Production of bamboo leaf ash by auto-combustion for pozzolanic and sustainable use in cementitious matrices

[EN] In the context of world concern with the environment, this study aims to characterize an auto combustion produced bamboo leaf ash (BLA) by its pozzolanic behaviour, reactivity and its influence in the total porosity, pore size distribution, tortuosity and mechanical behaviour of cementitious matrices. The chemical and physical characterization of the BLA was carried using X-ray fluorescence, determination of amorphous silica content, X-ray diffraction, Fourier Transform Infrared Spectrophotometry (FTIR), laser granulometry and field emission scanning electron microscopy (FESEM). The assessed BLA is a siliceous material (74.23%) with an amorphous nature due to the amorphous silica content, which represents 92.33% of the total silica. The BLA was classified as highly reactive by assessing its pH and conductivity in a saturated calcium hydroxide (CH) medium for different proportions and temperatures. Frattini analysis, the study of CH:BLA pastes (Thermogravimetric analysis and FTIR) and Portland cement (OPC)/pozzolan pastes (Thermogravimetric analysis and FESEM) are in agreement with this classification. The replacement of OPC by BLA improved the mechanical behaviour of the cementitious matrices, as well their durability. All the mortars containing BLA presented very similar compressive strength to a control mortar (100% OPC) after only 3 days of curing and at the following tested curing ages: 7, 28 and 90 days. In the mercury intrusion porosimetry analysis, the pastes with 20 and 30% BLA content presented higher tortuosity or fewer connected pores than the control paste. Thus, the auto-combustion method proved to be successful and BLA is a suitable alternative for sustainable high-performance matrices. (C) 2019 Elsevier Ltd. All rights reserved.The authors would like to thank São Paulo Research Foundation (FAPESP), grant #2016/16403-5 and #2017/21563-4.Moraes, M.; Moraes, J.; Tashima, M.; Akasaki, J.; Soriano Martinez, L.; Borrachero Rosado, MV.; Paya Bernabeu, JJ. (2019). Production of bamboo leaf ash by auto-combustion for pozzolanic and sustainable use in cementitious matrices. Construction and Building Materials. 208:369-380. https://doi.org/10.1016/j.conbuildmat.2019.03.007S36938020

Mass matrix Ansatz and lepton flavor violation in the THDM-III

Predictive Higgs-fermion couplings can be obtained when a specific texture for the fermion mass matrices is included in the general two-Higgs doublet model. We derive the form of these couplings in the charged lepton sector using a Hermitian mass matrix Ansatz with four-texture zeros. The presence of unconstrained phases in the vertices phi-li-lj modifies the pattern of flavor-violating Higgs interactions. Bounds on the model parameters are obtained from present limits on rare lepton flavor violating processes, which could be extended further by the search for the decay tau -> mu mu mu and mu-e conversion at future experiments. The signal from Higgs boson decays phi -> tau mu could be searched at the large hadron collider (LHC), while e-mu transitions could produce a detectable signal at a future e mu-collider, through the reaction e mu -> h0 -> tau tau.Comment: 17 pages, 9 figure

Effect of sewage sludge ash on mechanical and microstructural properties of geopolymers based on metakaolin

[EN] This paper explored the effect of sewage sludge ash (SSA) on the mechanical and microstructural properties of geopolymers based on metakaolin (MK) involving two different SiO2/Na2O molar ratios (0.8 and 1.6), two temperature curing conditions (25 degrees C and 65 degrees C) and various ages of curing (1, 3, 7, 14, 28, 90 or 180 days). The geopolymers were characterized using different techniques as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and compressive strength of mortars. The compressive strength tests showed that the replacement of MK by SSA in 10 wt% when cured at 25 degrees C with the highest SiO2/Na2O molar ratio reaches similar compressive strengths after 14 days of curing compared to the samples with only MK, which reached a maximum compressive strength of 50.8 MPa at 180 days. The FTIR analyses carried out in the geopolymer pastes with SSA (10 wt% of SSA and 90 wt% of MK) showed a formation of N-A-S-H gels in the samples cured at 25 degrees C. The microstructural studies by XRD, TGA and SEM pointed out the formation of a crystalline phase as Na P-type zeolite in MK/SSA based-geopolymer pastes cured at 65 degrees C, which explained the loss of compressive strength of the samples cured at high temperature. However, the SSA retarded the crystallization process in the MK based-geopolymer. (C) 2019 Elsevier Ltd. All rights reserved.This research has been supported by funding agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (processo n° 309015/2015-4).Istuque, D.; Soriano Martinez, L.; Akasaki, J.; Melges, J.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Paya Bernabeu, JJ.... (2019). Effect of sewage sludge ash on mechanical and microstructural properties of geopolymers based on metakaolin. Construction and Building Materials. 203:95-103. https://doi.org/10.1016/j.conbuildmat.2019.01.093S9510320

Optimum use of sugar cane straw ash (SCSA) in alkali-activated binders based on blast furnace slag (BFS)

[EN] Alkali-activated binders (AABs) are a material obtained from the combination of a solid precursor and an alkaline activating solution. In this study, one solid precursor used was blast-furnace slag (BFS) and the other was an agro waste: sugar cane straw ash (SCSA). Sodium hydroxide was used for preparing activating solutions. In order to reach the potential reactivity of the SCSA, a study varying the BFS/SCSA mass ratio and H2O=Na2O molar ratio was carried out. The BFS/SCSA ratio varied from 100=0 to 70=30, and H2O=Na2O was studied in the range of 11.1¿18.5. To fulfill this objective, specimens were assessed by their compressive strength of mortars and microstructural studies of pastes [X-ray diffraction (XRD); thermogravimetric analysis (TGA); Fourier transform infrared spectroscopy (FTIR); and field emission scanning electron microscopy (FESEM)] in the curing time range of 3¿90 days at 25°C. Results from these tests showed that the best BFS/SCSA and H2O=Na2O ratios were 70=30 and 18.5, respectively. This study revealed an interesting valorization of the SCSA as a complementary precursor in BFS-based AABs because of the improvement of mechanical properties and the reduction in the consumption of BFS in AABThe authors would like to thank CNPq processo n° 401724/2013-1, CNPq processo n° 140779/2015-0, and the Ministerio de Educación, Cultura y Deporte of Spain ( Cooperación Interuniversitaria program with Brazil PHB-2011-0016-PC). Thanks are also given to the Electron Microscopy Service of the Universitat Politècnica de València.Moraes, J.; Tashima, M.; Melges, J.; Akasaki, J.; Monzó Balbuena, JM.; Borrachero Rosado, MV.; Soriano Martinez, L.... (2018). Optimum use of sugar cane straw ash (SCSA) in alkali-activated binders based on blast furnace slag (BFS). Journal of Materials in Civil Engineering. 30(6):1-12. https://doi.org/10.1061/(ASCE)MT.1943-5533.0002261S11230

New use of sugar cane straw ash in alkali-activated materials: a silica source for the prparation of alkaline activator

[EN] Alkali silicates, expensive and highly pollutant chemical reagents, are required to produce the alkaline activator for high-performance alkali-activated materials. This study presents a new silica source for producing the alkaline activator, sugar cane straw ash (SCSA). An activating suspension was prepared with SCSA and NaOH by means of a thermal bottle. The ash reacting time inside the thermal bottle (s) was assessed from 0 to 48 h, and the SCSA amount in suspension, represented by the SiO2/Na2O ratio (e), was analysed from 0 to 1.82. Compressive strengths were obtained from blast-furnace slag-based mortars that were cured for three days at 65 C, with the optimal mortars produced when s = 24 h and e = 1.46. Comparison of these new SCSA systems with two common silica sources, sodium silicate chemical reagent and rice husk ash, revealed that SCSA yielded lower results than the former and similar results to the latter silica source.The authors would like to thank CNPq processo no 401724/2013-1 and CNPq processo no 140779/2015-0. The authors would also like to thank the Electron Microscopy Service of the Universitat Politecnica de Valencia.Moraes, J.; Font-Pérez, A.; Soriano Martinez, L.; Akasaki, J.; Tashima, M.; Monzó Balbuena, JM.; Borrachero Rosado, MV.... (2018). New use of sugar cane straw ash in alkali-activated materials: a silica source for the prparation of alkaline activator. Construction and Building Materials. 171:611-621. https://doi.org/10.1016/j.conbuildmat.2018.03.230S61162117

Utilisation of sugar cane straw ash (SCSA) as pozzolan in partially replacement of Portland cement

[ES] La producción de caña de azúcar en Brasil ha aumentado considerablemente en los últimos 10 años. Después del proceso de cosecha mecanizada, se genera un residuo llamado paja de caña de azúcar. Esta paja tiene un buen poder calorífico y puede ser utilizada para generar energía como una biomasa. Sin embargo, después de este proceso de generación de energía se obtiene otro residuo, el cual no tiene un destino adecuado, llamado ceniza de la paja de caña de azúcar (CPC). Una destinación para este residuo es su valorización como un material puzolánico. Para ello, la CPC ha sido caracterizada físicamente y químicamente. La ceniza ha presentado cantidad de sílice amorfa que puede ser utilizada como una puzolana sustituyendo parcialmente el cemento Portland. La reactividad de la ceniza ha sido evaluada por el ensayo de termogravimetría (TGA) en pastas de cal y puzolana. También fueron estudiadas cinco sustituciones del cemento Portland por CPC en morteros: 0 (control), 15, 20, 25 y 30%. En este estudio se prepararon probetas para romper a ensayos de resistencia a compresión en las edades de 3, 7, 28 y 90 días después de un curado a 25 ºC en atmósfera húmeda. Los datos mostraron que la CPC reacciona con la cal y presenta una importante contribución para la resistencia mecánica. Todos los morteros presentaron resistencias a compresión similares después de 90 días de aproximadamente 45 MPa. La conclusión de este trabajo es que esta ceniza CPC puede ser utilizada sustituyendo parcialmente el cemento Portland.[EN] Sugarcane production in Brazil considerably increased in the last 10 years. After the mechanized harvesting, it is generated a waste called by sugar cane straw. This straw presents good calorific value and it can be utilised in energy production as a biomass. However, after the energy generation, it is obtained another waste, which does not have a suitable destination, known as the sugar cane straw ash (SCSA). A destination to this material can be as pozzolanic material. Therefore, the SCSA was physically and chemically characterised. The ash presented amorphous silica that can be used in partial replacement of the Port land cement. The ash reactivity was assessed by thermogravimetric analysis (TGA) of lime/pozzolan pastes. Also five replacement percentages of the Portland cement by SCSA in mortars were evaluated: 0 (control), 15, 20, 25 and 30%. Specimens were moulded in order to be assessed by compressive strength after 3, 7, 28 and 90 days of curing at 25 ºC. All mortars presented similar compressive strength after 90 days of curing of approximately 45 MPa. It can be concluded that the SCSA can be used in partial replac ement of the Portland cement.Los autores desean agradecer al CNPq Brasil por la beca del primer autor, J.C.B. Moraes (proceso 153164/2016-6), y al proceso 401724/2013-1. También al Ministerio de Educación, Cultura y Deporte de España (Cooperación Interuniversitaria con Brasil, proyecto PHB-2011-0016-PC).Moraes, J.; Akasaki, J.; Tashima, M.; Soriano Martinez, L.; Borrachero Rosado, MV.; Paya Bernabeu, JJ. (2018). Utillizacion de la ceniza de paja de caña de azúcar (CPC) como puzolana en sustituciones parciales del cemento portland. Materiales compuestos. 2(1):6-9. http://hdl.handle.net/10251/147925S692

The exposure of the hybrid detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The "hybrid" detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic

The Relation Between the Surface Brightness and the Diameter for Galactic Supernova Remnants

In this work, we have constructed a relation between the surface brightness ($\Sigma$) and diameter (D) of Galactic C- and S-type supernova remnants (SNRs). In order to calibrate the $\Sigma$-D dependence, we have carefully examined some intrinsic (e.g. explosion energy) and extrinsic (e.g. density of the ambient medium) properties of the remnants and, taking into account also the distance values given in the literature, we have adopted distances for some of the SNRs which have relatively more reliable distance values. These calibrator SNRs are all C- and S-type SNRs, i.e. F-type SNRs (and S-type SNR Cas A which has an exceptionally high surface brightness) are excluded. The Sigma-D relation has 2 slopes with a turning point at D=36.5 pc: $\Sigma$(at 1 GHz)=8.4$^{+19.5}_{-6.3}$$\times10^{-12}$ D$^{{-5.99}^{+0.38}_{-0.33}}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ (for $\Sigma$$\le3.7\times10^{-21}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ and D$\ge$36.5 pc) and $\Sigma$(at 1 GHz)=2.7$^{+2.1}_{-1.4}$$\times$ 10$^{-17}$ D$^{{-2.47}^{+0.20}_{-0.16}}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ (for $\Sigma$$>3.7\times10^{-21}$ Wm$^{-2}$Hz$^{-1}$ster$^{-1}$ and D$<$36.5 pc). We discussed the theoretical basis for the $\Sigma$-D dependence and particularly the reasons for the change in slope of the relation were stated. Added to this, we have shown the dependence between the radio luminosity and the diameter which seems to have a slope close to zero up to about D=36.5 pc. We have also adopted distance and diameter values for all of the observed Galactic SNRs by examining all the available distance values presented in the literature together with the distances found from our $\Sigma$-D relation.Comment: 45 pages, 2 figures, accepted for publication in Astronomical and Astrophysical Transaction

Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory

Atmospheric parameters, such as pressure (P), temperature (T) and density, affect the development of extensive air showers initiated by energetic cosmic rays. We have studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of pressure and density. The former affects the longitudinal development of air showers while the latter influences the Moliere radius and hence the lateral distribution of the shower particles. The model is validated with full simulations of extensive air showers using atmospheric profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle Physic

Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{$6\times 10^{19}$eV}. The anisotropy was measured by the fraction of arrival directions that are less than $3.1^\circ$ from the position of an active galactic nucleus within 75 Mpc (using the V\'eron-Cetty and V\'eron $12^{\rm th}$ catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is $(38^{+7}_{-6})$, compared with $21$ expected for isotropic cosmic rays. This is down from the early estimate of $(69^{+11}_{-13})$. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201