Effects Of Expansive Agent And Carbon Fiber On The Mechanical Properties Of Cement-based Composites

Concrete is one of the most widely used building materials in civil engineering in recent decades.With the emergence of various special-shaped structures and large span structures,people put higher demands on the performance of concrete.The use of various fibers in the concrete to improve the mechanical properties,durability and other properties of concrete become a research hotspot of civil engineering materials.Carbon fiber has attracted researchers' attention because of its advantages of light weight and high strength.The effect of expansive agent and fiber on the deformation performance of cement-based materials has been studied at home and abroad.However,there is still little research on effects of expansive agent and fiber on the mechanical properties of cement-based composites.Therefore,effects of expansive agent and carbon fiber on the mechanical properties of cement-based composites was studied.and its mechanism is described.The main contents of this paper are as follows:Firstly,the dispersion method of carbon fiber and the influence of carbon fiber length and expansive agent on the fluidity of cement paste and the law of compressive strength and compressive strength of cement were studied.The results show that the expansive agent has little effect on the fluidity of carbon fiber cement paste.But with the increase of carbon fiber length,the fluidity of cement paste decreased significantly.The flexural strength of carbon fiber cement paste increases with the increase of carbon fiber length,but the compressive strength decreases with the increase of carbon fiber length but still higher than the cement paste.The expansive agent has no effect on the flexural strength and compressive strength of the cement paste,but it has a different amplitude enhancement effect on the carbon fiber cement paste.Moreover,the expansive agent has an optimum dosage(8%)which is not affected by the length of the carbon fiber and dosage.Secondly,the interfacial mechanical properties of carbon fiber-cement matrix under the action of expansive agent were studied by single fiber pull-out test.SEM was used to observe the micro morphology of carbon fiber cement paste with different expansive agent content.It was found that addition of expansive agent could increase the probability of carbon fiber breaking.The results show that the expansive agent can improve the mechanical properties of the interface between the carbon fiber cement matrix.Lastly,based on the results of macroscopic mechanical tests,the interfacial mechanical properties of carbon fiber-cement matrix and the microstructure of carbon fiber cement paste,the mechanism of carbon fiber and the synergistic effect of carbon fiber-expansion agent on improving the mechanical properties of cement was expounded.