Strength behavior of dredged mud slurry treated jointly by cement, metakaolin and flocculant

Application of the flocculation-solidification combined method (FSCM) for building a surface working platform is a reasonable option to resolve the personnel and equipment accessibility problem at a dumping site filled with dredged mud slurry at extra high water content (EHW-MS). In the originally proposed FSCM, the solidification component admixed is mainly cement, which tends to show some limitations under unfavourable conditions. This study focuses on discussing the rationality of an optimization measure, i.e., replacing a portion of cement by metakaolin in FSCM. 17 sets of laboratory experiments are performed to identify the influence of main factors on the strength behaviour of EHW-MS treated jointly by cement, metakaolin and flocculant (C-M-F treated EHW-MS). The microstructure and solidification mechanism of C-M-F treated EHW-MS are also analysed based on the X-ray diffraction spectrums and the field emission scanning electron microscopy images. Results indicate that replacing an appropriate portion of cement by metakaolin is a technically reasonable option to enhance the holistic performance of FSCM in EHW-MS treatment, and there is an optimal replacement ratio, beyond which the holistic performance of FSCM is likely to be discounted. When a portion of cement is replaced by metakaolin, the efficiency of flocculant at a given dosage tends to be degraded, and in this situation, increasing the flocculant dosage is a feasible measure to further improve the performance of FSCM. However, the flocculant dosage should not exceed a critical value, otherwise the strength gain tends to be hampered.