Abstract: Rainwater sludge and engineering slag soil are typical solid wastes generated from urban stormwater drainage
systems and construction engineering projects. Their stockpiling occupies substantial land resources,damages surface vegetation,
and disrupts ecological balance. This study focused on preparing non-sintered ceramsite using rainwater sludge and engineering
slag soil as primary raw materials,expanded perlite as an auxiliary material,and fly ash as an additive. The effects of
the fly ash contents,sodium hydroxide addition,water glass addition,and micro-nano bubble water (MNBW) addition on the
properties of the ceramsite were investigated. The results indicate that the optimal formulation for preparing non-sintered ceramsite
is fly ash mass contents of 33. 3%,with sodium hydroxide addition of 2. 8%,water glass addition of 38. 9% and MNBW addition
of 35 mL. The compressive strength of non-sintered ceramsite prepared under these condition is 6. 51 MPa,the 1 h water
absorption is 8. 40%,the bulk density is 852. 76 kg/ m3,and the apparent density is 1 570. 57 kg/ m3. BET and SEM analysis
revealed that the addition of MNBW resulted in an increase in the proportion of micropore area within the BET specific surface
area of ceramsite from 36. 8% to 78. 4%,accompanied by a reduction in the average pore diameter from 14. 028 1 nm to
10. 612 8 nm. Moreover,such modifications facilitated the formation of a uniform and compact microstructure inside the ceramsites,
significantly diminishing the presence of large-diameter pores,which were transformed into numerous micropores. These
structural evolutions contributed to an enhancement in the compressive strength of the ceramsites while effectively reducing
their density. XRD analysis revealed that the alkali-activated reaction generated N-A-S-H gel,which contributed to improving
the overall physical properties of the ceramsite. This research provides theoretical support for the resource utilization of solid
wastes in the production of non-sintered ceramsite.