| dc.description.abstract | Due to the wider coverage of sewer system in urban areas, it is predicted that the sewage sludge generated from pipe-end treatment plants in Taiwan will amount to 400,000m3 by the year 2009. Decreasing landfill sites, exacerbated by the continuing residents’ protest, has called for an urgent need for reducing and recycling sludge. In recognition of this, this study tried to produce lightweight concrete by using sewage sludge ash as main material, combined with cement and pulverized scrap metal. Cement was used to provide with proper alkalinity and work as binder, and pulverized scrap metal (mainly aluminum) and aluminum powder were used as vesicants. Primary factors influencing the bloating mechanism and engineering properties of the resultant lightweight concrete including cement/sludge ash ratio, vesicant quantity and water-to-solid ratio were varied to investigate the characteristics of the composite materials, their bloating mechanism, engineering properties of the resultant lightweight concrete, and its effect subject to high temperatures. Microanalysis was conducted on species changes and microstructure variations in the resultant concrete at tested temperature by applying SEM, XRD and MIP techniques Moreover, the optimum mix design was proposed based on CNS 13480“Autoclaved Lightweight Aerated Concrete Block.”
The results showed that under a mix design using 0.5%, 0.9% and 1.3% vesicant, with cement to sludge ash ratios ranging from 40：60, 30：70 and 20：80, and a water-to-solid ratio from 0.5, 0.6,0.7, and 0.8, the resultant sludge-ash-lightweight- concrete satisfied, in terms of density and compressive strength, the standards of CNS 13480 of which the requirements for specific gravity and compressive strength are <1.2 and 2.5MPa., respectively. The capillary pore volume of the resultant sludge—ash-lightweight-concrete fell in the range of 84.7%~96.4%; the thermal conductivity of the resultant concrete ranged from 0.0845~0.1024W/m.K, a value half of that of the ordinary concrete and lower than that of commercial ALC products. Heating test at 1093℃ showed that an increase in the density and compressive strength of the tested concrete specimen took place concurrently with the sintering of the concrete. Moreover, increasing the amount of sludge ash tended to increase the compressive strength of the concrete to some extent; however, a positive correlation between the degree of strength development and volumetric shrinkage suggested there was still room for further improvement. In conclusion, making blowing lightweight concrete with sludge ash and waste-metal power not only satisfies the requirement for waste reduction, recycling and energy conservation but also offers a light, economical and environment-friendly building material. | en_US |