| With the development and utilization of resources,a kind of waste mud with high moisture content has attracted people’s attention.Now,the curing technology has the disadvantages of high cost,small processing capacity and poor application,which can not meet the solidification of waste with high moisture content.It is of great practical significance to treat the waste with high moisture content,which can be used as agricultural resources,filling materials and building material.As a kind of waste with high water content,sewage sludge has the characteristics of high water content and large treatment capacity.In this paper,sewage sludge with high water content is taken as the main object of study,Magnesium potassium phosphate cement（MKPC）and composite cement were used as curing agent.Through the treatment of sewage sludge and gold slag,the effects of the ratio and dosage of curing agent on the compressive strength,water content,the ratio of compatibilization and the rheological properties of the solidified sludge were investigated.Through some test methods,such as laser particle size analysis,X ray diffraction（XRD）,scanning electron microscopy（SEM）and hydration heat analysis,the properties of raw materials,phase composition,microstructure and hydration process were analyzed.The main results are as follows:（1）In the solidification/ reducation system of sludge with MKPC mixed with silica fume,the strength,rheology,mositure content and volume shrinkage of the solidified sludge were closely related to the initial moisture content of the sludge,the amount of solidified body and the amount of silica fume.With the increase of MKPC content,the strength of solidified sludge increased gradually.The amplitude（slope）is closely related to the initial moisture content of sludge,the lower the moisture content,the higher the strength of solidified sludge.When the sludge moisture content decreased from 94% to 85%,the compressive strength（20 wt% MKPC）of solidified sludge were increased by 470 k Pa and 2400 k Pa at 3d and 7d,respectively;the appropriate amount of silica fume can improve the strength of solidified sludge,which reached the requirements of the landfill（≥350 k Pa）.MKPC and silica fume significantly increased the viscosity and yield stress of the solidified sludge and decreased the workability of the mixture.Both MKPC and silica fume can reduce the moisture content of sludge,the moisture content of solidified sludge can be reduced to 30% by curing,which can meet the landfill requirements（60%）.Both MKPC and silica fume can reduce the volume of sludge,the capacity ratio of solidified sludge（30 wt% MKPC）was 0.53 at 7d;the capacity ratio of solidified sludge（30 wt% MKPC with 30 wt% silica fume）was 0.68.With the increase of MKPC content from 20 wt% to 40 wt%,the volume shrinkage of solidified sludge increased from 40 wt% to 62 wt% at 7d.The larger the amount of MKPC,the greater the volume shrinkage.The shrinkage of solidified sludge（30 wt% MKPC）decreased with the increase of the content of silica fume.（2）In the solidification system of sludge with composite cement,HAC/C（?）H2 and HAC/PC has a great influence on mechanical properties,rheological properties,mineral composition and hydration process of solidified sludge.The moisture content of sludge was 94%,and the dosage of curing agent was 30 wt%.With HAC/C（?）H2 decreased,the compressive strength of solidified sludge was first increased and then decreased,which did not appear to fall down.With HAC/ C（?）H2 decreased,the viscosity and yield stress of the solidified sludge decreased gradually;HAC/C（?）H2 had the effect on the hydration process of solidified sludge,when the HAC/C（?）H2 decreased from 15/10 to 13/12,the hydration time of portland cement was delayed.With the decreased of PC/HAC,the compressive strength of solidified sludge increased firstly and then decreased,which did not appear to fall down.With the increased of PC/HAC,the viscosity and yield stress of solidified sludge decreased gradually.The compressive strength of the solidified sludge increases with the increase of the total amount of the curing agent,The compressive strength were 1.4 MPa,3 MPa and 4.8 MPa at 3d,7d and 28 d,respectively,when the dosage of the composite cement curing agent was 40 wt%;When the dosage of the composite cement curing agent is lower than 20 wt%,the maximum strength of the cured body will be less than k Pa,which can not meet the requirement of landfill（0.35 MPa）.（3）In the solidification of gold slag with composite cement,the properties of the gold slag and the ratio of the composite cement have a great influence on the strength,setting time and mineral composition.The dosage of curing agent is 15 wt%,the water to solid ratio is 0.53.In the HAC-PC-C（?）H2 system,the compressive strength of sample（HAC:PC:C（?）H2=15 wt%:10 wt%:75 wt%）were 1.2 MPa,3.4 MPa and 2.8 MPa at 1d,7d and 28 d,respectively.There is diffraction peak of gypsum in solidified slag,that may be the presence of soluble sulfate in the slag,which lead to the low solubility of gypsum in the liquid phase.In the HAC-PC-CH system,the compressive strength of sample（PC:HAC:CH=70 wt%: 10 wt%:20 wt%）were 1 MPa,3 MPa and 5 MPa at 1d,3d and 7d,respectively.In this system,a high grade filler with high early strength can be formed by adding appropriate amount of HAC and a small amount of CH.The addition of hydrated lime and high alumina cement will shorten the initial setting time. |
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