ABSTRACT

This study has studied the effects of dredged sediment addition, water-material ratio and autoclaved temperature parameters on the compressive strength, dry density and thermal conductivity of autoclaved aerated concrete blocks (AAC-B). The optimum sediment content is 30%, the water-material ratio is 0.55, and the temperature of autoclave is 200°C. The prepared AAC-B product has a compressive strength of 4.5MPa, a density of 650kg/m3, and a thermal conductivity of 0.18W/(m·K). The prepared AAC-B realizes the safe solidification of heavy metal pollutants through adsorption, sedimentation and physical encapsulation, and reduces environmental risks.

INTRODUCTION

In recent years, with the continuous promotion of the action to comprehensively control the endogenous pollution of river and lake sediment, the number of environmental dredging projects in China has maintained a rapid growth, with the annual production of dredged sediment exceeding 100 million m3. The main components of dredged river sediment are similar to clay and shale materials. The main components are SiO2, Fe2O3, MgO, Al2O3, CaO and other non-organic components. The solid particles in the sediment of polluted waters will also absorb certain heavy metals such as Zn, Pb and Cr. Landfill is a widely used disposal method for dredged river sediment. However, landfill occupies a large amount of land and there is a risk of pollutant diffusion.

The mineral composition of river sediment is very similar to that of building raw materials. Domestic and foreign researchers have done relevant research on the preparation of building materials from river sediment (Yang et al., 2021; Slimanou et al., 2020). Yang (Yang et al., 2018) used the dredged soil of Taihu Lake to prepare unburned pressed bricks. Its brick performance meets the requirements of Chinese national standard GB/T 28635-2012. They also deeply studied the interface performance between the aggregate and cement stone in the brick, providing rich theoretical basis and technical support for the application of dredged soil in the building materials industry. Yee (Yee et al., 2012) dehydrated the bottom mud and mixed it with cement to solidify and use it as subgrade soil. Dang (Dang et al., 2013) proposed to mix Portland cement with heat-treated bottom mud to make a new type of mixed cement. However, this new type of mixed cement needs longer curing time than ordinary cement to reach a certain strength. Chen (Chen et al., 2019) takes the sludge of Jin'an River in Fuzhou as raw material. They adopted the single factor variable method to test the effects of different water content, cement content and liquid soil stabilizer content on the performance of sludge solidified unburned pressed brick. Under the optimum mixing ratio, the strength grade of brick can reach MU10. Lim (Lim et al., 2019) mixes the dredged sediment, steel slag and furnace slag at 1175°C to prepare lightweight building materials aggregate. They reduced the content of water-soluble chlorides and heavy metals in sediments.

This content is only available via PDF.
You can access this article if you purchase or spend a download.