Study On The Preparation And Corrosion Resistance Of Aluminum Sludge Ash Modified Concrete Material

In recent years,the global population has continued to grow,and the demand for drinking water treatment has increased with population growth,resulting in a geometric increase in the amount of sludge produced by water treatment.Improper treatment of water supply sludge not only leads to resource waste,but also poses harm to the ecological environment and human health.Therefore,the treatment and management of water supply sludge is becoming a global issue of great concern.After investigating the composition of drinking water treatment sludge,it was found that the composition of high-temperature calcined activated drinking water treatment aluminum sludge is similar to that of metakaolin,which can be used as a supplementary cementing material,and has pozzolanic activity.Using it as a supplementary cementing material to replace some cement can improve the corrosion resistance of the material.In this paper,the water supply sludge from Xi’an Qujiang Water Plant after mechanical dehydration is pretreated by drying,grinding,sieving,and calcining,and the experimental formula is designed according to different mix ratios to prepare modified concrete materials by mixing it with ordinary Portland cement.The influence of the addition of aluminum sludge from water supply on the macroscopic properties and hydration characteristics of the material was investigated,and the optimal amount of aluminum sludge from water supply was determined.Chemical and microbial corrosion tests were conducted on modified concrete materials,and the impact of the addition of aluminum sludge from water supply on the corrosion resistance of the material was discussed.The results show that:（1）Aluminum sludge ash is a porous material with large specific surface area and pore size.The pozzolanic activity of aluminum mud ash calcined at 800℃is the highest,which contains 32.26%Al₂O₃and 35.58%Si O₂.Moreover,the aluminum sludge ash calcined at 800℃has relatively developed pore structure,so 800℃is considered to be the best temperature for water supply sludge pretreatment.（2）Aluminum sludge ash mainly affects material properties and hydration process through size effect,filling/dilution effect and pozzolanic effect.Aluminum sludge ash can play a good role in the size effect of the system,so as to accumulate and fill solid particles,and improve the flexural and compressive strength of the material.Active Si O₂and Al₂O₃with smaller size participate in the secondary hydration of pozzolanic reaction to generate gel like materials with smaller particle size,and provide more nucleation sites to promote hydration,thus changing the pore structure of the material in the middle of hydration,making the sample more compact.The dilution effect reduces Ca/Si in the hydrated gel and increases the compactness of hydrated products,which further improves the strength of hardened concrete.（3）Aluminum sludge ash can promote the formation of aluminum phase substances in hydration products.Calcium aluminate hydrate（C-A-H）gel can not only fill the internal structure of the material to make it more compact,but also C-A-H gel can be dissolved in acidic media,thus creating a calcium deficient and aluminum rich layer on the surface of the sample.This layer can provide a protective layer on the surface of the concrete sample,thus playing a certain anti-corrosion effect.The comprehensive evaluation of the change of the material after chemical corrosion and microbial corrosion shows that the 20%content is the best content of Aluminum sludge ash,which can improve the flexural compressive strength and compactness of the material to a certain extent,and make the corrosion solution difficult to enter the material.In addition,it can promote the formation of hydration and aluminum phase hydration products,so as to improve the corrosion resistance of the material.