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This paper presents the relative performance of nanosilica (nS)- and microsilica (mS)-added concrete with reference to durability under different transport mechanisms such as absorption, sorption, diffusion and migration. The concrete for this study was made with optimum quantities of mS and nS, which were determined based on maximum strength efficiency factor. The results showed that nS-added concrete exhibited superior durability properties compared to mS-added concrete under the above transport mechanisms, even at lower cement replacement. The beneficial effects of nS on the pore refinement of concrete were observed through the latter's high resistance to water absorption, sorptivity, chloride penetration and corrosion susceptibility. The relatively higher rapid chloride permeability and lower concrete resistivity of nS added concrete were attributed to the possible static surface charge of nS particles. The scanning electron microscopic image showed a compact and dense microstructure of nS-added concrete with increased finer-sized calcium–silicate–hydrate, reduced calcium hydroxide contents, and compact interfacial transitional zones.

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This paper presents results of an experimental investigation on fresh and hardened properties of high-performance concrete (HPC) containing nanosilica (nS), and a comparison with HPC containing microsilica (mS), and a reference concrete (RefCon). The temperature of fresh concrete was monitored using maturity sensors. The compressive strength, splitting-tensile strength, flexural strength, elastic modulus, rebound hammer number and ultrasonic pulse velocity of concrete were determined at different ages, and correlated with creep and drying shrinkage results reported earlier by the authors. The study revealed that nS has accelerated the strength development at early ages, whereas the mS addition showed no significant change. The nS-HPC exhibited improved mechanical properties as compared to the other concretes. The correlation between compressive strength and maturity, as obtained, would be useful for carrying out early-age construction activities. A good correspondence was also noted between the mechanical properties obtained from destructive and non-destructive testing. The correlation of mechanical properties and time-dependent properties revealed that, in spite of improvement in the former, the nS-HPC exhibited higher creep and drying shrinkage than other two concretes. As a result, suitable suggestions are made to account for this in the design of structural elements.