| dc.description.abstract | A substantial amount of sewage sludge, estimated 50,000 annual tons (on a dry base) by the year 2010, is expected to be generated with the increasing population served by the sewer system under development, this requiring further proper treatment and/or disposal. This study investigated the feasibility of recycling sewage sludge into lightweight aggregates by sintering the mixtures prepared using the incinerated sludge ash(ISA), with an addition of dry sludge powder(DSP) as a bloating material. The mix design ratios(ISA:DSP), tested were 100:0 to 70:30 (w/w %), with an 10% incriment of DSP. The engineering properties of a lightweight concrete, prepared by incorporating the resultant lightweight aggregates and OPC with aluminum powder as cement bloating agent were analyzed.
The results indicate that a proper mix design and sintering conditions, including a minimum sintering time of 10 minutes, combined with sintering temperature ranged from 1050-1150℃, are required to produce lightweight aggregates with bulk density less than 1.6 g/cm3. An increase in sludge powder addition (from 0% to 30%) was noted to decrease the required sintering temperature (from 1150℃ to 1050℃), showing the effects of fluxing and energy-saving.
Two types of typical lightweight aggregates, AH1 and CM1, prepared by mix ratio(ISA:DSP), 100:0 and 80:20, respectively, were evaluated. In general, the density, failure loading and crystallized intensity of AH1 lightweight aggregate were higher than those of CM1. Consequently, for lightweight concrete incorporating AH1 and CM1(referred to as LC-I and LC-II, respectively), the former showed a greater bulk density, compressive strength and thermal conductivity than the latter, under the corresponding conditions of preparation.
Moreover, for the bulk density and compressive strength, both the LC-I and LC-II, prepared without the addition of bloating aluminum powder, were found to correspond with the requirements of structural concrete and moderate strength concrete, respectively, as specified by ACI 213 R-87. However, in the cases of LC-I and LC-II with addition of 0.2~0.4% aluminum powder, the former corresponds with the moderate strength concrete requirement marginally, whereas the latter were found, for density and compressive strength, between the requirements of moderate strength concrete and non-structural concrete. The data reported here may be of importance to recycling sewage sludge into construction materials for a sustainable solution of waste treatment and management. | en_US |