Experimental investigation of the size effects of SiO2 nano-particles on the mechanical properties of binary blended concrete

Abstract

In the current study, the size effects of SiO2 nano-particles on compressive, flexural and tensile strength of binary blended concrete were investigated. SiO2 nano-particles with two different sizes of 15 and 80 nm have been used as a partial cement replacement by 0.5, 1.0, 1.5 and 2.0 wt.%. It was concluded that concrete specimens containing SiO2 particles with average diameter of 15 nm were harder than those containing 80 nm of SiO2 particles at the initial days of curing. But this condition was altered at 90 days of curing. Also from the viewpoint of free energy, it can be concluded that the C-S-H gel formation around the particles with average diameter of 15 nm was more at the primary days of curing. This can be as a result of more nucleation sites that causes acceleration in early age strength. On the other hand, the growth probability of C-S-H gel around the 80 nm particles was more at 90 days of moist curing. This is due to the fact that the nucleus of strengthening gel could simply reach to the critical volume of nucleation that causes increase in the strength.

Effects of the addition of nanosilica on the rheology, hydration and development of the compressive strength of cement mortars

“…This value is very close to the nS content that maximizes the density of fresh mortar (1.7%), as reported in a previous paper [38], and is consistent with the findings of other authors [14,23,26].…”

“…Therefore, there is no consensus regarding the most appropriate range for nS contents, as the values found in current literature are not congruent. It appears that a rule-of-thumb maximum nS content would be 5% over cement weight [7], but other authors have reported that this maximum is 2% over cement weight when the particle size is between 15 nm and 80 nm [26].…”

Durability Properties of High-Performance Concrete Incorporating Nano-TiO₂ and Fly Ash

“…This could be due to the unsuitable dispersion of the nanoparticles in the concrete matrix as per previous investigations (Nazari and Riahi, 2011a). The 1% nano-TiO 2 content seems to be an optimal percentage, as it has been already discussed in the literature (Nazari and Riahi, 2011b;Givi et al, 2010;He and Shi, 2008). When compared to the reference mixture, the mixture of 3% nano-TiO 2 has 13% compressive strength decrease after 7 days curing, but only 8% decrease after 28 days curing.…”

A Review of Effect on Compressive Strength of Concrete After Addition of Nano-Silica

“…These materials are very effective in changing the properties of concrete at the ultrafine level by the virtue of their very small size. The small size of the particles also means a greater surface area (Alireza Naji Givi, 2010). Since the rate of a pozzolanic reaction is proportional to the surface area available, a faster reaction can be achieved.…”