Study On Properties Of Recycled Permeable Concrete Modified By Basalt Fibre

With the massive accumulation of construction waste caused by urbanization,the pressure of emission reduction brought by the "carbon neutrality" construction goal,and the need to build a "sponge city",the demand for recycled aggregate permeable concrete(RAPC)has increased sharply.Due to the fact that increasing the replacement rate of recycled aggregate can reduce the mechanical properties of RAPC,the replacement rate of recycled aggregate in practical engineering is generally less than 30%.At the same time,due to the widespread selection of polyethylene fibers in previous studies,there has been less research on RAPC with the addition of other fibers.Therefore,this article focuses on using basalt fibers(BF)to modify RAPC,attempting to improve the replacement rate of recycled aggregate,conducting relevant research,and obtaining conclusions:(1)Find the best mix ratio of RAPC through orthogonal test.Set four factors: water cement ratio,target porosity,silica fume content,and fly ash content.Set three levels for each factor.After analysis,the optimal mix ratio combination for pressure resistance performance is obtained as follows: water cement ratio of 0.3,target porosity of 10%,silica fume content of 8%,and fly ash content of 20%.(2)Research on the RAPC stirring process with the addition of basalt fibers.Test the mechanical and permeability properties of specimens prepared by three mixing processes:pre mixing,sprinkling,and mixing.Use variance analysis to verify whether the mixing process has a significant impact on mechanical and permeability.After analysis,it is found that sprinkling is the most unfavorable method for fiber dispersion.The dispersion effect of pre mixing and mixing methods is similar,but the fiber loss of mixing method is smaller,and the degree of fiber bonding with cement slurry is higher;The influence of mixing process on compressive strength is significant,but the impact on flexural strength,connected porosity,and permeability coefficient is not significant;The RAPC obtained by the mixed method has the best compressive performance.(3)Study the optimal length and dosage of basalt fibers.Design and manufacture specimens with different BF lengths and dosages,and test their mechanical and permeability properties.After analysis,it was found that the compressive strength of the specimens is optimal when the BF length is 12 mm and the BF content is 0.9%,while the flexural strength of the specimens is optimal when the BF length is 6mm and the BF content is 0.9%.Through grey correlation analysis,it is found that the correlation between the length and content of BF and various properties is relatively important.As the replacement rate of recycled aggregate increases,the compressive strength is most likely to exceed the minimum value required by the specifications.Therefore,the fiber length and content at the optimal compressive strength are selected as the optimal length and content of BF.(4)Related research has been conducted to improve the RA replacement rate,and it has been found that the mechanical and water permeability properties of laboratory specimens can still meet the standard requirements when the RA replacement rate is 70%.It is recommended that the replacement rate should not exceed 60% when used in construction.