Experimental Research On Mechanical Properties Of Fiber Reinforcrd Iron Tailings Concrete

Iron tailings is a kind of mineral waste,which is a common method in open-air storage,This not only has a huge impact on the ecological environment,but also takes up a lot of land resources.Therefore,from the perspective of green,energy saving,environmental protection and sustainable development,iron tailings sand is used to replace the fine aggregate in ordinary concrete,and an appropriate amount of fly ash,high-strength high-modulus polyvinyl alcohol(PVA)fiber and metakaolin are added.The preparation of high ductility fiber-reinforced iron tailings concrete and its application to actual engineering structures have a good application prospect.Based on this background,this thesis mainly studies the mechanical properties of PVA fiber concrete with different iron tailings replacement rates,the main research work is as follows:(1)On the basis of the results of the research group,8 groups of 120 fiber-reinforced iron tailings concrete test blocks were designed and produced,the length of 12 mm PVA fiber is 1.5%,the first grade fly ash is 30%,the metakaolin is 15%,and the iron tailings replacement rate is 0%,20%,40% and 60% respectively.Based on the cube compression test,splitting tensile test,four point bending test and axial compression test of the test block,this thesis studied the effect of PVA fiber,fly ash and metakaolin,the main mechanical properties of fiber reinforced iron tailings concrete under different replacement ratio of iron tailings sand are analyzed,the reasonable value of replacement ratio of iron tailings sand and the corresponding improvement effect of mechanical properties are analyzed,and the general law is summarized.The results show that under the above test conditions,with the increase of iron tailings replacement rate,the main mechanical properties of the material show a trend of first increasing and then decreasing,due to the effect of PVA fiber,the iron tailings are effectively improved the ductility of concrete,its failure mode also shows that it is broken but not broken.Relatively speaking,when the replacement rate of iron tailings is 40%,the mechanical properties and ductility of the test block are improved significantly.(2)Based on the statistical analysis of the test results,the relationship between the replacement rate of iron tailings sand and the mechanical properties of the corresponding materials,such as compressive strength,splitting tensile strength,four-point bending bearing capacity and axial compressive strength is studied,at the same time,the relationship between compressive strength,splitting tensile strength and four-point bending strength is established.Then,based on the measured stress-strain curves of the corresponding materials,the stress-strain constitutive equation of the corresponding materials is established,and the damage constitutive model of the corresponding materials is established based on the Weibull probability distribution and the test results,the damage evolution law of the corresponding materials is discussed.The results show that the error value of the calculation formula given in the article is within ±5%,which shows that the fitting effect is better,the damage constitutive model established in the article is also in good agreement with the test results,which can be used as a reference for further research.(3)The relationship between the macro-mechanical properties and the internal damage of PVA fiber reinforced iron tailings concrete was analyzed by XRD,NMR and SEM,the general change rule of the macroscopic properties of the material is explained from the change of its microstructure.The results show that the iron tailing sand with 40%substitution rate can fully hydrate with cement and produce a large amount of cementitious material,which reduces the number of pores in the Matrix and makes the structure of the material more compact.After adding PVA fiber,the PVA fiber can be well wrapped in the Matrix,which makes the PVA fiber play a good toughening role,leading to the improvement of the material’s main mechanical properties and the corresponding reduction of the material’s internal damage,it is a good fiber reinforced iron tailings concrete material.