Hydration Chemistry of Sewage Sludge Ash Used as a Cement Component

Mechanical performance and capillary water absorption of sewage sludge ash concrete (SSAC)

“…The mixture with 20% sludge ash content shows an increase in the compressive strength with curing time, and at 90 days the strength almost reaches the same compressive strength as the mixture with just 10% sludge ash content. This could be attributed to a minor pozzolanic effect as reported by other authors (Cyr et al 2007) or to the fact that sludge ash particles could behave like extra sites for the nucleation and growth of hydration products, thus enhancing the overall hydration process (Neville 1997, Moosberg-Bustnes et al 2004, Dyer et al 2011. Results show that concrete mixtures with 5% or even 10% sludge ash show minor compressive strength loss.…”

Sewage sludge ash characteristics and potential for use in concrete

“…Quartz and hematite have been identified as the most abundant minerals in SSA, whilst many other iron oxides, iron phosphates, calcium phosphates and aluminium phosphates have been reported to a lesser degree [3][4][5][11][12][13]16,21,24,[29][30][31][32][43][44][45]51,58,59,64,68,74,76,77,79,94,95,99,102,[105][106][107][108][109][110]. The amorphous content of SSA ranged from 35-75%, which suggests that the material is somewhat reactive and, when ground sufficiently fine, may have potential as a cement component.…”

Hydration mechanisms of sewage sludge ashes used as cement replacement

“…standard for pozzolanic activity) and a high consumption of portlandite (amounts of Ca(OH) 2 fixed) have been reported when the SSA are used. These observations have inferred to SSA the characteristic of being pozzolanic [19,21,23,26] and aroused the interest in its use as an alternative supplementary cementitious material (SCM).…”