Quicklime Can Be Used for Sludge Solidification

The solidification of silt by quicklime relies on a combination of physical and chemical effects, which fundamentally improve the poor mechanical properties of silt. The main component of quicklime is calcium oxide, which undergoes a violent hydration reaction when contacting water, producing calcium hydroxide and releasing a large amount of heat. On the one hand, the high temperature generated by the reaction accelerates the evaporation of free water inside the silt, rapidly reduces the water content, and eliminates the fluidity of silt in a short time to realize rapid drying and consolidation. On the other hand, the generated calcium hydroxide is strongly alkaline, which can destroy the stable structure of silt colloidal particles, agglomerate scattered fine silt particles, significantly reduce the void ratio of silt, and improve soil compactness.

Inaddition, long-term secondary reactions occur in the solidified silt system. Calcium hydroxide continuously reacts with carbon dioxide in the air and active silicates in the silt to form stable cementitious substances such as calcium carbonate and hydrated calcium silicate. These cementitious materials fill soil pores and bond soil particles, gradually forming a stable soil skeleton structure. This converts the originally soft silt into soil with certain strength and stability, thoroughly improving its defects of easy deformation and permeability, and meeting the basic requirements of engineering backfilling and site hardening.

Compared with cement and special curing agents, quicklime has prominent advantages in silt solidification. Firstly, it delivers an extremely high cost-performance ratio. With accessible raw materials and low prices, it requires simple construction procedures and no complex equipment, greatly reducing the cost of silt disposal. Secondly, it features high solidification efficiency. The heat released by hydration enables rapid water removal and quick silt consolidation, making it suitable for urgent projects and temporary site construction with tight schedules. Thirdly, it achieves ecological improvement. The strong alkaline environment can kill harmful bacteria and decompose malodorous organic substances in silt, effectively solving the problems of odor and mosquito breeding caused by silt stacking, which is ideal for river dredging and municipal sludge treatment projects.

In engineering practice, composite solidification schemes are widely adopted to compensate for the defects of single materials. The mainstream approach is to compound quicklime with fly ash, mineral powder and a small amount of cement. The complementary advantages of these materials retain the rapid dehydration and deodorization functions of quicklime, while enhancing the strength and durability of solidified soil and reducing cracking through cementitious materials. For conventional projects, the dosage of quicklime is controlled at 6% to 15% of the dry weight of silt, which can be adjusted flexibly according to the water content and organic matter content of silt to adapt to different working conditions.