Study And Application Of Light Weight,High Strenght Fired Heat Preservation Block Made Of Lake Silt

China is a country with a large number of rivers and lakes, which occupy 0.95% of the total area of the country. And Jiangsu province is in possession of abundant lake resources.However, a large majority of them have been eutrophied or run the risk of heavy metal pollution. With increasing intensity of lake management, more than 100 million tons of dredged silt is excavated in China each year. How to achieve the harmless utilization of those dredged silt is an urgent problem at present. One of the effective way is treated them as a major component for manufacturing of fired bricks or blocks,which is used not only in solving the problem of secondary pollution, but also can alleviate the shortage of raw materials in producing of bricks. The fired heat preservation bricks and blocks are characterized with good insulation properties which are very popular in the market. However, the application of silt as major component for producing of bricks is very limited because of its high drying shrinkage and sensitive to deformation and crack. In this paper, a laboratory-scale and plant-scale study were conducted to assess the feasibility of the production of fired bricks from sediments dredged in order to provide a reference for the industrial production.Firstly, a laboratory-scale study was conducted to choose the optimum mix proportion and process parameters. Results showed that brick samples were better formed using the stiff mud extrusion process when the moisture content of the raw mix is 21%,the molding pressure 1.OMPa and the degree of vacuum is-0.075MPa,And no cracks and other defects appeared in the drying and firing processes. M, D, F1and F2 can be used as coarse aggregate to reduce the drying shrinkage of brick samples, and M is the optimum additive by considering the water absorption, strength and other indicators.Secondly, in this paper, M was used as coarse aggregate and S was used as pore forming agent to prepare fired brick samples. The results showed that the drying linear shrinkage, comprehensive strength, freeze-thaw resistance, thermal conductivity of brick samples decreased by the increase of M, while the water absorption increased. Drying linear shrinkage of fired bricks is 5.35%,bulk density is 1633kg/m3,water absorption is 16.5%,thermal conductivity is 0.533 1W/(m·k) and compressive strength is 20.5MPa containing 10% M and 5% S sintered at 950 ℃, which can meet the national criteria fired common bricks (GB 5101-2003) for brick graded for MU20.The heavy metal can be immobilized in the bricks steadily,and the leaching of heavy metals was much lower than the Identification standards for hazardous wastes-identification for extraction toxicity (GB5085.3-2007).The toxicity equivalence factor(TEF) is 0.176ngTEQ/m3,which was found to generally comply with the standard for pollution control on the municipal solid waste incinderation(GB 18485-2014).SEM and MIP were used to analyze microstrural properties of brick samples, and the results demonstrated that the micro-structure were getting more loose and the porosity increased with the increase of M, which play an important role in the performance of brick samples.Thirdly, in this page, solidified dredged silt were used to prepare fired bricks in laboratory. The results showed that a small amount addition of solidified agent did not change chemical composition, mineral composition and plasticity index of the lake silt obviously, but the formability of the lake silt were badly affected. Drying linear shrinkage of fired bricks made of solidified dredged silt is 5.42%,bulk density is 1639kg/m3,water absorption is 18.2%,thermal conductivity is 0.5331W/(m · k) and compressive strength is 15.8MPa containing 10% M sintered at 950 ℃,which were worse than the brick samples made of lake silt under the same dosage of coal cinder.Fourthly, a plant-scale study was conducted to produce fired heat preservation blocks using lake silt, B and C. The results showed that B can be used as coarse aggregate to reduce the drying shrinkage of blocks and to improve the drying property of the body. C can be used as interal fuel to promote the roasting of raw materials under a appropriate dosage of it, which can increase the compressive strength of the blocks. External wall blocks with the thermal conductivity of 0.249W/(m · k) and internal wall blocks with the thermal conductivity of 0.254W/(m · k) were prepared successfully, and compressive strength of both those two kinds of blocks were more than 5.0MPa,water absorption was less than11%.