Performance of Cement Systems with Nano- SiO 2 Particles Produced Using Sol-gel Method
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Performance of Cement Systems with Nano- SiO2 Particles Produced Using Sol-gel Method Konstantin Sobolev1, Ismael Flores1, Leticia M. Torres2, Enrique L. Cuellar3, Pedro L. Valdez2, and Elvira Zarazua2 1 Department of Civil Engineering, CEAS, University of Wisconsin-Milwaukee, 3200 N. Cramer St., Milwaukee, WI 53211, USA 2 Facultad de Ingeniería Civil, Universidad Autónoma de Nuevo León S/N, San Nicolás de los Garza, N.L. 66400, México 3 Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León S/N, San Nicolás de los Garza, N.L. 66400, México ABSTRACT The reported research examines the effect of 5-70 nm SiO2 nanoparticles on the mechanical properties of nanocement materials. The strength development of portland cement with nanoSiO2 and superplasticizing admixture is investigated. Experimental results demonstrate an increase in the compressive strength of mortars with SiO2 nanoparticles. The distribution of nanoSiO2 particles within the cement paste plays an essential role and governs the overall performance of these products. Therefore, the addition of a superplasticizer is proposed to facilitate the distribution of nano-SiO2 particles. The application of effective superplasticizer and high-speed dispergation are found to be very effective dispersion techniques that improve the strength of superplasticized portland cement mortars, reaching up to 63.9 MPa and 95.9 MPa after aging during 1 and 28 days, respectively. These values compare favorably with the observed compressive strengths of reference portland cement mortars of 53.3 MPa and 86.1 MPa. It is concluded that the effective dispersion of nanoparticles is essential to obtain the composite materials with improved performance. INTRODUCTION Recent research in cement and concrete has focused on the investigation of the structure of cement-based materials and their fracture mechanisms [1-5]. The application of Atomic Force Microscopy (AFM) for the investigation of the “amorphous” C-S-H gel revealed that at the nanoscale this product has an ordered structure [6]. Better understanding the nano-structure of cement based materials helps to control the processes related to hydration, strength development, fracture, and corrosion. For instance, the development of materials with new properties such as self-cleaning, discoloration resistance, anti-graffiti protection, and high scratch and wear resistance, is important for many construction applications [7-11]. Another example is related to the development of new superplasticizers for concrete, such as Sky, which is based on polycarboxylic ether (PCE) polymer. This product is developed by BASF with a nano-design approach targeting the extended slump retention of concrete mixtures [12]. Major improvements in concrete performance have been achieved by addition of superfine particles, for example: fly ash, silica fume, metakaolin and now nanosilica. The optimal performance of these systems is attributed to the high-density continuous packings of the binder
constituents that are realized at high fluidity
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