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•Production of compound MgO expansive agent (CMEA) using dolomite & serpentine.•Investigate the hydration process and macroscopic properties of CMEA.•Shrinkage-compensating concrete ...made by 20% CMEA generates enough volume expansion.
Ordinary MgO expansive agent is produced by calcining magnesite, a valuable and not abundant mineral. The objective of this paper is to propose a new method to produce a compound MgO expansive agent (CMEA) by calcining the mixture of dolomite and serpentine, both cheap tailings. The calcium in dolomite combines with the silicon in serpentine to form C2S, while magnesia in these two minerals is left out to act as expansive composition. The composition and microstructure of the clinkers were investigated by X-ray diffraction (XRD)-Rietveld quantitative analysis, X-ray fluorescence (XRF), second electron image (SEI) and backscattered electron image (BSEI) of scanning electron microscopy (SEM). The hydration process of CMEA was investigated by isothermal calorimetry. The expansive and mechanical properties of mortars containing CMEA were also investigated. Results indicate that the reaction of dolomite and serpentine is based on the contact of solid phase, the generating quantity of MgO and C2S in the CMEA clinker increases, but the hydration activity of CMEA decreases with the rise of calcining temperature during the range of 950℃~1150℃. Incorporating 20% CMEA into cement decreases its mechanical strength slightly, but generates a volume expansion significantly. The expansion rate and speed of mortars containing CMEA is controlled by the calcining temperature of CMEA clinker. For common concrete components, the preferential calcining temperature of CMEA clinker should be in the range of 1050℃-1150℃ to ensure an efficient expansive ability of CMEA.
This article analyses Mozambique's failed campaign to join the Council for Mutual Economic Assistance (CMEA). It explores the motives and strategies of the Mozambican politicians who led the campaign ...and the reactions of planners and politicians in Eastern Europe, embedding them in a longer history of their bilateral and multilateral economic relations and the various steps before, during and after the accession campaign from the 1960s to the late 1980s. The dynamics in this debate shed light on the CMEA's transition from geographical expansion to stagnation and the broader shift from visions of economic convergence to an acceptance of divergence.
This article analyses Cold War Romania's conceptualization of its relations with the European Economic Community (EEC) and its struggle to influence the policy of the Council for Mutual Economic ...Assistance (CMEA) towards the EEC in a way compatible with Bucharest's interests. Addressing a significant historiographical gap, in a sense, this study investigates the origins of Romania-EU relations. Multi-archival in approach, it argues that the period between 1969 and 1974 represents the formative years of Romania-EEC relations. Exploring the political rationale behind Romania's attitude towards the Common Market, the article finds that the country's 'strategy' in this respect had three main characteristics: it was pragmatic, active and, to some point, adaptive; drawing heavily from Romania's previous position, it took shape in the early 1970s; and, although it seemed to focus on the commercial aspects of relations, it reflected a far more complex interaction between the two political and social systems than previously acknowledged.
This article examines Romania’s opposition to the attempts of the Council for Mutual Economic Assistance (CMEA) in the early 1970s to adopt a common trade policy towards the European Economic ...Community (EEC). The article covers the period between 1969, when the CMEA embarked on negotiations regarding the deepening of the intra-bloc cooperation and integration, and 1 January 1973, which is the date marking the end of the derogations that the Eastern European states received with regard to the implementation of the EEC’s Common Commercial Policy. The article focuses on Romania’s reasons and tactics of opposition, but it also outlines its views with regard to the EEC, in general, and the CMEA-EEC relations, in particular. Corroborated by findings involving studies in other Eastern European archives, this article will help to create a better understanding of the CMEA debates on integration, on the CMEA-EEC relations, in general, and on Romania’s opposition to the CMEA’s intended common policy towards the EEC, in particular.
Dynamic multiobjective optimization problems (DMOPs) widely appear in various real-world applications and have attracted increasing attention worldwide. However, how to obtain both good population ...diversity and fast convergence speed to efficiently solve DMOPs are two challenging issues. Inspired by that the multiple populations for multiple objectives (MPMO) framework can provide algorithms with good population diversity and fast convergence speed, this paper proposes a new efficient algorithm called a co-evolutionary multi-population evolutionary algorithm (CMEA) based on the MPMO framework together with three novel strategies, which are helpful for solving DMOPs efficiently from two aspects. First, in the evolution control aspect, a convergence-based population evolution strategy is proposed to select the suitable population for executing the evolution in different generations, so as to accelerate the convergence speed of the algorithm. Second, in the dynamic control aspect, a multi-population-based dynamic detection strategy and a multi-population-based dynamic response strategy are proposed to help the algorithm maintain the population diversity, which are efficient for detecting and responding to the dynamic changes of environments. Integrating with the above strategies, the CMEA is proposed to solve the DMOP efficiently. The superiority of the proposed CMEA is validated in experiments on widely-used DMOP benchmark problems.
In aqueous anionic sodium lauryl ether sulfate (SLES) solution, presence of nonionic cocamide monoethanolamine (CMEA) depicts intriguing interfacial and bulk properties. CMEA has poor water ...solubility but can be readily solubilized in SLES solution to form mixed micellar aggregates as revealed by surface tension measurements. Sphere-to-rod micellar transition in aqueous SLES-CMEA binary mixtures occurs at higher surfactant concentration (total surfactant concentration beyond 15 wt%), inducing a sharp growth in the viscosity (>1000 cP). Nevertheless, adding NaCl in SLES-CMEA mixtures, substantial growth in viscosity is perceived at much lower surfactant concentration (~5–10 wt%) attributed to the formation of intertwined worm-like micelles. Micellar sizes were obtained by dynamic light scattering (DLS) measurements and small-angle neutron scattering (SANS) investigations is used to determine micellar shapes and aggregation number for SLES-CMEA mixtures. Furthermore, it is observed that foaming behavior of SLES can be modulated by CMEA ascribed to the change in foam film rigidity. Corresponding experiments were also performed with nonethoxylated counterpart sodium lauryl sulfate (SLS) under analogous condition for comparison. The study reported here may prove to be an appropriate tactic to alter not only the rheology or foaming behavior of SLES-CMEA mixed surfactant system but also provide pre-solubilized composition of CMEA which could be highly beneficial for personal care products enabling CMEA blending at room temperature, which otherwise needs high temperature mixing.
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•SLES-CMEA in NaCl depicts intriguing interfacial and rheological properties.•The formulations are useful in preparation of cosmetic compositions.•Suitable tactic to amend rheology or foaming behavior of SLES-CMEA in NaCl.•Provide pre-solubilized CMEA highly beneficial for personal care products.
AbstractAs a potential long-life pavement material, the high brittleness of epoxy asphalt prevents its application. Recycled from waste tires, crumb rubber (CR) can be used with ...styrene-butadiene-styrene (SBS) to prepare SBS/CR composite modified asphalt. The main objective of this paper is to conduct the material design of epoxy asphalt with SBS, CR, and core-shell rubber (CSR) to toughen the epoxy asphalt and enhance its performance. First, SBS modified epoxy asphalt and SBS/CR composite modified epoxy asphalt (CMEA) were prepared to optimize the toughening materials based on tensile tests. Subsequently, based on the optimized material, the optimal proportion was determined through the response surface method by the Design-Expert software. Third, the microscopic morphology of different epoxy asphalt was observed by laser scanning confocal microscopy (LSCM), and the changes in functional groups were tracked using Fourier transform infrared spectroscopy to reveal the toughening mechanism. Finally, the viscosity test was carried out on the optimal SBS/CR-CSR CMEA at different temperatures to determine its mixing temperature and allowable time. The results show that the SBS/CR-CSR CMEA is the best toughening method, and the optimal epoxy and CSR proportion is 37% and 12%, respectively. Its tensile strength increases by 467.11% and elongation at break increases by 68.73% compared with unmodified epoxy asphalt. The formation of interpenetrating polymer network structure between the SBS/CR network and epoxy resin network, as well as the change in the benzene ring that determines the softness and toughness, may be the main strengthening and toughening mechanisms. The suitable mixing temperature is 160°C for the optimal SBS/CR-CSR CMEA in this paper, which reduces about 20°C compared with conventional CR or SBS/CR composite modified asphalt, providing better environmental benefits. Overall, the SBS/CR-CSR CMEA presents a new solution for the promotion and application of epoxy asphalt.
