Study on mix proportions and mechanical properties of controlled low strength material (CLSM) using river sludge

This study examines the preparation of controlled low strength material (CLSM) utilizing dredged river sludge as the primary raw material. Laboratory experiments were conducted to analyze the influence of various mix ratios-particularly the water-to-solid ratio (W/S), lime-to-soil ratio (L/S), and supplementary materials including fly ash and slag-on the flowability and unconfined compressive strength (UCS) of the solidified material. The findings indicate that flowability increases with both W/S and L/S ratios. The UCS displays an inverse relationship with the W/S ratio and a positive correlation with the L/S ratio. The addition of slag and fly ash enhances performance, with slag demonstrating superior strengthening properties. Drawing from the experimental results, the study concludes that the optimal mix proportion is highly dependent on specific engineering requirements. For higher-strength road subgrade backfill (requiring 400-800 kPa UCS), an L/S ratio of 0.20 and a W/S ratio of 0.72 was identified as optimal. Conversely, for high-flowability pipeline trench backfill (requiring 200-400 kPa UCS), an L/S ratio of 0.15 and a W/S ratio of 0.80 was found to be ideal.