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

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

Developing autonomous learning in first year university students using perspectives from positive psychology

Autonomous learning is a commonly occurring learning outcome from university study, and it is argued that students require confidence in their own abilities to achieve this. Using approaches from positive psychology, this study aimed to develop confidence in first‐year university students to facilitate autonomous learning. Psychological character strengths were assessed in 214 students on day one at university. Two weeks later their top three strengths were given to them in study skills modules as part of a psycho‐educational intervention designed to increase their self‐efficacy and self‐esteem. The impact of the intervention was assessed against a control group of 40 students who had not received the intervention. The results suggested that students were more confident after the intervention, and that levels of autonomous learning increased significantly compared to the controls. Character strengths were found to be associated with self‐efficacy, self‐esteem and autonomous learning in ways that were theoretically meaningful

Impact strength and abrasion resistance of high strength concrete with rice husk ash and rubber tires

The paper discusses the application of High Strength Concrete (HSC) technology for concrete production with the incorporation of Rice Husk Ash (RHA) residues by replacing a bulk of the material caking and rubber tires with partial aggregate volume, assessing their influence on the mechanical properties and durability. For concrete with RHA and rubber, it was possible to reduce the brittleness by increasing the energy absorbing capacity. With respect to abrasion, the RHA and rubber concretes showed lower mass loss than the concrete without residues, indicating that this material is attractive to be used in paving. It is thus hoped that these residues may represent a technological and ecological alternative for the production of concrete in construction works.O trabalho aborda a aplicação da tecnologia do Concreto de Alta Resistência (CAR) para a produção de concretos com incorporação dos resíduos de Cinza de Casca de Arroz (CCA) através da substituição em massa de parte do material aglomerante, e borracha de pneus em substituição parcial do agregado miúdo em volume, avaliando suas influências sobre as propriedades de durabilidade e mecânicas. Para os concretos com CCA e borracha, foi possível verificar a redução da fragilidade através do aumento da capacidade de absorção de energia. Com relação à abrasão, os concretos contendo CCA e borracha apresentaram perda de massa inferior ao concreto sem resíduos, indicando que este material é atrativo para o uso em pavimentação. Contudo, espera-se que estes resíduos venham representar uma alternativa tecnológica e ecológica para a produção de concretos na construção civi

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. © 2021 American Society of Civil Engineers

Impact strength and abrasion resistance of high strength concrete with rice husk ash and rubber tires

The paper discusses the application of High Strength Concrete (HSC) technology for concrete production with the incorporation of Rice Husk Ash (RHA) residues by replacing a bulk of the material caking and rubber tires with partial aggregate volume, assessing their influence on the mechanical properties and durability. For concrete with RHA and rubber, it was possible to reduce the brittleness by increasing the energy absorbing capacity. With respect to abrasion, the RHA and rubber concretes showed lower mass loss than the concrete without residues, indicating that this material is attractive to be used in paving. It is thus hoped that these residues may represent a technological and ecological alternative for the production of concrete in construction works

Assessment of sugar cane straw ash (SCSA) as pozzolanic material in blended portland cement: Microstructural characterization of pastes and mechanical strength of mortars

The aim of this paper is to assess the pozzolanic reactivity of sugar cane straw ash (SCSA) obtained through an auto-combustion process and the mechanical properties of SCSA-containing systems. Characterization of SCSA (X-ray diffraction, chemical composition, particle size, and microscopy) and reactivity studies on hydrated lime/SCSA and Portland cement/SCSA pastes through infrared spectroscopy, thermogravimetric analysis, and microscopy demonstrated the high pozzolanic activity. This reactivity made it possible to achieve good mechanical properties in mortars in which 15 30% of the cement was replaced by SCSA. After 90 days of curing, the SCSA fixed 100% of the lime present in lime/SCSA pastes, and the compressive strength of mortars containing SCSA reached 44 MPa, a value similar to those found for control mortars after the same number of curing days. The results for the microstructural and mechanical properties showed that SCSA is a good pozzolanic material.The authors would like to thank CNPq-Brazil (process no 401724/2013-1) and the Ministerio de Educacion, Cultura y Deporte of Spain (the Cooperacion Interuniversitaria program with Brazil: PHB-2011-0016-PC). We also thank CAPES-Brazil for the Grant for J.C.B. Moraes and Electron Microscopy Service of the Universitat Politecnica de Valencia.Moraes, JCB.; Akasaki, JL.; Melges, JLP.; Monzó Balbuena, JM.; Borrachero Rosado, MV.; Soriano Martinez, L.; Paya Bernabeu, JJ.... (2015). Assessment of sugar cane straw ash (SCSA) as pozzolanic material in blended portland cement: Microstructural characterization of pastes and mechanical strength of mortars. Construction and Building Materials. 94:670-677. doi:10.1016/j.conbuildmat.2015.07.108S6706779

Desenvolvimento, partição de assimilados e produção de matéria seca de plantas de soja (Glycine max (L.) merrill) submetidas a quatro doses de metribuzin Development,assimilate partition and dry matter production in soybean (Glycine max (L.) merrill) plants treated with four doses of metribuzin

O desenvolvimento, a partição e a produção de matéria seca, foram estudados em soja (Glycine Max (L. ) Merri ll, cv. 'Uberaba'), cultivadas em condições de campo, sob quatro doses de metribuzin - (0,0; 0,35; 0,70 e 1,05 kg i.a. ha-1). O metri buzin não reduziu a população e nem alterou significativamente a razão parte aérea/sistema radicular. A altura média das plantas aumentou significativamente com o incremento das doses de metribuzin, sendo que as alturas máximas das plantas foram 761, 784, 815 e 812 mm, em ordem crescente de dose de metribuzin. As variações das taxas de acúmulo de matéria seca foram nitida mente seqüenciais em todos os tratamentos, ocorrendo mudanças do dreno metabólico preferencial de um órgão para outro, de acordo com as transformações morfológicas das plantas, ressaltando-se que o metribuzin não alterou esse comportamento. Os tratamentos não influencia ramo acumulo de matéria seca das vagens (Wv), no entanto, a partir do inicio da maturação, as plantas-controle apres entaram maiores Wv, provavelmente, devido a maior taxa assi milatória líquida verificada a partir da floração plena. A matéria seca acumulada nos pericarpos (Wp) diminuiu, a partir das sementes completamente desenvolvid os, para todos os tratamentos com exceção de Wp das plantas tratadas com 0,7 kg i.a. ha-1 de metribuzin que, manteve-se estável. Por outro lado, a matéria seca nas sementes (Ws) aumentou de forma acentuada, desde o seu aparecimento até a colheita final , em todas as doses do herbicida.<br>Development, assimlate partition and dry matter production in soybean (Glycine Max (L.) Merri ll, cv. Uberaba) plants treat ed with four metri buzin doses (0,0; 0,35; 0,70 and 1,05 kg i.a.ha-1) were studied in a field experiment. Metribuzin did not reduce the stand or alter ed significantly shoot /root ratio. Plants height average incre ased as the doses of metribuzin increased; maximum heights were 761, 784, 815 and 812 mm, for increasing metribuzin doses. Metribuzin did not alter the pattern of sequential dry matter partition in the plants. Metribuzin did not affect dry matter accumulation in pods (Wv); however, from initiation to the end of maturation of seeds the control presented greater Wv values than trea plants, due to its highest net assimilation rate after blooming. Pericarp dry matter (Wp) was decre ased from full development se eds to final harvest for all treatments, except for Wp of plant streated with 0,7 i.a.ha-l that was maintained practically. Constant on the other hand, seed dry matter increased accentuately, from formation to last harvest, for all doses employed