Study On Preparation And Performance Of Artificial Cobblestone By Unburned Method Of Dredged Soil

In order to ensure the smooth flow of waterways and ports,hundreds of millions of tons of dredged sediment are produced by dredging every year in the world.The accumulation of dredged sediment not only occupies a large amount of land resources,but also causes secondary pollution.In the environment of energy saving and emission reduction and sustainable development,dredged soil ean be obtained by physical dehydration of dredged sediment,which can be used as raw material in the production of building materials.Natural pebbles are hard and beautiful stone with unique decorative effect formed by Rain Water scouring and friction with each other for millions of years,but its resources are limited.In this paper,using Taihu Lake dredged soil as raw material,unburned ceramic sand was prepared by unbuned method,and unburned ceramic sand was wrapped in shell to get the artificial cobblestone core phase of dredged soil prepared by auxiliary bonding of wrap-shell lightweight aggregates(WSLAs).Preparation of dredged soil artificial cobblestones(DSACs).The polishing process of DSACs was investigated,and the strength,durability and environmental safety of DSACs with different particle sizes were analyzed and compared with those of three kinds of natural cobblestones and artificial cobblestones sold in the market.The microstructure and interfacial bonding mechanism of DSACs were studied.The specific contents and results of the study are as follows:(1)DSACs has a unique multi-layer core-shell structure,which consists of two parts:DSACs core phase and shell phase.The shell phase of DSACs is formed on the basis of the core phase of DSACs,which is connected with each other in a point-by-point manner,and its shell structure forms a reticulate three-dimensional structure.The core phase of DSACs forms a dense and hard structure by enveloping the shell in the form of a dense structure and a hard texture.The core phase of DSACs is formed on the basis of the core phase of DSACs.(2)The optimum material ratio of DSACs nuclear phase prepared by dredged soil was determined.The higher the nuclear phase density,the tighter the internal structure and the greater the particle strength.In the DSACs core phase with different particle sizes,the unbumed ceramic sand has the best particle size gradation,and the WSLAs,WSLAs shell material is 10%of that of the DSACs core phase when all the core ceramic sand is wrapped in the shell.The optimum blend structure of the fiber is WSLAs shell.The particle strength of DSACs core phase is 0.51 MPa,saturated water absorption 3.48%,and the mass loss rate of 30 freeze-thaw cycles is 11.02%.When the mass content of carbon fiber is 0.06%of that of DSACs nuclear phase and the mass content of glass fiber is 0.1%of that of DSACs nuclear phase,the particle strength of DSACs nuclear phase is 0.67 MPa,0.50 MPa.,respectively.Because of its high tensile strength and high elastic modulus,carbon fiber has the greatest influence on the strength of DSACs nuclear phase particles.(3)The optimum proportion of materials for preparing DSACs shell phase from dredged soil was deternined.In order to make the artificial pebbles of dredged soil as hard,bright and colorful as natural pebbles,inorganie eementitious material was chosen to eover the core phase of DSACs to form a hard shell.DSACs shell phase admixture glass powder,nano-SiO2,The optimum content of dispersible rubber powder was 20%,3.0%and 2.0%,respectively.(4)The polishing process of DSACs with different particle sizes was studied and its properties were characterized and compared with those of natural pebbles and artificial pebbles sold in the market.A hand-held polishing machine was used to grind the surface of DSACs by changing the grinding head.The particle strength of 10?20 mm,20?25mm,25?30 mm DSACs,the density of 1.23 MPa,2.031 g/em3,1.15 MPa,1.844 g/cm3,and 1.01 MPa,1.745 g/cm,of particles were obtained in turn.The larger the particle size of DSACs is,the smaller the density is and the smaller the particle strength is.The density of DSACs is between natural pebbles and artificial pebbles,and its water absorption is 1.84%higher than that of other pebbles,and the density of DSACs is between natural pebbles and artificial pebbles sold in the market,and the density of DSACs is between natural pebbles and artificial pebbles.After 50 cycles of freezing and thawing,there was no mass loss in salt solution imlersion for 50 days.(5)The interfacial bonding strength of ceramic sand-WSLAs shell in DSACs core phase and DSACs core-DSACs shell phase was measured by oblique shear test.The interfacial bonding strength of DSACs core-DSACs shell phase was 2.86 MPa,5.93 MPa.respectively.The bond strength of ceramic sand-WSLAs shell is lower than that of DSACs core-DSACs shell phase.Because both the core phase of DSACs and the shell phase of DSACs are mainly cement-based cementitious materials to form C-S-H gel,the ceramic sand is prepared from dredged soil,although its main composition is pozzolanic reaction activity.However,the activity of the cement cementitious material is very low compared with that of the ceramic sand shell cementitious material.The particle size of the dredged soil is very fine,which will adhere to the surface of the ceramic sand,which affects the bonding between the clay and the cement paste,resulting in the lower bond strength of the ceramic sand-WSLAs shell.