Use of Waste Polypropylene Fibres for Strengthening of Structural Members

Transcription

1 Use of Waste Polypropylene Fibres for Strengthening of Structural Members Khot Anirudh Shivaji Kore Rohan Ramesh Koli Amit Laxmanrao Gore Mitesh Mahesh ABSTRACT The purpose of this study is to comparatively evaluate the failure pattern of the strengthened RCC columns jacketed with fiber reinforced concrete 8 no. of a short columns of size 150mm*150mm*500mm were initially casted using plain cement concrete of grade M20. After the 15 days of curing the specimens were initially tested under compression just after the beginning of cracks propagation. The testing is stopped after this the cracked column surfaces was prepared for jacketing produce Waste Polypropylene fibers obtained from plastic articles manufacturer Samruddhi industries at Sangli used in a cover concrete of jacked. Along with waste fiber specimens. The standard fibrillilated fiber jacked columns were also casted for comparison purpose. The waste Polypropylene fibers is the by product waste generated from casting of plastic articles within the factory. This can form the excellent materials for FRC since the physical and chemical properties of the Polypropylene fibers and waste fiber were the same. The jacketed columns with waste and conventional Polypropylene fibers were tested foe ultimate compressive strength and their failure and crack pattern is observed along with their compressive strength. Keywords Fiber reinforced concrete, Polypropylene fiber, Jacketing, strengthening, Fibrillated fiber Introduction - Fibres have been used as reinforcement since ancient times, for example, horse hair and coconut fibres in mortar and asbestos fibres in concrete. Fibres are added to concrete to control cracking caused by plastic shrinkage and drying shrinkage. The addition of small quantity of uniformly spaced fibres will act as crack controllers and enhance the tensile, fatigue, impact and abrasion resistance of concrete. They also reduce the permeability of concrete. Steel, Glass, Polypropylene, Carbon and besaltfibres have been used successfully. To overcome some disadvantages of conventional concrete such as low tensile and flexural strength, poor toughness, high brittleness fibre reinforced concrete (FRC) has been developed in recent years.the ductility of fibre reinforced concrete depends on the ability of the fibres to fill up cracks at high levels of strain. Addition of polypropylene fibres decreases the unit weight of concrete and increases its strength. Good concrete must have high strength and low permeability. Inclusion of polypropylene fibres reduces the water permeability, increases the flexural strength due to its high modulus of elasticity. The amount of fibres added to a concrete mix is expressed as a percentage of the total volume of the concrete and termed as percentage by volume. Polypropylene fibres are hydrophobic, that is they do not absorb water.they have hydrophobic levels, which protect them against wetting with cement paste. The hydrophobic nature of polypropylene has no effect on the amount of water needed for concrete.therefore, 255

2 when placed in a concrete matrix they need only be mixed long enough to insure dispersion in the concrete mixture. Fibresare used in concrete for the following purposes in concrete: to reduce plastic shrinkage and permeability, to increase impact resistance, abrasion resistance, fatigue, and cohesiveness.polypropylenefibres also improve spallingbehaviour of concrete. Materials Properties 1 Cement: Cement used is Ordinary Portland Cement (OPC) having 53 Grade as per IS cement. This cement is bought from ULTRATECH CEMENT PVT.LTD. 2. COARSE AGGREGATE: Locally available coarse aggregate passing through 20mm sieve and retained on 4.75mm sieve were used for this experimental study. 3 FINE AGGREAGATE:Locally available sand with zone II specification passing through 4.75mm sieve as per IS WATER: Portable water used for this experimental study during both casting as well as curing of specimen as per IS STANDARD POLYPROPYLENE FIBER: Polypropylene fiber is composed of crystalline and noncrystalline regions. The fiber ranges in size from micrometer to centimetres in diameter. In present work the polypropylene fibers with 12mm cut length is used. Table no 01 - POLYPROPYLENE FIBER PROPERTIES Sr.No. Properties Result 1 Geometry Of Fiber Fibrillated 2 Length Of Fiber 12 mm 3 Tensile Strength MPA 6 WASTE POLYPROPYLENE FIBER: Waste Polypropylene fiber is obtained from grinding the waste generated at Samruddhi Industries Pvt Ltd.The fiber ranges in size from micrometer to centimetres in thickness. In present work the polypropylene fibers upto 8mm cut length is used. Fig 1. Waste pp fibers Standard Fibrillted pp fibers 256

3 Experimental work: Initially 8 no. of short RC column were casted using M20 concrete and with #12mm dia. As longitudinal steel of fe415 grade and stirrups of 6mm 150mm c/c. The entire mixing and concreting is done as per the IS concrete mix design and with the help of detail specifications giver for RC works (From estimation, casting, specification and valuation in civil engineering by M. chakraburti) After the 15 days of curing of specimen were tested on the universal testing machine by applying gradually increasing compressive loading. As the initial structural cracks began to appear on the faces column showing signs of structural weakness, the loading process is stopped and column were removed over UTM. The loose cover concrete so damaged from the initial testing is removed carefully and the column surface is first cleared and then roughened with wire brush. To ensure the good bond between old concrete and cover concrete a epoxy bonding adhesive is applied on the roughened concrete surface in combination with cement in proportion 1:2 forming a cement paste. The cement paste is applied over the roughened surface in the approximate estimated quantity at 500 ml per m^2 surface. Soon after the application of chemical, damaged column is enclosed with a jacketing steel cage and cover concrete is coated around the damaged column completely covering the steel cage. 2 specimen were jacketed with using waste PP fibers in by volume of cover concrete, Also for the comparision analysis and no. of specimens were jacketed with standard fibrillated PP fibers in quantity of and 1.5% (2 each) by volume of cover concrete and 2 no. of specimen with no fiber addition in the cover concrete Details of initial casted specimen Details of jacketed specimen Size -150*150*500 mm Size -250*250*500 mm Grade of concrete- M 20 Grade of concrete- M 15 Grade of steel- Fe 415 Grade of steel- Fe 415 Longitudinal steel-4#10mm dia. Longitudinal steel-4#10mm dia. Stirrups-6 mm dia@150 c/c Stirrups-6 mm dia@75 c/c Table no 02- details of initial and jacketed sections Fig no 02 details of initial section 257

4 Fig no 03 details of jacketed section RESULTS: Table no 03 Experimental Results Column No. 1 no fiber 2 no fiber 3 std. 4std. 5std. 1.5% 6std. 1.5% 7waste 8waste Peak load(kn) Compressive strength(kn/sq.mm) Peak load(kn) Compressive strength(kn/sq.mm) FIG NO O4 CRACK PATTERN AT YIELD STRESSES OF COLUMN WITH NO FIBERS IN JACKETING COVER 258

5 A B FIG NO -05 A CRACK PATTERN AT YIELD STRESSES OF COLUMN WITH 1 % OF STANDARD FRC B CRACKPATTERN AT YIELD STRESSES OF COLUMN WITH 1.5 % OF STANDARD FRC. FIG NO 06 : CRACK PATTERN AT YIELD STRESSES OF COLUMN JACKETED WITH OF WASTE PP FIBRES 259

6 CONCLUSION :- a) At the ultimate load, the use of stndard substantially reduced the apparent damage which can allow the column to be serviceable. b)standard did not have the brittle compression failure that of regular reinforced concrete due to the bridging mechanism of fibers. c) No visible buckling of inner longitudinal bars occurred due to the intact between outer and inner longitudinal bar layers in case of standard. d) Because the standard cover concrete of jacketed column, the cover conrete did not spall in a brittle manner compared to regular reinforced concrete columns and waste although vertical cracks occurred on the cover concrete. e) In case of waste polypropylene fiber reinforced concrete, interlocking of fibers is abent which ultimately affects on compressive strength of tha member.the ductility performance remains same as that of regular reinforced concrete specimen. f) As a result the ductility performance of standard was improved and compressive strength was upto the mark but in case of waste, there is slight decrease in compressive strength due to the irregular waste. It happens because the waste irregular grinded polypropylene fibers disturbs the cohesive force between the adjacent concrete partical. REFERENCES 1) Bowman, Subramanian N. and T. GnanaSambanthan (1979), Polymers to Improve the Properties of Concrete, proceedings, All India Seminar on Prestressed Concrete Structures, Thiagarajar College of Engineering, Madhurai 2-3 May, pp ) BenturA. and Mindess S (2007), Fibre Reinforced Cementitious Composites, 2nd Edition, Taylor and Francis, Oxon, p.624 3) ACI 440R -07 (2007), Report on Fibre-Reinforced Concrete, American Concrete Institute, Farmington Hills, p ) Balaguru P.N. and Shah S.P.,( 1992), Fibre-Reinforced Cement Composites, McGraw- Hill Inc., New York, United State of America. 5) Alhozaimy, A. M., Soroushian, P., & Mirza, F. (1996).Mechanical properties of Polypropylene fibre reinforced concrete and the effects of pozzolanic materials. Cement and Concrete Composites, 18(2),