Flexural Strength Characteristics of Ternary Concrete Reinforced with Sisal Fibre Patrick Oguguo Nwankwo 1 Mathew Aho 2 & Joseph Danjuma Goh 3 1&3 Department of Building, Faculty of Environmental Sciences, University of Jos, Jos, P.M.B 2084 Plateau State Nigeria 2 Department of Civil Engineering, School of Engineering, University of Agriculture, Makurdi, P.M.B 2373 Benue State Nigeria International Journal of Research in Civil Engineering, Architecture & Design Volume 2, Issue 4, October-December, 2014, pp. 01-09 ISSN Online:2347-2855, Print:2347-8284, DOA : 03112014 © IASTER 2014, www.iaster.com ABSTRACT This experimental study investigates the flexural strength characteristics of ternary concrete blended with two pozzolanas (fly ash (FA) and calcined waste crushed clay bricks (CWCCB)), and ordinary Portland cement (OPC). In this study, five different mix ratios of concrete and ternary concrete specimens were prepared and cast in 100mmx100mmx500mm mould comprising: (1) Plain concrete of 1:2:4 mix ratio as control specimens (i.e. one part of cement as binder, two parts of river sand as fine aggregates and four parts of 19mm crushed granite as coarse aggregate), (2) Concrete specimens of 1:2:4 mix ratio, reinforced with 3% volume fraction of 40mm average length sisal fibre, (3) Ternary concrete specimens of 1:2:4 mix ratio with binders consisting of 50% (OPC) + 20% (FA) + 30% (CWCCB), (4) Ternary concrete specimens of 1:2:4 mix ratio with binders consisting of 50% (OPC) + 25% (FA) + 25% (CWCCB), and (5) Ternary concrete specimens of 1:2:4 mix ratio with binders consisting of 50% (OPC) + 30% (FA) + 20% (CWCCB). Water/binder ratio was kept constant at 0.6. All ternary concrete specimens were reinforced with 3% volume fraction of 40mm average length locally sourced sisal fibre. The beam specimens were cured and tested at 28 and 90 days curing age. With the incorporation of 3% volume fraction of sisal fibre, flexural strength decreased from 5.3N/mm 2 to 2.3N/mm 2 at 28 days curing age. Flexural strength was greatly reduced with blending of matrix with the two pozzolanas. The ternary concrete specimens containing 30% FA + 20% CWCCB gave the highest flexural strength among all ternary mixtures. Keywords: Flexural Strength, Sisal Fibre, Ternary Concrete, Fly Ash, Calcined Waste Crushed Clay Bricks. 1. INTRODUCTION The utilization of vegetable fibres and other naturally occurring fibres to toughen building products such as bricks and poultry can be traced back to many centuries. Since then, mankind has been strongly dependent on vegetable fibres for all other kind of purposes. However the engineering principles in the use of vegetable fibres for reinforcement of brittle matrices such as concrete, only came to fore in the last forty years. The application of concrete in the field of structural engineering often involves a technique of reinforcing with other materials so as to compliment its undesirable low tensile capacity. Plain concrete is weak in tension, and the limiting tensile force is carried between cracks. When fibres are added to the plain concrete, the tensile capacity is increased through the transfer of tensile forces at the cracks by fibre interferences. A wide variety of fibres have been used