| Water treatment plant sludge is the solid waste produced by water supply plant.If sludge is not treated reasonably,it will not only pollute the environment,but also result in the waste of resources.Water treatment plant sludge is mainly composed of Si O2,Al2O3,Fe2O3and other inorganic components,the composition is similar to clay.Clay is often used as raw soil for highway base,thus sludge may be used instead of clay for secondary and lower highway subbase.The sludge has some disadvantages such as high water content and low strength,it cannot be directly applied in road engineering.According to the characteristics of water treatment plant sludge,lime,cement and super absorbent polymer were selected to solidify the sludge,and the ratio of stabilizer was optimized.The road performance of solidified sludge under the best ratio was investigated in order to provide technical reference for sludge used in highway subbase.The main conclusions are as follows:（1）When lime and cement were used to improve the sludge,according to the comprehensive analysis method,the best dosage of quicklime and cement in the solidified sludge was 45%and 15%,the unconfined compressive strength of solidified sludge reached503.2KPa at 7d and 572.3KPa at 28d.（2）On the basis of applying lime and cement to stabilize water treatment plant sludge,super absorbent polymer（SAP）was added as the composition of stabilizer.Through Box-Behnken Design test in response surface method,variance analysis and interaction analysis of fitting equation were carried out.The best dosage of quicklime,cement and SAP in the three-doped solidified sludge was 47.43%,13.11%and 0.45%,the unconfined compressive strength of solidified sludge was 524.8KPa at 7d and 613.8KPa at 28d.（3）It was found that the unconfined compressive strength and splitting strength of solidified sludge enhanced with the increase of curing age and compaction degree.In order to ensure that the solidified sludge meets the requirements,the construction time should be controlled within 6h.（4）The water stability of double-doped and three-doped solidified sludge were investigated by soak periods test and drying-moistening cycle test.The strength of the three-doped solidified sludge was larger than that of the double-doped solidified sludge after several soak periods or drying-moistening cycle,and the rate of strength decline was smaller than that of the double-doped solidified sludge.（5）For double-doped sludge,total price of stabilizers mixed with wet sludge was 159.8yuan per ton.For three-doped sludge,total price of stabilizers mixed with wet sludge was190.5 yuan per ton.Both the double-doped sludge and the three-doped sludge can be used for secondary and sub-secondary highway subbase.Once solidified sludge is applied in secondary and sub-secondary highway subbase,it can not only realize resource utilization of water treatment plant sludge,but also produce economic benefits. |
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