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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 33 Abstracts search results
Document:
SP229-30
Date:
September 1, 2005
Author(s):
L. Bertolini, M. Carsana, D. Cassago, M. Collepardi, and A.Q. Curzio
Publication:
Symposium Papers
Volume:
229
Abstract:
The paper describes the results of research on the properties of concrete with the replacement of part of portland cement with bottom ash from municipal solid waste incinerators (MSWI). Results showed that MSWI bottom ash is potentially attractive as mineral addition for the production of concrete, provided that the risk of entrapment of hydrogen bubbles produced by corrosion of aluminium metallic particles in the fresh concrete is prevented. This could be achieved by wet grinding the bottom ash so that reactions leading to gas development could start within the slurry. A great variability was observed in the time required to exhaust the hydrogen gas production; a key factor for this variability was found in the pH of the slurry. A modest amount of cement added in slurry could increase the pH, reduce the time required to exhaust hydrogen evolution and allow manufacturing of quality concrete suitable for aggressive chloride bearing environments.
DOI:
10.14359/14754
SP229-31
A.C. de Albuquerque, N.P. Hasparyk, M.A.S. Andrade, and W.P. de Andrade
In this research, three types of different surface treatments were used: acrylic, vinylic and styrene-butadiene polymeric admixtures in order to improve the bond between rubber and cement. Specimens of concrete were evaluated considering the incorporation of three different sizes of tire rubber, and applied in five treated and untreated contents (5% to 25%), resulting in a total of 31 different conditions of analysis . It was observed that the concrete specimens with incorporating of treated tire rubber had its mechanical behavior improved compared to those without treatment. In addition, rubber particles with 1.5 mm in dimension featured a minor negative influence on the concrete properties when compared to the reference and the ones with 0.42 mm and 4.8 mm particles. Some concrete samples were selected to be analyzed by scanning electron microscopy in order to correlate microstructure with their properties.
10.14359/14755
SP229-32
A.M. Buttler and E.F. Machado, Jr.
A great quantity of construction and demolition wastes are produced every day in Brazil, representing about 60% of the total solid waste stream. A high proportion of demolition waste, particularly the fraction derived from concrete, is well suited to being crushed and recycled as a substitute for natural aggregates. This paper presents the results of an experimental study to evaluate the physical properties of the recycled concrete coarse aggregates and the physical and mechanical properties of the concretes produced with these aggregates. Results indicate that the residues of concrete that were recycled right after generation exhibit higher compressive and tensile strengths when compared to those concretes with natural aggregates because of the presence of a large amount of nonhydrated cement particles. On the other hand, the mechanical properties of recycled aggregate concrete (for example, modulus of elasticity and drying shrinkage) were not as favorable when compared to reference concrete.
10.14359/14756
SP229-27
M.P. Barbosa, R.C.A. Pinto, and L.D.P. Peres
The use of the maturity approach has been increasing in various fields of concrete construction. In order to estimate the development of a mechanical property of the concrete mixture reliably, it is necessary to previously determine the apparent activation energy of the mixture. This thermal sensitivity index is a function of several parameters including cement type, presence of admixtures, and w/c. This study investigates the influence of silica fume on the apparent activation energy of high-performance concrete mixtures. Following the procedure in ASTM C 1074, various mortar mixtures were prepared with 6 different types of Brazilian cements (CP-I-S, CP-II¬F-32, CP-II-Z-32, CP-III, CP-IV-RS e CP-V-ARI), and with addition of silica fume at two levels (8% and 16% of cement mass). The results indicate that the presence of silica fume increases the value of the apparent activation energy.
10.14359/14751
SP229-28
M.A.M. Coelho, M.G. da Silva, F.L. dos Santos Souza, R. Sarmento, R.P. de Moraes Frasson, S.M. de Moraes Pinheiro, E. Zandonade and T. Morimoto
This paper reports the results of an investigation on concrete containing alkali-activated slag (AAS). The activators used were liquid sodium silicate (3%, 4% or 5% Na2O, mass of binder) + lime (5%, mass of binder); clinker (10%, mass of binder) + lime (10%, mass of binder); lime (2%, mass of binder) + gypsum (6%, mass of binder) and clinker (16%, mass of binder). The activator of liquid sodium silicate (4% Na2O, mass of binder) + lime (5%, mass of binder) showed better compressive strength when compared to normal portland cement concrete. Other properties were studied such as elastic modulus, flexural strength, absorption of water by capillary forces, drying shrinkage and sulfate attack and the results are discussed in this paper.
10.14359/14752
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