Kinetic modeling of microscopic processes during electron cyclotron resonance microwave plasma-assisted molecular beam epitaxial growth of GaN/GaAs-based heterostructures

Microscopic growth processes associated with GaN/GaAs molecular beam epitaxy (MBE) are examined through the introduction of a first-order kinetic model. The model is applied to the electron cyclotron resonance microwave plasma-assisted MBE (ECR-MBE) growth of a set of delta-GaNyAs1–y/GaAs strained-layer superlattices that consist of nitrided GaAs monolayers separated by GaAs spacers, and that exhibit a strong decrease of y with increasing T over the range 540–580 °C. This y(T) dependence is quantitatively explained in terms of microscopic anion exchange, and thermally activated N surface-desorption and surface-segregation processes. N surface segregation is found to be significant during GaAs overgrowth of GaNyAs1–y layers at typical GaN ECR-MBE growth temperatures, with an estimated activation energy Es ~ 0.9 eV. The observed y(T) dependence is shown to result from a combination of N surface segregation/desorption processes

Evaluation of the long-term compressive strength development of the sewage sludge ash/metakaolin-based geopolymer

[EN] This paper aimed to evaluate the long-term compressive strength development of the sewage sludge ash/metakaolin (SSA/MK)¿based geopolymer. SSA/MK¿based geopolymeric mortars and pastes were produced at 25ºC with different SSA contents (0 - 30 wt.%). Compressive strength tests were run within the 3-720 curing days range. A physicochemical characterisation (X-ray diffraction and scanning electron microscopy) was performed in geopolymeric pastes. All the geopolymeric mortars presented a compressive strength gain with curing time. The mortars with all the SSA evaluated contents (10, 20, 30 wt.%) developed a compressive strength over 40 MPa after 720 curing days at 25ºC. The maximum compressive strength of the mortars with SSA was approximately 61 MPa (10 wt.% of SSA), similarly to the reference mortar (100% MK-based geopolymer). The microstructure analyses showed that the SSA/MK¿based geopolymer presented a dense microstructure with N-A-S-H gel formation.This study was financed partly by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Su-perior -Brasil (CAPES) -(Finance Code 001 and CAPES/DGU n. 266/12), and the National Council of Scientific and Technological Development -Bra-sil (CNPq) -(n. 14/2013, process 478057/2013-0 and 309015/2015-4). The authors would like to thank Programa Institucional de Internacionalizacao - CAPES -PrInt. The authors acknowledge the Scanning Electron Microscopy Service of FEIS/UN-ESP, Servico Municipal Autonomo de Agua e Es-goto (SEMAE) from the Sao Jose do Rio Preto city -SP, Brazil and Diatom Mineracao Ltda. The authors would like to thank Programa Institucional de Internacionalizacao CAPES -PrInt.Istuque, D.; Soriano Martinez, L.; Borrachero Rosado, MV.; Paya Bernabeu, JJ.; Akasaki, JL.; Melges, JLP.; Tashima, MM. (2021). Evaluation of the long-term compressive strength development of the sewage sludge ash/metakaolin-based geopolymer. Materiales de Construcción. 71(343):1-10. https://doi.org/10.3989/mc.2021.13220S1107134

New method to assess teh pozzolanic reactivity of mineral admixtures by measn of pH and electrical conductivity measurements in lime: pozzolan suspensions

A very simple method based on electrical conductivity and pH measurements was proposed for assessing reactivity of pozzolans. Calcium hydroxide:pozzolan water suspensions were monitored by means of measurements of electrical conductivity and pH values. In these suspensions, Ca(OH)2 in solid state was initially present, being them, thus, saturated in this reagent. Three testing temperatures were selected (40, 50 and 60 °C). In the experiments carried out, calcium hydroxide was suspended in deionized water for yielding a lime saturated suspension. The addition of siliceous pozzolan (two types of rice husk ash RHA and two types of densified silica fume DSF were tested) to the saturated lime suspension can produce the unsaturation of the system, depending on the testing time, testing temperature and reactivity of pozzolan. When unsaturation was reached, the loss of electrical conductivity was higher than 30% and the variation of pH was higher than 0.15 units. These threshold values were selected for characterizing the reactivity of pozzolans by means of a proposed template, classifying the pozzolan in three different reactivity levels.Mitsuuchi Tashima, M.; Soriano Martinez, L.; Monzó Balbuena, JM.; Borrachero Rosado, MV.; Akasaki, JL.; Paya Bernabeu, JJ. (2014). New method to assess teh pozzolanic reactivity of mineral admixtures by measn of pH and electrical conductivity measurements in lime: pozzolan suspensions. Materiales de Construcción. 64(316):32-44. doi:10.3989/mc.2014.00914S324464316Schneider, M., Romer, M., Tschudin, M., & Bolio, H. (2011). Sustainable cement production—present and future. Cement and Concrete Research, 41(7), 642-650. doi:10.1016/j.cemconres.2011.03.019Altmann, F., & Mechtcherine, V. (2013). Durability design strategies for new cementitious materials. Cement and Concrete Research, 54, 114-125. doi:10.1016/j.cemconres.2013.08.008Shi, C., Jiménez, A. F., & Palomo, A. (2011). New cements for the 21st century: The pursuit of an alternative to Portland cement. Cement and Concrete Research, 41(7), 750-763. doi:10.1016/j.cemconres.2011.03.0164. Payá, J. (2012) La "transmutación" sostenible de los residuos para nuevas materias primas en el ámbito del concreto. Dyna 79, 38–47.Donatello, S., Freeman-Pask, A., Tyrer, M., & Cheeseman, C. R. (2010). Effect of milling and acid washing on the pozzolanic activity of incinerator sewage sludge ash. Cement and Concrete Composites, 32(1), 54-61. doi:10.1016/j.cemconcomp.2009.09.002Soriano, L., Monzó, J., Bonilla, M., Tashima, M. M., Payá, J., & Borrachero, M. V. (2013). Effect of pozzolans on the hydration process of Portland cement cured at low temperatures. Cement and Concrete Composites, 42, 41-48. doi:10.1016/j.cemconcomp.2013.05.0077. Villar-Coci-a, E.; Frías, M.; Valencia-Morales, E.; Rojas, M.I.S. (2005) Validation of a kinetic-diffusive model to characterize pozzolanic reaction kinetics in sugar cane straw-clay ash/lime systems. Mater. Construcc. 55 [278], 29–40.8. Cruz, J.M.; Payá, J.; Lalinde, L.F.; Fita, I.C. (2011) Evaluation of electric properties of cement mortars containing pozzolans. Mater. Construcc. 61 [301], 7–26.Luxán, M. P., Madruga, F., & Saavedra, J. (1989). Rapid evaluation of pozzolanic activity of natural products by conductivity measurement. Cement and Concrete Research, 19(1), 63-68. doi:10.1016/0008-8846(89)90066-5Payá, J., Borrachero, M. ., Monzó, J., Peris-Mora, E., & Amahjour, F. (2001). Enhanced conductivity measurement techniques for evaluation of fly ash pozzolanic activity. Cement and Concrete Research, 31(1), 41-49. doi:10.1016/s0008-8846(00)00434-8Villar-Cociña, E., Valencia-Morales, E., González-Rodrı́guez, R., & Hernández-Ruı́z, J. (2003). Kinetics of the pozzolanic reaction between lime and sugar cane straw ash by electrical conductivity measurement: A kinetic–diffusive model. Cement and Concrete Research, 33(4), 517-524. doi:10.1016/s0008-8846(02)00998-5Frías, M., Villar-Cociña, E., Sánchez de Rojas, M. I., & Valencia-Morales, E. (2005). The effect that different pozzolanic activity methods has on the kinetic constants of the pozzolanic reaction in sugar cane straw-clay ash/lime systems: Application of a kinetic–diffusive model. Cement and Concrete Research, 35(11), 2137-2142. doi:10.1016/j.cemconres.2005.07.005Sinthaworn, S., & Nimityongskul, P. (2009). Quick monitoring of pozzolanic reactivity of waste ashes. Waste Management, 29(5), 1526-1531. doi:10.1016/j.wasman.2008.11.010Payá, J., Monzó, J., Borrachero, M. ., Mellado, A., & Ordoñez, L. . (2001). Determination of amorphous silica in rice husk ash by a rapid analytical method. Cement and Concrete Research, 31(2), 227-231. doi:10.1016/s0008-8846(00)00466-xMartínez-Velandia, D., Payá, J., Monzó, J., & Borrachero, M. V. (2011). Effect of sonication on the reactivity of silica fume in Portland cement mortars. Advances in Cement Research, 23(1), 23-31. doi:10.1680/adcr.8.00027Tashima, M. M., Fioriti, C. F., Akasaki, J. L., Bernabeu, J. P., Sousa, L. C., & Melges, J. L. P. (2012). Cinza de casca de arroz (CCA) altamente reativa: método de produção e atividade pozolânica. Ambiente Construído, 12(2), 151-163. doi:10.1590/s1678-86212012000200010Payá, J., Monzó, J., Borrachero, M. V., Peris-Mora, E., & Amahjour, F. (2000). Mechanical treatment of fly ashes. Cement and Concrete Research, 30(4), 543-551. doi:10.1016/s0008-8846(00)00218-

Electronic dielectric constants of insulators by the polarization method

We discuss a non-perturbative, technically straightforward, easy-to-use, and computationally affordable method, based on polarization theory, for the calculation of the electronic dielectric constant of insulating solids at the first principles level. We apply the method to GaAs, AlAs, InN, SiC, ZnO, GaN, AlN, BeO, LiF, PbTiO$_3$, and CaTiO$_3$. The predicted \einf's agree well with those given by Density Functional Perturbation Theory (the reference theoretical treatment), and they are generally within less than 10 % of experiment.Comment: RevTeX 4 pages, 2 ps figure

Pozzolanic reactivity studies on a miomass-derived waste from sugar cane production: sugar cane straw ash (SCSA)

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021%2Facssuschemeng.6b00770.”Biomass has gained in importance as an energy source in recent years. One of the crops that presents interesting opportunities with regard to biomass is sugar cane. In Brazil, sugar cane production is increasing for alcohol and sugar manufacture. Some by-products, such as sugar cane straw, also are obtained during harvesting. Due the calorific value of the sugar cane straw, its use as biomass is increasing. After the straw is burned to produce energy, an ash is obtained: sugar cane straw ash (SCSA). This waste needs an appropriate destination and, since the recent publication of successful studies using biomass derived-ashes as pozzolanic material, the present study aimed to assess the pozzolanic reactivity of sugar cane straw ash. The pozzolanic activity was assessed using a new and simple recently proposed method: evaluation of the electrical conductivity of calcium hydroxide (CH) and pozzolan suspensions, in which solid CH is initially present. These results were compared to those of two other well-established techniques: Fourier transformed infrared spectroscopy and thermogravimetric analysis. The evaluation by all three techniques is similar and shows that sugar cane straw ash is a good pozzolanic material: high lime fixation values for CH:SCSA mixes were determined by thermogravimetric analysis and unsaturation respect to CH in 3.5:6.5 CH:SCSA suspension was achieved at 60ºC. According to this behaviour, a bright future for SCSA as a replacement for Portland cement is expected.We thank CNPq (processo no. 401724/2013-1) and the "Ministerio de Education, Cultura y Deporte" of Spain ("Cooperacion Interuniversitaria" program with Brazil PHB-2011-0016-PC). Thanks are also due to the Electron Microscopy Service of the Universitat Politecnica de ValenciaMoraes, J.; Melges, JLP.; Akasaki, JL.; Tashima, MM.; Soriano Martínez, L.; Monzó Balbuena, JM.; Borrachero Rosado, MV.... (2016). Pozzolanic reactivity studies on a miomass-derived waste from sugar cane production: sugar cane straw ash (SCSA). ACS Sustainable Chemistry and Engineering. 4(8):4273-4279. https://doi.org/10.1021/acssuschemeng.6b00770S427342794

Acceptor binding energies in GaN and AlN

We employ effective mass theory for degenerate hole-bands to calculate the acceptor binding energies for Be, Mg, Zn, Ca, C and Si substitutional acceptors in GaN and AlN. The calculations are performed through the 6$\times$6 Rashba-Sheka-Pikus and the Luttinger-Kohn matrix Hamiltonians for wurtzite (WZ) and zincblende (ZB) crystal phases, respectively. An analytic representation for the acceptor pseudopotential is used to introduce the specific nature of the impurity atoms. The energy shift due to polaron effects is also considered in this approach. The ionization energy estimates are in very good agreement with those reported experimentally in WZ-GaN. The binding energies for ZB-GaN acceptors are all predicted to be shallower than the corresponding impurities in the WZ phase. The binding energy dependence upon the crystal field splitting in WZ-GaN is analyzed. Ionization levels in AlN are found to have similar `shallow' values to those in GaN, but with some important differences, which depend on the band structure parameterizations, especially the value of crystal field splitting used.Comment: REVTEX file - 1 figur

Valorization of sugarcane bagasse ash (SCBA) with high quartz content as pozzolanic material in portland cement mixtures

[EN] Portland cement (OPC) production is one of the most contaminating greenhouse gas producing activities. In order to reduce OPC consumption, several alternatives are being assessed, and the use of pozzolanic material is one of them. This paper presents study on the reactivity of sugarcane bagasse ash (SCBA), a residue from sugarcane industry, as a pozzolanic material. In order to evaluate SCBA reactivity, it was mixed in pastes with hydrated lime and OPC, which were microstructurally characterised. These studies showed that SCBA presents some pozzolanic characteristics. Studies on mortars in which OPC was replaced by SCBA in the range 10¿30% were also carried out. Replacement in the range 15¿20% yielded the best behaviour in terms of compressive strength. Finally, it can be concluded this ash could be valorised despite its relative low pozzolanic reactivity.[ES] Valorización de la ceniza de bagazo de azúcar (SCBA) con alto contenido de cuarzo como material puzolánico en mezclas de cemento Portland. La producción de cemento Portland (OPC) presenta una elevada emisión de CO2. Con el objeto de reducir el consumo de OPC, se están evaluando algunas alternativas, y el uso de materiales puzolánicos es una de ellas. En este trabajo se presenta el estudio de la reactividad de la ceniza de bagazo de caña de azúcar (SCBA) como material puzolánico, un residuo procedente de la industria de la caña de azúcar. Al objeto de evaluar la reactividad de SCBA, se realizaron pastas con cal hidratada y con OPC, las cuales fueron caracterizadas microestructuralmente. Estos estudios mostraron que SCBA presenta una cierta característica puzolánica. Se llevaron a cabo estudios en morteros en los que OPC se sustituyó por SCBA en el intervalo de 10-30%. La sustitución en el intervalo 15-20% produjo el mejor comportamiento en términos de resistencia a compresión. Finalmente, se puede concluir que esta ceniza puede ser valorizada a pesar de su baja reactividad puzolánica.The authors would like to thank the Ministerio de Educacion, Cultura y Deporte of Spain (Cooperacion Interuniversitaria Program with Brazil, Project PHB-2011-0016-PC), CAPES-Brazil (Project CAPES/DGU No. 266/12), CNPq (Project 401724/2013-1) and Electron Microscopy Service of the Universitat Politecnica de Valencia.Pereira, A.; Moraes, J.; Bassan De Moraes, M.; Akasaki, J.; Tashima, M.; Soriano Martinez, L.; Monzó Balbuena, JM.... (2018). Valorization of sugarcane bagasse ash (SCBA) with high quartz content as pozzolanic material in portland cement mixtures. Materiales de Construcción. 68(330):153-163. https://doi.org/10.3989/mc.2018.00617S153163683301. World cement production. CEMBUREAU – The European Cement Association Website; https://cembureau.eu/media/1503/2015activityreport_cembureau.pdf2. Guo, X.; Shi, H.; Dick, W.A. (2010) Compressive strength and microstructural characteristics of class C fly ash geopolymer. Cem. Concr. Compos. 32, 142–7.3. Mehta, P.K.; Monteiro, P.J.M. Concrete: Microstructure, Properties, and Materials. 3rd ed. New York: McGraw- Hill, (2006).4. Mo, K.H.; Alengaram, U.J.; Jumaat, M.Z. (2016) Structural performance of reinforced geopolymer concrete members: A review, Constr. Build. Mater. 120, 251-264.5. Sharp, J.H.; Gartner, E.M.; Macphee, D.E. (2010) Novel cement system (sustainability). Session 2 of the Fred Glasser cement science symposium. Adv. Cem. Res. 22(4), 195–202.6. BS EN 197-1. Cement – Part 1: Composition, specifications and conformity criteria for common cements. London: European Committee For Standardisation; (2011).7. Siddique, R.; Khan, M.I. Supplementary Cementing Materials. 1st ed. Berlin: Springer, (2011).8. Siddique, R. Waste Material and By-Products in Concrete. 1st ed. Berlin: Springer, (2008).9. Küçükyıldırım, E.; Uzal, B. (2014) Characteristics of calcined natural zeolites for use in high-performance pozzolan blended cements. Constr. Build. Mater. 73, 229–34.10. Tashima, M.M.; Soriano, L.; Monzó, J.; Borrachero, M.V.; Akasaki, J.L.; Payá, J. (2014) New method to assessthe pozzolanic reactivity of mineral admixtures by means pH and electrical conductivity measurementsin lime:pozzolan suspensions. Mater. Construc. 64 [316], e032.11. Wongkeo, W.; Thongsanitgarn, P.; Chaipanich, A. (2012) Compressive strength and drying shrinkage of fly ash-bottom ash-silica fume multi-blended cement mortars. Mater. Des. 36, 655-62.12. Lee, C.L.; Huang, R.; Lin, W.T.; Weng, T.L. (2012) Establishment of the durability indices for cement-based composite containing supplementary cementitious materials. Mater. Des. 37, 28-39.13. Sinsiri, T.; Kroenhong, W.; Jaturapitakkul, C.; Chindaprasirt, P. (2012) Assessing the effect of biomass ashes with different finenesses on the compressive strength of blended cement paste. Mater. Des. 42, 424-33.14. Pereira, C.L.; Savastano Jr., H.; Payá, J.; Santos, S.F.; Borrachero, M.V.; Monzó, J. (2013) Use of highly reactive rice husk ash in the production of cement matrix reinforced with green coconut fiber. Ind. Crop. Prod. 49, 88–96.15. Paiva, H.; Velosa, A.; Cachim, P.; Ferreira, V.M. (2016) Effect of pozzolans with diferent physical and chemical characteristics on concrete properties. Mater. Construc. 66 [322], 1-12. 516. Hoi, L.W.S.; Martincigh, B.S. (2013) Sugar cane plant fibres: Separation and characterization. Ind. Crop. Prod. 47, 1–12.17. Hugot, E. Handbook of Cane Sugar Engineering. 3rd ed. Amsterdam:Elsevier Science Publishers, (1986).18. Sugarcane production. FAOSTAT – Food and Agriculture Organisation of the United Nations, Statistics Division; http://www.fao.org/faostat/en/#data/QC19. Sugarcane production. UNICA – União da Indústria de Cana-de-Açúcar Website; http://www.unicadata.com. br/index.php?idioma=220. A Geração Termoelétrica com a Queima do Bagaço de Cana-de-Açúcar no Brasil. CONAB – Companhia Nacional de Abastecimento; http://www.agricultura.gov.br/assuntos/sustentabilidade/agroenergia/arquivos-termoeletrica-com-a-queima-do-bagaco-de-cana-de-acucar/termoeletrica-com-a-queima-do-bagaco-de-cana-de-acucar-no-brasil-safra-2009-2010.pdf21. Cortez, L.A.B.; Gómez, E.O. (1998) A method for exergy analysis of sugarcane bagasse boilers. Braz. J. Chem. Eng. 15 [1].22. Souza, A.E.; Teixeira, S.R.; Santos, G.T.A.; Costa, F.B.; Longo, E. (2011) Reuse of sugarcane bagasse ash (SCBA) to produce ceramic materials. J. Environ. Manage. 92, 2774–80.23. Hofsetz, K.; Silva, M.A. (2012) Brazilian sugarcane bagasse: Energy and non-energy consumption. Biomass Bioenerg 46, 564–573.24. Cordeiro, G.C.; Toledo Filho, R.D.; Tavares, L.M.; Fairbairn, E.M.R. (2009) Ultrafine grinding of sugar cane bagasse ash for application as pozzolanic admixture in concrete. Cem. Concr. Res. 39, 110–115.25. Frías, M.; Villar, E.; Savastano, H. (2011) Brazilian sugar cane bagasse ashes from the cogeneration industry as active pozzolans for cement manufacture. Cem. Concr. Compos. 33, 490–496.26. Fairbairn, E.M.R.; Americano, B.B.; Cordeiro, G.C.; Paula, T.P.; Toledo Filho, R.D.; Silvoso, M.M. (2010) Cement replacement by sugar cane bagasse ash: CO2 emissions reduction and potential for carbon credits. J. Environ. Manage. 91, 1864–1871.27. Cordeiro, G.C.; Toledo Filho, R.D.; Fairbairn, E.M.R. (2009) Effect of calcination temperature on the pozzolanic activity of sugar cane bagasse ash. Constr. Build. Mater. 23, 3301–3303.27. UNE-EN 196-5. Método de ensayo de cementos. Parte 5: Ensayo de puzolanicidad para los cementos puzolánicos. Madrid: Asociación Espa-ola de Normalización y Certificación – AENOR; (2011).29. NBR 7215. Cimento Portland – Determinação da resistência à compressão. Rio de Janeiro: Associação Brasileira de Normas Técnicas – ANBT; (1996).29. ASTM C-618. Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. Philadelphia: ASTM International; (2005).31. Allahverdi, A.; Shaverdi, B.; Kani, E. (2010) Influence of sodium oxide on properties of fresh and hardened paste of alkali-activated blast-furnace slag. Int. J. Civ. Eng. 8, 304–314.32. Yu, P.; Kirkpatrick, R.J.; Poe, B.; McMillan, P.F.; Cong, X. (1999) Structure of calcium silicate hydrate (C-S-H): Near-, mid-, and far-infrared spectroscopy. J. Am. Ceram. Soc. 82(3), 742–748.33. Moraes, J.C.B.; Akasaki, J.L.; Melges, J.L.P.; Monzó, J.; Borrachero, M.V.; Soriano, L.; Payá, J.; Tashima, M.M. (2015) Assessment of sugar cane straw ash (SCSA) as pozzolanic material in blended Portland cement: Microstructural characterisation of pastes and mechanical strength of mortars. Constr. Build. Mater. 94, 670–677.34. Murat, M. (1983) Hydration reaction and hardening of calcined clays and related minerals: II. Influence of mineralogical properties of raw-kaolinite on the reactivity of metakaolinite. Cem. Concr. Res. 11, 511–518.35. Serry, M.A.; Taha, A.S.; El-Hemaly, S.A.S.; El-Didamony, H. (1984) Metakaolin-lime hydration products. Thermochim. Acta 79, 103–110.36. Lorca, P.; Calabuig, R.; Benlloch, J.; Soriano, L.; Payá, J. (2014) Microconcrete with partial replacement of Portland cement by fly ash and hydrated lime addition. Mater. Des. 64, 535–541

Behavior of metakaolin-based geopolymers incorporating sewage sludge ash (SSA)

[EN] In recent years, geopolymers have become a widely researched binding material. There are technological and environmental advantages tousing this type of binder instead of Portland cement. In this study, binary systems of geopolymers were produced by using mixtures of metakaolin (MK) ,a well-known aluminosilicate raw material, and a residue from sewage sludge incineration: sewage sludge ash (SSA). This ash was used to partially replace the metakaolin in proportions of 0 20%. The mixtures were activated with alkaline solutions and they were cured by using two different conditions: at room temperature (25 °C) and in a thermal bath (65 °C). The samples were assessed by X-ray diffraction, scanning electron microscopy (pastes) and compressive strength (mortars). The results from these studies showed zeolite formation (faujasite) in geopolymers cured in the thermal bath, which caused a decrease in the compressive strength of the alkali-activated mortars.Replacement of MK with SSA caused a lower reduction in the compressive strength of mortars cured at 65 °C. However, at room temperature, similar mechanical strength was observed for the MK and MK-SSA systems. These results demonstrated that SSA is a suitable mineral precursor for partial replacement of MK in geopolymer production.The authors acknowledge Santander Universidades for the grant to Lucia Reig (program: Becas lberoamerica Jovenes Profesores Investigadores Espana 2014), CAPES (CAPES/DGU no 266/12), CNPq (no. 14/2013 processo 478057/2013-0) Scanning electron microscopy service of FEIS/UNESP and CNPq (processo 309015/2015-4).Istuque, D.; Reig Cerdá, L.; Moraes, J.; Akasaki, JL.; Borrachero Rosado, MV.; Soriano Martínez, L.; Paya Bernabeu, JJ.... (2016). Behavior of metakaolin-based geopolymers incorporating sewage sludge ash (SSA). Materials Letters. 180:192-195. https://doi.org/10.1016/j.matlet.2016.05.137S19219518

New geopolymeric binder based on fluid catalytic cracking catalyst residue (FCC)

This paper provides information about the synthesis and mechanical properties of geopolymers based on fluid catalytic cracking catalyst residue (FCC). FCC was alkali activated with solutions containing different SiO 2/Na 2O ratios. The microstructure and mechanical properties were analysed by using several instrumental techniques. FCC geopolymers are mechanically stable, yielding compressive strength about 68 MPa when mortars are cured at 65°C during 3 days. The results confirm the viability of producing geopolymers based on FCC. © 2012 Elsevier B.V. All rights reserved.We acknowledge the Ministerio de Ciencia e Innovacion (MICINN) of the Spanish Government and FEDER funds (MAT-2011-19934 project) and the PROPG-UNESP "Universidade Estadual Paulista Julio de Mesquita Filho", Brazil.Mitsuuchi Tashima, M.; Akasaki, JL.; Castaldelli, V.; Soriano Martínez, L.; Monzó Balbuena, JM.; Paya Bernabeu, JJ.; Borrachero Rosado, MV. (2012). New geopolymeric binder based on fluid catalytic cracking catalyst residue (FCC). Materials Letters. 80:50-52. https://doi.org/10.1016/j.matlet.2012.04.051S50528

Alkali activated materials based on fluid catalytic cracking catalyst residue (FCC): Influence ofSiO2/Na2O and H2O/FCC ratio on mechanical strength and microstructure

Reuse of industrial and agricultural wastes as supplementary cementitious materials (SCMs) in concrete and mortar productions contribute to sustainable development. In this context, fluid catalytic cracking catalyst residue (spent FCC), a byproduct from the petroleum industry and petrol refineries, have been studied as SCM in blended Portland cement in the last years. Nevertheless, another environmental friendly alternative has been conducted in order to produce alternative binders with low CO2 emissions. The use of aluminosilicate materials in the production of alkali-activated materials (AAMs) is an on going research topic which can present low CO2 emissions associated. Hence, this paper studies some variables that can influence the production of AAM based on spent FCC. Specifically, the influence of SiO2/Na2O molar ratio and the H2O/spent FCC mass ratio on the mechanical strength and microstructure are assessed. Some instrumental techniques, such as SEM, XRD, pH and electrical conductivity measurements, and MIP are performed in order to assess the microstructure of formed alkali-activated binder. Alkali activated mortars with compressive strength up to 80 MPa can be formed after curing for 3 days at 65 C. The research demonstrates the potential of spent FCC to produce alkali-activated cements and the importance of SiO2/Na2O molar ratio and the H2O/spent FCC mass ratio in optimising properties and microstructure.Authors would like to thank to the Ministerio de Ciencia e Innovacion (MICINN) of the Spanish Government (BIA2011-26947) and to FEDER for funding, and also to the PROPG - UNESP "Universidade Estadual Paulista Julio de Mesquita Filho'', Brazil.Mitsuuchi Tashima, M.; Akasaki, JL.; Melges, J.; Soriano Martínez, L.; Monzó Balbuena, JM.; Paya Bernabeu, JJ.; Borrachero Rosado, MV. (2013). Alkali activated materials based on fluid catalytic cracking catalyst residue (FCC): Influence ofSiO2/Na2O and H2O/FCC ratio on mechanical strength and microstructure. Fuel. 108:833-839. https://doi.org/10.1016/j.fuel.2013.02.052S83383910