Study On Mechanical Properties And Heavy Metal Curing Capacity Of Cement-based Materials Mixed With Sludge

Sludge is the waste generated during the sewage treatment process,which contains many harmful substances such as virus microorganisms and heavy metal ions,if disposed improperly,will cause secondary pollution to the environment.With the development of society and economy,governmental consciousness of environmental protection has grown,China's capacity to treat sewage has rapidly expanded,and the amount of sludge produced is also increasing year by year.Faced with such a large amount of sludge,to seek an effective trearment method is very urgent.Therefore,how to treat the sludge properly and use it effectively has become one of the key issues to all countries in the world.The purpose of this project is to find a low-energy pretreatment method for sewage sludge,then add the pretreated sludge powder as a admixture into the cement products,to study the mechanical properties and heavy metal ions curing capacity of cement-based materials mixed with sludge.This technologie can realize the waste water sludge reclamation and reuse,with social benefits,environmental benefits and economic benefits.First,this paper attempts to find a reasonable method of sludge pretreatment,so that after pretreatment of sludge powder can be used as cement admixture,with low energy consumption.Mainly,study the influence of the sludge heat treatment process and grinding process,The microwave treatment was carried out for 5min,10 min and 15 min.The grinding process was selected for grinding 10 min,30min and 60 min.The evaluation index was the mechanics properties of cement mortar.The results show that the sludge is treated by microwave 10 min and grinding 10 min.Then it is incorporated into the cement mortar and has little effect on the mechanical properties of the cement mortar.It can be considered as a reasonable way of sludge pretreatment.Second,this paper studies the effect of cement-based materials mixed with pretreatment sludge powder on the standard consistency water consumption,the setting time and stability performance,and try to improve the fluidity of cement paste by adding an appropriate amount of naphthalene superplasticizers and try to to improve the early strength of cement paste by adding different kinds and dosage of early strength agent.The results show that the pretreatment of sludge powder will increase the standard consistency water consumption of cement paste,prolong the initial setting time and final setting time of cement,but it has no obvious effect on the cement volume stability.When the dosage of pretreted sludge powder is 0%,10% and 20%,the saturated content of the corresponding naphthalene superplasticizers is 1%,1.25% and 2% respectively,and the fluidity is about 220 mm.When the content of sodium sulfate(NaSO4)is 1%,the early strength of cement paste mixed with pretreated sludge powder is improved,and the late strength also has a slight increase.Finally,in order to study the effect of cement mortar on the solidification of heavy metal ions in sludge powder,electrochemical accelerated dissolution test of cement mortar was carried out by using the self-made electrochemical accelerated dissolution device.Study the influence of the sludge powder calcination temperature,sludge powder fineness,sludge powder content and curing time on the concentration of heavy metal ions in cement mortar test specimen,.then analyze the effect of cement solidification on heavy metal ions in the sludge powder.The results show that the curing rate of heavy metal ions in cement can reach more than 97% and the curing effect is obvious.Therefore,the use of pretreated sludge powder as an admixture does not cause a hazard to human health and the natural environment.