Performance of SBR-Latex Modified Polypropylene Fibre Reinforced PSC SBR Latex Railway Sleepers under Static LoadingLoading. G.R.Harish1, S.A.K.Zai2, N. Munnirudrappa3, Ajay.N4, Ambika.M.R4, Deepak Deepak.B.V4, Venugopal.K4. 1, 2 Professor Facility of Civil Engineering, University of Visvesvaraya Collage of Engineering, Bangalore University, Bangalore-560 056, India. 3 Professor, Department of Civil Engineering, Dayanand Sagar College of Engineering, K.S.Layout, Shivage Malleshwara Hills,Bangalore-560 078, India. 4 Former P.G Students, University of Visvesvaraya Collage of Engineering, Bangalore University, Bangalore-560 056, Bangalore India. ABSTRACT This paper presents a study on the behaviour of SBR-latex modified polypropylene fibre reinforced prestressed concrete railway sleeper SBR olypropylene under static loading. The prestressed concrete sleeper is an imperative component of ballasted railway tracks. Its main function is to restressed distribute axle loads on rails to the soil beneath The prestressed concrete sleeper is subjected to sagging moment at the rail seat section beneath. and hogging moment at the mid section. The emphas of this paper is on ductility aspect of new advanced materials over conventional emphasis material used in the manufacture of railway prestressed concrete sleepers. The test specimens are casted in sleeper factory at Birur, facture Karnataka, in accordance with IRS T-39 39-1985. The PSC sleepers are tested under two-point static loading. From the experimental loading study, first crack load, load - deflection behavior upto first crack load, ductility factor, energy absorption capacity and toughness index upto first crack load are observed. Keywords: Railway pre-stressed concrete sleepers, Static loading, Ductility factor, energy absorption capacity and toughness index. stressed tion I. INTRODUCTION A. Concrete Sleepers Railway tracks have been designed based on consideration to overcome the heavier loadload carrying capacity and more energy absorption ore capacity. Usually, ballasted railway track which consists of rails, ballast formation and fastening system is widely constructed for transportation [4]. The railway sleepers are importantly functioned to: - Uniformly transfer and distribute loads from the rail to underlying ballast bed. - Sustain and retain the rails at the proper gauge by keeping anchorage for the rail fastening system; preserve rail inclination; Provide support for rail; restrain longitudinal, lateral and vertical rail movements by ertical embedding itself onto substructures (see Fig.1). It is clear that the sleeper has a major role in distributing axle loads to formation. The axle loads could be considered static or quasi-static when the speeds of trains are quite static moderate. However, in general, the axle loading tends to physically behave like the dynamic impact pulses due to the continual moving ride over track irregularities and faster speeds. Fig.1 Components of Railway Track 1 B. Behaviour of Sleepers Although the dynamic effects have evidently prevailed over the failures of railway concrete sleepers, most of the design criteria are on the basis of the static sectional capacity of the concrete sleepers. Theoretical concepts of strength, ductility, stability, fracture mechanics refer to static behaviour of prestressed sleepers. By nature, the concrete sleeper is subjected to sagging moment at the railseat zone and hogging moment at the middle section. C. Research Significance Strength and ductility are the two major important factors to be considered in the design of structures subjected to static and dynamic loads, hence many attempts have been made in the recent past to develop a new material, which exhibits higher strength and ductility than the conventional concrete. It has been understood from the literature that many of the engineering properties such as tensile strength, compressive strength, flexural strength, fracture toughness, energy absorption capacity, etc of the conventional concrete could be improved by the addition of fibers. Similarly incorporation of polymers into concrete has also come across on the combined effect of fibers and polymer on the strength and behaviour of concrete. Considering this gap in the existing knowledge an attempt has been made to study the combined effect of polymers and fibers on flexural behaviour of Pretensioned Prestressed concrete (PSC) sleeper. The polymer considered in this study is Styrene Butadiene Rubber (SBR) Latex. The main aim of present study is to detailed experimental investigation of conventional Pre-Tensioned PSC sleeper and modifying the PSC sleepers with advanced construction materials such as SBR-latex, polypropylene fibres, silica fume and new generation superplasticizer to enhanced the structural properties, ductility aspects and durability aspect, so that introduction of such 2 composite material in novel technology in the field manufacture of sleeper industries with a benefit of increase in life span of existing PSC sleeper and increase in loading carrying capacity with quality production. II EXPERIMENTAL PROGRAMS Experimental setups were carried out complying with Indian Standards: IRS-T39-1985 Pretensioned Prestressed concrete sleepers. A. Materials used - Special grade 53-S cement (As per IRST-39). - Coarse aggregate with fraction 52%:23%. - Natural river sand (Confirm to Zone-I). - Water. - Silica Fume (Microsilica 920-D). - Superplasticizer (Glenium ACE-30). - SBR-latex. - Polypropylene Fibres. - High Tensile Wires. B. Mix proportions The M-60 grade of concrete is designed by Erntroy and Shaklock’s Empirical Graphical Method. The mix proportions are 1:0.92:2.65:0.31. Then modified M-60 grade of concrete achieved by adding 10% SBRlatex, 0.25% of polypropylene fibres, 10% of silica fume and 0.6% of superplasticizer. The mix proportions are 1:1.02:2.94:0.28. C. Test Specimens The eight standard sleepers (SS, MS-1 &MS2) are casted with trapezoidal cross section at railseat 150x250x210 mm and at the centre 150x220x 180 mm with span of 2750 mm in Malu Sleepers. Pvt. Ltd, Karnataka, India. D. Static Bending Test for Sleepers Tests were conducted as per IRS: T-39-85 (Third Revision-May-1996). The arrangement is shown in Fig.2. The sleepers are tested under different supports conditions such as centre top, centre bottom and railseat bottom. The PSC sleepers were tested under two point loading. All PSC sleepers were tested in the loading frame of capacity 500 KN with gradually increment of load at rate of 30 to 40 KN per minute up to the first crack load. load III. EXPERIMENTAL RESULTS . A. Compressive strength of concrete Fig. 4 shown the compressive strength, there will be 21% increasing in plain M-60 concrete and 11% of compressive strength is increased due to the modified latex fibre reinforced concrete as compare to M-55 concrete. As per M the Railway Specification the minimum compressive strength for 15 days is 55 N/mm2 i: e 63.2 N/mm2. Compressive Strength in Mpa 70 60 50 40 30 20 10 0 0 3 6 9 12 15 M-55 M-60 Fig.2 The Arrangement of Static bending test on Sleeper. E. Electrical Resistance Test for Sleepers Tests were conducted as per IRS: T T-39. The arrangement is shown in Fig.3. The sleeper shall be checked for electrical resistance at 230 volts AC supply. The 230 volts AC supply will be passed through a not less than 300 W test lamp in series with the pairs of inserts being tested. M60+SBR+Fibr es Ages (Days) Fig.4 Variation of Compressive strength with Ages Flexural Strength in Mpa 14 12 10 8 6 4 2 0 0 10 20 M-55 M-60 M60+SBR+Fibr es Ages in Days Fig.5 Variation of Flexural strength with Ages B. Flexural strength of concrete Fig. 5 shown the flexural strength of concrete, concrete the values are more than 5 N/mm2, hence cracks occurs within middle third of the span. As per Railway specification T-39, flexural T Fig.3 The Arrangement Resistance test on Sleeper. of Electrical 3 strength of concrete is should not be less than 5 N/mm2. C. Load- deflection behavior of Sleepers 160 140 120 Load (KN) 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 Deflection (mm) M60+SBR+Fib re M-55 M-60 bottom of sleeper shows 3% of load carrying capacity is increased and due to modification of latex and fibre 13% load carrying capacity is increased. And Moment of failure it will take more than 500 KN. The values of moment of resistance & moment of failure are more than control specimen and also more than RDSO acceptance criteria. E. Ductility Factor Table-2 Ductility Factor values Sleeper Designation SS(M55) MS-1(M60) MS-2(M60+SBR+Fibre) Ductility Factor 2.5 4.6 7.3 Fig.6 Load versus Deflection Curves Fig. 6 shown the first crack loads of sleepers, it will vary from 100KN to 130 KN. The deflection corresponding to first crack loads are 0.26mm, 0.6mm and 1.7mm for M-55, M60 and M-60 with latex modified sleepers respectively. D. Static Bending Strength of Sleepers Table - 1 Static Bending strength values Sleeper Designation Centre Top Rail Seat Bottom Mome nt of Resista nce 335 350 382 220 Moment of Failure 435 >500 >500 370 From Table-2, it can be seen that the values of ductility factors [8] computed from the loaddeflection curve upto first crack load. It indicates, ductility factor up to first crack load has obtained 7.3 in MS-2 and in MS-1 it is 4.6 as compare to control specimen SS (M-55) 2.5. Hence, modified SBR-latex fibre concrete sleeper show more flexible than control specimen. F. Energy Absorption Capacity Table-3 Energy Absorption Capacity values Sleeper Designation SS(M55) MS-1(M60) MS-2(M60+SBR+Fibre) Ductility Factor 1.68 4.55 16.01 SS(M55) MS-1(M60) MS-2(M60+SBR+Fibre) As per RDSO 100 110 130 60 The static bending test results values are shown in Table-1. All values given in Table are average values of 3 sleepers. In centre top of sleeper shows 10 % of load carrying capacity is increased in M60 sleepers and due to modification of latex and fibre, 30% load carrying capacity is increased. Hence, values are greater than standard values. In Rail seat 4 From Table-3, it can be seen that the values of energy absorption capacity [8] computed from the load-deflection curve upto first crack load. It indicates, energy absorption capacity up to first crack load has obtained 16.01KN-mm in MS-2 sleepers and in MS-1 4.55 KN-mm as compare to control specimen SS (M-55) 1.68 KN-mm. Hence, energy absorption capacity increases significantly. G. Toughness Index Table-4 Toughness Index values Sleeper Designation SS(M55) MS-1(M60) MS-2(M60+SBR+Fibre) Ductility Factor 2.5 3.5 23.03 From Table-4, it can be seen that the values of Toughness Index computed [8] from the loaddeflection curve upto first crack load. It indicates, toughness index up to first crack load has obtained 23.03 in MS2 sleepers and in MS1 3.5 as compare to control specimen SS 2.5.Hence, toughness index increases significantly. IV CONCLUSIONS The experimental programme deals with the study of static bending strength, electrical resistance test, load deflection behaviour, energy absorption capacity and toughness index. Some conclusions are given below. 1. Load carrying capacity 30% more than the control specimen. 2. The electrical resistivity is good for the all the test specimens tested. 3. It is experimentally evident that from results obtained for static bending test, load carrying capacity, ductility factor, energy absorption capacity and toughness index for the material chosen in present study is more than conventional material used in control specimen. 4. The static behaviour of PSC sleeper can be increased by using higher toughness and higher fracture capacity, which can be achieved by addition of fibre and SBR- latex to concrete matrix. V. REFERENCES 1. S.K. Chaturvedi, R. S. Yadav, S. A.Soni and R. D. Baria, “Project on Concrete Sleepers and Quality Control”, Western Railway. 2. A.G.Madhava Rao, V.S.Parameswaran and E.Abdul Karim, “Experimental Investigation on Pre-Stressed Railway Sleepers”, International symposium on PSC pipes, pressure & sleeper, PP SL/3. 3. Sakdirat Kaewunruen and Dr.Alex. M.Remennikov, “Rotational Capacity of Railway Prestressed Concrete Sleeper under Static Hogging Moment”, University of Wollongong, Year 2006, PP 399-404. 5 4. Sakdirat Kaewunruen and Dr .Alex.M.Remennikov, “Post-failure mechanism and residual load-carrying capacity of railway pre-stressed concrete sleeper under hogging moment”, University of Wollongong, Year 2006, PP 331-336. 5. Sakdirat Kaewunruen & Dr.Alex.M.Remennikov,“Investigations of static and dynamic performance of railway PSC sleepers”. University of Wollongong, 2007. 6. R.Ramamani, “Investigation of Static Behavior of Pre-Stressed Concrete Sleepers Reinforced with Steel filings”, Dissertation Report, Bangalore University, UVCE, Oct-2007. 7. Chaitra. B. R, “Design of PSC Sleepers Using Portland Slag Cement”, Dissertation Report, Bangalore University, UVCE, Oct2007. 8. Shivananda. K.P, “Study on Polymer Modified Steel Fibre Reinforced Concrete”, Ph.D report, University of Calicut, Regional Engineering College, December-1998. 9. Dr. Sadath Ali Khan Zai, “Impact Behaviour of Steel Fibre Reinforced High Strength Concrete Beams”, Ph.D report, Bangalore University, U.V.C.E, November -2006. 10. Dr.Amlan.k.Sengupta & Prof. Devdas Menon, “Pre-stressed concrete structures”, IIT-Madras. 11. Indian Railway Standard: T-39-85 Third Revision Indian railway Standard specification for Pre-tensioned prestressed concrete sleepers for Broad gauge and Meter gauge. 12. IS: 1343 -1980 Practice for Prestressed concrete. 6 7