Zhang Peng, Sha Dehao, Li Qingfu, Zhao Shikun, Ling Yifeng
School of Water Conservancy Engineering, Zhengzhou University, Zhengzhou 450001, China.
Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA 50011, USA.
Nanomaterials (Basel). 2021 May 14;11(5):1296. doi: 10.3390/nano11051296.
In this study, the effect of adding nano-silica (NS) particles on the properties of concrete containing coal fly ash were explored, including the mechanical properties, impact resistance, chloride penetration resistance, and freezing-thawing resistance. The NS particles were added into the concrete at 1%, 2%, 3%, 4%, and 5% of the binder weight. The behavior under an impact load was measured using a drop weight impact method, and the number of blows and impact energy difference was used to assess the impact resistance of the specimens. The durability of the concrete includes its chloride penetration and freezing-thawing resistance; these were calculated based on the chloride diffusion coefficient and relative dynamic elastic modulus (RDEM) of the samples after the freezing-thawing cycles, respectively. The experimental results showed that the addition of NS can considerably improve the mechanical properties of concrete, along with its freezing-thawing resistance and chloride penetration resistance. When NS particles were added at different replacement levels, the compressive, flexural, and splitting tensile strengths of the specimens were increased by 15.5%, 27.3%, and 19%, respectively, as compared with a control concrete. The addition of NS enhanced the impact resistance of the concrete, although the brittleness characteristics of the concrete did not change. When the content of the NS particles was 2%, the number of first crack impacts reached a maximum of 37, 23.3% higher compared with the control concrete. Simultaneously, the chloride penetration resistance and freezing-thawing resistance of the samples increased dramatically. The optimal level of cement replacement by NS in concrete for achieving the best impact resistance and durability was 2-3 wt%. It was found that when the percentage of the NS in the cement paste was excessively high, the improvement from adding NS to the properties of the concrete were reduced, and could even lead to negative impacts on the impact resistance and durability of the concrete.
在本研究中，探讨了添加纳米二氧化硅（NS）颗粒对含粉煤灰混凝土性能的影响，包括力学性能、抗冲击性、抗氯离子渗透性和抗冻融性。NS颗粒按胶凝材料重量的1%、2%、3%、4%和5%添加到混凝土中。采用落锤冲击法测量冲击载荷下的行为，并通过冲击次数和冲击能量差来评估试件的抗冲击性。混凝土的耐久性包括其抗氯离子渗透性和抗冻融性；这些分别基于冻融循环后样品的氯离子扩散系数和相对动弹模量（RDEM）进行计算。实验结果表明，添加NS可显著改善混凝土的力学性能及其抗冻融性和抗氯离子渗透性。与对照混凝土相比，当以不同替代水平添加NS颗粒时，试件的抗压强度、抗折强度和劈裂抗拉强度分别提高了15.5%、27.3%和19%。添加NS增强了混凝土的抗冲击性，尽管混凝土的脆性特征没有改变。当NS颗粒含量为2%时，首次开裂冲击次数最多达到37次，比对照混凝土高23.3%。同时，样品的抗氯离子渗透性和抗冻融性显著提高。混凝土中NS替代水泥的最佳水平为2-3 wt%。研究发现，当水泥浆体中NS的百分比过高时，添加NS对混凝土性能的改善会降低，甚至会对混凝土的抗冲击性和耐久性产生负面影响。
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