Supplementary cementitious materials are considered a viable and affordable way to reduce CO₂ emissions from the cement industry’s perspective since they can partially or nearly entirely replace ordinary Portland cement (OPC). This study compared the impact of adding spent coffee grounds (SCGs), fly ash (FA), and volcanic ash (VA) to two types of cement: OPC and calcium sulfoaluminate cement (CSA). Cement samples were characterized using compressive strength measurements (up to 210 days of curing), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy, and hydration temperature measurements. In all the studied systems, the presence of SCGs reduced compressive strength and delayed the hydration process. CSA composite cement containing 3.5% SCGs, 30% FA, and 30% VA showed compressive strength values of 20.4 MPa and 20.3 MPa, respectively, meeting the minimum requirement for non-structural applications. Additionally, the results indicate a formation of cementitious gel, calcium silicate hydrate (C-S-H) in the OPC-based composite cements, and calcium alumino-silicate hydrate (C-A-S-H) as well as ettringite in the CSA-based composite cements.

In this paper, the analysis of electrochemical corrosion performance and mechanical strength of weld joints of aluminum 6061 in two-heat treatment conditions was performed. The joints were produced by gas metal arc welding in pulsed mode. The original material exhibited precipitates of $\beta$ and $\beta$” phases in a volume fraction (Vf) of 2.35%. When it was subjected to a solubilization process, these phases were present in a Vf = 2.97%. This increase is due to their change in shape and distribution in clusters within the aluminum matrix. After the welding process, the best sample in the solubilization condition reached 117 MPa, while the original material achieved 104 MPa, but all samples showed a fracture in the fusion zone. This is attributed to the heat input that produces high and low hardness zones along the heat-affected zone and the welding zone, respectively. Moreover, the change in microstructure and phase composition creates a galvanic couple, susceptible to electrochemical corrosion, which is more evident in the heat-affected zone than in the other weld regions, exhibiting uniform and localized corrosion, as was evident by electrochemical impedance spectroscopy. The heat from the welding process negatively affects the corrosion resistance, mainly in the heat-affected zone.

La microestructura y propiedades mecánicas del Inconel 718 fueron estudiadas bajo el tratamiento térmico estándar solución + envejecido (SE), el tratamiento térmico estándar homogenizado + solución + envejecido (HSE) y el metal base. La precipitación de fases y microestructuras fueron examinadas usando métodos de análisis como microscopía óptica (MO), microscopía electrónica de barrido (SEM) y difracción de rayos X (DRX). El tamaño promedio de grano del metal base es 9 según la norma ASTM E-112 acompañado con partículas de carburos tipo MC. Después del tratamiento térmico estándar SE, solamente una porción de recristalización ocurre y la mayoría de los granos permanecen finos, con un tamaño promedio de 4.64 m. En comparación con el tratamiento HSE, donde ocurre recristalización y crecimiento de grano, con un tamaño promedio de 32 mm; además se disuelve la fase Laves dentro de la matriz austenitica para precipitar fases de endurecimiento y algunas partículas de fase delta ((d). La fase d en el tratamiento SE precipita por un mecanismo de corte con un tamaño promedio de 0.72 mm en comparación con 2.39 mm obtenido con el tratamiento HSE. Se observó poca variación en la microdureza después del tratamiento térmico HSE comparado con las muestras del tratamiento SE, donde una pequeña disminución (⁓1) está presente.