Mechanical properties and microstructure of high performance concrete containing stabilized nano-silica

Abstract

Nanotechnology can significantly improve the mechanical strength and durability of concrete. At the nanoscale, good dispersion of constituent materials is an essential factor for the improvement of concrete properties. In this scenario, the objective of this research was to evaluate the mechanical properties of high performance concrete containing stabilized nano-silica. The incorporation of nano-silica to the polycarboxylate chemical admixture allowed its application in concrete, since the nano-silica was evenly dispersed in the concrete mass. For this study, three different concretes were employed: a reference concrete, one containing stabilized nano-silica and another containing a mixture of silica fume and stabilized nanosilica. The evaluated concrete mechanical properties were the axial compressive strength and secant modulus of elasticity measured in three different ages. The results indicated a substantial increase in concrete compressive strength and modulus of elasticity with the addition of stabilized nano-silica combined with a reduction in cement content. The results also showed that use of stabilized nano-silica proved to be very advantageous, especially when mixed with silica fume. When they were combined, a synergy effect occurred in the concrete that was of chemical nature in addition to the physical effect of better concrete particle packaging. Analysis by scanning electron microscopy showed the improvement in microstructure of concretes with stabilized nano-silica, which contributed to gains in mechanical properties.

Recent Progress in Nanomaterials for Modern Concrete Infrastructure: Advantages and Challenges

“…They used a nano-silica content of 0.25% by weight of cement-based materials. Other researchers such as Braz de Abreu et al [22] reported the use of stabilized nano-silica particles (between 3 and 200 nm in size) in Brazilian-type CP V ARI PLUS Portland cement. They fabricated three types of concrete mixes: a reference concrete, a concrete added with stabilized nano-silica and a concrete including stabilized nano-silica with silica fume.…”

“…For this, nanomaterials can be mixed with cementitious matrices to obtain concrete with high mechanical strength [1,2,3,4,5,6,7,8,9,10]. Nanotechnology can facilitate the development of nanomaterials incorporated into cement-based materials to increase their mechanical strength [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25], decreasing their environment impact [26]. The CO 2 emissions generated during the production of ordinary Portland cement can represent approximately between 5% and 7% of the world man-made emissions of this gas [27,28].…”

Nano-silica added to Portland cement

“…Comparing nano-silicas in suspension and powdered forms, with similar particle size distributions, Quercia, Lazaro, Geus and Browers (2013) related a higher compressive strength for concretes formulated with the suspension of nano-silica. For nano-silica stabilized in polycarboxylate dispersant, Abreu et al (2017) revealed a gain on the compressive strength, when compared with the reference concrete without nano-silica. Haruehansapong, Pulgern and Chucheepsakul (2014) evaluated the effect of particle size for nano-silica with different specific surface areas.…”

Effect of Nano-SiO2 on the Microstructure and Mechanical Properties of Concrete under High Temperature Conditions

“…NS reacts with lime (CH) during cement hydration and generates the production of hydrated calcium silicates (C–S–H) phase, improving the mechanical strength and durability of concrete [ 13 , 14 , 15 ]. Reduction of silica particles size to the nanoscale can significantly affect the cement hydration leading to substantial improvement of strength and compaction of cement matrix microstructure [ 16 , 17 , 18 ]. The studies described in [ 19 , 20 ] have confirmed that the superficial activity of NS in the presence of cement and water is significantly higher than that of SF and Portland cement itself.…”