Experimental Study On Carbonation And Chloride Ion Penetration Of Fine Aggregate Concrete From Municipal Solid Waste Incineration Ash

The progress of human civilization and science and technology promotes the development of world material culture,but also brings many serious environmental problems,such as over exploitation of non renewable resources,greenhouse effect,ozone layer destruction and so on.In recent years,the amount of domestic waste is increasing day by day,which has become a serious social problem in China and even in the world.Garbage disposal methods mainly include composting,landfill and incineration.Incineration treatment can reduce the volume of domestic waste to a large extent,and has become the main treatment method of domestic waste.However,about 20% of the total amount of domestic waste remains after incineration.Most of the incineration ash will be landfilled,which will occupy a lot of land resources and affect the ecological environment.Therefore,to find a proper way to deal with municipal solid waste incineration ash(MSWI)has attracted much attention.Over exploitation of resources is also a global problem,especially in recent years,over exploitation of sand and stone has caused a series of environmental problems,so it is urgent to find a material that can replace natural sand.It is found that the main chemical composition of MSWI ash is basically the same as that of granulated blast furnace ash and cement,which has the potential to replace natural sand.In order to broaden the application field of MSWI,scholars began to study municipal solid waste incineration bottom,and try to apply in civil engineering,in order to alleviate the environmental pressure and industry crisis caused by the depletion of domestic waste incineration ash and sand resources.Our research mainly studies the feasibility of replacing part of fine aggregate in concrete with MSWI.As one of the sub topics,this paper studies the carbonation and anti chloride ion permeability of MSWI fine aggregate concrete.The main research contents include: the anti chloride ion permeability and anti carbonation of concrete with different ages and different sand replacement rate of MSWI micro pore structure analysis.It involves rapid chloride penetration test,accelerated carbonation test,capillary water absorption test,SEM-EDS test,optical pore structure test and nuclear magnetic resonance test.The main results are as follows:(1)Compared with natural sand,the fineness modulus of MSWI is larger and the content of fine particles is higher,which can play a better filling effect on the pore structure of concrete.However,the surface of ash is porous,the crushing value is large,the cementation degree with cementitious material is lower than that of natural sand,the interface is not cohesive enough,and the overall structure is loose,so the higher the sand replacement rate is the lower the strength.(2)The results show that the anti chloride permeability of MSWI concrete is better than that of ordinary natural sand concrete with the same water binder ratio and age;the use of MSWI ash can improve the air content of concrete,increase the specific surface area of bubbles,reduce the spacing coefficient and average chord length of bubbles,and improve the anti chloride permeability of concrete.(3)The test results show that the soluble alkalinity of MSWI is higher than that of natural sand,and the concrete structure is loose due to the properties of MSWI.Therefore,compared with natural sand concrete,the ability of MSWI concrete to resist carbonation is weaker,so carbonation reaction is more likely to occur.(4)The primary pore structure parameters that affect the chloride permeability of MSWI concrete in different ages are different.When the age is 28 days,the bubble spacing has the greatest impact on the chloride permeability.When the age is 90 days,the average chord length of bubbles becomes the primary factor affecting the chloride permeability.