Experimental Study On Mechanical Properties And Durability Of Slag-rubber Powder Lightweight Aggregate Concrete

In this paper,slag-rubber powder lightweight aggregate concrete made from slag powder and other quality substitutes for some cement,the concrete was subjected to cubic compression test,freeze-thaw cycle test in water,and 5%Na2SO4 salt erosion-freeze-thaw cycle coupling test,study the macro mechanics and durability of concrete,at the same time with the help of bubble spacing analyzer,environmental scanning electron microscope,nuclear magnetic resonance analyzer and energy spectrum analyzer,analyze the microscopic changes of concrete,combining the mechanical properties and durability of concrete with microscopic analysis using grey system theory.The main research contents and results are as follows:(1)It is shown by concrete mechanics test and micro test:Addition of proper amount of slag powder can improve the mechanical properties of slag-rubber powder lightweight aggregate concrete.When the content of mineral powder is less than 15%,the mechanical properties of concrete increase with the increase of the amount,when the amount of mineral powder is greater than 15%,the mechanical properties of concrete decrease with the increase of the content,when the slag content is 15%,the mechanical properties of the concrete are optimal.The proper amount of mineral powder makes the concrete’s internal structure more dense.(2)The freeze-thaw cycle test and micro-experimental research of concrete clear water show that:Addition of proper amount of slag powder can improve the slag-resistance of lightweight aggregate concrete against freeze-thaw water resistance,the relative dynamic elastic modulus index is more accurate to evaluate the resistance of concrete to freeze-thaw resistance to clean water.When the amount of slag powder is less than 10%,the frost resistance of concrete is improved,on the contrary,the frost resistance is decreased,when the content of slag powder is 5%,the frost resistance of concrete is optimal.Increasing the number of bubbles with a chord length less than 240μm can improve the frost durability of concrete.From the porosity change rate greater than 10 μm,a preliminary judgment of the freeze-thaw damage of concrete can be made.(3)The 5%Na2SO4 salt erosion-freeze-thaw cycle test and micro-experimental studies of concrete show that:Addition of proper amount of slag powder can improve the slag-resistance of lightweight aggregate concrete against salt erosion-freeze-thaw cycle,the damage degree of concrete under salt erosion-freeze-thaw cycle is higher than that of water,the relative dynamic modulus of elasticity is used to evaluate the resistance of concrete to salt erosion-freeze-thaw durability.When the amount of slag powder is less than 10%,the resistance to salt erosion-freeze-thaw durability of the concrete is improved,on the contrary,the resistance to salt erosion-freeze-thaw durability is reduced,when the amount of ore powder is 5%,the salt salt-freeze-thaw durability of concrete is the most.With the increase of salt erosion-freeze-thaw cycle,small pores in concrete will evolve to large pores.Porosity changes of 0～1μm and>1μm can reflect the salt erosion-freeze-thaw damage of concrete.(4)Analysis by grey system theory show that:Specific surface area and pore size distribution of 0～0.1 mm are the most important factors affecting the 28-day compressive strength of concrete.Spectral area and pore size distribution of 1～10μm are the most important factors affecting the durability damage of concrete in freeze-thaw cycles.Free fluid saturation and pore size interval distribution of 0.1～1μm are the most important factors affecting the damage degree of concrete salt erosion-freeze-thaw cycle durability damage degree.(5)Slag-rubber powder lightweight aggregate concrete with less than 10%slag powder content can better meet the requirements of mechanical properties and durability.