Research To Urban Sewage Sludge Activation And Its Cementing Performance

This paper put forward a research, using sludge to prepare mineral admixture, the core technology are calcining with high temperature and mechanical grinding. Taking dehydrated sludge of Guangzhou Liede sewage treatment plant as the research object, exploring the activation of sludge and its gelling properties preliminarily, the main research contents are as follows:1,Study the changing of structure characteristics in the process of calcining. Research shows that the whole process of sludge calcined has two obvious weightlessness section 160～380℃and 180～360℃, respectively exhalation of organic and the burning of volatile, remaining more than 50% inorganic ash; Inorganic mineral of sludge original sample are mainly quartz and kaolinite, before 800℃, the minerals of sludge mainly happens kaolinite dehydrate into partial kaolinite, when calcining to 800℃, X-ray diffraction peak is diffuse shape, being typical no finalize the design structure diffraction peak, crystal mineral became amorphous, with activity increasing; SEM analysis shows that the surface of sludge ash samples of 800℃and stomatal pore surface can see pore and stomatal.2,Explore the best activation technology of sludge through the cement grinding strength experiment. Experiment shows that ash activity of sludge burned different temperatures is different, the ash active is best when 800℃; Holding time has an influence on the ash active of sludge, 2.5h is best; Warming time has a little influence on the ash active of sludge; grinding time has an effect on the sieve of sludge powder, specific surface area and volcanic activity, when grinding 1.0 h to specific surface area for 1342m2/kg, the effect is best. Therefore, the best activation technology of sludge:warming dry sludge from normal temperature to 800℃with 30min and holding 800℃with 2.5h, then take it out and cooling under natural conditions, then grinding 1.0h to powder, called "sludge powder".3,Study the chemical and physical properties of sludge powder. Size distribution of sludge powder mainly scatter between 0.5～10μm, about 78% of total quality, thinner than cement particles, when used as admixture, it not only has pozzolanic effect, but also has filling effect; its ignition loss is 2.08%, density is 2.61 g/cm3 and specific surface area is 1342kg/m2. 4,Inspect the various performance indicators of cement after partly replaced with sludge powder. (1) With the improvement of the admixture of sludge powder, standard consistency of cement gradually increases; (2) with the increasing of admixture of the sludge powder, setting time of cement gradually reduced. When the admixture is 10%～30%, obviously improving the setting time of cement, when the admixture increased to 40%, initial setting time of lower than blank group and final set time higher than blank group; (3) dosage of sludge powder 10%～40%, stability are all qualified; (4) when the sludge powder mixing into cement, it will affect will affect the compatibility of cement and water-reducing, when admixture is 20%, The result is very serious.5,Research the strength of mortar mixing with sludge powder and cement. Experiments show that sludge powder has the strong enhancement effect, when replace cement with 20%, it can make the cement mortar compressive strength improving 7.03 MPa. Considering replacing cement with 20% sludge powder will affect the compatibility between cement and water reducer, the reasonable dosage should be 10%. In addition, this paper study the compound result of sludge powder and steel slag powder, the effect is inferior to only mixed sludge of pink, but better than the only mixing steel slag powder.6,Research hydration sclerosis mechanism of slurry mixing the cement and sludge powders. Known by XRD analysis, With the admixture of sludge powder (0%～30%) increasing, diffraction peak strength of C-S-H gel gradually strengthened and diffraction peak intensity of Ca(OH)2 weakened gradually, it account for the active components of sludge powder with Ca(OH)2 happen volcanic ash, generating C-S-H gel, and the greater dosage is, the stronger the ash reaction is. In addition, with the increase of the admixture of sludge powder, diffraction peak of ettringite crystal weaken, SEM analysis also found that the greater the admixture of sludge powder is, the denser slurry structure is, the more difficult to find needle stick ettringite crystals.7,Research to workability and mechanical properties of concrete containing sludge powder. The workability of concrete containing 30% sludge powder (uni doped) turn bad significantly, but its compressive strength of 7d better than the strength of concrete containing slag, steel slag and cinders(uni doped),even higher than the blank. It can improve the workability of concrete containing sludge powder by remixing slag, but the compound proportion between slag and sludge powder needs further research.