Long-Term Behavior and Durability of Alkali-Activated Clay Mortars

The need to increase the durability of clay-based materials, due to their inherent low strength and vulnerability in contact with water, led researchers to examine different options. In this paper, clay mortars were produced using four different activating solutions. Alkali hydroxides, alkali carbonates, and alkali silicates activating solutions were used. Interest is given to long term properties while their behavior to wetting–drying and freeze–thaw cycles is recorded. In total, the results of the experiments indicated the positive effect of the potassium metasilicate on mechanical characteristics presenting, however, low performance at wetting–drying. The combination of sodium metasilicate with sodium hydroxide solution has also presented a positive effect on both mechanical and physical properties. In contrast, sodium carbonate acted better in enhancing physical properties and granting water-resistant abilities. Moreover, the performance of the specimens mixed with water–glass addition presented excellent volume stability and low mass loss in durability tests.

Design & Implementation of an Automated Protective Film Applying Machine for the Aluminum Fabrication

- Aluminum is the third most abundant element in the nature and extrusion is valuable due to commercial fenestration and manufacturing products. Aluminum profiles are causing severe damage during the fabrication and installation process. Sawing, drilling, and tapping are the most common mechanical damages cause in aluminum profiles when subjected to the organic coating. Aluminum is interacting with the Alkali Hydroxides (Ca(OH)2, NaOH, KOH, RbOH, and CsOH) during the cement-based installation process [1]. There are several companies that involving to the manufacturing of aluminum profiles in Sri Lanka. In Sri Lanka, the film applying process of aluminum profiles is carried out by human hand. Due to this problem, companies are looking for solutions to minimize time consumption and cost. The aim of this study is to find a possible solution and design a machine to protect the surface of the aluminum profiles. The objective is to minimize the time consuming and cost-effective method for the film application process. The system was tested with different profile shapes and results were analyzed with the existing manual method. We observed that the designed machine was 87.04% more efficient than the manual existing method in Sri Lanka.

Green Process for Industrial Waste Transformation into Super-Oxidizing Materials Named Alkali Metal Ferrates (VI)

The investigation presented here features the design of a cleaner and greener chemical process for the conversion of industrial wastes into super-oxidizing materials. The waste of interest is the iron sulfate heptahydrate (FeSO4·7H2O) mainly generated through the sulfate route used for titanium dioxide industrial production. The products of this transformation process are alkali ferrates (A2FeO4, A = Na, K) containing iron in its hexavalent state and considered as powerful oxidants characterized by properties useful for cleaning waters, wastewaters, and industrial effluents. The proposed process includes two steps: (i) The first step consisting of the pre-mixing of two solids (AOH with FeSO4·xH2O) in a rotary reactor allowing the coating of iron sulfate in the alkali hydroxides through solid–solid reactions; and (ii) the second step involves the synthesis of alkali ferrates in a fluidized bed by oxidation of the single solid obtained in the first step in diluted chlorine. The chemical synthesis of alkali ferrates can be carried out within a timeframe of a few minutes. The usage of a fluidized bed enhanced the energy and mass transfer allowing a quasi-complete control of the ferrate synthesis process. The alkali ferrate synthesis process described here possesses many characteristics aligned with the principles of the “green chemistry”.

Influence of the Quartz Deformation Structures for the Occurrence of the Alkali–Silica Reaction

Defects in the crystalline structure of quartz facilitate the connection with the alkali hydroxides, since under a high alkalinity condition (e.g., in concrete), the Si-O bonds of quartz are easily broken. This study set out to investigate the influence of the deformation structures of quartz on its susceptibility to the alkali–silica reaction. A granite, a protomylonite, and a mylonite were selected for this study. Using optical microscopy, the quartz grains contained in these rocks were quantified and their texture characterized. The quartz samples extracted from the rocks were analyzed by magnetic nuclear resonance, to evaluate their potential for dissolving silica as well as changes in their atomic scale before and after the reaction with alkali hydroxides. These analyses were compared with the results of the accelerated mortar bar test. The study showed that the quartz with intense undulatory extinction and deformation bands denotes the most favorable condition to the development of the alkali–silica reaction. However, on an atomic scale, the slightly deformed grains were highly prone to react. Thus, in a high alkalinity condition, over a long period of time, any quartz tends to develop the alkali–silica reaction, regardless of the deformation degree of the grain.

Phase transformation from α-Fe2O3to Fe3O4and LiFeO2by the self-reduction of Fe(iii) in Prussian red in the presence of alkali hydroxides: investigation of the phase dependent morphological and magnetic properties

A simple surfactant and calcination free phase transformation from hematite to magnetite and lithium ferrite with a number of different morphologies was obtained.

Acceleration and improved control of aqueous RAFT/MADIX polymerization of vinylphosphonic acid in the presence of alkali hydroxides

The effect of adding various alkali hydroxides to the conventional and reversible RAFT/MADIX radical polymerizations of vinylphosphonic acid (VPA) has been investigated.