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Concrete is manmade multiphase composite where coarse granular materials are embedded in a hard matrix of binder, filling the space between the aggregate particles and gluing them all together that strengthens with time on hydration. Addition of nanoparticles further enhances the properties of the concrete such as early strength, refined micro structure and enhanced durability. Nanoparticles are added to cementitious composites by dry mixing with cement or dispersion in water. The challenge associated with it is the uniform dispersion of the nanoparticles in the matrix of the composite. The type of mixer and the mixing pattern affect the fresh and hardened properties of the concrete. This article reviews the effect of dispersion of nano particles, type of mixer and mixing pattern on the properties of cementitious composites.

Fly ash based geopolymer composite cubes were cast using class F fly ash, ground granulated blast furnace slag (GGBFS) as binders. The fluid-to-binder ratio was varied keeping all other parameters constant. The geopolymer composites were cured in different conditions. The composites were tested for compression at different ages. It is interesting to note that the variation of the strength with various fluid-to-binder ratios is unique irrespective of combination of materials, curing conditions, fluid content, and molarity of the fluid. The strength data generated was generalized to arrive at a phenomenological model. The model represents an unique pattern of strength development for the series of composite materials. The validity of the model was examined with an independent set of experimental data generated by the authors and Rangan. It was found that the predicted strengths were in line with the experimental strengths having a percentage error less than 6.0. The model is effective in re-proportioning of geopolymer composites in the field.

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