MICROSCOPIC AND CHEMICAL CHARACTERIZATION OF ELEPHANT GRASS AND CORN LEAVES AND THEIR ASHES Josefa Roselló 1,a , Lourdes Soriano 2,b , Holmer Savastano Jr 3,c , María V. Borrachero 2,d , Pilar Santamarina 1,e , Jorge L. Akasaki 4,f , Jordi Payá 2,g* 1 Departamento de Ecosistemas Agroforestales, Universitat Politècnica de Valéncia, Valencia, Spain 2 Instituto de Ciencia y Tecnología del Hormigón (ICITECH), Universitat Politècnica de València, Valencia, Spain 3 Departamento de Engenharia de Biossistemas, Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de São Paulo, Pirassununga, SP, Brazil 4 Departamento de Engenharia Civil, Universidade Estadual Paulista UNESP Campus de Ilha Solteira, SP, Brasil a [email protected], b [email protected], c [email protected], d [email protected], e [email protected], f [email protected], g [email protected]Keywords: corn, elephant grass, leaves, silica, ash, phytolith Abstract. Many agrowastes are being used for energy production by combustion in thermal power plants. This process generates huge amounts of ashes, which have a potential pozzolanic activity for blending with Portland cement or hydrated lime. Elephant grass (Pennisetum purpureum) and corn straw (Zea mays) are two types of biomass whose ashes could be valorized in construction materials. The aim of the present research was to analyze the chemical composition of leaves and the corresponding ashes in terms of inorganic elements characterization (silicon, potassium, calcium, sodium, chloride,..). Microscopic studies (FESEM) on the dried leaves and the characterization of the ashes obtained at different calcination temperatures have been carried out. Energy dispersive X-ray spectroscopy (EDX) has been applied for quantifying the percentage of the main chemical elements. Elephant grass ashes (EGA) maintained the spodogram after calcinations at 450 and 650ºC. Silica (SiO 2 ) was the main oxide in EGA (55.7%); also CaO, MgO and K 2 O were in high percentage and chloride content was very low. In corn leaf ashes (CLA) the spodogram was maintained at 350 and 450ºC. Silica was also the main oxide (62.6%). The amount of K 2 O was also high (26.8%) and chloride content was significant (2.4%) which must taken into account for the use of CLA in concrete. Both ashes could be interesting for OPC-based blended cements because their potential pozzolanic properties. Introduction Supplementary cementing materials (SCMs) in the production of cements and concretes are widely studied by many researchers [1]. The key of their use is due, in many cases, to the presence of amorphous silica and alumina in the compositions of SCMs. These SCMs are usually obtained as byproducts or wastes from different human activities: industrial, agricultural, energetic and decontamination processes. Silica (SiO 2 ) and alumina (Al 2 O 3 ) amorphous phases are usually present and they reacts towards hydrated lime Ca(OH) 2 by means of the pozzolanic reaction: this is the reason because this type of SCMs are called pozzolans. This pozzolanic reaction yields hydraulic cementing products, similar to those found in the hydration of ordinary Portland cement
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MICROSCOPIC AND CHEMICAL CHARACTERIZATION OF ELEPHANT GRASS AND CORN LEAVES AND THEIR ASHES
Josefa Roselló 1,a, Lourdes Soriano2,b, Holmer Savastano Jr 3,c, María V. Borrachero 2,d,
Pilar Santamarina 1,e, Jorge L. Akasaki 4,f, Jordi Payá 2,g*
1 Departamento de Ecosistemas Agroforestales, Universitat Politècnica de Valéncia,
Valencia, Spain
2 Instituto de Ciencia y Tecnología del Hormigón (ICITECH), Universitat Politècnica de
València, Valencia, Spain
3 Departamento de Engenharia de Biossistemas, Faculdade de Zootecnia e Engenharia de
Alimentos, Universidade de São Paulo, Pirassununga, SP, Brazil
4Departamento de Engenharia Civil, Universidade Estadual Paulista UNESP Campus de
Keywords: corn, elephant grass, leaves, silica, ash, phytolith Abstract. Many agrowastes are being used for energy production by combustion in thermal power
plants. This process generates huge amounts of ashes, which have a potential pozzolanic activity for
blending with Portland cement or hydrated lime. Elephant grass (Pennisetum purpureum) and corn
straw (Zea mays) are two types of biomass whose ashes could be valorized in construction
materials. The aim of the present research was to analyze the chemical composition of leaves and
the corresponding ashes in terms of inorganic elements characterization (silicon, potassium,
calcium, sodium, chloride,..). Microscopic studies (FESEM) on the dried leaves and the
characterization of the ashes obtained at different calcination temperatures have been carried out.
Energy dispersive X-ray spectroscopy (EDX) has been applied for quantifying the percentage of the
main chemical elements. Elephant grass ashes (EGA) maintained the spodogram after calcinations
at 450 and 650ºC. Silica (SiO2) was the main oxide in EGA (55.7%); also CaO, MgO and K2O were
in high percentage and chloride content was very low. In corn leaf ashes (CLA) the spodogram was
maintained at 350 and 450ºC. Silica was also the main oxide (62.6%). The amount of K2O was also
high (26.8%) and chloride content was significant (2.4%) which must taken into account for the use
of CLA in concrete. Both ashes could be interesting for OPC-based blended cements because their
potential pozzolanic properties.
Introduction
Supplementary cementing materials (SCMs) in the production of cements and concretes are
widely studied by many researchers [1]. The key of their use is due, in many cases, to the presence
of amorphous silica and alumina in the compositions of SCMs. These SCMs are usually obtained as
byproducts or wastes from different human activities: industrial, agricultural, energetic and
decontamination processes. Silica (SiO2) and alumina (Al2O3) amorphous phases are usually
present and they reacts towards hydrated lime Ca(OH)2 by means of the pozzolanic reaction: this is
the reason because this type of SCMs are called pozzolans. This pozzolanic reaction yields
hydraulic cementing products, similar to those found in the hydration of ordinary Portland cement