Papers by Keyword: Alkali-Activated

Abstract: The paper summarizes partial results of a study of degradation of materials based on alkali-activated blast-furnace slag (AAS) and comparative on cement CEM III/A 32.5 R after exposure to aggressive environments. It further specifies the possibilities for utilising destructive and non-destructive techniques to determine the progress of degradation and characterizes the degree of their correlation. After 28 days of ageing in a water environment, the produced test specimens (40×40×160 mm beams) were placed in aggressive media (ammonium nitrate solutions; sodium sulfate, rotating water) and after subsequent 28, 56 and 84 days of degradation were subjected to testing. Testing comprised both a destructive form (determination of compressive strength and flexural strength) and a selected non-destructive technique (Impact-echo method). The partial outputs were supplemented by the results acquired from monitoring weight changes. In addition, the development of Ultrasonic Pulse Velocity in relation to the progress of the degradation processes was also monitored. While the exposure of both test specimens to water and sodium sulfate did not result in any significant changes, the exposure to the ammonium nitrate solution exhibited rapid signs of degradation associated with a significant reduction in functional characteristics.

Abstract: The paper deals to create alkali activated composite based on the recipe of high-strength concrete. The paper includes the review of conditions for high-strength concrete proposing and preparation. Principles of design of high performance concrete based on Portland cement as a binder were described. The experiment was focused on the strength investigation of composites with different ratios of cement to slag, and also the effect of used activator on strength parameters was investigated.

Abstract: The hydration products, microstructure and development principle of intensity of cement-glass powder cementitious materials acted in alkali and activation effect of chemical activation on waste glass powder were investigated. The principle of intensity and effect of curing time was analyzed by changing alkali type, content of alkali, incorporation of glass powder, incorporation method of activators and other factor. The result shows that: sodium carbonate and sodium silicate can single stimulate activity of glass powder under a certain condition, the activated effect of combined admixture is superior to the effect on single-doped activator, under the action of an excitation agent, surface hydrolysis of glass powder takes place on the glass body first and the hydration products occurs, The pozzolanic reactivity of glass powder increases gradually and generated a larger amount of hydration products，which has lapped and interlocked growth between each other，and form the compact hardened matrix. In addiation, the shorting of curing time is used by activator, the result may be lead to initial curing and against in engineering construction.

Abstract: This study presents the compressive strength and physical properties of alkali-activated lightweight concrete. Alkali-activated lightweight concrete was synthesized with fly ash, calcium carbonate and sodium hydroxide solution. Calcium carbonate was designed to replace part of fly ash at 5 and 10 wt.%. Sodium hydroxide solution at 5, 7.5 and 10 M was used as a liquid solution. Liquid to ash ratio (L/A ratio) at 0.45 was designed and aluminium powder was used as a foaming agent. The results showed that, the compressive strength of alkali-activated lightweight concrete made with fly ash was increased with NaOH concentration increased. The maximum compressive strength at 6.0 MPa was obtained from 10M NaOH mixture. For fly ash-calcium carbonate system, the compressive strength of lightweight concrete was improved when containing calcium carbonated, especially at 5 and 7.5 M NaOH mixtures. The maximum of compressive strength at 8.1 MPa and bulk density were obtained from the 5 wt.% calcium carbonated with 10M NaOH mixture. Water absorption and voids of all mixtures trend to decrease with increased NaOH concentration. XRD showed the sodium aluminum silicate hydrated as an alkali-activated product and composed of Si/Al atomic ratio at 2.1 and Na/Al atomic ratio at 1.4, respectively. Bulk density and compressive strength of alkali-activated lightweight concrete made with both fly ash and fly ash-calcium carbonated were acceptable in accordance with the specified criteria of TIS 2601. The well pore structure distribution of alkali-activated lightweight concrete was acceptable.

Abstract: Mechanical properties of alkali-activated materials are intensively studied nowadays. Great attention is paid to the economic problems and the effort to reduce the price of the finished product. This paper deals with usage of secondary raw materials from building industry used as aggregate for alkali-activated material. The mechanical and durability properties are tested and compared with porosity determined by mercury porosimetry.

Abstract: Alkali-activated materials are formed by the alkaline activation of inorganic materials and are characterized by the wide range of potential use. The objective of experiment was to investigate the possibility of use fine-grained alkali activated composites in the construction industry. Selected properties of alkali-activated systems based on granulated blast furnace slag and fine-grained aggregates were determined. At the beginning of the experiment, different samples prepared of 3 types of activators were tested, basic properties (time of workability, initial and final setting time, compressive and flexural strength) and also a possibility of selected retarder use was determined. Then, samples with the best potencial to presumed use were tested in detail and a possibility use as a substitute for selected construction materials were evaluated. On the basis of determined properties, prepared composites could be used as reprofiling mortars, materials for cracks repairing or socle plasters.

Abstract: Alkali activated systems are materials formed by alkali-activation of latent hydraulic or pozzolanic materials. The outcome is a polymeric structure with properties comparable to materials based on cement.The principle of the experiment is to compare selected properties of alkali-activated materials based on blast furnace slag and using various types of activator (sodium water glass, potassium water glass, DESIL AL and sodium metasilicate) to binders based on white and Portland cements of the highest quality. The samples were left for one year in environments simulating the conditions in the interior and exterior. Selected physical-mechanical properties were evaluated and compared.

Abstract: The most modern methods are used for study of alkali-activated material nowadays. Due to structure of these materials which is less structured most of these methods provide only limited information. Thermal analysis is partially applicable to alkali activated materials based on blast furnace slag. The article describes the application possibilities of thermal analysis to the study of thermal transformations of these materials and their applicability to the description of the tested structure.

Abstract: Alkali-activated systems, formed by the alkaline activation are inorganic materials characterized by the potential of ecological use. The objective of experiment was to investigate the influence of different activators on selected properties of alkali-activated systems based on granulated blast furnace slag. At the beginning of the experiment, 21 different samples prepared of 12 types of activators were tested to the basic properties. Then, selected samples with the best potencial to use were tested to compressive and flexural strength, frost resistance and surface resistance to chemical de-icing substances. The initial setting time achieved 25 - 95 minutes and final setting time achieved 30 - 105 minutes, compressive strengths were in the range 40 - 100MPa, frost resistance and resistance of surface to water and defrosting chemicals were confirmed.

Abstract: These are many factors that can influence the properties of alkali-activated slag cementitious material, such as the modulus and content of water glass, water-cement ratio, curing conditions, and so forth. The rules that how these factors affect setting time and strength of the material are systematically discussed in the paper. It is found that the setting time of the material depends on the concentration of alkaline ions in solution; The material will have the best strength when the modulus and content of water glass are 1.4 and 8%, respectively. The curing temperature increase will be helpful to compressive strength increase.