The thermal conductivity mechanism of sewage sludge ash lightweight materials

Sewage sludge ash characteristics and potential for use in concrete

“…1b) can achieve well graded size distributions similar to Portland cement clinker (PC) and fly ash (class F). BET specific surface area and Blaine fineness however varied over a wide range from 2500-23,100 m 2 /kg [4,9,11,21,24,25,36,38] and 500-3900 m 2 /kg [4,12,21,24,31,40] respectively. The marked variability and discrepancies compared to typical Portland cement (e.g.…”

“…A group of the same authors [25,38,98,152] have used SSA in bulk quantities (up to 80% by weight of cement) in ''lightweight foamed materials" mixes. The process of casting the cubes, de-moulding, curing and cutting away any excess bulging, is symptomatic of aerated concrete production rather than foamed concrete, which typically involves the addition of premade foam to a base mix.…”

“…SSA consists of irregular particles with rough surface textures and a porous microstructure [3,4,7,12,13,16,17,25,31,37,38,[42][43][44][45][46] which may lead to high absorption and an increase in the water demand of concrete using SSA. Indeed, water absorption values ranging from 8-20% have been reported [10,13,47,48], which is substantially higher than natural sand, which is typically 1-3%.…”

“…Although of filler fineness, the material has been used as replacement of cement [25,38,98,152] and PFA [153] to enhance the lightweight characteristics and thermal properties, rather than for its potential pozzolanic activity.…”

Evidence for a new mechanism of Fe2O3 decomposition in lightweight aggregate formation

“…Due to the depletion of natural resources and increasing public concerns with the environmental effects of mining, a worldwide trend is emerging toward using wastes (such as the ashes from incinerators and coal power plants, sediments, sewage sludge, and slag) to produce lightweight aggregates (Cheeseman et al 2005;Huang et al 2007). To be successfully fired into lightweight aggregates, the raw material must have the proper chemical composition and particle size distribution for the sintering and gas releasing process to occur within the desired time span at high temperatures, such as 31,150°C (Holm and Valsangkar 1993;Wang et al 2005;Tsai et al 2006). For clay, the proper chemical composition for this process expressed as oxide weight percent is as follows: 48-70%, SiO 2 ; 8-25%, Al 2 O 3 ; 3-12%, FeO ?…”