Optimizing mix design of hybrid fiber reinforced concrete with abaca and polypropylene fibers through Taguchi method and Grey Relational analysis approach

In the present investigation, the effect of hybrid fiber reinforcement on the performance of concrete is evaluated by adding two different types of fibers: abaca and polypropylene. Polypropylene fibers are the thermoplastic material widely used in concrete composites for increasing durability, and abaca fibers are prominent naturally available plant fibers used to enhance mechanical properties. The water–cement ratio, abaca fibers, and polypropylene fibers are considered variables for optimizing the mix proportions. The Taguchi method with a grey relation approach has been adopted for the present study to reduce the number of hybrid fiber reinforced mixes from 27 to 9 and also to optimize results. The parameters such as larger the better for compressive strength, flexural strength, and smaller the better for water–cement ratio are assigned to evaluate results. A total of twelve mixes were cast and tested. Among the twelve mixes, nine are attained from the L9 orthogonal matrix given by the Taguchi method, and the other three are control mixes. The workability of mixes ranges from very low to medium slump. The mix with lower hybrid fiber content and higher w/c ratio showed better workability among hybrid fiber-reinforced mixes. The hardened properties of mixes are evaluated after 7 days and 28 days of water curing. The results obtained are analyzed using the Taguchi and Grey Relational Approach. The optimum mix proportions are derived and validated. The statistical analysis identified that the mix containing abaca fiber (0.25%) and polypropylene fiber (0.125%) with a water–cement​ ratio of 0.4 outperformed with optimum strength and water absorption properties. From this study, it is concluded that the predicted and experimental results are in good correlation.