Influence Of Imposed Load And Self-healing On Permeability Of Ultra-high Performance Fiber Reinforced Concrete

Since Ultra-High Performance Fiber Reinforced Concret（eUHPFRC）successfullydeveloped in the1990s, it has caused wide attention of the experts of concrete aroundthe world, and became a new research focus in the field of international engineeringmaterials due to its ultra-high mechanical properties and durability. At present, thedomestic and foreign experts make a series of researches on its mixture ratio, curingsystem, mechanical properties, and get a lot of valuable research results. At the sametime, durability of UHPFRC, such as carbonation resistance, freeze resistance,chloride-ion erosion resistance is also widely researched. But almost all of the existingresults of permeability are fail to consider the actual working condition. So the researchresults can not guide engineering practice well. In addition, UHPFRC may have goodself-healing ability due to its own characteristics, the effect of self-healing on itspermeability is still unclear. So the primary coverage of this paper is as follows:(1) Mechanical properties test. Using ANSYS analyze the specimen size under theaction of the uniaxial tensile to obtaine the optimal uniaxial tensile specimen size. Andthrough ‘Cement-base material permeability testing device under uniaxial tensile load’measure its stress-strain curve. Different content of steel fiber on the stress-strain curveswere compared, to research the influence of steel fiber content on uniaxial tensileperformance, results indicate that strength and toughness with the incorporation of steelfiber improves obviously. Through the existing experiment condition, measuredstress-strain curves raise section under uniaxial compressive load.(2) Permeability test under uniaxial tensile load. Apply different percentages ofuniaxial tensile stress on specimens, respectively in the condition of under load and afterunloading, measure its capillary water absorption coefficient and chloride-ion diffusioncoefficient by the capillary water absorption test and the chloride-ion erosion test. Toresearch the influence of imposed tensile load on permeability of UHPFRC. Results indicate that in the condition of under load and after unloading, the permeability ofUHPFRC increases with the increase of stress level, and under the same stress level, thepermeability under load is greater than after unloading.(3) Permeability test under uniaxial compressive load. Apply different percentagesof uniaxial tensile stress on specimens. After unloading, measure its capillary waterabsorption coefficient and chloride-ion diffusion coefficient by the capillary waterabsorption test and the chloride-ion erosion test. To research the influence of imposedcompressive load on permeability of UHPFRC. Results indicate that in the condition ofafter unloading, the permeability of UHPFRC increases with the increase of stress level.(4) Permeability test after self-healing. Store the pre-cracked specimens insaturated Ca(OH)2solution for one week and for four weeks. Measure capillary waterabsorption coefficient and chloride-ion diffusion coefficient by the capillary waterabsorption test and the chloride-ion erosion test. To research the influence ofself-healing on permeability of UHPFRC. Results indicate that the permeability ofUHPFRC decreases with self-healing, and the longer the self-healing, the more obviousthe test results.