Low Liquid-to-solid Ratio of Mining Waste and Slag Binary Alkali-activated Material

This study investigates the effect of the increasingly compressing pressures on the properties of the low liquid-to-solid (L/S) ratio binary alkali-activated binder to use as a binder for the manufacturing of engineered stones. The binders were a combination of two types of wastes (aluminosilicate source) as precursors (TMWM 50 Vt.% + EAF-Slag 50 Vt.%), blended with (11.11 wt.%) alkaline activator solution (NaOH/Na2SiO3 with weight ratio 4/1). The mixtures were molded in cube and exposed to five different pressures (20, 40, 60, 80 and 100 MPa) in order to obtain a compressed alkali-activated binder. The main evaluation techniques in this study were compressive strength, and Fourier Transform Infrared Spectroscopy (FTIR). The results showed that the maximum compressive strength (50.57 MPa) was obtained at a pressing pressure 100 MPa at twenty-eight days of testing

Preliminary Study of the Rheological and Mechanical Properties of Alkali-activated Concrete Based on Tungsten Mining Waste Mud

The rheological properties of Portland cement (PC) concrete have been extensively studied and compared with those of alkali-activated concrete (AAC). This study discusses the effect of the liquid to solid ratio on the rheological and mechanical properties of AAM concrete, based on mining waste mud as the binder phase, and compares them with those of Portland cement concrete (PCC). The AAM concrete studied is a mix of coarse aggregate 6/15, two types of sand (finer and coarse sand), and a precursor. The precursor is a mix of 70% tungsten mining waste mud, 15% waste glass and 15% metakaolin. This mix was activated by a combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) and the PCC was a mix of the same aggregate but with cement as binder and water as a liquid. The activator/precursor ratio was studied 0.5, 0.52, 0.54, 0.56 and 0.58. The results obtained show a similar rheological behaviour between AAC and PCC, the workability affected by L/S increases with the increasing ratio L/S in AAC and for L/S=0.5 slump was 6 cm and was 16 cm for L/S =0.58. Regarding the mechanical properties, the results obtained in 7 days showed similar performance in AAC and PCC. The compressive strength also decreases with the increasing of L/S, in AAC with L/S=0.5 the compressive strength was 15.9 MPa and for L/S =0.58 was 10.5. Keywords: Tungsten mining waste, Rheology, Mechanical properties, Portland cement, alkali-activated concret

Microstructure Features of Ternary Alkali-activated Binder Based on Tungsten Mining Waste, Slag and Metakaolin

This study determines the effect of ground granulated blast furnace slag (GGBFS) and metakaolin (MK) on the microstructural properties of the tungsten mining waste-based alkali-activated binder (TMWM). During this investigation, TMWM was partially replaced with 10 wt.% GGBFS and 10 wt.% MK to improve the microstructure of the binder. In order to understand the effect of the substitutions on the microstructure, two pastes were produced to make a comparative study between the sample contain 100% TMWM and the ternary precursors. Both precursors were activated using a combination of alkaline activator solutions (sodium silicate and sodium hydroxide) with the ratio of 1:3 (66.6 wt.% sodium silicate combined with 33.33 wt.% of NaOH 8M). The alkali-activated mixes were cured in oven at temperature of 60 °C in the first day and at room temperature for the next 27 days. The reaction products N-A-S-H gel and (N,M)-A-S-H gel resulted from the alkaline activation reaction process. In addition, a formation of natrite (Na2CO3) with needles shape occurred as a reaction product of the fluorescence phenomena. However, a dense matrix resulted from the alkline activation of the ternary precursors containg different gels such as N-A-S-H, C-A-S-H and (N,M)-C-A-S-H gel, these results were obtained through SEM-EDS analyses, as well FTIR tests. Keywords: Mining Waste, Alkali-activated, Microstructure, Slag, Metakaoli

Strength Development and Pore Structure Characterisation of Binary Alkali-activated Binder Based on Tungsten Mining Waste

The mineralogical properties of tungsten mining waste mud (TMWM) make its valorisation and re-usage as an alumino-silicate source material to produce an alkali-activated binder without calcination is a challenge. Moreover, the dissolution of silicate and alumina species from TMWM is very slow. Despite the crystallinity of TMWM, this study demonstrates that its combination with other sources of the alumino-silicate source was the materials–such as red clay brick waste(RCBW),ground granulated blast furnace slag (GGBFS) and electric arc furnace slag (EAFS) – improved the compressive strength and the pore structure of the alkali-activated matrix.Thecombinedprecursors (90 vt.%TMWM+10 vt.%RCBW, 90 vt.%TMWM+10 vt.%GGBFS, and 90 vt.%TMWM+10 vt.%EAFS) were activated using a combination of alkaline activator solutions (sodium silicate and sodium hydroxide) with the ratio of 1:3(66.6wt.%sodiumsilicatecombined with 33.33 wt.% of NaOH 10M). The results show that the compressive strength increased from11.23MPa at 28 days to reach 24.98MPawhentheTMWMwaspartially replacedby10vt.%RCBW. In addition,this study shows that the interconnected porosity decreased where the critical pore size was reduced from 21.28 µm to 0.55 µm for the tungsten mining waste-based alkali-activated binder and the binary alkali-activated binder based on TMWM and RCBW. Keywords: Mining Waste, Alkali-activated, Microstructure, MIP, Metakaoli

Early Age Compressive Strength of Waste-based-glass-powder Magnesium Silicate Binders on Initial Carbonation Curing

In this preliminary study, the effect of glass powder content at early age compressive strength and its effect at strength retention coefficient during water immersion period on magnesium silicate hydroxide cement pastes on carbonation curing was investigated. A magnesium oxide-rich powder with a maximum grain size of 150 μm was used, as well as, a waste glass powder with a maximum grain size of 250 μm, which was obtained from grinded flint glass bottles. Cement pastes were produced with 0, 10, 20, 30, 40, and 50 glass powder weight percentage. The specimens were compacted into cubic moulds (e = 20 mm) under 70 MPa and, subsequently, cured on accelerate carbonation chamber for 2h at >99% CO2 concentration. The compressive strength was determined 3 days after CO2, period which the specimens were preserved on room conditions (20∘C and 60%RH), and also at 3, 7 and 14 days of water immersion period. Comparison of the results obtained for different mixing compositions, as well as, different water immersion periods are discussed in this work

Preliminary Study on the Influence of Different Carbonation Curing Processes on Binders Based on Magnesium Oxide-Rich Powder Blended with Tungsten Mining Waste Mud

In this preliminary study, the effect of the pre-drying stage, water immersion, carbonation curing cycles, and/or drying stage on carbonation curing of magnesium oxide-rich powder (MRP) was investigated. In addition, a blend of tungsten mining waste mud (TMWM) with MRP was also evaluated. The MRP and TMWM used have maximum grain sizes of 125 μm. The cement pastes were produced with 0 and 50 of TMWM weight percentage. The specimens were compacted into cylindric moulds (∅ = 20 mm; h = 40 mm) under 30 MPa and, subsequently, submitted to five different processes of curing involving a pre-drying stage before carbonation, rapid water immersion cycles, additional drying periods, and different carbonation curing periods. The atmosphere of the pressurized carbonation curing chamber was controlled to provide  a  CO2 concentration of > 99%, the partial pressure of 1 bar and temperature of 60°C. The influence of the curing processes on the compressive strength of each mix was determined 12 hours after the carbonation curing period. This study demonstrates that the water content during the curing process plays an important role in the increase of the hardening process and on the compressive strength. Keywords: Carbonation curing, magnesium oxide, mining waste, curing processes, magnesium-based cemen

Monitoring of Reinforced Concrete for Decision Support in Maintenance Management Systems

The goal of this study is to collect and validate relevant information on the degradation of reinforced concrete exposed to aggressive environments, such as chlorides or sulfates, for later incorporation in maintenance management systems compatible with the BIM methodology (Building Information Modeling). To achieve this, two simultaneous monitoring systems were used, one that allows measuring the ionic resistivity of the concrete and another that measures the corrosion potential and polarization resistance of the reinforcement. With the first monitoring system, it is intended to monitor the changes occurring in the concrete at the level of its ionic conductivity during the contamination process. The second system allows, at a later stage of the concrete degradation process, to detect signs of corrosion of the reinforcement inserted therein. Both systems provide readings at 10mm and 30 mm depth measured from the face exposed to the action of the degradation agents. The results obtained for chloride contamination show that the ionic resistivity of the concrete tends to decrease with the progression of the chlorides in depth, leading at a later stage to the corrosion of the reinforcement, which can be detected by the reduction of corrosion potential. Also, the polarization resistance of the reinforcement has been reduced when corrosion phenomena begin to develop in the reinforcement. The results related to the sulfate attack suggest a mechanism that leads to the formation of a barrier that prevents the progression of the attack in depth. The consequence of this phenomenon is a reduction of the ionic mobility of the concrete, leading to the increase of resistivity. This mechanism associated with the absence of mechanical actions that force the progression of sulfates in depth inhibits the development of corrosion processes of the reinforcement

Deploying Smart Community Composting in Estrela UNESCO Global Geopark: A Mobile App Approach

Community composting is a key pillar of circular economy and sustainable food production. This paper presents the development of a regional composting network in Estrela UNESCO Global Geopark, using mobile technologies and geographic information systems. This design science research project presents the community composting model and the instantiation of a mobile solution layer. For theory, this paper reveals the concept of smart community composting inspired by the 5.0 movement expanding in society, cities, and industries. For practice, this work presents a mobile information system tailored for UNESCO Geoparks and their recently created GEOFood brand to promote sustainable production practices

Estudo experimental de soluções de reabilitação térmica

As habitações rurais são, em geral, constituídas com materiais tradicionais, pedra e madeira, e apresentam um fraco comportamento térmico e higrométrico. Por outro lado, este tipo de habitação encontra-se em geral degradado, tornando-se necessário estudar soluções para reabilitar coberturas (estruturas de madeira), paredes (alvenaria de pedra) e pavimentos (madeira), melhorando a sua impermeabilização e conforto térmico, bem como, estudar metodologias adequadas para a reabilitação de construções com as características indicadas

International Open Innovation Strategies of Firms in European Peripheral Regions

The involvement of companies in different open innovation activities, through knowledge outputs and inputs, has become increasingly important for the success of companies. However, the existing literature on open innovation is scarce concerning the internationalization process of companies. The internationalization of companies is fundamental in the continuous search to increase the performance of companies externally. The objective of the present research is to explain the strategic processes in the internationalization of companies located in peripheral regions at the time of the COVID-19 pandemic from the perspective of dynamic capabilities. The sample used for this research is composed of seven Portuguese companies. The methodology of qualitative nature is exploratory and uses a case study approach. Regarding the foremost modes of operation in international markets and strategies, we find that (1) companies have partnerships with local distributors or appoint exclusive importers/distributors, and (2) companies prefer to place their products in the market through their brand, “co-branded” projects with retailers, or “private label” projects. Of the seven companies under study, six use a standardization strategy, and one opts for a configuration-coordination strategy. Our findings clarified the literature on export and internationalization strategies in a peripheral country, allowing a closer incept of the organizational and dynamic capabilities and an overview of the supporting tools these companies have to compete in the global market. Our study is original because few articles study the internationalization strategies of companies at the time of the COVID-19 pandemic and in peripheral regions of Europe.info:eu-repo/semantics/publishedVersio