Performance-based design and optimization of rheological and strength properties of self-compacting cement composite incorporating micro/ nano admixtures

Due to a variety of cement composites found at different parts of the world, rheological and strength properties which are key properties of self-compacting composites (SCC) can vary in a wide range, and hence development of an optimum and practical design of rheological properties along with the strength and microstructure in terms of mix design ingredients is of great practical significance. This paper presents an optimal design range for rheological properties of self-compacting mortar (SCM) through mini slump and v-funnel tests by optimizing the influencing components of the mix design using Taguchi method. Concurrent design of rheology and strength was also considered in the design methodology to reach the highest strength, while maximizing the cement replacement with micro/nano admixture. For this aim, the influencing factors for rheology and strength were taken into account in two phases of design as binder content (BC), water to binder ratio (w/b), superplasticizer (SP), and limestone powder (LSP) percentage, Slag (S), fly ash (FA), and nano silica (NS), with each being designed at 4 levels. Two main factors i.e. economical and practical aspects were considered for the levels selection of the variables in Taguchi design. It was found that Taguchi method can be used to come up with a practical and economical design range for rheology of SCM in terms of the mix design components. Yield stress (tau(0)) of the SCM mixes was also calculated according to the slump flow diameter obtained from the experiment. Mix design optimization for strength was also implemented and validated for microstructure through SEM images. Laser particle size analyzer (LPSA) along with FE-SEM was also used to investigate the particles' size and, based on which a virtual microstructure was developed to explain the rheological and packing behaviors.