Abstract
Nano-technology (NT) and nano-materials (NMs) has attracted considerable scientific attention, due to the new potential uses of nano-particles (NPs), which can change the concrete world. There is a great interest in replacing a long time used materials in concrete structure by NMs to improve the different properties of concrete. In this study, the hydration characteristics and microstructure of cement pastes and mortars with and without nano-silica (NS) were studied. Blended cement mix containing 10 mass, % silica fume (SF) was prepared, then the cement mix was partially replaced by NS up 1.5 mass, %. The results show that, NS increases the water of consistency and final setting time The values of chemically combined water, free lime, bulk density and compressive strength prove that, NS up to 1% seems to be an effective mineral additive for blending with OPC to improve its chemical and engineering properties. This is mainly attributed to that; NS behaves not only as filler to improve microstructure, but also as pozzolanic material (PZM). The formation of more hydrated silicates in presence of NS was confirmed by XRD, DTA, IR and SEM examinations. At 1.5 mass, % NS, the density and strength are reduced but still higher than those of 0.0 and 0.5% NS. Also, the results indicate that, the substitution of blended cement mix (OPC+10% SF) with 1 mass, % NS gives a reasonable hydration characteristics and improved engineering properties more than those of 0.0 and 0.5% NS at all hydration ages up to 90 days. Therefore, this level of NS is suggested to be the most suitable replacement level.
Highlights
Nanotechnology (NT) is advanced technology, which deals with the synthesis of nanoparticles (NPs), and their applications
The results suggest that, with a small amount of NS, the Ca(OH)2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in High Performance Concrete (HPC)
The increase in water demand is attributed to the acceleration of hydration process of cement clinker phases under the effect of high fineness and surface energy of NS particles [41,42,43,44]
Summary
Nanotechnology (NT) is advanced technology, which deals with the synthesis of nanoparticles (NPs), and their applications. NT has attracted considerable scientific interest, due to the new potential uses of particles in nanometer (10-9m) scale; the advent of NT has brought in various types of nano-materials (NMs), which may have good applications in civil engineering, especially concrete production, due to their major effects: size effect, surface effect, and interface effect [1,2,3,4]. NMs show unique chemical, physical and engineering properties different from those of the conventional materials. NMs can change the concrete world, due to their properties at ultra-fine level [7]. There is a great interest in replacing a long time used materials in concrete structure by NMs to improve the engineering properties of concrete [8, 9]. If NMs are combined with traditional building materials; this may lead to production of building materials with unique
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