| As a widely used building material,concrete has the advantages of high compressive strength,easy construction and good durability.But it also has its own major,low tensile strength,easy to crack and other shortcomings.With the development of building structure,the performance of concrete is more and more demanding,and some high-performance concrete has appeared one after another Self-Compacting Concrete(SCC)also belongs to high performance concrete with good fluidity and no need for vibration during construction.At the same time,adding fiber to self-compacting concrete can also improve its cracking defects,and improve its tensile strength and toughness.However,the content of fiber is limited,and the excessive content of fiber will result in the unsatisfied fluidity of self-compacting concrete Although it can be improved by increasing the dosage of water reducer,the high price of the water reducer and the high dosage of the water reducer easily lead to the concrete bleeding.However,the flow performance and strength of self-compacting concrete mixed with magnetized water are improved obviously.In this paper,basalt fiber and polypropylene fiber with different volume contents were first mixed into SCC,and a series of SCC performance tests and mechanical performance tests were conducted to determine the optimal content of the two fibers Then,on the basis of obtaining the optimal fiber content,magnetized water with different magnetic field strength and different water flow velocity was used to mix the fiber reinforced self-compacting concrete,and the working performance tests,mechanical performance tests and scanning electron microscope tests were carried out.The main research contents are as follows:(1)single or mixed basalt fiber and polypropylene fiber were used in SCC,and a series of performance tests were conducted for the fiber mixed SCC,including:slump flow,T500,internal and external height difference of J ring,J ring extension and v-shaped funnel flow time.Then,the compressive strength tests,tensile strength tests and flexural strength tests of fiber reinforced self-compacting concrete for 28 days were carried out.The influence of fiber content on its workability and mechanical strength was analyzed,and it was concluded that the increase of fiber content would significantly reduce the flow performance of SCC,and the failure morphology of SCC changed from brittle failure to plastic failure.At the same time,combined with the experimental results of compressive strength tests,,tensile strength tests and flexural strength tests,when the content of basalt fiber is 0.05%and the content of polypropylene fiber is 1.0%,it is the optimal content of self-compacting concrete with hybrid fiber.(2)on the basis of determining the optimal dosage of the two fibers,magnetized water with magnetic field strength of 285mT and 810mT and water velocity of 2 L/min,4 L/min,6 L/min and 8 L/min were used to mix the fiber self-compacting concrete,and then a series of working performance tests and 3d compressive strength tests and tensile strength tests were conducted on it.The influence of magnetic field strength and water velocity of magnetized water on the performance and early strength of fiber self-compacting concrete was analyzed.It is concluded that magnetized water with different parameters can significantly improve the flow performance of fiber reinforced self-compacting concrete,without segregation or bleeding,and reduce the amount of water reducer,which has certain economic benefits.When the magnetic field strength is 810mT and the water velocity is 2L/min,magnetized water has the most significant effect on the 3d strength enhancement of fiber reinforced self-compacting concrete.By comparing the SEM images of ordinary self-compacting concrete and magnetized water self-compacting concrete,it is found that magnetized water can refine the microstructure of fiber reinforced self-compacting concrete.(3)on the basis that the fiber content and magnetic field strength and water velocity of magnetized water have been determined,that is:basalt fiber and polypropylene fiber content are 0.05%and 0.1%,respectively.the magnetic field strength and water velocity of magnetized water respectively are 810mT and 2L/min.To investigate the effect of magnetized water on compressive strength,tensile strength and flexural strength of fiber reinforced self-compacting concrete at different curing ages of 3d,7d,14d and 28d.The results show that magnetized water can improve the mechanical strength of fiber reinforced self-compacting concrete at different curing ages,and the enhancement effect of early strength is obviously better than that of later strength.At the same time,under the action of magnetized water,the formation of hydrates inside the fiber reinforced self-compacting concrete,the internal mechanism of the microstructure changes of the fiber and matrix bonding surface and the interface transition zone were observed and analyzed by SEM test.Figure 32 table 16 references 90... |
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