| Along with the accelerating pace of urbanization,sewerage treatment rate in the urban area improved year by year, and the number of municipal sewage treatment plant and sludge yield increased sharply too. Therefore, scientific disposal and utilization of sludge had been a difficult problem in the current urban management, this paper started with physicochemical properties of sludge, the the possibilities of application of sludge in the building materials production are studied mainly.Main content and conclusion are as follows:(1)Physicochemical properties of sludge shows that according to the existing sludge treatment craft, the moisture content of sludge after dewatering is over 80%,TOC is about 280 g/kg, the content of SiO2, Fe2O3, Al2O3, CaO and MgO are 18.88%, 2.69%, 5.45%, 5.24% and 1.67%, respectively.The content of water and organic matter are higher than clay significantly, the chemical composition is similar to clay, so it can be used in producing building materil; Ignition loss quantity of sludge is as high as 642.75 g/kg, average heat of dry base is about 14977kJ/kg , so it can be used as porosity agents and coal-fired substitutes of sludge fired bricks. The heavy metal content of sludge is more than clay, heavy metals can be transfered to undissolved state or fixed within the grid bricky system completely so as to minimize its potential harm to the environment.(2) Cement, fly ash, lime, gypsum and Al2O3 etc. were took as solidarity material, and the feasibility of sludge unburned bricks production was studied. The optimum content of solidarity material were explored through L9 (34) orthogonal test, the results indicated that sludge unburned bricks can only be used as nonbearing bricks for the maximum compressive strength can only achieve 6.32 MPa.(3) Study on formula and process technology of sludge fired bricks .The sludge with moisture content of 60% was took as admixtures directly in the sintered bricks preparation, the change of the physical mechanical performance were studied under the conditions of different sludge content, molding pressure, sintering temperature and holding time, the optimum conditions of bricks production can be obtained: adding amount of sludge was 12%, compacting pressure was 20 MPa, sintered at 1100℃for 1.5h ,the fired bricks with compressive strength of 12.44 MPa and water absorption of 20.04% were obtained.(4) The engineering test of sludge fired bricks preparation. The engineering test of producing sludge fired bricks was carried out based on the laboratory process. Sludge fired bricks were produced with 12.5%,25% and 37.5% wet sludge refering to common clay sintered bricks production process. The compressive strength after sintering were 20.73,18.26 and 16.98 Mpa, respectively. The compressive strength of sludge brick dropped significantly with the increase of the admixture of sludge, but all conformed to the building bricks standard. So, in order to realize the maximization of sludge resources utilization, the best admixture of sludge was determined 37.5% in this text, the heavy metal toxicity leaching experiment showed that Cd was not detected, the leaching concentration of Cu, Zn, Cr, Pb and Ni were 0.11, 0.014, 0.15, 0.11, 0.068 and 0.022 mg/L, respectively, the leaching toxic was far less than the national standard, so it was safe and feasible to produce sintered brick with sludge.(5) The advantages of making bricks with sludge. It is safe and feasible to produce bricks with sludge,save water 0.23 kg/block, save coal 0.023 kg/block and the leaching toxic is far less than the national standard. In addition, sludge can play a role as porogenic agent in high temperature for it’s organic matter content is high, sludge fired brics are environment- friendly bricks good in performance for they are light , noise reduction , sound absorption, heat preservation and insulating. Therefore, it has remarkable economic, environmental and social benefits to producing building bricks with sludge. |
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