High water content in dredged silt leads to elevated costs for drying and solidification. By fully utilizing the porous water absorption of Expanded Perlite (EP), we can locally separate free water from the silt, resulting in an uneven water distribution and creating a silt-water separation solidification environment. Experimental results indicate that incorporating EP with silt can effectively enhance the unconfined compressive strength (UCS) of the solidified silt, but the method of incorporation affects the rate of strength increase and pore distribution. The stewing method, which involves pre-mixing EP into the silt and then adding cement after 24 hours, proves most favorable for promoting the solidification effect. After 28 days of curing, the strength of the stewing sample is 1.56 times that of the sample directly solidified with cement after EP incorporation, and 2.15 times that of the sample solidified with cement only. This indicates that the local silt-water separation effect facilitated by EP can effectively enhance the strength of the solidified silt. Meanwhile, hydration heat test results show that EP promotes cement hydration. According to the pore distribution curve and surface morphology images of EP-silt-solidified soil, while EP introduces porosity, it also provides growth space for hydration products, resulting in an embedded bond that forms a solidified soil skeleton between the interface of silt and EP. The method of regulating water content using EP is a physical one, which is convenient and efficient, differing from energy-intensive methods like machinery. Additionally, as a high-silica lightweight aggregate, EP exhibits good compatibility with silt and is environmentally friendly.

The use of both recycled coarse aggregates (RCAs) and recycled sand (RS) derived from weathered residual soil of granite (WRSG) into concrete has the potential to greatly enhance the recycling of construction and demolition waste. However, the characterization of RS from WRSG and the compressive and flexural performance in fresh concrete containing RCAs and RS have not been thoroughly investigated. In this study, clay content, fineness modulus, chemical compositions, mineral compositions, and pore structure of RS from WRSG were tested. On this basis, the optimized preparation parameters of RS were suggested. The compressive behavior, flexural behavior, and cement hydration degree of recycled aggregate concrete (RAC) simultaneously containing RS and RCAs were investigated comprehensively. A stereological model was proposed to explain the results related to cement hydration. The results showed that: (a) the optimized preparation could substantially lower the clay content of RS; (b) RS was more porous than natural sand (NS), resulting in a higher water absorption during mixing; (c) the compressive strength of concrete containing RS developed faster than the concrete with NS; (d) at day 90, the compressive and flexural strength of the concrete containing RS were not less than those of the concrete with NS; and (e) RS was shown to have a greater influence on the hydration degree of cement paste than RCAs, due to RS significantly reducing the average value of inter-aggregate spacing in concrete, making the cement paste more susceptible to the internal curing effect induced by the water in aggregate pores.