Analysis of High Performance Concrete Mixed with Nano-Silica in Front of Sulfate Attack

Abstract

Nano-silica (NS) is an effective material to improve the strength and durability of high-performance concrete (HPC), but little information is available regarding its role in HPC response to long-term sulfate attack. In this study, six different dosages of NS (0%, 1%, 2%, 3%, 4%, and 5%) as cement partial replacement were mixed into HPC and the casted specimens were soaked in sulfate solution for different periods (0, 100, 200, and 300 days). The mass change, dynamic elastic modulus, compressive and splitting strength, microstructure morphology, and porosity characteristics of HPC specimens were measured by mass tests, mechanical properties tests, scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) tests. The results showed that the incorporation of NS decreased the mass loss, elevated the compressive and splitting strength, and reduced the porosity formation of HPC in front of sulfate attack. The percentage of 1% NS was among the most effective dosages as, after soaking for 300 days, it decreased the mass loss by 13.5%, elevated the elastic modulus as well as compressive and splitting strength by 50.4%, 31.7%, and 69.8% in comparison of unmodified HPC, respectively. The sulfate attack resistance was delayed in a higher (2–5%) mixed dosage, mainly due to the agglomeration of nano particles, especially after long-term reactions. This study can provide experimental references regarding the performance of HPC mixed with NS in front of sulfate attack.

Investigation of Performance of Nano Silica Cement Additive on Sulphate Attack In Geothermal Wells

“…It also reduced the dimensions of the pores present and hence contributed to the reduction in permeability. Similar findings were reported by (Makwana et al, 2021;Nie et al, 2022;Thakkar et al, 2020). Mercury Intrusion Porosimetry (MIP) tests by (Ghafoori et al, 2020) showed that for mortars containing 6% Nano silica, the void volume proportion of gel pores and micropores increased in comparison with those of the control, and there was an overall reduction in the capillary macro pores.…”

“…Addition of Nano silica was reported to increase the compressive strength of cement (Makwana et al, 2021;Moslemi et al, 2014;Nie et al, 2022;Thakkar et al, 2020;Wang et al, 2020) . Research (Rzepka & Kȩdzierski, 2020) found that early compressive strength amounting to 3.5 MPa was achieved by slurries after times between approximately 7 h and 14 h. After 28 days of hydration, the compressive strength of the hardened cement stones had very high values up to 50 MPa (Rzepka & Kȩdzierski, 2020).…”

“…Scanning Electron Microscope test results indicated that the addition of hybrid Nano silica and PVA fibres was effective in limiting the generation of sulphate erosion products and keeping materials from expansive failure after sulphate attack (Huang et al, 2022). During the analysis of high-performance concrete (HPC) that was mixed with Nano-Silica and exposed to sulphate attack, (Nie et al, 2022) discovered that the incorporation of Nano silica decreased the mass loss in prepared specimens. Nano s ilica replacement of 1% decreased the mass loss by 13.5% in comparison to unmodified HPC.…”

“…It was found that mortars with 5 and 10 % of Nano silica decreased expansion by 90% and 95 % respectively after two years of immersion. However, higher concentrations of Nano silica were reported to delay or decrease the sulphate resistance of concrete and mortars due to agglomeration of the Nanoparticles (Nie et al, 2022), especially after long-term reactions. In a contrast study by (Ghafoori et al, 2020), conclusions from the results were that doubling the concentration of colloidal Nano silica had a positive effect on the sulphate resistance of mortars.…”

“…Nano silica improved sulphate resistance (Moslemi et al, 2014) by reducing the porosity and permeability of the concrete or mortar specimens (Ghafoori et al, 2020;Huang et al, 2020;Nie et al, 2022). ii)…”