| dc.description.abstract | With the increasing coverage rate of sewage systems, the substantial generation of sewage sludge has overwhelmed traditional disposal methods. Therefore, this study explores the feasibility of incorporating sewage sludge into Controlled Low-Strength Material (CLSM) from a materialization perspective. To enhance the benefits of recycling sewage sludge, incinerated recycled aggregates were introduced into the related experiments. This research focuses on three types of sewage sludge treated by different drying processes: belt-filter dewatered sludge, paddle dryer-dried sludge, and heat pump dryer-dried sludge, with a particular emphasis on dewatered sludge. The study examines the material properties of sludge and its application in CLSM through experiments. By utilizing the metal ions in the admixtures to chemically precipitate with the unfavorable factors in the sludge, a reaction with cement promotes the formation of ettringite to address the severe retardation issue caused by sewage sludge.
The study conducts a comprehensive evaluation from the perspectives of engineering benefits, cost benefits, and carbon reduction benefits, and provides recommendations for sewage sludge disposal based on the results. The experimental results indicate that applying sewage sludge in CLSM is feasible. However, as the amount of sludge increases, the strength of the specimens decreases, and the setting time changes significantly, thus limiting the amount of sludge that can be added and requiring a high cement content. Aluminum sulfate quick-setting agents are suitable for all three types of sewage sludge, significantly improving the setting time of sludge CLSM, with the optimal usage being 10% to 12% of the cement content. Excessive aluminum sulfate quick-setting agents can affect the strength development. For belt-filter dewatered sludge, using slaked lime as an admixture significantly enhances the strength of sewage sludge CLSM, but too much slaked lime can affect the setting time. The addition of incinerated recycled aggregates to sewage sludge CLSM meets usage requirements, but the substitution amount should not be excessive.
The cost-benefit evaluation shows that the future production of sewage sludge will continue to increase, and sludge disposal costs will rise, making the direct use of belt-filter dewatered sludge reduce energy consumption and treatment costs, thus providing economic benefits. Carbon emissions calculations should be based on the entire life cycle of sewage sludge. When only considering its use as a raw material for CLSM, the carbon reduction benefits are not significant. However, if the carbon emissions from sludge treatment and disposal are included, the overall carbon reduction benefits increase. Furthermore, with the decreasing capacity of landfills and the increasing carbon emissions from transportation distances, the environmental advantages of materialization disposal models will enhance annually. | en_US |