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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 33 Abstracts search results
Document:
SP229-32
Date:
September 1, 2005
Author(s):
A.M. Buttler and E.F. Machado, Jr.
Publication:
Symposium Papers
Volume:
229
Abstract:
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.
DOI:
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
SP229-29
P.S. Bardella and G. Camarini
The aim of this experimental work was to evaluate the physical and mechanical performance of concretes steam cured at a maximum temperature of 60 °C. It explores the potential benefits of steam-cured concrete products in the precast industry that are made with different cements and with supplementary cementitious materials. All concretes had the same workability and were produced with two cements: high- early strength portland cement and blast-furnace slag portland cement. Concretes also had the addition of 10% of silica fume by mass of cement. The concretes were tested at different ages (mechanical strength, air permeability, capillary absorption and voids). The results showed that steam curing is beneficial to concretes made with blended slag cement, and silica fume addition improved the properties of steam-cured concretes.
10.14359/14753
SP229-24
D.L. Araujo and M.K. El Debs
The connection between precast beam and deck is formed by steel bar associated with a shear key. The steel bar is bent in hoop form and is inserted in the pocket in deck, which is filled by cast-in-place concrete. The strength of cast-in-place concrete varied from 65 MPa to 90 MPa, and a maximum volume of 1.50 % short steel fibers was added. The tests were carried out in push-out specimens submitted to three stages of no reversed cyclic load. Connections submitted to 40% of their ultimate strength show lower shear stiffness degradation when steel fibers were added. After twenty cycles of loading and unloading, the connection with fibers still maintained 85% of its initial stiffness, whereas the connection without fibers retained only 75% of its initial stiffness. The volume of fibers did not influence the stiffness degradation due to void in the cast-in-place concrete introduced by fibers. The diameter of the connector had little influence on the stiffness degradation, independent of the presence of the fibers. The addition of 1.5% of fibers to the concrete cast in the pockets also increased the ultimate shear strength of the connection up to 42% when connector of 12.5 mm diameter was used.
10.14359/14748
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