| Fibers and nanomaterials are mixed into concrete,and they can improve the performance of concrete from different scales by exerting their respective advantages,and solve the problem of inherent defects of low tensile strength and high brittleness of concrete.Basalt fiber(BF)also known as green fiber,has high tensile strength,low price and good dispersion.In this paper,cost-effective BF and highly active Nano-SiO2(NS)particles were added to concrete in the form of single admixture and mixed admixture,respectively,to explore the effects of BF and NS on the performance of concrete under different ratios.The failure modes of various types of specimens are compared,and the reinforcement and modification mechanism of BF and NS on concrete is analyzed based on the microscopic test results,which provides a parameter basis for the application of BF and NS new composite materials in engineering.The main contents of this article are as follows:(1)Statistical analysis of the effects of BF and NS on the performance of concrete against freezing,impermeability and sulfate corrosion in many literatures shows that an appropriate amount of BF or NS can have a positive effect on the performance of concrete,but when the content exceeds the optimum When the dosage is increased,the improvement effect of the two on concrete gradually decreases,and its performance may even be lower than that of ordinary specimens.(2)The effects of single admixture,admixture of BF and NS on the mechanical properties of concrete under different dosages were explored.By analyzing the enhancement coefficient and the mixing coefficient,it is found that the compressive,split tensile and axial compressive strength of the specimens can be improved by mixing an appropriate amount of BF and NS better than the effect of single mixing.NS has basically no effect on the failure morphology of the specimen.Compared with the ordinary specimen and the specimen doped with NS alone,the failure morphology of the specimen doped with BF has been significantly improved.(3)The advantages and disadvantages of five kinds of flexural toughness evaluation standards used in the literature were evaluated and analyzed,and the American ASTM-C1609 standard was selected to evaluate the flexural toughness of fiber nanoconcrete.The effect of mixing an appropriate amount of BF and NS on the peak bending strength,energy absorption value and residual strength of concrete is better than that when mixing the two materials alone,that is,the mixing of BF and NS enhances the flexural toughness of concrete.(4)Through the SEM microscopic test of the microscopic topography of the concrete,combined with the cement hydration process,composite mechanics theory and fiber spacing theory,the strengthening and toughening effects of NS and BF were analyzed respectively.Comparing the local morphology of the fiber when the two materials are mixed with BF alone and mixed with two materials,combined with the strengthening mechanism of NS and BF,the strengthening mechanism of the two materials after mixing is analyzed.It is of great significance to analyze and explore the reinforcement and toughening effect of BF and NS mixed materials on concrete,which can provide a reference for its application in practical engineering. |
