纳米碳纤维改性混凝土的力学性能及抗冻性能研究

Study on mechanical properties and frost resistance of carbon nanofibers modified concrete

纳米碳纤维凭借着高的抗拉强度和弹性模量,被广泛应用于水泥混凝土的增韧剂。通过在混凝土材料中掺入不同含量(0,0.3%,0.6%和0.9%(质量分数))的纳米碳纤维,研究了纳米碳纤维掺杂量对混凝土力学性能和抗冻性能的影响。结果表明,纳米碳纤维的掺杂未生成新的产物,但加速了水化反应的进行,增加了改性混凝土的结构致密性,减小了孔隙和缺陷的数量。当纳米碳纤维的掺杂量为0.6%(质量分数)时,改性混凝土的形貌结构最佳。随着纳米碳纤维掺杂量的增加,改性混凝土的抗压强度、抗折强度和磨损量降低比率先增大后减小,单位面积的磨损量和80次冻融循环时刻的质量损失率先减小后增大。当纳米碳纤维的掺杂量为0.6%(质量分数)时,改性混凝土28 d的抗压强度和抗折强度达到最大值,分别为47.83和5.92 MPa,单位面积的磨损量最小为1.12%,磨损量降低比率最大为55.56%,80次冻融循环时刻的质量损失率最小为1.23%。综合各分析可知,纳米碳纤维的最佳掺杂量为0.6%(质量分数)。

With high tensile strength and elastic modulus,carbon nanofibers are widely used as toughening agent of cement concrete.By adding different contents of carbon nanofibers(0,0.3 wt%,0.6 wt%and 0.9 wt%)into concrete,the effects of the doping amount of carbon nanofibers on the mechanical properties and frost resistance of concrete were studied.The results show that the doping of carbon nanofibers does not produce new products,but accelerates the hydration reaction,increases the structural compactness of the modified concrete and reduces the number of pores and defects.When the doping amount of carbon nanofibers is 0.6 wt%,the morphology and structure of modified concrete are the best.With the increase of carbon nanofibers doping,the reduction ratio of compressive strength,flexural strength and wear of modified concrete first increases and then decreases,and the wear per unit area and the mass loss at 80 freeze-thaw cycles first decrease and then increase.When the doping amount of carbon nanofibers are 0.6 wt%,the compressive strength and flexural strength of modified concrete at 28 d reach the maximum,which are 47.83 and 5.92 MPa respectively.The minimum wear per unit area is 1.12%,the maximum wear reduction rate is 55.56%,and the minimum mass loss rate at 80 freeze-thaw cycles is 1.23%.According to the analysis,the optimum doping amount of carbon nanofibers is 0.6 wt%.