氯盐冻融循环下碳纳米管改性RPC性能衰减规律

Degradation Law of Mechanical Properties of RPC Modified by Carbon Nanotubes under Chloride-Freeze-Thaw Cycles

为研究碳纳米管改性活性粉末混凝土(reactive powder concrete,简称RPC)在氯盐侵蚀与冻融循环作用下的力学性能衰减规律,更好地推动RPC的工程应用,以碳纳米管掺量、冻融循环次数为参数变量,对碳纳米管改性的RPC试件进行Cl~-侵蚀与冻融循环共同作用的试验,分析参数变化对改性后的RPC力学性能指标的影响,并发现材料力学性能衰减规律。研究结果表明:在同一冻融循环次数作用下,适量的碳纳米管均能有效地提高RPC的力学性能,且冻融次数越多,纤维对混凝土力学性能的增幅愈发明显。力学性能衰减分析发现,在冻融循环过程中各组试件的力学性能随冻融次数的增加不断衰减,纤维的掺入有效地抑制了衰减趋势,在第200次冻融循环时,纤维质量分数为0.05%的试验组抗压强度和抗折强度衰减程度最低,分别为5.28%和7.03%。而200次冻融循环后,混凝土强度衰减现象出现遏制,分析为二次水化作用的影响。氯盐-冻融耦合作用下的寿命预期结果表明,碳纳米管的掺入能有效地提升混凝土的使用寿命,且平均使用寿命在60 a以上。

For the study of carbon nanotubes modified RPC(reactive powder concrete)under the action of Cl-erosion and freeze-thaw cycles on the mechanical properties of attenuation rule,to better promote the engineering application of RPC,with carbon nanotubes content,freeze-thaw cycles times for the parameter variables,the RPC specimens modified by carbon nanotubes were tested by the interaction of Cl-erosion and freeze-thaw cycles,the influence of parameter changes on the mechanical properties of modified RPC was analyzed,and the attenuation rule of the mechanical properties of the materials was found.The results showed that under the same number of freeze-thaw cycles,an appropriate amount of carbon nanotubes can effectively improve the mechanical properties of RPC,and the more the number of freeze-thaw cycles,the more obvious the increase of fiber on the mechanical properties of concrete.The attenuation analysis of mechanical properties showed that the mechanical properties of each sample decreased continuously with the increase of the number of freeze-thaw cycles,and the fiber incorporation effectively inhibited the attenuation trend.In the 200 th freeze-thaw cycle,the compressive strength and flexural strength of the experimental group with the fiber content of 0.05%had the lowest attenuation,which were 5.28%and 7.03%,respectively.However,after 200 cycles of freeze-thaw,the concrete strength attenuation phenomenon appeared to restrain,which was analyzed as the influence of secondary hydration.The life expectancy results under the chlorine-freeze-thaw coupling action showed that the addition of carbon nanotubes can effectively improve the service life of concrete,and the average service life was more than 60 years.