An introduction to Steel Fiber Reinforced Concrete Fiber Reinforced Concrete Fiber Reinforced Concrete is a composite material consisting of cement, aggregate and discontinues, discrete, uniformly dispersed suitable fibers Why to use FRC Plain concrete is a brittle material with limited ductility and low tensile strength and strain capacity. Internal micro-cracks are present in that concrete. Thus the concrete leads to heavy brittle fracture. The role of randomly distributed fibers is to bridge across the cracks and to provide some post-cracking ductility. If the fibers are sufficiently strong and bonded to material then FRC will carry significant stress over a relatively large strain capacity in the post cracking stage. Ahsanullah University of Science and Technology Department of Civil Engineering Classification of Fibers Steel Fiber Reinforced Concrete (SFRC) Glass Fiber Reinforced Concrete (GFRC) Synthetic Fiber Reinforced Concrete (SNFRC) Natural Fiber Reinforced Concrete (NFRC) Recently some new FRC named High Performance Fiber Reinforced Concrete (HPFRC) and Ultra High Performance Fiber Reinforced Concrete (UHPFRC) have introduced which shows significant changes over plain concrete. Different Types of Fiber Steel Fiber Reinforced Concrete ( SFRC ) SFRC is concrete made of hydraulic cements containing fine and coarse aggregate and discontinuous discrete steel fibers. Classification of Steel Fibers ASTM A 820 provides a classification of four general types of steel fibers. Type I - Cold-drawn wire Type II - Cut sheet Type III – Melt-extracted Type IV – Other fibers The Japanese society of civil engineers (JSCE) has classified steel fibers based on the shape of their cross-section. Type I – Square section Type II – Circular Section Type III – Crescent Section Cross Section of Steel Fibers Steel Fiber cutting machine Property 3/8- in. maximum sized aggregate ¾- in. maximum sized aggregate 1½- in. maximum sized aggregate Cement (kg/m3) 350-600 300-550 250-450 w/c ratio 0.35-0.45 0.35-0.5 0.35-0.55 Percent of fine to coarse aggregate (%) 45-60 45-55 40-55 Entrained Air Content (%) 4-8 4-6 4-5 Deformed Fiber (%) 0.4-1.0 0.3-0.8 0.2-0.7 Smooth Fiber (%) 0.8-2.0 0.6-1.6 0.4-1.4 Mix design of SFRC Fiber Content, (% of total volume) Properties of Concrete Improved Compressive Strength In compression the ultimate strength is only slightly affected by the presence of Steel Fibers. The presence of steel fibers increases compressive strength from 0 to % for up to 2 % of volume of fibers. Tensile Strength In direct tension, the improvement in strength is reported from 30 - 40 % for addition up to 2 % by total volume of fibers. It is observed that the split tensile strength increases from 10 - 45 % for addition up to 3 % by total volume of fibers. Flexural Strength The changed elastic distribution is importantly plastic in the tension zone and elastic in the compression zone, which poses a shift of neutral axis towards the compression zone. It changes from 20 - 100 % for addition up to 3 % by total volume of fibers. Application of SFRC SFRC has been tried on overlays of air-field, road pavements, industrial floorings, bridge decks, canal lining, explosive resistance structures, refractory linings etc. It can also be used for the fabrication of precast products like pipes, boats, beams, stair case steps, wall panels, roof panels, manhole covers etc. SFRC is also being tried for the manufacture of prefabricated formwork molds of “U” shape for casting lintels and small beams. Limitations of SFRC Unless steel fibers are added in adequate quantity, the desired improvements cannot be obtained. As the quantity of fibers is increased, the workability of the concrete is decreased. Another problem is the corrosion of the surface which may influence the appearance of the surface. Steel fibers are not cost effective. Due to the addition of 1% steel fiber of the total volume, there will be a massive change in the total cost of the construction. INNOVATIVE BUILDERS Zubayer Ibna Zahid (Group Leader) -- 12.02.03.061 Hasan Jubair Siam -- 12.02.03.037 Soaib Imran Abir -- 12.02.03.003 Abdullah Al Mamun -- 12.02.03.019 Jarin Tasnim Hiya -- 12.02.03.039 Eden Chakma -- 12.02.03.001 Md Omar Faruk Rupak -- 12.02.03.010 Sohan Ahmed Tonmoy -- 12.02.03.016 Kanak Chakma -- 12.01.03.003 Steel Fiber Natural Fiber Glass Fiber Synthetic Fiber Some SFRC Constructions