دانلود رایگان مقاله انگلیسی امکانات تولید بتن سبک با قدرت بالا از جنس خاکستر هوابرد متراکم شده - الزویر 2017

Abstract

Heat power plants based on coal combustion are produced fly ash as a by-product. Fly ash is not only a by-product. It is due to its pozzolanic activity very useable as a fine additive to concrete in the building industry. It has not only environmental aspect, but also an economic. Potential of use of fly ash in cement concrete technology is only as an additive. But there is a technology of building material production, which use up to 100 % of fly ash in the “mixture”. It is sintered artificial aggregate. It can be used for some filter layers, for lightweight flat roof, ceiling or for lightweight concrete composite. There can be made different strength classes of the concrete. It is possible also produce high-strength lightweight concrete reaching strength up to 55 MPa. The paper is about possibilities of different types of fly ash for artificial sintered aggregate to achieve the parameters of lightweight high strength concrete. An interesting aspect of evaluating the quality of the composite is also synergistic interaction of aggregate joined to a cement paste.

6. Conclusion

Pilot firings in a horizontal furnace showed that the best raw material for this technique is FA1 ash which was the finest of the tested ashes with the largest specific surface. Aggregate with a resistance to crushing of at least 2.3 N∙mm-2 was thus obtained.

During the experiments with the production of high-strength lightweight concrete containing ash, in the majority of cases after 28 days of curing the measured aggregate strengths were below the value of 55 N∙mm-2 needed for the inclusion of lightweight concretes in the LC 50/55 strength class. The required strength value of 55 N∙mm-2 was measured when sintered FA1 ash aggregate was used. LC 50/55 could be attained in concretes containing artificial ash aggregates if cement and plasticizer dosages were increased. However, this raises the risk of increasing the bulk density beyond 2 000 kg∙m-3, which is the limit value for lightweight concretes. Further research could be performed regarding the increase in strength which could be achieved, e.g. with an increased proportion of the 4-8 mm fraction.