Abstract:

Objective The cement-based grouting material is widely used in secondary grouting, equipment installation, prefabricated construction, anchor bolt anchoring, and grouting repair. However, it has been found that the impact resistance and crack resistance of grouting material will gradually deteriorate after long-term use. Therefore, improving the crack resistance and toughness of grouting material is crucial for its applications in the engineering field.

Metheod The length of carbon fiber had a significant impact on the flowability of cement matrix, in order to reduce the influence of carbon fiber on the fluidity of grouting material, short cut carbon fiber with a length of 1 mm was used to reinforce cement-based grouting material. In order to improve the dispersion uniformity of carbon fiber in the cement matrix and the performance of grouting material, the carbon fiber was pre dispersed with Sodium polyacrylate (PAAS) before adding to grouting material. The proportion of water reducing agent was increased, and the preparation process was adjusted during the process of making the carbon fiber reinforced cement-based grouting material. After curing and shaping grouting material, the influence of carbon fiber on the flexural strength and compressive strength of grouting material at different ages was studied. SEM was used to study reinforcing mechanism of carbon fiber reinforced cement-based grouting material.

Results It was found that water reducing agent can effectively reduce the influence of carbon fiber and PAAS on the flowability of grouting material. but with the increase of carbon fiber content, the flowability of grouting material still gradually decreased. Meanwhile, with the increase of carbon fiber content, PAAS and water reducing agent enhanced the retarder effect on grouting material, resulting in an extension of its initial setting times. The research also revealed that the addition of carbon fiber significantly improved the 1-day, 3-day, 28-day compressive strength and 28-day flexural strength of grouting material, and the flexural and compressive strength of grouting material showed a trend of first increasing and then decreasing with the proportion increase of carbon fiber. When the carbon fiber content was low, uniformly dispersed carbon fiber effectively enhanced the cement matrix. However, when the carbon fiber content was too high, PAAS can't effectively disperse carbon fiber, and incompletely dispersed carbon fiber formed many clusters in the grouting material, resulting in a significant decrease in the mechanical strength of grouting material. In addition, its compressive and flexural strength respectively reached its peak when the volume fraction of carbon fiber was 0.4% and 0.3%. By observing the microstructure of grouting material with different proportion of carbon fiber, it was found that the increasing proportion of carbon fiber significantly reduced the number of cracks in the cured grout and delayed crack propagation. After adding carbon fiber to grouting material, the viscosity of the grouting material was increased, which played an effective connecting role on the cement matrix. The interface of carbon fiber observed in the microstructure indicated that carbon fiber had fractured and slid when subjected to internal forces in the grouting material, thus proving that carbon fiber shared the pressure borne by grouting material inside the material. Through studying the working performance, mechanical properties, and microstructure of the high-performance grouting material with carbon fiber, it was found that the comprehensive performance of the carbon fiber reinforced cement-based grouting material was optimal when the volume fraction of carbon fiber was kept at 0.3%.

Conclusion The experimental results show that the addition of carbon fiber disperses the pressure and bending force borne by grouting material, improves the cohesion of grouting material, and transforms brittle failure into flexible failure, ultimately significantly improving the compressive and flexural strength of grouting material.

Key words: carbon fiber, cement-based grouting material, sodium polyacrylate, mechanical property, microstructure, composite material