•The inclusion of fiber in concrete, mortarand cement paste can enhance many ofthe engineering properties of thematrix, such as fracturetoughness, flexural strength andresistance to fatigue, impact, thermalshock and spalling.•The fibres may act as shearreinforcement and also improve thecapacity of the bars due to increasedcrack distribution
The main objectives of this study are: To investigate the use of steel scraps as a Steel Fiber Reinforcement in FRC To study the mechanical characteristics of the SSFRC To optimize the fiber proportions To check the toughness resistance of the SSFRC To check the abrasive resistance of the SSFRC To find out the cost effective cross section of the pavement. *Scrap Steel Fiber Reinforced Concrete (SSFRC)
Chettinad brand Ordinary Portland Cement (OPC) 43 Grade confirming to IS: 4031-1988. Locally available river sand confirms to Zone II of IS: 383-1970 as fine aggregate, Crushed granite aggregate of maximum size 20 mm confirming to IS: 383 as coarse aggregate and Potable water are used. Steel Scraps of length 25 mm to 30 mm, width 1.5 to 2 mm and thickness 0.3 to 0.4 mm which is obtained from the lathe machines as waste or by product are used as reinforcing material in the concrete. Super plasticizer – Conplast SP432 MS supplied by M/S FOSROC India Private Ltd. Is used to improve the workability of the concrete. The dosage of super plasticizer to be added with the concrete is found out from the slump test conducted in the laboratory.
Pavement Design and Analysis Pavement slab is designed as per IRC 58:2002. The flexural strength is directly taken from the beam flexural test. The design details are tabulated in Table 6. The Axle load spectrum is taken from IRC: 58 -2002 and other data used in this design is given below: Elastic modulus of concrete = 3 x 10-5 N/mm2 Tyre pressure = 8 kg/cm² Spacing of contraction joints = 4.5m Design life = 20 years Poisson’ ratio = 0.15 Rate of traffic increase = 0.075 Present traffic =1000 cvpd Elastic Modulus of Sub grade Reaction of the DLC sub-base = 8 kg/cm³ Coefficient of thermal Expansion of concrete = 10x 10-6 /ºC From Table 6, it is clear that the addition of small amount of fiber will also reduce the thickness of the pavement slab. For M30 Concrete thickness saved in construction with SSFRC is 41%, for M35 concrete thickness saved with SSFRC is 38% and for M40 concrete thickness saved in SSFRC is 33%.
According to Gopalaratnam (1991) for a given type of fiber, a higher volume fraction provides more energy absorption capacity or toughness as long as the fibres can properly be mixed and the composite can be cast and compacted properly. This result should be expected because more fibres provide more resistance, especially in the tension zone. For the given fibre geometry, longer fibres typically provide greater toughness
Balasubramanian et al. (1996)Shave investigated the impact resistance of the specimens with 0.5%, 1.0%, 1.5%, and 2.0% for each of the three types of steel fibres using Schrader’s test Device. Ravishankar (2006)investigated the mix design aspects of steel fibre reinforced concrete and concluded that there is an increase of 42% in modulus of rupture due to addition of fibres in plain concrete.
From the experimental studies and subsequent pavement analysis carried out as per IRC: 58-2002, it is concluded that the compressive strength of SSFRC increased when compared to plain cement concrete. Addition of steel scraps increases the flexural strength of SFRC to great extent. The mechanical properties of the concrete are increased by increasing the proportion of the steel scrap up to 1.5%. From 1.5% to 2.0%, it shows slight decrease in mechanical strength. At 2.0% of steel proportion, there is considerable reduction in the mechanical strength of SSFRC. It the pavement thickness is decreased by 41% and which is economical when compared to plain cement concrete slab.
U. Ravisankar, H.V. Venkata Krishna and Sures ‘Mix Design Aspects of SFRC PavementDesign’ Indian Highways (May 2006) Vol.34, No.5 and pp 44-50. K. Sankar, ‘A Study on the Effect of Fiber Reinforcement in Concrete Pavements,’ M.TechThesis, Department of Civil Engineering, National Institute of Technology, Tiruchirappalli –620-015. ‘Method of Test for Determining Pavement and Structures’, Department of Transportation,Engineering Service Centre, Sacramento, California 95819– 4612 (Feb.2000). IRC-58:2002, ‘Guidelines for the Design of Rigid Pavements.’ Figure 5: Control Concrete specimens failed under Impact Figure 6: SSFRC specimen failed under impact IRC:SP:46-1997, ‘Steel Fibre Reinforced Concrete for Pavements’. V. S. Gopalaratnam, S. P. Shah, G. B. Batson, M.E. Criswell, V. Ramakrishnan and M. Wecharatana, ‘Fracture Toughness of Fiber Reinforced Concrete’. ACI Material Journal, 88 4 (1991), pp. 339–353. K. Balasubramaniam, B. H.Bharat Kumar, S. Gopalakrishnan and V.S. Parameswaran, ‘Impact Resistance of Steel Fibre Reinforced Concrete,’ The Indian Concrete Journal (May, 1996), pp. 257-262. N. P. Banthia, S. Mindess and A. Bentur, ‘Impact Behavior of Concrete Beams,’ RILEM, Mater.Struct.20(1987) pp. 293- 302