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Pdf 314.52 K Int. J. Nanosci. Nanotechnol., Vol. 11, No. 4, Dec. 2015, pp. 263-273 Short Communication Nanoscience and Nano Engineering in Concrete Advances A Review M. Jafarbeglou1, M. Abdouss *2 and A. A. Ramezanianpour 3 1. Department of Nanotechnology, Amirkabir University of Technology, Hafez Ave, Tehran, I. R. Iran 2. Department of Chemistry, Amirkabir University of Technology, Hafez Ave, Tehran, I. R. Iran 3. Department of Civil Engineering, Amirkabir University of Technology, Hafez Ave, Tehran, I. R. Iran (*) Corresponding author: [email protected] (Received: 24 March 2015 and Accepted: 07 Jun 2015) Abstract This paper reviews some progressive studies and innovations in cement and concrete materials in nano field. Due to the widespread acceptance of the special properties of nano materials and using them for engineering concrete performance, understanding and directing their properties are not achievable without instructing concepts and investigating interactions among components. Due to achievement of different properties of matters at the nanoscale, evaluating their physical and chemical effects on micro and macro scales in concrete and understanding the mechanisms that govern the interactions of nanoscale materials with appropriate characterization are essential. Advanced characterization techniques should be used for concrete to distinguish components of concrete multiphase composite. The other aim of this study was to better understand the importance of probably future advanced techniques and how they can be used as valuable tools to study the nanostructure and microstructure of cement and cement hydration products. Keywords: Nano, Concrete, Structure, Characterization, Engineering. 1. INRODUCTION Concrete is considered to be the most innovations in nanotechnology, nano- widely used construction material. modification of cement-based materials Nowadays consumption rate of concrete is has generated much research interest [4]. estimated to be around 20000 million The main hydration product of ordinary metric tons per year [1]. It is a Portland cement is a calcium-silicate nanostructured multiphase composite hydrate (C−S−H) having a material [2]. Concrete in definitions is pseudotobermoritic like crystal chemistry. composed of an amorphous phase, C−S−H is a slightly crystalline and nanometer- to micrometer-size crystals, nanoscale phase formed from the reaction and bound water. The properties of of the calcium-silicate phases with water. concrete exist in according the degradation Its colloidal-like behavior and self- mechanisms occur across, multiple length organization into an interconnected scales (nano-micro-macro) where the network convey cohesive properties to the properties of each scale derive from cement paste. The other hydration products smaller one [3]. Due to the complex are Ca(OH)2 (portlandite) and an hydrous structure of concrete and its heterogeneity sulfo-aluminate (ettringite). Ettringite has a at all length scales, and the recent major influence on the early stage 263 rheology, but it has a negligible effect on unknown and effective elements in micro determining the mechanical properties in and nano scale could not be recognized to long term [10]. The mechanical behavior obtain better and directed results till now. of concrete materials depends to a great For instance, the addition of nanofine extent on structural elements and adventure particles could improve the properties of that affect micro and nano scale reactions concrete due to the effect that increased [5-6]. surface area has on reactivity and through An analysis of new and published filling the nanopores of the cement paste. solubility data for C–S–H, illustrates an Nanosilica and nanotitanium dioxide have unrecognized family of solubility curves in been the most reported additives used in the CaO–SiO2–H2O system at room nanomodified concrete [18-26]. temperature and observed differences in Nanomaterials also could improve the solubility arise from systematic variations compressive strength and ductility of in Ca/Si ratio, silicate structure and Ca–OH concrete [21]. Carbon nanotubes or content [7]. This has significant impact on nanofibers (CNT-CNF) have also been the performance of concrete because the used to modify strength, modulus and structure is sensitive to moisture ductility of concretes. Durability of movement, during hydration. This may concretes could also be improved through result in shrinkage and consequent crack reduced permeability and improved [8]. Thus, nanotechnology may have the shrinkage properties. These effects could potential to engineer concrete with arised be obtained through nano modified properties through the optimizing behavior cements or the use of nano developed of material and performance is required to additives to the paste [18]. intensively improve mechanical Utilization of nanomaterials into the performance, durability and sustainability cement matrix to improve its mechanical [7-14]. properties reputedly has appeared as a The properties and procedures that promising research field. A few studies on occurring at the nanoscale define the incorporation of nanoiron, nanoalumina interactions that occur between particles and nanoclay particles have also been and phases at the microscale and the reported [18- 23]. effects of working loads and the When a small quantity of nanoparticles is surrounding environment at the macroscale uniformly dispersed in a cement paste, the [15-17]. hydrated products of cement deposit on the It goes without saying that nanoparticles due to their higher surface nanotechnology-based development in energy. Thus nanopaticles act as nucleation concrete materials requires a sites for lattice growth. Nucleation of multidisciplinary approach, consisting hydration products on nanoparticles further some expert teams of concrete materials, promotes and accelerates cement civil engineers, chemists, physicists and hydration. It has been reported that adding materials scientists. colloidal nano silica causes acceleration of C3S dissolution and rapid formation of C- 2. NANOTECHNOLOGY- BASED S-H phase in cement paste [18]. RESEARCH IN CONCRETE TO The second mechanisms for improving DATE the performance are that: (a) nanoparticles 2.1. High performance properties fill the nanosize pores of the cement paste Scientists could mostly achieve and (b) nano-SiO reacts with Ca(OH) improvement in performance, durability 2 2 and sustainability of concrete until now. (i.e., pozzolanic reaction) and generates Although these studies goes to create a additional C-S-H [3]. Both processes are huge evolution in concrete industry, some influenced by the particle size and the 264 Jafarbeglou et al proper dispersion of the nanoparticles (with effective binding qualities) within the within the cement paste, with colloidal capillary pores and in contact with dispersions being more effective than the microscale crystals; this nanomaterial cannot effectively interact with the powder. A reduction in Ca(OH) content 2 cementitious paste. It may still produce and increase in C-S-H content in cement physical benefits, but would not effectively mortar as a result of nano-SiO2 addition contribute to the mechanical properties of was noticed through Differential Thermal the matrix [14]. Analysis (DTA) and X-Ray Diffraction The particulate matter of uniform grain (XRD) testing . With the addition of 3 wt% size cannot realize very high packing densities. Spherical grains of similar size of nano-SiO2, significant improvement of can reach packing densities of only 0.52 early-age interfacial transition zone (ITZ) and 0.74 in cubic and tetrahedral packing structure with respect to reduction in structures respectively. Sbia et al. reported content, crystal orientation degree and packing density can be increased through crystal size of portlandite crystals was the use of particles of different dimensions obtained. In another study, it is reported accompanied by finer particles filling the that the improvement in strength due to space between coarser particles [14]. nanosilica addition was not related to The effect of the debulking procedure on the dispersion and the reinforcing pozzolanic reaction, but due to the efficiency of carbon nanofibers, was formation of denser microstructures studied by Zoi et al in 2013. They through growth of silica chains in C-S-H illustrated lower ultrasonic energies could [21]. According to the study done by not effectively disperse the CNFs, while Raiess Ghasemi et al. in 2010, applying higher ultrasonic energies possibly reduced the aspect ratio of the nanofibers, which in mixture of colloidal Nano SiO2 with 50 turn decreased their reinforcing efficiency wt% of solid content which contains 0.75 in the cementitious matrix. The addition of wt% nano-SiO2 and 3 wt% silica fume has CNF to cement paste was found to mainly shown better performance of compressive increased flexural strength and stiffness, strength on 7th, 28th ,91th and 180th day and crack control at the nanoscale. SEM respectively. Review of compressive analysis also confirmed the results of the strength, RCPT and DWPT results, shows mechanical testing; nanoimaging showed the influence of NS on improvement of that good bonding existed between all types of carbon nanofibers and the matrix. concrete properties, both are due to filling At early ages of hydration, CNFs with an ability (Filler) and the Pozzolanic activity, outer layer of multiwall graphene tubes but based on the results of RCPT, it is (CVD layer) improved the mechanical expected
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