Durability and Microstructural Behavior of Nano Silica-Marble Dust Concrete

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The Effect of Elevated Temperature on Engineered Cementitious Composite Microstructural Behavior: An Overview

This paper discusses the quantitative bibliographic data derived from scientific publications on Engineered Cementitious Composites (ECC) subjected to elevated temperature, the influence of elevated temperature on the mechanical properties, particularly the compressive strength and microstructure behavior of Engineered Cementitious Composites (ECC) mixtures based on the review of previous pieces of literature. Systematic literature reviews were employed as the methodology in this study. The age of related publications selected to be reviewed was limited to publications for the past ten years, 2010 to December 2020. It was found from available research that exposure of the ECC specimen at the elevated temperature starting from 200oC significantly reduced the compressive strength when the temperature increases, melting of fiber and increase of porosity causes the dramatically increase micro-cracks.

Mechanical and microstructural behavior of concrete containing marble and nano silica

Purpose The purpose of this study is to perform comprehensive investigation to assess the mechanical properties of nano-modified ternary cement concrete blend. Nano silica (NS) (1%, 2% and 3%) and waste marble dust powder (MD) (5%, 10% and 15%) was incorporated as a fractional substitution of cement in the concrete matrix. Design/methodology/approach In this experimental study, 10 cementitious blends were prepared and tested for compressive strength, flexural strength, splitting tensile strength and static modulus of elasticity. The microstructural characteristics of these blends were also explored using a scanning electron microscope along with energy dispersive spectroscopy and X-ray reflection. Findings The results indicate an enhancement in mechanical properties and refinement in pore structure due to improved pozzolanic activities of NS and the filling effect of MD. Originality/value To the best of the authors’ knowledge, no study has reported the mechanical and microstructural behavior of concrete containing marble and NS.

INVESTIGATION ON PREPARATION, CHARACTERIZATION AND PROPERTY EVALUATION OF FGM AL-SI ALLOY CASTINGS PRODUCED BY CAST-DECANTCAST (CDC) PROCESS

Aim of this research paper is to study the microstructural behavior and mechanical properties of Functionally Gradient (FG) layer of Al-Si alloy castings produced by CDC process. The effect of decantation time on the thickness of functionally gradient castings of Al-4.5 wt % Si alloy as an inner layer and Al-Si alloy with 12.5 wt %Si as outer layers was studied by CDC process. The three different combinations of FGM castings were characterized for microstructural and wear behavior using metallurgical characterization and mechanical testing. From the microstructural and wear behavior of FGM casting at outer layer, FG layer and inner layer, it is observed that the FG layer of FGM casting showed very wear resistance compared to other two layers in the FGM casting.

Influence of the Increase in Aluminum Concentration on the Microstructural Behavior and Hardness of a Cu-Al Alloy (ASTM B-824)

In this work, the effect of the increase in the concentration of aluminium (Al) on the microstructure and the hardness of bronze to aluminium was studied using optical emission spectrometry, scanning electron microscopy, dispersion spectroscopy techniques of energy, conventional optical microscopy and hardness tests. Alloys with three concentrations by weight of aluminium (Cu-4.5 wt.% Al, Cu-7 wt.% Al and Cu-10 wt.% Al) were studied, with the chemical parameters established in the (ASTM B-824), were manufactured and cast in a permanent mold according to the standard (ASTM B-208), to determine the influence of the chemical concentration of aluminium the response surface methodology was used. It was observed that bronzes with a content of 4.5 wt.% Al and 7 wt.% Al, remain with a constant microstructure of phase α, and bronzes of 10 wt.% Al, undergo a change from monophasic to biphasic microstructure (α + β) evidencing the appearance of a martensitic microstructure similar to steels providing a better behaviour to resistance to indentation. It is concluded that the increase in the concentration of Al, in the Cu-Al alloy, presents a microstructural change, and the appearance of a β and β 'phase generates a better property in hardness, the hardness has a behaviour k proportional to the aluminium concentration obtaining 53 Brinell value for an increase in the concentration of 5.5 wt.% Al. Keywords: alloy, microstructure, bronze, spectrometry, spectroscopy. Resumen En el presente trabajo, se estudió el efecto del aumento de la concentración de aluminio (Al) sobre la microestructura y la dureza del bronce al aluminio, mediante el uso de espectrometría de emisión óptica de chispa, microscopia electrónica de barrido, técnicas de espectroscopia de dispersión de energía, microscopia óptica convencional y pruebas de dureza. En la investigación se estudiaron aleaciones con tres concentraciones en peso de aluminio (Cu-4,5 wt.% Al, Cu-7 wt.% Al y Cu-10 wt.% Al), con los parámetros químicos establecidos en la norma (ASTM B-824), fueron fabricadas y coladas en un molde permanente de acuerdo con la norma (ASTM B-208); para determinar la influencia de la concentración química del aluminio se usó la metodología de superficie de respuesta. Se observó que los bronces con un contenido de 4,5 wt.% Al y 7 wt.% Al, permanecen con una microestructura constante de fase α, y los bronces de 10 wt.% Al, sufren un cambio de microestructura monofásica a bifásica (α+β) evidenciando la aparición de una microestructura martensítica similar a los aceros aportando un mejor comportamiento a la resistencia a indentación. Se concluye que el aumento en la concentración de Al, en la aleación Cu-Al, presenta un cambio microestructural, y la aparición de una fase β y β’ genera una mejor propiedad en la dureza, la dureza posee un comportamiento k proporcional a la concentración de aluminio obteniendo en valor de 53 Brinell para un incremento en la concentración de 5,5 wt.% Al. Palabras claves: aleación, microestructura, bronce, espectrometría, espectroscopia.