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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:
SP229-19
Date:
September 1, 2005
Author(s):
C. Alonso, C. Andrade, E. Menendez, and E. Gayo
Publication:
Symposium Papers
Volume:
229
Abstract:
A concrete exposed to environments of high temperature or directly to fire undergoes microstructural changes that result in loss of mechanical properties. The present paper deals with the study of high-performance concretes (HPC) and ultra high-performance concretes (UHPC) resistance to high temperatures. Microstructural changes are followed up to temperatures of 700°C. Changes on residual permeability and porosity, together with weight losses, due to moisture, binding water, aggregates and fibre transformations, are considered. The study, performed on a wide variety of concretes, indicates that UHPC seem to be less resistant at high temperatures than HPC, but the addition of fibres improves the fire resistance of UHPC.
DOI:
10.14359/14743
SP229-14
P. Castro-Borges, C. Andrade, C. Alonso, and E. Pazini Figueiredo
It has been demonstrated that the galvanic current is given by a macrocell which is formed during the curing of the repairs to a concrete member. After this time, the macrocell effect disappears giving place to a microcell behavior that lasts with time in spite of changes to the exposure conditions. This has been demonstrated for concrete containing 0.7% of chloride ion that was repaired, and where the reinforcement was primed with systems that provide protection by repassivation, inhibition, barrier or cathodic protection. However, not enough papers have been published about the electrochemical behavior of the juxtaposed regions (those in non-repaired zones but face to face to the repaired ones) after the repairs. This paper shows that repair approach, as presented here, has no adverse effects in the short and at medium term exposures to different environmental conditions.
10.14359/14738
SP229-15
S.M.M. Pinheiro, M.R. Silva, and F.L. dos Santos Souza
In order to satisfy the needs of concrete durability, it is important to know the deterioration mechanisms to which the material could be submitted. Among the different mechanisms of concrete deterioration, biodeterioration is one of the most recently observed in structures. Its study is complex and demands a multidisciplinary research which involves different disciplines. This paper addresses biodeterioration concepts, the mechanisms involved, and the impact on concrete phases (cement paste and aggregate). An example of aesthetic and microstructural impacts on the mortar phase of a normal concrete when it is colonised by the Cladosporium sphaerospermum fungus is presented.
10.14359/14739
SP229-16
T. Yamaji, K.-I. Komure, and H. Hamada
The south part of Japan is located in the subtropics. Therefore, steel corrosion in concrete in this region easily tends to initiate and progress due to chloride ion ingress into concrete from the seawater. Under this environment, in order to enhance the durability of reinforced concrete structures in which sufficient concrete cover depth can not be secured due to some restrictions, it is very effective to apply adequate surface coating materials on the concrete surface at early age of exposure. To study the durability of concrete with various surface coating materials under marine environment in the subtropics, exposure test was carried out in the south part of Japan. Various tests such as bond strength of surface coating materials, chloride ion content in concrete and corrosion evaluation of steel bar in concrete were carried out after 15 years of exposure. These results indicate that these surface coating materials are very effective in enhancing the durability of concrete under marine environment. This protection against chloride attack was well maintained for 15 years of exposure to a marine environment.
10.14359/14740
SP229-11
R. de Oliveira Pinto, A.L.B. Geyer, and A. Liduario
Only few recent studies on the curing procedures applied to the HPC are available in Brazil, because it’s use hasn’t been a common practice in the civil construction industry. The present work reports the experimental production of high-performance concrete with compressive strengths ranging from 60 to 100 MPa, using materials available in the metropolitan regions of Goiania and the silica fume as a mineral addition. The specimens were exposed to five different curing conditions: 1 day of wet curing, 7 days of wet curing, membrane curing based on paraffin, membrane curing based on chloride rubber, and air storage. The results obtained for the compressive strength at 28 days indicate the different concrete performance under several curing conditions, allowing therefore a better knowledge of the HPC behavior, so that it may used safely where it is needed.
10.14359/14735
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