Influence Of Steam Curing On Mechanical Properties And Impermeability Of High Performance Concrete With Mechanism Sand

With the decrease of the supply of natural sand in different places,the use of mechanism sand is bound to cover a wider area of construction.The research on the performance of mechanism sand concrete under various working conditions is helpful to lay a foundation for the popularization and use of mechanism sand.In this paper,the experimental research and theoretical analysis methods were used to complete the following research contents:(1)The influence of steam curing on the compressive strength,dynamic elastic modulus,pore structure and chloride ion permeability resistance of mechanized sand concrete,as well as the regulation effect of stone powder on the above properties were studied;(2)Based on the theory of constant temperature time and maturity,the compressive strength model and impermeability regression model of sand concrete with steam curing mechanism were established;(3)The influence of steam curing on mechanical properties and impermeability of mechanism sand concrete was evaluated.The main work of this paper includes:(1)the mix ratio design of mechanism sand concrete with different stone powder content;(2)Design of steam curing scheme and study on the variation of compressive strength of mechanism sand concrete under different constant temperature with constant temperature time;(3)Comparative study on the performance of mechanism sand concrete under standard curing and steam curing;(4)Comparative study on properties of mechanism sand concrete and natural sand concrete under steam curing and standard curing methods;(5)Study on the influence of stone powder content on the performance of mechanism sand concrete;(6)The regression model of compressive strength and impermeability of sand concrete with steam curing mechanism is established.The main conclusions of this paper are as follows:(1)Adding proper amount of stone powder into mechanism sand can improve the fluidity of mechanism sand concrete.In the case of the same water-binder ratio,the fluidity of natural sand concrete is obviously better than that of mechanism sand concrete.When the amount of cement(or cementifying material)is the same,if mechanism sand concrete with the same fluidity as that of natural sand concrete is configured,the amount of mixing water or water reducing agent should be appropriately increased.(2)In the process of constant temperature steam curing,the compressive strength of mechanism sand concrete and natural sand concrete increases gradually with the increase of constant temperature time,and the higher the constant temperature is,the higher the compressive strength of each age,and the shorter the constant temperature time is needed to reach the designed curing strength of concrete.(3)The compressive strength of concrete under steam curing(mechanism sand or natural sand concrete)at 28 d is basically the same as that of concrete under standard curing.However,its dynamic elastic modulus,chloride ion permeability resistance and porosity are all inferior to those of concrete under standard curing mode,and the effect is more obvious with the increase of constant temperature in steam curing stage.(4)In both steam curing and standard curing methods,the compressive strength,dynamic elastic modulus,pore structure and chloride permeability resistance of mechanism sand concrete and natural sand concrete with reasonable mix ratio are relatively small.In other words,the performance of mechanism sand concrete is similar to river sand concrete under reasonable mix ratio.(5)Adding appropriate amount of mechanism sand stone powder,could improve the mechanism sand concrete pore structure,and improve the dynamic modulus of elasticity and resistance to chloride ion permeability,In the test,the dynamic elastic modulus,pore structure and impermeability of the four kinds of mechanism sand concrete are in order from best to worst:A2(stone powder content of 5%)> A3(stone powder content of 10%)> A1(stone powder content of 0%)A4(stone powder content of 15%);that is,in C50 mechanism sand concrete,the concrete with 5% stone powder content has the best performance.(6)Based on the theory of constant temperature time and maturity,the regression model of steam curing to the compressive strength of concrete can better reflect the relationship between the compressive strength of concrete and the steam curing time in the process of steam curing;The regression model of impermeability of sand concrete with steam curing mechanism,which considers the influence of aggregate and steam curing temperature,also agrees well with the test results.