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Hands-on STEM in Ghana: Inspiration for Culturally Relevant Pedagogy Globally
No full textMany educators are increasingly seeking culturally relevant pedagogies they can employ to effectively engage their students. In Ghana a substantive set of hands-on STEM content has been created, incorporating locally available materials and cultural approaches while maintaining alignment to the national curricula. Against a backdrop of almost no public primary or junior high schools in the country containing any lab equipment, this approach leverages and celebrates the abundance of what is available within the locality. This challenges narratives of what is considered “good” and recenters power back with those in the classroom. Three sample activities and three firsthand stories are used to depict how this approach enhances academic success, cultural competence, and sociopolitical consciousness among students. Educators should look to their counterparts in Africa for inspiration in developing culturally relevant pedagogies for Black students globally
The E-Strip® As A Tool For Predictive Maintenance To Monitor And Control Shot Peening Processes
No full textThe primary objective of this paper is to demonstrate the E-Strip® is capable of providing real-time feedback to the machine controller for making necessary process adjustments due to external forces, such as machine wear. Adjustments may include regulating air pressure and shot flow within pre-defined tolerances dictated by specification. It is anticipated that this integrated approach will significantly reduce variations in intensity levels observed from part to part and lot to lot
Investigation Of Topography Changes Of Blasted Surfaces: An Experimental Perspective Using Fiducial Markers
No full textAbrasive blasting is a process that intentionally modifies surface topography to meet specific functional requirements. The blast media is accelerated and interacts directly with the surface through impact. It is evident that the number of impacts and the overlap increase with time. This study aims to investigate these alterations to surface topography through repeated examinations of the same location. A methodology has been developed that employs the use of fiducial markers, which are protected during blasting by a custom 3D-printed cover. This method was used to observe changes in the topography of smooth and rough initial surfaces that had been blasted. Furthermore, the evolution over time has been analysed. It is evident that the developed method has enabled these alterations to be observed
Origin And Interpretation Of Psi-Splitting And Out Of Plane Shear Stress When Using Diffraction Techniques
No full textPsi-splitting is a phenomenon often observed in interplanar d-spacing vs. sin²ψ plots during the analysis of residual stress measurement data when employing the X-ray diffraction (XRD) method. Deviations from the expected linear relationship between interplanar d-spacing and sin²ψ are typically caused by the presence of out-of-plane shear stresses or inhomogeneous stress distributions within the measured phase of the material. In such cases, the d-spacing values measured at different ψ tilt angles deviate from the anticipated linear trend, resulting in a characteristic splitting of the d-spacing vs. sin²ψ plot data, where the shape of the data in the plot takes the form of an ellipse. When this occurs, the stress state in the material cannot be accurately described by a simple biaxial stress model, necessitating a more comprehensive analysis to account for the triaxial nature of the stress field and to accurately calculate the components of the stress tensor. Most critically, the presence of non-zero out-of-plane shear stresses directly affects the accuracy of the normal and shear stress tensor components being determined in the plane of the measurement. Psi-splitting typically occurs in inhomogeneous and multiphase materials subjected to cold working processes such as machining, shot peening, or other surface treatments.
This paper aims to explain the origin and mechanism of Psi-splitting, detailing how it occurs and how it should be interpreted in single and multiphase materials. It also seeks to bridge the gap between materials scientists and mechanical engineers. It is important to note that this phenomenon does not alter the biaxial macroscopic stress state of the material, and that the boundary conditions at the surface remain valid because the overall effect is balanced at the macroscopic level if all constituent phases present in the material are considere
Hydrogen Embrittlement In Shot-Peened Steel
No full textThis work investigates the role of shot peening on hydrogen embrittlement resistance in quenched and tempered 1070 steel. Thermal desorption spectroscopy results revealed that shot-peened specimens contained nearly twice the hydrogen (H) content of unpeened samples when charged under the same electrochemical conditions, suggesting the introduction of additional trapping sites occur during peening. The mechanism underlying this behavior can be associated with increased dislocation density and is more consistent with the HELP mechanism. Residual stress measurements show a significant relaxation of compressive stresses in shot-peened specimen after H charging, indicating H enhanced dislocation rearrangement. Both unpeened and peened specimens exhibited reduced ductility and strength after H charging; however, the peened samples demonstrated a smaller reduction (72.6% vs 55.8%). Despite higher overall H uptake, the shot-peening reduced susceptibility to embrittlement as compared to the unpeened condition
Change in Property of Hardened Cement Specimens Having Different Mineral Composition Cured in High Concentration CO2 from the Very Early Material Age
No full textWe conducted research of CO2 capture behavior and rate of CO2 diffusion into hardened cement specimens of different pre-curing period before starting accelerating carbonation curing for ordinary portland cement (herein after OPC), OPC mixed with ground granulated blast furnace slag (herein after BB), and OPC mixed with an amorphous calcium aluminate-based accelerator (hereinafter ACC) respectively. We prepared two-type of hardened cement specimens, the first was in the case of powder shape hardened cement paste specimen which is designed to avoid carbon dioxide diffusion’s influence as much as possible and to evaluate fixation capacity of CO2, as a result CO2 content increases with getting pre-curing period longer in any cases after accelerating carbonation curing. The other one was in the case of balky mortar specimens which evaluated carbon dioxide diffusion, carbon dioxide diffusion got slower with getting pre-curing period longer in the case of OPC, BB, however ACC’s CO2 diffusion was almost constant even pre-curing period is different. The mineral composition and hydrate before carbonation differed by difference of cement type. Phase diagram after carbonation was also changed. In fact, More vaterite was formed with getting pre-curing period longer in any case, especially its phenomenon was remarkable in ACC system
Deep Decarbonization of UHPC Using Carbonated Steel Slag
No full textElectric arc furnace (EAF) slag was carbonated using an aqueous solution approach with a liquid-to-solid mass ratio of 10:1, under an environment of 99.9% purity CO2 and 2 bar pressure. The carbonated EAF was used to partially replace cement to develop low-carbon ultra-high performance concrete (UHPC) binder. The compressive strength of UHPC binder was marginally reduced by less than 5% up to a substitution level of 50%, after which a significant reduction of 23.68% was observed
Characterization of local 2:1 clays for utilization in limestone calcined clay cements
No full textAs calcined clays are gaining prominence as supplementary cementitious materials (SCM), demand for kaolinite-based 1:1 clay has surged, especially for Limestone Calcined Clay Cements (LC3). However, the potential of readily available 2:1 clay remains underexplored. Clays vary in composition, microstructure, and reactivity, with most becoming viable SCMs when activated. This study characterizes three local 2:1 clays in India against pure kaolinite to assess their suitability for LC3. Clays were characterized based on geotechnical properties, XRD and thermogravimetric analysis. Based on the TGA analysis, the dehydroxylation temperature for each clay was ascertained and calcined accordingly. The reactivity of the calcined clays was assessed by the Strength Activity Index (SAI). The blended cements with local 2:1 clays seemed to gain strength with an increase in age despite the poor early-age strength
Calcium Sulfoaluminate-Belite Cement Production using Industrial Wastes
No full textThis study explores the development of calcium sulfoaluminate-belite (CSAB) cement using alternative raw materials such as low-CaO limestone and red mud, aiming to reduce cost and environmental impact. CSAB clinkers were synthesized, and the mineralogy and mechanical performance were assessed. The findings demonstrate that CSAB cement with comparable phase composition and mechanical performance to commercial variants can be achieved, supporting the feasibility of sustainable raw material utilization
Improving Workability of Recycled Cement Pastes
No full textLaboratory produced cement stone was reactivated through thermal treatment at 650°C. Superplasticizers added to improve flowability of reactivated cement pastes and reduce their water demand