Study on the production of artificial sand from non-hazardous dredged sludge in Hanoi City factors affecting strength of material GFM

Abstract

This paper presents the factors affecting the strength of recycled granular fill material (GFM) from dredged sludge in Hanoi city. Based on laboratory experiments, the paper investigates some factors affecting the strength of the recycled material such as: mixing method; cement and polymer content; cement type. In the experiments, West Lake sludge (B) is non-toxic sludge, after dredging, it is dewatered to a moisture content in the range [WP; WL], then mixed with cement (X) and polymer (P). The product after mixing is granular, however, due to the high moisture content of the sludge, the particles still have plasticity, which makes it easy to prepare test specimens. Therefore, to simplify the experiment while still accurately assessing the factors affecting the strength of GFM, the paper chooses a free-swelling uniaxial compression test to preliminarily evaluate the strength index of soil. The research results show that the mixing method has a significant effect on the strength development of GFM. With the same mixing ratio, the samples mixed with (B+X) first and P later gave a higher strength value than the other mixing methods. In addition, the strength values of GFM samples increase proportionally with the cement content, with a lean cement content of 5% to 10%, GFM samples achieve a strength of 170.8 (kPa) to 262.05 (kPa), well meeting the requirements of filling materials. At the same time, the content of chemical substances in cement such as CaO, SO3, Al2O3 also significantly affects the strength of GFM, the experimental results show that the strength of soil is inversely proportional to the content of CaO and proportional to the content of Al2O3 and SO3.

Keywords: Artificial sand; granular fill material (GFM); factors affecting strength.