Optimization of Self-cured High-Strength Concrete by Experimental and Grey Taguchi Modelling

Conventional curing methods like water curing, ponding, spraying, etc., are mostly preferred methods for curing any type of concrete and are the external curing methods. In case of high-strength concrete due to its impermeable nature, it does not allow to penetrate the water in the concrete body. As a result, the conventional curing methods were found superficial and hence ineffective in the case of high-strength concrete. The curing of high-strength concrete by using superabsorbent polymers (SAPs) is found to be more effective in internal curing of such high-strength concrete (HSC) rather than external curing methods. The internal curing (self-curing) silica fume-based HSC was found through literature but the self-curing of HSC produced using high reactive metakaolin is yet not examined. Hence, the aim of this investigation is to study possibilities of internal curing using superabsorbent polymers, study also directed by the objective of evaluating the mechanical properties of metakaolin-based HSC in combination with SAP. In this study, Taguchi design of experiment method was used to get the best possible combination of factors. The design of the experiment is prepared by deciding control factors. The specimens like cubes, cylinders, and beams were cast of all combinations and cured under different curing conditions (moist curing, self-curing and non-self-curing) for 28 days. The results obtained showed that the compressive strength of self-cured concrete is about 50–55% more than the compressive strength of conventional non-self-cured mix, and it nearly equals the strength of moist cured concrete. X-ray diffraction test conducted showed better hydration of all the constituents in self-cured and moist cured curing condition, non-self-cured paste showed poor hydrated compounds. This indicates that self-cured concrete retains the water and supplies it internally for the hydration process hence selected SAPs are suitable to use as self-curing agents. The study conducted suggests the Taguchi technique is the most appropriate method of mix optimization and it does reduce time and cost of experimentation. The multi-regression analysis also proposes the equations which give the predicted values of all mechanical properties and that strongly correlates with the values found experimentally.