The influence of bagasse fibre and fly ash on the long-term properties of green cementitious composites

Both the long-term physical and mechanical properties of new green cementitious composites reinforced with bagasse fibre and steel fibre with ultra high volume of fly ash are investigated in this paper. Newly cast specimens were cured in the lab for the first 28 days, then these specimens were moved outside to be cured in weather conditions for up to 10 months. The physical properties (including bulk density, apparent porosity and water absorption), mechanical properties (such as compressive strength, Young's modulus and modulus of rupture) are investigated experimentally at the age of 28 days, 3 months, 6 months and 10 months. SEM tests are also conducted to study the microstructure of the new composites. Through comparison with the mechanical behaviour of the composites at the age of 28 days, the long-term effect on the physical and mechanical properties of the composites are discussed, and the impact of fly ash content and bagasse fibre content on the composites under the weathering conditions are also analysed. The experimental results show that the compressive strength, Young's modulus, modulus of rupture and tensile strength of the composites decrease with the reduction of the content of fly ash and bagasse fibre, but bending toughness of the material increases with fly ash content and peaks as fly ash to cement ratio achieves 2.0. The mechanical properties of the new composites are found to be comparable to those of conventional concrete and they are very promising green and sustainable construction and building materials for the next generation infrastructures.