纳米碳纤维增韧水泥基复合材料的力学性能和耐久性能研究

Mechanical properties and durability of cement-based composites toughened by nano carbon fibers

以普通硅酸盐水泥P.O 42.5为基体材料,不同掺杂量(0,0.4%,0.8%和1.2%(质量分数))的纳米碳纤维为增强相,制备了纳米碳纤维增韧水泥基复合材料,研究了纳米碳纤维的掺杂量对水泥基复合材料晶体结构、力学性能和耐久性能的影响。结果表明,纳米碳纤维的掺杂在水泥基复合材料中未出现新的水化产物,但加速了水化反应的进行;纳米碳纤维的“连接”作用使水泥基复合材料的孔结构变得致密,裂纹和孔隙减少;随着纳米碳纤维掺杂量的增加,水泥基复合材料的抗压强度和抗折强度先增大后减小,当纳米碳纤维的掺杂量为0.8%(质量分数)时,水泥基复合材料28 d的抗压强度和抗折强度均达到了最大值,分别为82.4和13.1MPa;采用单面盐冻法对水泥基复合材料进行抗冻性能测试,发现纳米碳纤维的掺杂改善了水泥基复合材料的抗冻性能,当纳米碳纤维的掺杂量为0.8%(质量分数)时,水泥基复合材料在28次冻融循环后单位面积质量损失量最小为0.114 kg/m^(2)。综合力学性能和耐久性能分析可知,纳米碳纤维的最佳掺量为0.8%(质量分数)。

Using ordinary Portland cement P.O 42.5 as matrix material and nano carbon fibers with different doping contents(0,0.4 wt%,0.8 wt%and 1.2 wt%)as reinforcing phase,nano carbon fiber toughened cement-based composites were prepared,and the effects of the doping amount of nano carbon fibers on the crystal structure,mechanical properties and durability of cement-based composites were studied.The results showed that the doping of nano carbon fibers didn’t produce new hydration products in cement-based composites,but accelerated the hydration reaction.The“connection”effect of nano carbon fibers made the pore structure of cement-based composites become dense and the cracks and pores were reduced.With the increased of the doping amount of nano carbon fibers,the compressive strength and flexural strength of cement-based composites first increased and then decreased when the doping amount of nano carbon fibers was 0.8 wt%,the compressive strength and flexural strength of cement-based composites reached the maximum at 28 d,which were 82.4 and 13.1 MPa respectively.The frost resistance of cement-based composites was tested by single-sided salt freezing method.It was found that the doping of nano carbon fibers improved the frost resistance of cement-based composites when the doping amount of nano carbon fibers was 0.8 wt%,the minimum mass loss per unit area of cement-based composites after 28 freeze-thaw cycles was 0.114 kg/m^(2).The comprehensive analysis of mechanical properties and durability shows that the optimal content of carbon nanofibers is 0.8 wt%.