Hydration characteristics of cement for co‐sintered from washed‐fly ash and waste sludge

Abstract

The purpose of this study is to co‐sinter washed‐fly ash, limestone sludge, stone sludge, and iron‐oxide sludge to fabricate 4 types of eco‐cement clinkers. The compound raw materials were burned for 2 h at 1400°C to form the eco‐cement clinkers, all of which met the toxicity characteristic leaching procedure requirements. The results show that the major components of ordinary Portland cement (OPC), C3S, C2S, C3A, and C4AF, were present in the eco‐cement clinkers. The compressive strength development indicated that the EcoA pastes were similar to those of commercial OPC products. The compressive strength in the EcoG pastes decreased because of the amount the α‐C2S increased. The mercury intrusion porosimetry results showed that the pore volume in the pastes gradually decreased when the curing time increased. Additionally, from the X‐ray diffraction results, all the eco‐cements produced Ca(OH)2 during hydration, which also increased with curing age. The scanning electron microscopy images of OPC and EcoA pastes showed that the pore volume decreased and the denser structural increased with the curing time increased. In addition, adding higher amounts of 1% washed‐fly ash caused to increase the content of α‐C2S. The result show that this co‐sintered process from 1% washed‐fly ash and 99% waste sludge (77% limestone sludge, 19.51% stone sludge and 2.49% iron‐oxide sludge) to produce eco‐cement with excellent mechanical characteristics. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 964–972, 2015

Hydration characteristics of recycling reduction slag and waste sludge by co‐sintered treatment produced as eco‐cement

“…For preparing cement mixtures, appropriate amounts of starting materials in predetermined wt % proportions, as shown in Table , were computed, after considering the hydration modulus (1.7 ≤ HM ≤ 2.3), the lime saturation factor (0.8 ≤ LSF ≤ 0.95), the silica modulus (1.9 ≤ SM ≤ 3.2), and the iron modulus (1.5 ≤ IM ≤ 2.5) []. The four unknown modulus were solved using simultaneous first‐order equations.…”

Co-processing of raw and washed air pollution control residues from energy-from-waste facilities in the cement kiln

“…Volatilisation of both alkalis and metals was reduced by APCR washing, but remained substantial for Pb and Cd, and significant for Zn and Cr (Saikia et al 2007, Wang et al 2010. Although co-processing of very low proportions of APCR (e.g., 1%, Wang et al 2010, or 1.75%, Pan et al 2008) only slightly affects the strength of cement made with the resulting clinker, cement strength was found to decline with increasing content of both APCR (Shi et al 2004;Ma et al 2009) and w-APCR (Lin et al 2015).…”

“…Previous laboratory studies of APCR co-processing have investigated the effect of raw mix composition on: formation of the required mineral phases for Portland cement, 3CaO•SiO 2 , 2CaO•SiO 2 , 3CaO•Al 2 O 3 , and 4CaO•Al 2 O 3 •Fe 2 O 3 (C 3 S, C 2 S, C 3 A and C 4 AF in cement chemist's notation; also known as alite, belite, aluminate and ferrite); occurence of free lime, f-CaO, i.e., that did not react to form the desired calcium silicates (Shi et al 2004;Saikia et al 2007;Pan et al 2008;Ma et al 2009;Lam et al 2011;Wang et al 2010;Lin et al 2015); volatilisation of alkalis and metals (Saikia et al 2007, Wang et al 2010; and strength of cement paste made using the resulting clinkers (Shi et al 2004;Pan et al 2008;Ma et al 2009;Wang et al 2010;Lin et al 2015). Other aspects not of direct relevance to the present work are reviewed in a separate paper (Stegemann et al, unpublished).…”

Onsite treatment of wastes in municipal waste incinerator: Co-sintering of fly ash and leachate sludge into value-added ceramic granule

“…Considering the ability of removal and stabilization of pollutants during the high temperature sintering process, there is a growing concern on recycling of waste materials for production of lightweight aggregate. Numerous literatures had applied this technology on municipal sludge, fly ash, coal fly ash, sewage sludge, etc [ [24] , [25] , [26] , [27] , [28] ]. Xingrun Wang et al successfully manufactured lightweight aggregate from sewage sludge and coal ash, and the concentration of heavy metals ranged well within the limit of China's regulatory requirements [ 29 ].…”