Multi-response optimization of hybrid fibre engineered cementitious composite using Grey-Taguchi method and utility concept

This paper presents an experimental investigation conducted to assess the suitability of Taguchi-Grey relational analysis (GRA) and Taguchi method with utility concept (UC) for mix design optimization of a hybrid fibre engineered cementitious composite (ECC). Slag, fly ash and dolomite are utilized as binder materials and the quantity of various constituents of ECC is optimized to achieve improved compressive and tensile performance. In addition, two weighting techniques based on equal weight and maximum deviation are employed in the analysis and their effects on improving the efficiency of the optimization approach is also assessed. The design of experiments is first carried out using a standard Taguchi orthogonal array consisting of five factors viz. total cement replacement level, dolomite to binder ratio, slag to fly ash ratio, fibre proportions, and water binder ratio, at four levels. Thereafter, GRA and UC are applied to evaluate the composite indices and compute the optimal proportions targeting five response parameters namely compressive strength, peak compressive strain, elastic modulus, tensile strength, and ultimate tensile strain. Results indicate that both GRA and UC can be effectively integrated with Taguchi method for obtaining an optimal mix design of the ECC. Moreover, the use of weighting technique based on the maximum deviation method is found to be more appropriate as it can distinguish between relative effectiveness of different response parameters. The best performing mix had total cement replacement of 60%, 15% dolomite content by binder, slag to FA ratio of 1:0.2, 2.25% total fibre content, water-binder ratio of 0.20 and exhibited desired compressive and tensile properties for structural applications.