Experimental Study On Durability Of Alkali-Resistant Basalt Fiber Reinforced Cement-Based Composites Mixed By Seawater And Sea-Sand

Marine engineering is an area where China and the world are striving to develop and construct.In order to promote the development of marine engineering and reduce the difficulty and cost of marine engineering development,alkali-resistant basalt fiber reinforced seawater and sea sand cement-based composite(or seawater and sea sand concrete for short)with high strength and high durability and high workability is developed,and the studies is carried out on the following three aspects:(1)Through accelerated corrosion tests in NaOH and Ca(OH)₂solutions,and using a series of characterization methods,including mass loss,ICP and SEM,the alkali resistance of four types of basalt fibers was tested,and the corrosion mechanism of basalt fibers in different alkali solutions was analyzed.The results show that the alkali resistance of basalt fibers with different chemical compositions is obviously different.The erosion mechanism of basalt fibers in NaOH solution is mainly based on OH^-destructive fiber framework components Si O₂ and Al₂O₃,and in saturated Ca(OH)₂ solution it is mainly caused by massive erosion;the addition of zirconia can effectively improve the alkali resistance of basalt fiber,and the mass loss rate of the alkali resistant basalt fiber is only 34.4%and 3.87%in the solution of NaOH at 90?and Ca(OH)₂at 100?for 24 hours.(2)Orthogonal experimental test design is carried out to study the mix ratio of seawater and sea sand concrete in cement-silica fume-fly ash cementing system,and alkali-resistant basalt fiber and alkali-resistant basalt fiber dipped yarn were used to set up experimental groups with different chopped lengths and dosages to study the basic mechanical properties.The results show that silica fume has higher activity,plays a leading role in the early stage,and fly ash has lower activity,but can increase strength in the later stage,and sea sand as the only bone material is the key factor for the stability of the matrix in the long term;although the alkali-resistant basalt fiber original yarn mostly makes the workability reduced and the strength slightly weakened,the reinforcement effect of alkali-resistant basalt fiber dipped yarn is better than that of the original yarn,especially the 12mm length of the fiber has a stable reinforcement effect.(3)The sulfate resistance experiment of fiber-reinforced seawater and sea sand concrete is carried out,ordinary basalt fiber,alkali-resistant basalt fiber filament,alkali-resistant basalt fiber dipped yarn and steel fiber test group for comparison test is set and 30d,60d,90d,120d,and 150d are test ages.The results show that the seawater and sea sand concrete has good resistance to sulfate corrosion and the loss of concrete appearance is little;ordinary basalt fiber has the weakest reinforcement effect and the greatest degree of strength degradation by sulfate erosion;the surface of the specimens of the steel fiber showed serious rust,which affected the appearance,but the internal steel fiber is well preserved and work effectively;the alkali-resistant basalt fiber dipped yarn and steel fiber experimental group have the best resistance to sulfate erosion,for after 150 days of erosion,specimens still have a strength corrosion resistance coefficient of more than 75%.