AC32 is that breaking strength of the fibre should be retained at least 90% of the control 26 sample (untreated by Test 1). The results of breaking strength of test sample and control sample are given in Table 16. Table 16 : breaking strength for untreated control sample and fibres subjected to above-mentioned test Control Sample Sample subjected to Test1 Breaking strength 43.8 41.8 (gms) The breaking tensile strength retained was 95.5%. 27 We claim 1. Short polyester fibres for secondary reinforcement in cement matrix having characterized fineness of the fibres in the range of 1 to 20 denier, aspect ratio of fibres in the range of 85 to 500, tenacity of the fibres in the range of 2 to 6 g/denier, or unique non-round multilobal geometrical shape of the fibres or combinations thereof. 2. The fibres as cliamed in claim 1, wherein the geometrical shape of the fiber is trilobal. 3. The fibres as cliamed in claim 1, further coated with a coating comprising anionic surfactants or noninonic surfactants or combinations thereof for excellent dispersability and stability in alkaline condition. 4. The fibres as claimed in claim 3, wherein the anionic surfactants are selected from sodium or potassium salts of phosphate esters of long chain alkyl groups such as decyl, tridecyl, cetyl, stearyl etc. and/or sulphonated salts of derived from sulphosuccinic acids. .t. 5. The fibres as cliamed in claim 3, wherein the nonionic surfactants are selected from alkoxylated polypropylene glycol, alkoxylated long chain acids, alkoxylated long chain alcohols, alkoxylated alkyl phenol ethers, alkoxylated natural oils and fats. 6. The fibres as cliamed in any one of the preceding claims wherein the fibres are produced by a continuous 28 polymerization route in which polymer melt from last polymerization reactor, termed finisher fed directly through a melt distribution manifold to the spinning machine to obtain fibers followed by coating the fibers with anionic surfactants or nonionic surfactants or combinations thereof. 7. The fibres as cliamed in any one of the preceding claims wherein a number average molecular weight of the fibres is in the range of 16000 - 24000. 8. The fibres as claimed in any one the preceding claims, used in the range of 0.05% to 2% by weight of cementitious material in cement matrix for reinforcement. 9. The fibres as cliamed in any one the preceding claims used in the cement matrix for secondary reinforcement having characteristic 5 - 30% increase in compressive strength of the cement matrix, 10 - 60% reduction in the water penetration in the cement matrix and 5 - 30 % increase in flexural strength of the cement matrix. Dated this the 25th day of July 2005 29 Abstract Short polyester fibers for secondary reinforcement in cementitious matrix which increases 5 - 30% compressive strength of the cement matrix and 5 - 30 % flexural strength of the cement matrix and reduces 10 - 60% water penetration in the cement matrix are disclosed herein. 30

Full Text

COMPLATE AFTER PROVISIONAL. LEFT ON 28 JUL 2004

FORM 2
THE PATENT ACT 1970
(39 of 1970)

& The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION: Short polyester fibres as secondary
reinforcement i n cementitious Materials.
2 APPLICANT
(a) NAME : Reliance Industries Limited
(b)NATIONALITY: Indian company incorporated under the Companies Act
1956
(c) ADDRESS : Reliance Technology Centre, B-4 MIDC Industrial Area,
Patalganga- 410220, Dist- Raigad, Maharashtra, India.
3. INVENTORS i
(a) Name : Nadkarni Vikas Madhusudan
(b) Nationality: Indian
(c) Address A18 Garden Estate, Off D P Road, Aundh, Pune -41 1007,
Maharashtra, India.
(a) Name Deshpande Amit Avinash
(b)Nationality : Indian
(c) Address : 203, Kanuma Apartments, Hendrepada, Kulgaon, Badlapur (west),
Pin 421 503, Dist: Thane, Maharashtra, India
(a) Name : Gajelli Chandramouli Gangaram
(b) Nationality : Indian
(c)Address : F/401, Padmashali CHS, R. P. Nagar, Mahim (East),
Mumbai - 400 019. Maharashtra, India
(a) Name : Patil Kirti Gajanan
(b) Nationality : Indian
(c) Address : C/6/4/1:4 Sector 18, New Panvel (E), Dist Raigad - 410 206
Maharashtra, India
(a) Name : Rekhi Sushant Suresh
(b) Nationality : Indian
(c) Address : B- 404, Vrindavan Society, Tirth Dham Complex, Near Lai
Chowky, Andharwadi-Road, Kalyan (West) - 42130
Maharashtra, India
(a) Name : Joshi Ajit Hemant
(b) Nationality : Indian
(c) Address : 2, Diamond House, D. L. Vaidya Road, Dadar - Mumbai 400 028
Maharashtra India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in
which it is to be performed.
2 8 JUL 2004

Field of Invention:
The invention relates to short polyester fibres particularly suited for reinforcing cementitious matrix. Particularly, the present invention relates to short polyester fibres as secondary reinforcement in cementitious matrix, wherein the fibres have a modified surface characteristic for excellent dispersibility and a unique geometrical shape for better anchoring in the cementitious matrix.
Background and Prior art:
Concrete is the most frequently used human-made material in the world. It is durable, inexpensive, readily molded into complicated shapes and has adequate compressive strength and stiffness. However, concrete has low tensile strength, low ductility and low energy absorption. Due to lack of its tensile strength, concrete is often reinforced with steel bars in structural applications. Such applications under abusive environmental conditions often result in corrosion of steel bars, subsequently contributing to the decay of reinforced concrete structures.
An intrinsic cause of the poor tensile behaviour of concrete is its low toughness and the presence of defects. An effective way to improve the toughness of concrete is by adding small fraction of short fibres to concrete during mixing. In the fracture process of fibre reinforced concrete (FRC), fibres bridging the cracks in the matrix provide resistance to crack propagation and crack opening before being pulled out or stressed to rupture.
2

Concrete undergoes a volume change as it dries with casting. Deformation due to drying shrinkage when restrained, is one of the major reasons of cracking in concrete. Positive effects of fibre reinforcement in controlling concrete drying shrinkage and shrinkage cracking have been reported.
In the prior art there is a mention of the use of Polyolefin fibres, PVA fibres, Carbon fibres, Para aramid fibres, Glass fibres or even the bi-component fibres as secondary reinforcement in concrete.
US 6582511 reports a non-alkaline resistant glass and in particular E-glass as reinforcement for concrete to reduce the occurrence of plastic shrinkage cracks. This is directed toward short-term crack abatement of concrete. The glass fibers are generally brittle and therefore prone to damage or strand seperation during the conventional concrete mixing process. The handling of glass fibers is also particularly hazardous.
US 5855663 disclose carbon fibres for reinforcement of cement particularly suitable for a direct spray method. The carbon fibres conventionally have a weak bonding with the concrete matrix, the mentioned art tries to improve the bonding of Carbon fibre with the concrete matrix by using a particular sizing agent. The Carbon fibers are expensive and are not cost effective in the use.
US 4968561 disclose a synthetic fibre, in particular a PVA fibre, showing good reinforcing property when added to a hydraulic substance such as cement. The mentioned art discloses a coarser
3

denier exceeding 1000 Dr., flat cross section PVA monofilament which can be used as an admixture to the cementitious matrix.
JP10279335 discloses a multifilament fibre preferably para-aramid fibre or parapheylenebenzoxazole fibre to improve the fibre reinforcing effect for aerated lightweight concrete (ALC).
The fibres such as PVA, Carbon fibres, Para aramid fibres and glass fibres reported in the abovementioned prior art are expensive, further the glass fibres used are hazardous in the end use application.
US 5753368 discloses fibres with enhanced bonding strength using a coating material selected from certain glycol ethers, having atleast three carbon atoms in an oxyalkylene group and glycerol ethers. The coated fibre is preferably polypropylene.
US 3(345961 reports an impact resistant concrete admixture comprising inorganic hydraulic cement and selected aggregate together with a plurality of finite fibres distributed substantially throughout the admixture. The said fibres are selected from a group consisting of nylon, polypropylene, polyethylene and polyvinylidene chloride.
US 5399195 disclose a method for producing cement material with reduced development of self-induced cracking. The said synthetic fibres consist essentially of polyolefin, a polyolefin derivative, polyester or a mixture thereof. The fibres are added as filament
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bundles with 10 to 10000 filaments per bundle. Further the filaments in each bundle are held together by wetting agent.
US 5985449 discloses crimped thermoplastic fibres for reinforcing concrete. The fibres have a crimp frequency of 20 per inch and are formed in bundles wherein the outer wrapping is a crepe paper wrapping wound spirally.
US 6569526 discloses reinforcing matrix materials having a
quadrilateral cross-sectional profile. The fibre body consists of at
least one synthetic polymer selected from the group of
polyethylene, polypropylene, polyoxymethylene, poly(vinylidine
fluoride), poly(methyl pentene), poly(ethylene-
chlorotrifluoroethylene), polyvinyl fluoride), poly(ethylene oxide), polyethylene terephthalate), poly(butylene terephthalate), polyamiide, polybutene. More preferably Polypropylene
US 6592790 discloses mechanically flattened fibres with elongated bodies, the said fibres selected from polyolefins, nylon, polyester, cellulose, rayons, acrylics, polyvinyl alcohol or mixtures thereof.
US 6503625 disclose high performance fibres made by mechanical flattening processes and methods for reinforcing matrix materials against cracks. The said fibres comprise one or more synthetic polymers e.g. polypropylene, polyethylene, styrene etc., metals such as steel etc. or mixtures thereof.
KR 9405536 disclose concrete reinforcement using organic monofilament fibres made from cutting sheets of synthetic resin
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films. The synthetic resin films comprise of either polyolefin, nylon, polyester.
In the above mentioned prior art the Polyolefin fibres used are Polypropylene, Polyethylene which are low-density fibres hence float on the water surface, suggesting a dispersibility problem. Also these fibres are hydrophobic in nature and in most cases having ribbon cross-section, this indicates lower adhesion strength with hydrophilic cementitious matrix. This low density of Polyolefin fibre suggests dispersion problems in the aqueous concrete mix. Further the pull out resistance in ribbon like fibre is an issue of concern.
To improve the state of the art and taking cost into consideration the present work was initiated to develop a polyester fibre as a secondary-reinforcing agent for concrete.
The main object of the invention is to provide short polyester fibres with unique nonround multilobal geometry for better anchoring in cementitious matirx.
Another object of the invention is to provide the short polyester fibres with surface modification to improve dispersability in cement matrix and stability in alkaline condition of cement matrix and thus making it useful for secondary reinforcement in cement matrix.
Another object of the invention is to provide the short polyester fibres as secondary reinforcement in cement matrix by which
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curing shrinkage cracks are reduced and thus reduced crack propogation.
Another object of the invention is to provide the short polyester fibres with unique non round mulitilobal geometry when used in cementitious matrix for secondary reinforcement may increase time required for complete break of concrete matrix.
Another object of the invention is to provide low cost short polyester fibres for secondary reinforcement in cementitious matrix produced by continuous polymerization.
Summary of the Invention:
The present invention discloses short polyester fibres for secondary reinforcement in cement matrix having characterized fineness of the fibres in the range of 1 to 20 denier, aspect ratio of fibres in the range of 85 to 500, tenacity of the fibres in the range of 2 to 6 g/denier or unique non-round multilobal geometrical shape of the fibres or combinations thereof.
The fibres of the invention have the trilobal geometrical shape.
The fibres of the invention are further coated with a coating comprising anionic surfactants or noninonic surfactants or combinations thereof for excellent dispensability and stability in alkaline condition.
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The anionic surfactants are selected from sodium or potassium salts of phosphate esters of long chain alkyl groups such as decyl, tridecyl, cetyl, stearyl etc and/or sulphonated salts of derived from sulphosuccinic acids.
The nonionic surfactants are selected from alkoxylated polypropylene glycol, alkoxylated long chain acids, alkoxylated long chain alcohols, alkoxylated alkyl phenol ethers, alkoxylated natural oils and fats.
The coating composition comprises 1-10% of anionic surfactants or non ionic surfactant or combinations thereof in the form of emulsions and/or aqueous solutions.
The coating used in the invention is in the range of 0.1 to 1.5 % by weight of total weight of the fibres. Preferably, the coating used in the invention is in the range of 0.2% to o.6% by weight of the total weight of the fibres.
According to the invention, the fibres are produced by a continuous polymerization route in which polymer melt from last polymerization reactor, termed finisher, fed directly through a melt distribution manifold to the spinning machine to obtain fibers followed by coating the fibers with anionic surfactants or nonionic surfactants or combinations thereof.
Number average molecular weight of the fibers is in the range of 16000-24000.
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The polyester herein is intended to include any polyester but preferably polyethylene terephthalate or copolymers thereof.
Detailed description:
The present invention discloses short polyester fibres, suited for secondary reinforcement in cementitious matrix. Particularly, the present invention relates to short polyester fibres with excellent dispersibility, alongwith a unique geometrical shape that helps in better anchoring of the fibres in the cementitious matrix. Further the cross sections of the unique geometrical shape of the fibres is multi-lobal and thus have broader surface area to improve the pull out resistance. Further, these fibres are substantially stable in the alkaline conditions of the cementitious matrix and can be used employing the conventional mixing equipment used for cementitious matrix.
The modified multi-lobal cross-section of the short polyester fibres of the invention also provides a substantial more surface area compared to conventional circular cross-section fiber. Thus for given fiber loading the multilobal cross-section fiber gives a substantially more surface area coverage in the cementitious matrix compared to circular cross -section or vice versa for a given surface area coverage, a substantially less mulitlobal fiber loading is required.
The short polyester fibres monofilaments have a multi lobal cross-section for broader surface area to improve pull out resistance of the fibres, with the fineness in the range of 1 - 20 denier. Further,
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the Aspect ratio of the polyester fibre monofilaments is in the range of 85 to 500 while the tenacity range of 2 to 6 gm/denier.
Further, short Polyester fibres used in the present invention are spun from a polymer produced on a continuos polymerization plant. The process produces fibres of high molecular weight thus producing fibres of higher modulus and strength. Further, the effective cost of the product also goes down due to its production by continuous polymerization.
A process for preparing the short polyester fibres comprising esterifiication or trans-esterification of monomers, melt condensation of esterified monomer to obtain oligomer, further polycondensation of oligomer to obtain polyester.
In most industrial processes, the melt-phase reaction or continuous polymerization is performed in three to six or some times even more continuous reactors in series. The final stage reactor is generally termed as finisher. Once the desired IV of the molten polymer is achieved, the same is pumped from finisher through manifolds to the extruder for spinning into desired denier spun tow. The spun tow is drawn heat set and cut into desired lengths for getting fibers of desired denier and cut length.
The polyester herein is intended to include any polyester but preferably polyethylene terephthalate or copolymers thereof.
Further the short polyester fibres of the invention are coated with coating comprising anionic surfactants or nonionic surfactants or
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combinations thereof by the conventional coating techniques like kiss roll, dipping, spraying, metering or lip roll. The coating composition comprises 1-10% of anionic surfactants or non ionic surfactant or combinations thereof in the form of emulsions and/or aqueous solutions.
The coating used in the invention is in the range of 0.1 to 1.5 % by weight of total weight of the fibres. Preferably, the coating used in the invention is in the range of 0.2% to o.6% by weight of the total weight of the fibres.
The coating used on the short polyester fibres, is based on combination of anionic/nonionic surfactants, which improve the dispersibility of fibres in the cementitious matrix compared to the standard textile coating used on the fibres. The coating with anionic surfactants or nonionic surfactants or combinations thereof gives more hydrophilicity to the fibre surface thus improving the adhesion of fibre with the cementitious matrix, suggesting better interfacial stress transfer.
The short polyester fibres of the invention are coated with the coating composition comprising anionic surfactant or non-ionic surfactant in the form of emulsion or solution and further coated fibres were tested for their dispersability. A method to rate the fibres for dispersion in water is developed in-house, which comprises dispersing measured amount of fibers in a specific quantity of water followed by stirring the mixture using a magnetic stirrer for 30 sec and observing openability of fibers in water in 30 sec. The rating of 1 is poor when the fibers clump together and do
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not open, while the rating of 5 is best when all the individual fibers open up and disperse evenly through out the water. Comparative dispersion rating of coated short polyester fibres of the invention with the fibres coated with conventional textile coating, fibres without coating and polypropylene was observed and shown in Table A. Table A : Comparative dispersion rating

Type of fibres used Dispersion Rating
With out surface coating 2
Polypropylene fibre 3 (Fibre Floats)
Coating 1 (conventional textile coating) 4
Coating 2 (coating of the invention) 5
Further improvement observed with coated short polyester fibre is the sinking time, which determines the uniformity of the surface coating on the fibre surface. Lower the sinking time better is the uniformity of the coating on the fibre surface. The lower sinking time indicates the faster wettability of fiber surface by water, thus indicating increased hydrophilicity, and this suggests better dispersion in hydrophilic cementitious material. Comparative sinking time data is given in Table B Table B: comparative sinking time data

Sinking Time in seconds (Average of 10 readings)
Finish Identity of the fibres Fibre Cut length Minimu m Average Maximu m %CV
Without surface 12 mm 15 22.0 30.2 22.99
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coating
Coating 1 12 mm 2.77 3.01 3.25 4.41
Coating 2 12 mm 2.08 2.15 2.22 2.45
Note: PP fibre does not sink
Coating 1 : conventional textile coating Coating 2 : coating of the invention
In the present invention an enhancement in concrete properties is achieved with addition of the short polyester fibres of the invention at the dosing level of 0.05% to 2% by weight of cementitious material.
The drying shrinkage strain studies of the short polyester fibres of the invention showed a marked reduction in drying shrinkage strain, depending on the cement grade and the drying condition. This implies reduced generation of shrinkage related microcracks, which would in turn reduce the seepage of water and aggressive chemicals into concrete, thus increasing the durability and service life of concrete structure
The water penetration actually goes down after using short polyester fibres of the invention in cement matrix indicating the reduction in cracks in the cementitious matrix.
By adding of the short polyester fibres as a secondary reinforcement it is observed that there is increase in compressive strength and flexural strength of the cementitious matrix indicating
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good interfacial stress transfer between the secondary reinforcement fibres and the matrix.
The aging effect shows no deterioration in properties of concrete after adding the fibres of the invention. The impact property of the aged concrete suitably reinforced with the claimed short polyester fibre shows a substantial improvement. Thus rendering improved toughness in the concrete with the addition of the short polyester fiber.
Thus the short polyester fibres of the invention improve compressive strength, flexural strength and impact resistance and reducing water penetration and drying shrinkage strain of the cement matrix. Therefore the short polyester fibres of the invention are used for secondary reinforcement in the cement matrix.
Advantages of the invention:
1. Provides cross-section that would have broader surface area to improve the pull out resistance.
2. Improves dispersion by modifying surface characteristics with application of surface coating on the fibre.
3. Modifies the surface with application of surface coating to have a hydrophilic surface thereby improving adhesion between cementitious matrix and fibre, thus suggesting better interfacial stress transfer.
4. Significantly reduces cost, as the product is made on a continuous polymerization platform.
5. Improves in performance characteristics of cementitious material by using the fibres.
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The invention is illustrated below by Examples of the property improvement of concrete with the addition of claimed fibres
Example 1
The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 1. Concrete used was conventional OPC mixed concrete and fiber used was of 10 denier and of cut length 12 mm. Control sample (without short polyester fibres of the invention) and cement matrix with fibres were studied for the compressive strength. The results of compressive strength are tabulated in table 2. The control as well as cement matrix with fibre were also studied for water penetration by standard method and results are tabulated in Table 3. The flexural strength of the control and cement matrix with fibres was studied and tabulated in Table 4.
Table 1: Cement composition with the short polyester fiber loading to the tune of 0.25 wt % on the weight of cement (Per CUBIC METER).

Ingredients Quantity Used
Control With Fibre
Cement 350 kg 350 kg
Fibre - 0.9 Kg
20 mm Aggregate 740 kg 740 kg
10 mm Aggregate 350 kg 350 kg
0-5 mm unwashed sand 229.1 kg 229.1 kg
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0 - 5 mm washed sand 430 kg 430 kg
Dune Sand 234 kg 234 kg
Admixture 6.5 Liters 6.5 Liters
Free Water 131 Liters 131 Liters
Tabel 2 : Compressive strength (N/mm2) for control and cement matrix with fibres.
(Standard Used: BS 1881 Part 116 : 1983)

Age of Test Control With Fibre % Improvement Remark
7 days 50.3 61.8 22.8 Significant increase inearlystrengthseen incementmatrix withfibres
28 days 63.7 73.0 14.7 SignificantIncrease inCompressivestrengthseen incementmatrix withfibres
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Table 3: Water penetration in mm for control and cement matrix with fibres.

Age of Test Control With Fibre % Improvement Remark
SignificantReduction inwater
28 days 26.3 10.7 59.5 penetrationseen incement matrixwith fibres
Table 4: Flexural Strength in N/mm2 for control and cement matrix with fibres. (Standard Used: BS 1881 Part 118: 1983)

Age of Test Without Fibre With Fibre % Improvement Remark
SignificantIncrease inFlexural
28 days 6.5 8.3 22.0 Strengthseen incementmatrix withfibres
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Example 2:
The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 5. The short polyester fiber used was of 10 denier and of cut length 6 mm. Control sample (without short polyester fibres of the invention) and cement matrix with fibres were studied for the compressive strength. The results of compressive strength are tabulated in table 6. The control as well as cement matrix with fibre were also studied for the flexural strength and the results are tabulated in Table 7.
Table 5 : Cement composition with the short polyester fiber loading to the tune of 0.25 wt % on the weight of cement (Per CUBIC METER).

Ingredients Quantity Used
Control With fibres
Cement 330 kg 390 kg
Microsilica 35 kg 35 kg
Fibre - 0.9 Kg
20 mm Aggregate 740 kg 740 kg
10 mm Aggregate 350 kg 350 kg
0-5 mm unwashed sand 195 kg 195 kg
0-5 mm washed sand 430 kg 430 kg
Dune Sand 234 kg 234 kg
Admixture 6.5 Liters 6.5 Liters
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Free Water 134 Liters 134 Liters
Table 6: Compressive strength (N/mm2) for control and cement matrix with fibres.
(Standard Used: BS 1881 Part 116: 1983)

Age of Test Control With Fibre % Improvement Remark
7 days 67.7 70.8 4.7 Increase in strength is observed incement matrix withfibres
28 days 70.8 81.5 6.3 Increase in strength is observed incement matrix withfibres
Table 7: Flexural Strength in N/mm2 for control and cement matrix with fibres. (Standard Used: BS 1881 Part 118: 1983)

Age of Test Control With Fibre % Improvement Remark
28 days 8.9 10.1 12.7 Significant Increase in Flexural
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Strength in cement matrix with fibres
Example 3:
The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 8. The short polyester fiber used was of 10 denier and of cut length 12 mm. Control sample (without short polyester fibres of the invention) and cement matrix with fibres were studied for compressive strength. The results of compressive strength are tabulated in table 9. The control as well as cement matrix with fibres v/ere also studied for the drying shrinkage upto 23 days after initial curing period of 7 days and the results obtained are tabulated in Table 10. The abrasion resistance of control and cement matrix with fibres are tabulated in Table 11.
Table 8 : Cement composition with the short polyester fibre loading to the tune of 0.25 wt % on the weight of cement (Per CUBIC METER).

Ingredients Quantity Used for M20 Concrete matrix Quantity Used for M40 Concrete matrix
Without fiber (Control) With Fiber Withoutfiber (Control) With Fiber
Cement 350 kg 350 kg 350 kg 350 kg
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Fiber - 0.9 Kg Nil 0.9 Kg
Sand (Zone II) 807 kg 807 kg 794 kg 794 kg
CoarseAggregate(12 mm) 398 kg 398 kg 392 kg 392 kg
CoarseAggregate(20 mm) 722 kg 722 kg 710 kg 710kg
Water 172 kg 172 kg 164 kg 164 kg
Superplasti cizer 0.75% byweight ofcement 0.75% byweight ofcement 1 % byweight of cement 1 % byweight ofcement
Table 9: Compressive strength (N/mm2) of control M20 sample and cement matrix of M20 with fibres (Testing Standard: IS 516)

Age of Test Without Fibre With Fibre % Improvement Remark
7 days 27.3 30.4 11.35 Increase in strength is observed in M20 cement matrix with fibres
28 days 33.9 38.0 12.09 Increase instrength isobserved inM 20 cement
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matrix with fibres
Drying shrinkage strain was observed up to 23 days after initial curing period of 7 days. For this study cement composition tabulated in Table 8 was used with two different grades of cement which are OPC grade and PPC grade.
Table 10: Drying Shrinkage results with fibre loading of 0.25% on wt. of cement

Cement type CuringConditions % Reduction in Shrinkage after fibre addition (After 23 days) over the control sample without fiber
M20 concrete with OPC grade cement Air Dried 20 - 25 %
Inside Water Reduced shrinkage marginally
M20 concrete with PPC grade cement Air Dried 80%
Inside water 80%
The above results indicate that compared to control cement matrix, the cement matrix with the short polyester fibers showed reduced drying shrinkage strain. This implies a reduced generation of shrinkage related micro-cracks, which would in turn reduce the
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seepage of water and aggressive chemicals into concrete, thus increasing the durability and service life of concrete.
The abrasion resistance was carried out on both the above-mentioned M20 grade concrete (Table 8) and also on M40 grade concrete (Table 8). The testing of abrasion was carried out on both the control sample (Without fiber) and the samples with fiber. The fiber loading is to the tune of 0.25% on the weight of fiber.
The abrasion Resistance is calculated as follows:
% wearwithoutfibre - % wearwithfibre
% Increase =
%wearwithoutfibre
Table 11: Increase in Abrasion Resistance of the cement matrix with fibres over the control sample (Without fiber) (Standard Used: BS 812)

Concrete Grade % Increase in Abrasion Resistance of concrete with fiber over control concrete without fiber
.
M20 Grade 18.8%
M40 Grade 23.7%
Example 4:
The impact resistance of concrete was measured by drop weight test. This test method is designed to obtain the relative performances of control and fiber reinforced concrete.
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A 150 mm diameter and 64 mm thick concrete disc is subjected to repeated impact loads (blows) by dropping a 4.54 kg hammer from a height of 460 mm. The load is transferred from the hammer to the specimen through a 64 mm steel ball placed at the center of the disc.
The number of blows that cause first visible crack is recorded as the first crack strength. The loading is continued until the disc fails completely. The results of these tests exhibit high variability.
The short polyester fibres were added in cement matrix. Typical composition of cement matrix used for the study is shown in Table 12. The short polyester fiber used was of 10 denier and of cut length 12 mm. Control sample (without short polyester fibres) and cement matrix with fibres were studied for Impact resistance. Impact resistance was studied for control and cement matrix with fiber after normal curing of 28 days. The durability test was performed by aging the samples in a 50 °C lime saturated water for a period of 35 days after normal curing of 28 days.
Table 12: Cement matrix composition of control and cement matrix with fibres

Ingredients Quantity Used
Control With fibres
Cement 350 kg 350 kg
Fibres - 4.7 kg
Sand (Zone II) 807 kg 794 kg
Coarse Aggregate (12 398 kg • . ' 392 kg
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mm)
Coarse Aggregate (20 mm) 722 kg 710 kg
Water 172 kg 164 kg
Superplasticizer 0.75% by weight of cement 1.0% by weight of cement
Table 13: Impact Testing on Disc Specimen (Normal Curing):

Specimen No Control With fiber loading of 4.7 Kg/m3
1st Crack Through out crack 1st Crack Throughout crack
1 34 38 16 43
2 36 42 28 39
3 62 67 71 86
The above results indicate that with the fibre loading, the number of blows for complete failure increases substantially after the first crack is seen, suggesting improvement in toughness.
Table 14: Impact Testing on Disc Specimen (After Aging):

Specimen No Control With fiber loading of 4.7 Kg/m3
1st Crack Through out crack 1st Crack Throughout crack
1 166 169 508 511
2 172 174 701 709
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3 239 241 667 675
According to the results obtained after ageing, cement matrix with the fibre acted as a very good stress transfer medium through out the concrete matrix and dissipated energy pretty evenly. The number of blows for the first crack had gone up substantially higher. Thus indicated a good adhesion between the matrix and the fibre.
Example 5:
The short polyester fiber is tested for alkaline resistance. For this study we have selected the polyester fiber made from polyethylene terephthalate with the number average molecular weight in the range of 16,000 to 18,000 and was of 10 denier. The test is carried in more harsh conditions compared to ICBO AC 32, which is termed as Test 1. The test conditions are tabulated in Table 15. Table 15 : Test conditions for standard ICBO AC 32 and Test employed in-house for Alkaline resistance

Test Condition ICBO AC 32 criteria Test1
Alkaline Medium Calcium Hydroxide Calcium Hydroxide, saturated
Range of pH 11.0 to 13.0 13.5
Temperature Room Temperature 50 °C for two days40 °C thereafter for onemonth
The criteria for acceptance as per ICBO AC32 is that breaking strength of the fibre should be retained at least 90% of the control
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sample (untreated by Test 1). The results of breaking strength of test sample and control sample are given in Table 16. Table 16 : breaking strength for untreated control sample and fibres subjected to above-mentioned test

Control Sample Sample subjected to Test1
Breaking strength 43.8 41.8
(gms)
The breaking tensile strength retained was 95.5%.
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We claim
1. Short polyester fibres for secondary reinforcement in cement matrix having characterized fineness of the fibres in the range of 1 to 20 denier, aspect ratio of fibres in the range of 85 to 500, tenacity of the fibres in the range of 2 to 6 g/denier, or unique non-round multilobal geometrical shape of the fibres or combinations thereof.
2. The fibres as cliamed in claim 1, wherein the geometrical shape of the fiber is trilobal.
3. The fibres as cliamed in claim 1, further coated with a coating comprising anionic surfactants or noninonic surfactants or combinations thereof for excellent dispersability and stability in alkaline condition.
4. The fibres as claimed in claim 3, wherein the anionic surfactants are selected from sodium or potassium salts of phosphate esters of long chain alkyl groups such as decyl, tridecyl, cetyl, stearyl etc. and/or sulphonated salts of derived from sulphosuccinic acids.
.t.
5. The fibres as cliamed in claim 3, wherein the nonionic
surfactants are selected from alkoxylated polypropylene glycol, alkoxylated long chain acids, alkoxylated long chain alcohols, alkoxylated alkyl phenol ethers, alkoxylated natural oils and fats.
6. The fibres as cliamed in any one of the preceding claims
wherein the fibres are produced by a continuous
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polymerization route in which polymer melt from last polymerization reactor, termed finisher fed directly through a melt distribution manifold to the spinning machine to obtain fibers followed by coating the fibers with anionic surfactants or nonionic surfactants or combinations thereof.
7. The fibres as cliamed in any one of the preceding claims wherein a number average molecular weight of the fibres is in the range of 16000 - 24000.
8. The fibres as claimed in any one the preceding claims, used in the range of 0.05% to 2% by weight of cementitious material in cement matrix for reinforcement.
9. The fibres as cliamed in any one the preceding claims used in the cement matrix for secondary reinforcement having characteristic 5 - 30% increase in compressive strength of the cement matrix, 10 - 60% reduction in the water penetration in the cement matrix and 5 - 30 % increase in flexural strength of the cement matrix.
Dated this the 25th day of July 2005

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Abstract
Short polyester fibers for secondary reinforcement in cementitious matrix which increases 5 - 30% compressive strength of the cement matrix and 5 - 30 % flexural strength of the cement matrix and reduces 10 - 60% water penetration in the cement matrix are disclosed herein.
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SHORT POLYESTER FIBRES AS SECONDARY REINFORCEMENT IN CEMENTITIOUS MATERIALS

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