Experimental Study On Mechanical Properties And Frost Resistance Of Basalt Fiber Reinforced Recycled Concrete

Basalt fiber is widely used to improve the performance of concrete material due to its corrosion resistance and high toughness.The performance of recycled concrete reinforced by basalt fiber has also become a hot research topic.However,the improvement effect of fiber is significant influence by the quality of recycled coarse aggregate and production technology.Therefore,combined with the strengthening of coarse aggregate and the improvement of production technology,it has important theoretical value and practical significance to study the influence of basalt fiber on the mechanical properties and durability of recycled concrete.The main contents and conclusions of this paper are as follows:Firstly,the independent development grinder was used to remove the slurry of recycled coarse aggregate produced by simple crushing.The strengthening effect of recycled coarse aggregate was verified by testing the basic performance of recycled coarse aggregate.The results show that the mechanical strengthening treatment can effectively remove the wrapped old mortar on the aggregate surface and reduce the weak links such as the interface transition zone between aggregate and old mortar.The water absorption and crushing value of coarse aggregate are reduced,which improves the quality of coarse aggregate to a certain extent.Secondly,combined with the strengthening of recycled coarse aggregate and the improvement of production technology,the experimental research on the mechanical properties of basalt fiber recycled concrete was carried out.The effects of recycled coarse aggregate reinforcement,basalt fiber with different content and length on the mechanical properties of recycled concrete were studied,and the effects of ordinary and vibration mixing technology on fiber reinforcement were compared and analyzed.The results show that the tensile and flexural strength of recycled concrete can be significantly improved by strengthening coarse aggregate,appropriate length and amount of basalt fiber,but the effect of fiber on the compressive strength is not obvious.The improvement effect of fiber can be enhanced by vibrating mixing.Then,the freeze-thaw resistance test of basalt fiber reinforced recycled concrete produced by vibration mixing process was carried out.The freeze-thaw resistance of basalt fiber recycled concrete was analyzed from three aspects: mass loss,strength attenuation and change of relative dynamic elastic modulus,and the influence law of basalt fiber on the freeze-thaw resistance of recycled concrete was explored.The results show that basalt fiber can significantly improve the freeze-thaw resistance of recycled concrete.Among them,when the length of basalt fiber is appropriately increased,the frost resistance of basalt fiber recycled concrete is significantly improved.The effect of improving the frost resistance is the best when the volume content of fiber is 0.2%.Finally,the compactness,fiber distribution,microstructure of aggregate-mortar interface and pore structure of basalt fiber recycled concrete fore-and-aft freezing were analyzed by scanning electron microscope and mercury injection method,and the improvement mechanism of production process and fiber on recycled concrete was clarified from the micro point of view.The results show that the vibration mixing are conducive to the distribution of fiber in concrete and increase the density of recycled concrete.Fiber can effectively prevent the generation and expansion of cracks and reduce the porosity of harmful pores in recycled concrete.