Autoclaved Composites with Nanostructured Silica Additive
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Autoclaved Composites with Nanostructured Silica Additive Victoria Nelubova1, Valeria Strokova1, Alla Cherevatova1, Nataliya Altynnik1 and Konstantin Sobolev2 1 The Belgorod State Technological University named after V.G. Shoukhov, Belgorod, Russia 2 Department of Civil Engineering and Mechanics, University of Wisconsin-Milwaukee, Milwaukee, USA ABSTRACT This article deals with the development of autoclaved composites (AC) with nanostructured additive (NSA) and reports on the beneficial effects of NSA in autoclaved limesilica mixtures. Based on the results of X-ray diffraction and electron microscopy investigation, the effects of hydrothermal conditions on the mechanisms of lime-silica interaction are revealed. It is demonstrated that the addition of NSA intensifies the formation of the C-S-H phase, reduces the quantities of amorphous phases and enables the formation of low-base calcium hydrosilicates (11Å-tobermorite and xonotlite). The physical and mechanical properties of autoclaved composites with NSA are investigated and optimized. The reported research demonstrates the feasibility of NSA application to improve the performance of autoclaved materials. INTRODUCTION Lime-silicate based autoclaved materials are among the most common masonry materials in Europe and Russia [1]. However, these materials are often characterized by reduced durability [2]. The development of low-cost autoclaved materials with improved quality based on local raw materials is an important task. High-quality building materials can be developed by the formation of an optimal structure controlled at the micro- and nano- scales. The application of nanomaterials and nanotechnology for the development of new types of construction materials can greatly enhance the materials performance including strength, durability, thermal- and chemical-resistance [3, 4]. The use of a nanostructured additive (NSA) can improve the performance of lime-silicate autoclaved materials [5–7]. Nanostructured silica (NSS) can be used as a binder in construction materials. The NSS system includes about 10% of nanoscale particles which are formed by mechano-chemical activation of raw materials and complex modification, for details see references [8, 9]. The developed NSS system can be applied not only as a binder, but also as an active component, e.g., as a nanostructured additive (NSA) [9]. Based on the composition and properties of NSS/NSA, it can be used as an active component of autoclaved silicate materials with improved strength, moisture- and frost- resistance. EXPERIMENTAL PROCEDURE In this research program, the main raw materials for manufacturing of silicate autoclaved materials were quartz sand (from Razumensky field, Belgorod), slaked lime Grade I (from public corporation "Building Materials," Belgorod) and tap water. For production of NSA the same quartz sand was used. The reference specimens were obtained using the following method. First, lime and siliceous components were milled in a vibratory mill to a specific surface of 300–350
111
m2/kg. Then, the
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