Study On Macro Properties And Pore Structure Of Iron Tailings Mortar Mixed With Seawater

The coastal area is short of fresh water,river sand and other resources,and engineering construction needs a lot of fresh water,sand and stone resources.At present,most of the research uses sea sand or desalinated sea sand,sea stone,coral and shell to replace natural aggregate,while the research on using sea water to replace fresh water and iron tailings to replace natural sand to prepare sea water mixed iron tailings mortar is relatively less.In order to study the effects of seawater replacing fresh water and iron tailings replacing natural sand on the macro properties and pore structure of mortar,the common mortar(NSM),seawater common mortar(SSM),seawater common mortar with additives(YSSM),seawater iron tailings mortar(STM)and seawater iron tailings mortar with additives(YSTM)were used,In standard water condition 20±2℃ for 28,60,120,180,240 and 300 days,the compressive strength,flexural strength,chloride ion diffusion coefficient,chloride ion content titration and pore structure tests were carried out respectively.The correlation among macro properties,pore structure parameters,macro properties and pore structure characteristics of different mortars was analyzed,and the sensitive parameters affecting macro properties were studied.With the increase of curing age,air content,specific surface area and bubble frequency are negatively correlated with compressive strength and flexural strength,and positively correlated with chloride ion diffusion coefficient and chloride ion content;The bubble spacing coefficient,the average chord length of bubbles and the ratio of rubber to air are positively correlated with the compressive strength and flexural strength,and negatively correlated with the chloride ion diffusion coefficient and chloride ion content.The correlation of YYB mortar containing marine additive is high,because the reaction of Al2O3 in the additive and NaCl in sea salt inhibits the corrosion of sea salt on mortar;The STM correlation of iron tailings mortar is low because iron is contained in iron tailings,and sea salt has strong erosion effect on it.Gas content is a sensitive parameter that affects the change of macroscopic properties.In order to accurately describe the infiltration path of seawater mixed iron tailings mortar,the characteristic parameters of pore structure were measured by rapidair 457 concrete pore structure analyzer,and the length of pore axis was calculated with bubble spacing,diameter and number as parameters.The spacing box dimension method was established to calculate the fractal dimension of pore axis by combining the spacing method and box dimension method.In order to avoid repeated counting of holes,accurately calculate hole spacing and obtain more realistic hole axis length,Image J image processing software and rapidair457 concrete hole structure analyzer test results are combined to obtain the maximum freiter diameter and coordinate position of each hole and calculate the fractal dimension of hole axis.By analyzing the variation of fractal dimension of hole axis with curing age,the correlation between fractal dimension of hole axis and macro properties and pore structure characteristics is explored,and the macro properties and pore structure characteristics of mortar are explained from fractal dimension of hole axis.With the increase of curing age,the fractal dimension of hole axis of different materials is positively correlated with the air content,and the correlation is high.The air content is a sensitive parameter affecting the fractal dimension of hole axis.It shows that the characteristic parameters of pore structure are consistent with the fractal dimension of pore axis.The fractal dimension of hole axis based on freiter diameter has better correlation with macro performance and hole structure characteristic parameters,because considering the hole diameter and hole position coordinates at the same time,it can more accurately calculate the hole spacing and obtain more real hole axis length.In order to study the correlation of hole axis reliability with mechanical properties,permeability and pore structure of seawater mixed iron tailings slurry,the critical hole axis length of hole axis reliability was set by comprehensively considering chloride diffusion coefficient,air content and reliability index,and the hole axis reliability was calculated by Monte Carlo method,The sensitive parameters affecting the reliability of hole axis are determined.With the increase of curing time,the reliability index of hole axis of different materials increases first and then decreases,showing a good negative correlation with the curing time.The air content is a sensitive parameter affecting the change of hole axis reliability.The fractal dimension of hole axis caused by the change of hole structure is consistent with the change of hole axis reliability.