Abstract
In this study, the effects of the mixing conditions of waste paper sludge ash (WPSA) on the strength and bearing capacity of controlled low-strength material (CLSM) were evaluated, and the optimal mixing conditions were used to evaluate the strength characteristics of CLSM with recyclable WPSA. The strength and bearing capacity of CLSM with WPSA were evaluated using unconfined compressive strength tests and plate bearing tests, respectively. The unconfined compressive strength test results show that the optimal mixing conditions for securing 0.8–1.2 MPa of target strength under 5% of cement content conditions can be obtained when both WPSA and fly ash are used. This is because WPSA and fly ash, which act as binders, have a significant impact on overall strength when the cement content is low. The bearing capacity of weathered soil increased from 550 to 575 kPa over time, and CLSM with WPSA increased significantly, from 560 to 730 kPa. This means that the bearing capacity of CLSM with WPSA was 2.0% higher than that of weathered soil immediately after construction; furthermore, it was 27% higher at 60 days of age. In addition, the allowable bearing capacity of CLSM corresponding to the optimal mixing conditions was evaluated, and it was found that this value increased by 30.4% until 60 days of age. This increase rate was 6.7 times larger than that of weathered soil (4.5%). Therefore, based on the allowable bearing capacity calculation results, CLSM with WPSA was applied as a sewage pipe backfill material. It was found that CLSM with WPSA performed better as backfill and was more stable than soil immediately after construction. The results of this study confirm that CLSM with WPSA can be utilized as sewage pipe backfill material.
Highlights
With the aging of buried pipes, incidents of ground subsidence around them have become increasingly frequent in South Korea
When the cement content was 10%, the strength characteristics characteristics differed depending on the sand content. This may be because both waste paper sludge ash (WPSA) and fly ash, differed depending on the sand content. This may be because both WPSA and fly ash, which act as which act as binders, have a significant impact on the overall strength when the cement content is binders, have a significant impact on the overall strength when the cement content is low (5%), whereas low (5%), whereas sand has a larger impact on the strength characteristics than ash materials when sand has a larger impact on the strength characteristics than ash materials when the cement content is the cement content is high (10%)
These results suggest that when controlled low-strength material (CLSM) with WPSA is used as sewage pipe backfill material, it is possible to achieve acceptable performance immediately after construction
Summary
With the aging of buried pipes, incidents of ground subsidence around them have become increasingly frequent in South Korea. Poor compaction of the ground around sewage stressAs concentration on the pipes when loaded from above, causing long-term damagepipes as thecauses pipes age. It is possible to control it can be used as is a countermeasure against ground subsidence by the faulty installation of its strength
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