Evaluation of the Pozzolanic Activity of Uncontrolled-Combusted Sewage Sludge Ash

[EN] Waste management is a crucial issue facing modern society. The generation of sewage sludge is increasing annually due to the urbanization and improvement of sanitation systems of cities. The construction sector has emerged as a solution for the elimination of waste due to the enormous volume of materials that this sector can absorb. This paper evaluates the pozzolanic activity of sewage sludge ash (USSA) obtained following an uncontrolled-combustion process, a simple and economic procedure. Compressive strength of Portland cement/USSA mortars with 5%¿25% by weight USSA were evaluated. Calcium hydroxide/USSA and Portland cement/USSA pastes were chemically and physically characterized through thermogravimetric/differential-thermogravimetric (TG/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The increase in the replacement of Portland cement by USSA is associated with an increase in the compressive strength of mortars. These values for USSA containing mortars cured for 90 days were in the range of 49.6¿55.4 MPa, higher than the one reached by the reference mortar. According to the microstructural analysis, the increment on the compressive strength can be attributed to the formation of hydrated products (C¿S¿H, C¿A¿S¿H, and C¿A¿H) by the pozzolanic reaction of USSA.This research was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (Capes)Finance Code 001, and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) (Processo Nos. 309015/2015-4 and 478057/2013-0). Thanks go to the Scanning Electron Microscopy Service of FEIS/UNESP, Servico Municipal Autonomo de Agua e Esgoto (SEMAE) from the Sao Jose do Rio Preto city (Sao Paulo, Brazil).Istuque, DB.; Reig, L.; Soriano Martinez, L.; Borrachero Rosado, MV.; Pinheiro Melges, JL.; Akasaki, JL.; Paya Bernabeu, JJ.... (2021). Evaluation of the Pozzolanic Activity of Uncontrolled-Combusted Sewage Sludge Ash. Journal of Materials in Civil Engineering. 33(6):1-12. https://doi.org/10.1061/(ASCE)MT.1943-5533.000376511233

Evaluation of the Pozzolanic Activity of Uncontrolled-Combusted Sewage Sludge Ash

Waste management is a crucial issue facing modern society. The generation of sewage sludge is increasing annually due to the urbanization and improvement of sanitation systems of cities. The construction sector has emerged as a solution for the elimination of waste due to the enormous volume of materials that this sector can absorb. This paper evaluates the pozzolanic activity of sewage sludge ash (USSA) obtained following an uncontrolled-combustion process, a simple and economic procedure. Compressive strength of Portland cement/USSA mortars with 5%–25% by weight USSA were evaluated. Calcium hydroxide/USSA and Portland cement/USSA pastes were chemically and physically characterized through thermogravimetric/differential-thermogravimetric (TG/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The increase in the replacement of Portland cement by USSA is associated with an increase in the compressive strength of mortars. These values for USSA containing mortars cured for 90 days were in the range of 49.6–55.4  MPa, higher than the one reached by the reference mortar. According to the microstructural analysis, the increment on the compressive strength can be attributed to the formation of hydrated products (C─ S─ H, C─ A─ S─ H, and C─ A─ H) by the pozzolanic reaction of USSA

Cinza de bagaço de cana-de-açúcar (CBC) como adição mineral em concretos para verificação de sua durabilidade

O setor sucroalcooleiro vem se expandindo nos últimos anos, alavancado principalmente pelo advento da bionergia. No Brasil, a produção de cana-de-açúcar vem avançando em áreas destinadas à pecuária extensiva e a outras culturas importantes como a soja, o milho e a laranja, e concerne à geração de energia elétrica pela queima do bagaço (cogeração) e ao uso de etanol como combustível de veículos automotores. Contudo, a produção de açúcar, álcool e energia a partir de cana-de-açúcar pode causar problemas ambientais em decorrência da geração de resíduos como a cinza do bagaço de cana-de-açúcar (CBC). Deste modo, este trabalho apresenta a viabilidade técnica da utilização de cinza resultante do processo de queima do bagaço de cana para a geração de energia como adição mineral, em concretos. Para isso foram realizados ensaios de caracterização química e difração de raios-x na CBC. Produziram-se concretos contendo a CBC nos teores de 5%, 10%, 15% e 20%, em massa, como substituição parcial ao agregado miúdo. Realizaram-se ensaios mecânicos e, a partir dos resultados obtidos, o traço de concreto que apresentou os melhores resultados foi submetido aos seguintes ensaios de durabilidade: resistência ao ataque químico, absorção por capilaridade, penetração de cloretos e abrasão. O trabalho foi realizado com CBC de baixa atividade pozolânica, entretanto, os resultados indicaram ser possível utilizar a CBC como substituição parcial do agregado miúdo na produção de concretos, pois seus resultados são similares ao concreto sem adição da cinza

The role of dissolved rice husk ash in the development of binary blast furnace slag-sewage sludge ash alkali-activated mortars

[EN] This study evaluated the compressive strength performance and microstructure of binary blast furnace slag-sewage sludge ash (BFS-SSA) alkali-activated mortars, in which rice husk ash (RHA) was dissolved in NaOH solution to replace commercial sodium silicate. The dissolution of RHA, performed in a thermal bottle with NaOH solution, enhanced the compressive strength of the alkali-activated mortars based on BFS up to 4.5-fold. BFS-SSA based mortars (10¿40% SSA), activated with NaOH/RHA-based sodium silicate suspensions, reached a compressive strength up to 30 MPa after 28 curing days at 20¿C. The RHA dissolution enhanced the strength and sustainability of the BFS-SSA alkali-activated mortars.This study was financed partly by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior - Brazil (CAPES) - (Finance Code 001). Thanks go to Cementval, the DACSA Group and the Pinedo Wastewater Treatment Plant for supplying some raw materials. Thanks go to the Electron Microscopy Service of the Universitat Politècnica de Valencia.Istuque, DB.; Paya Bernabeu, JJ.; Soriano Martinez, L.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Mitsuuchi Tashima, M. (2022). The role of dissolved rice husk ash in the development of binary blast furnace slag-sewage sludge ash alkali-activated mortars. Journal of Building Engineering. 52:1-14. https://doi.org/10.1016/j.jobe.2022.1044721145

Impedance Spectroscopy as a Methodology to Evaluate the Reactivity of Metakaolin Based Geopolymers

The aim of this study was to use the electrical impedance spectroscopy technique (IS) to carry out a systematic study on the mechanism of metakaolin geopolymerization for up to 7 curing days. The study was developed on two batches of metakaolin (MK), and their reaction processes were compared. Interpretative fundamental elements were developed based on the effective electrical conductivity curves regarding the metakaolin geopolymerization. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were previously carried out and used to interpret and validate the electrical behavior of the fresh and hardened MK-based geopolymer pastes. The results highlighted the sensibility of the impedance technique to the identification and description of the MK geopolymerization process, as well as the changes resulting from even slight variations in the metakaolin composition. Furthermore, this indicated that the geopolymerization process in highly alkaline solutions could be divided into seven stages, including the processes of dissolution, nucleation, precipitation and formation of the gel and, eventually, the retraction/microcracks constitution. Late dissolution processes could be observed during the more advanced stages and were attributed to particles not being fully hydrated