Papers by Keyword: Fly Ash (FA)

Abstract: Using self-leveling cement mortar, we can make a solid flat surface economically in accordance with the requirements, which is widely recognized and applied. Because of the demands of self-leveling, the mortar required materials have good liquidity and flow retention. Therefore, the raw materials must have a supporting role. Analyzing the raw materials, the paper study the effects of raw materials for the self-leveling cement mortar.

Abstract: The development of new alternative type of fly ash bricks using the locally available local soil from Ratchaburi province were mixed with fly ash from Kanchanaburi province, where both sources in western of Thailand, is the main purpose of this study. These are compared to the ratchaburi local soil cement bricks without the mixing of western fly ash in different proportions. It is concluded that the addition of western fly ash reduces the thermal conductivity. The compressive and flexural strength decrease when the ratio of western fly ash is more than 30 percentages. However, considering the various factors it can be concluded that appropriate ingredient toward producing the good commercial western fly ash bricks is 5 percentages of portland cement and 30 percentages of western fly ash by weight basis of ratchaburi local soil. The compositions of western fly ash at more than 25 percentages by weight basis of ratchaburi local soil and since up to 14 days of curing time are proved to be economical mixtures for load bearing panels or brick type structural elements according to the Thai Industrial Standard for structural clay load-bearing tile.

Abstract: A series of foam concrete with different content of fly ash or red mud were experimentally investigated in this study. The results indicated that the water-solids ratio of optimized material proportion and curing conditions were 0.5, and the compressive strength and density of the concrete compressive would fall with the addition of fly ash or red mud.

Abstract: The accelerated carbonation test was carried out for the ordinary concrete and fly ash concrete. Influences of water-cement ratio, carbonation age and fly ash content on pH value were researched. The results show that carbonation depth, including incomplete carbonized zone, can be effectively reduced by reducing water-cement ratio. So lower water-cement ratio means high performance of resistance of carbonate. The use of fly ash can optimize concrete pore morphology, it’s beneficial for anti-carbonation. However, It disadvantageous to anti-carbonation because of less carbonation material. By taking appropriate mixture of fly ash we can not only enhance the anti-carbonation ability of concrete, but also reduce the use of cement to get well economic benefits.

Abstract: This paper offers a model that can estimate the 28-day compressive strength of concrete containing fly ash (FA) using the concept of cementing efficiency. Using various statistical analyses, the prediction model was derived from a wide range of mix proportions and a number of strength test results of concretes used in eight construction sites. A strength prediction model was proposed in terms of a function of the modified cement-water ratio reflecting the equations for cementing efficiency. This prediction model that has R² of 0.88 and root mean squared error (RMSE) of 1.6MPa is capable of properly predicting the 28-day compressive strength within strength variation of FA concrete.

Abstract: ABSTRACT It is a very well known fact that the use of fly ash in masonry and concrete make the structures durable. Properties of Fly Ash depend upon coal source. For acceptability of fly ash in cement, mortar and concrete various specifications and standards are available. The Indian standard IS 3812: 2003(Part I and Part II) expects some physical and chemical properties similar to world standards, while differs in some, like lime reactivity test. As a part of research activity the authors have collected 23 different fly ash samples from various hoppers of three power stations near Nagpur. The samples were tested as per most of the provisions of IS 3812 and tests specified in IS 1727. Test results are compared with major world standards and specifications. Gain of strength is the most important character of fly ash, especially from the usage in cement and concrete. The paper discusses comparison of various standard specifications and interpretation of pozzolanic reactivity.

Abstract: To determine the reaction degrees of Portland cement and fly ash in complex pastes, an experiment of hydration degree for composite pastes, hydrochloric acid dissolution method for fly ash and solution heat method for cement is applied. It is shown from the test that a rather precise result has been obtained by the combined method. The hydration degrees of cement and fly ash in composite pastes agree well with those from theoretical analysis.

Abstract: In order to study the effect of fly ash (FA) and slag powder (SP) on coefficient of thermal expansion (CTE) of concrete, the influence of FA and SP to CTE of concrete was compared, the influence of replacement proportion of FA to CTE of concrete was tested, and the unhydrate mineral admixture particles were observed with SEM and validate with Energy Spectrometry. The results showed that the influence of FA and SP to CTE of concrete is different, the CTE of SP concrete is near to the norm concrete，but is higher than the FA concrete; With the replacement proportion of FA increased, the CTE of concrete decreased; The per strength CTE increased obviously when the replacement proportion exceed 10%, and the decrease of strength badly when the replacement proportion of FA exceed 30%; The unhydrate mineral admixture particles is one of the most important factors that influence the CTE of concrete, and the mineral admixture could influence the composite and the microstructure of cement paste, then cause the change of porosity and density.

Abstract: The microstructure and hydration mechanism of alkali-activated fly ash-based geopolymer were studied by means of scanning electron microscope (SEM) coupled with energy dispersive X-ray analysis (EDXA) and field emission scanning electron microscope (FESEM). The FESEM photomicrographs indicted that the fly ash-based geopolymer showed three dimensional frameworks with an average particle size of 50 nm. EDXA results demonstrated that the Na-PSS type geopolymer was produced via the disintegration of Si-O-Al and Si-O-Si chemical bonds and the polycondensation reaction between [SiO4]4-and [AlO4]5- tetrahedrons in spherical fly ash particles under alkaline condition.

Abstract: The cement powder materials are evaluated by fractal theory. Fractal characteristic parameters are analysed and evaluated by the method of laser particle size analyzer, microscope, transmission electron microscope. In this paper, cement powder materials has good self-similarity. Fractal dimension of grading is tested and evaluated by laser particle size analyzer, fractal dimension of cluster is tested by microscope, fractal characteristic of particle distribution is tested by transmission electron microscope. Compared with traditional weight of screen residue and specific surface area, those methods are more careful. Fineness fractal parameters and activity of ultra fine fly ash and pulverized slag have good linear dependence relation that is evaluated by fractal dimensions. Fractal characteristics provide an important basis to further explore the inherent relation of cement powder materials and concrete material density effect.