dc.description.abstract | Sludge and ash recycled as pozzolanic material and fine aggregate applying to cement mortar would not only solve treatment problem of waste, but also reduce the consumption of sandstone and natural materials which used in cement manufacturing. To increase the amounts of using sludge and ash, the objective of this study was to make cement and aggregate in mortar totally be composed by these recycled materials. This study expected to improve the poor engineering properties of using single recycled material (e.g. sewage sludge ash) as cement by additionally adding high pozzolanic activity of slag and/or fly ash simultaneously in multiple cement-replaced formed. Therefore, the potential of using recycled sludge and ash could be enhanced.
This study used sewage sludge ash(SSA), coal fly ash(FA), granulated blast furnace slag(S) as pozzolanic material and municipal solid waste incineration bottom ash(BA) as fine aggregate in cement mortar. In one hand, the cement in cement mortar was replaced by two types. In dual-replaced type, cement was replaced by SSA and S or FA. In triple-replaced type, SSA,FA, and S were all used to replace cement. On the other hand , in addition to cement, fine aggregate in mortar were also replaced by BA.
According to the experimental results, slag which have high pozzolanic activity and high content of CaO and MgO can increase pozzolanic activity in mortar, even other recycled materials with low pozzolanic activity such as FA and SSA were used. Therefore, dual or triple-replaced type for cement in mortar have better engineering properties than single-replaced one indicated by previously researches which only used FA or SSA for cement replacement. When the cement replacement rate of SSA with FA and/or S reached 50%, the percentage of compressive strength in mortar at the age of 28 days reached to 88.9~93.1% compared to controlled mortar. The modifications by adding calcium chloride and lime mixed with SSA could improve the limiting factor of longer setting time. Further more, the modifications had potential to increase cement replacement rate to 70%, and owned good engineering property of compressive strength at the age of 28 days, (i.e. meeting the standard of structural concrete). In durability tests, expect for the mixes of control mortar, because the consumption of calcium hydroxide by pozzolanic reaction and the filling porosity by C-S-H gel, the mortar structure was more dense and sulfate attack could be avoided. The compressive strength was thus increased with age during 120 days. | en_US |