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Hydration kinetics, freeze-thaw resistance, leaching behavior of blended cement containing co-combustion ash of sewage sludge and rice husk
Graphical abstract
HighlightsCo-combustion of rice husk and sewage sludge.The hydration is dominated by NG initially and then dominated by D.The novel cementitious material yields excellent mechanical properties.Leaching toxicity tests show the blended cement is environmentally acceptable.F-T action has negative impact on the leaching of HMs in the novel material systems.
AbstractThe application of co-combustion of sewage sludge together with rice husk is expected to increase in the coming years because of the economic and environmental benefits. Hence, resources of massive residues from co-combustion process deserve particular attention. In this study, cementitious materials that are composed of co-combustion ash, H (co-combustion of 20% sewage sludge+80% rice husk) or W (co-combustion of 30% sewage sludge+70% rice husk), were developed. Hydration characteristics, mechanical properties, freeze-thaw (F-T) durability, and environmental performance were investigated. Results show that the cumulative hydration heat increases along with the increase in the amount of amorphous SiO2 in blended cement. The inclusion of H and W inhibits hydration at the early hydration stage and decreases the diffusion coefficient of paste at the later hydration stage. Moreover, the addition of H or W reduces the unconfined compressive strength (UCS) of sample at an early age. However, the UCS for 7-day and 28-day specimens even exceeds that of the reference. Blended cement containing co-combustion ash possesses leach resistance and poor frost resistance. Meanwhile, a significant increase of leached heavy metals is generated after F-T cycle. This phenomenon is a negative environmental impact of F-T action.
Hydration kinetics, freeze-thaw resistance, leaching behavior of blended cement containing co-combustion ash of sewage sludge and rice husk
Graphical abstract
HighlightsCo-combustion of rice husk and sewage sludge.The hydration is dominated by NG initially and then dominated by D.The novel cementitious material yields excellent mechanical properties.Leaching toxicity tests show the blended cement is environmentally acceptable.F-T action has negative impact on the leaching of HMs in the novel material systems.
AbstractThe application of co-combustion of sewage sludge together with rice husk is expected to increase in the coming years because of the economic and environmental benefits. Hence, resources of massive residues from co-combustion process deserve particular attention. In this study, cementitious materials that are composed of co-combustion ash, H (co-combustion of 20% sewage sludge+80% rice husk) or W (co-combustion of 30% sewage sludge+70% rice husk), were developed. Hydration characteristics, mechanical properties, freeze-thaw (F-T) durability, and environmental performance were investigated. Results show that the cumulative hydration heat increases along with the increase in the amount of amorphous SiO2 in blended cement. The inclusion of H and W inhibits hydration at the early hydration stage and decreases the diffusion coefficient of paste at the later hydration stage. Moreover, the addition of H or W reduces the unconfined compressive strength (UCS) of sample at an early age. However, the UCS for 7-day and 28-day specimens even exceeds that of the reference. Blended cement containing co-combustion ash possesses leach resistance and poor frost resistance. Meanwhile, a significant increase of leached heavy metals is generated after F-T cycle. This phenomenon is a negative environmental impact of F-T action.
Hydration kinetics, freeze-thaw resistance, leaching behavior of blended cement containing co-combustion ash of sewage sludge and rice husk
Wang, Teng (author) / Xue, Yongjie (author) / Zhou, Min (author) / Lv, Yi (author) / Chen, Yuchi (author) / Wu, Shaopeng (author) / Hou, Haobo (author)
Construction and Building Materials ; 131 ; 361-370
2016-11-17
10 pages
Article (Journal)
Electronic Resource
English
HMs , represents heavy metals , RHA , represents rice husk ash , F-T , represents freezethaw , H , represents final ash from co-combustion of 20% sewage sludge<hsp></hsp>+<hsp></hsp>80% rice husk , W , represents final ash from co-combustion of 30% sewage sludge<hsp></hsp>+<hsp></hsp>70% rice husk , PC , represents pozzolanic cement , C10 , represents pure pozzolanic cement pastes , W3C7 , represents cement pastes composed of 30% W and 70% PC , H3C7 , represents cement pastes composed of 30% H and 70% PC , C10-5T and C10-10T , represent pure pozzolanic cement pastes exposed to 5 and 10 , cycles, respectively , W3C7-5T and W3C7-10T , represent blended cement pastes composed of 30% W and 70% PC, exposed to 5 and 10 F-T cycles respectively , H3C7-5T and H3C7-10T , represent blended cement pastes composed of 30% H and 70% PC exposed to 5 and 10 F-T cycles respectively , FT<inf>HM</inf> , leaching concentration of HM during F-T cycle , Co-combustion ash , Blended cements , Hydration kinetics , Freeze-thaw durability , Environmental performance
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