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International Concrete Abstracts Portal

Showing 1-5 of 70 Abstracts search results

Document: 

SP212-26

Date: 

June 1, 2003

Author(s):

M. Raupach and L. Wolff

Publication:

Symposium Papers

Volume:

212

Abstract:

Supplementary hydrophobic treatments of the concrete surface can be a durable and potent method to lower the moisture content of the concrete and to improve its durability by inhibiting the migration of aggressive substances as well as slowing down the corrosion process. At the Institute for Building Materials Research in Aachen, ibac, comparative tests have been carried out on the efficiency and long-term durability of different hydrophobic agents on different types of concrete. The effectiveness and durability of the hydrophobic treatment was monitored using a sensor called multiring-electrode, which indicates the variation of humidity of the concrete in different depths by measurement of its electrolytic resistivity. The results hsow that the applied dosage on the specimens influenced the durability and efficiency of the hydrophobic treatment most significant. Other factors like active content, type of active agent or penetration depth have only a subordinate influence. The results showed also that a drying tendency of the specimen was only ob- served on the specimens weathered artificially in the VENUS test facility. Short rain periods of some minutes per day as simulated in the VENUS testing facility do not result in a high moisture content of the specimens. In contrast, a drying behaviour was observed also under a relative humidity of 95%. Long rain periods of several hours per day and a typical autumn weather with drizzle lead to a rising moisture content of the naturally weathered specimens even with an applied hydrophobic treatment.

DOI:

10.14359/12699


Document: 

SP212-08

Date: 

June 1, 2003

Author(s):

M. Brugger

Publication:

Symposium Papers

Volume:

212

Abstract:

During the production of the precast concrete tunnel lining segments (at low at- mospheric pressure steam curing) for the Adler Tunnel, a new system with simultaneous curing and protective coating was successfully applied for the first time (1996 and 1997). The segments are exposed to aggressive groundwater and high loads. As a follow-up of the Adler Tunnel the same system was used for tunnel sections of the Singapore Metro (1998 and 1999) and Metro Caracas (2002). The straight forward method with only a few production steps, consist of high- performance concrete with silica fume and a protective coating for excellent curing and for additional protection against aggressive environment. The coating consist of an aqueous epoxy resin dispersion, applied immediately after stripping on the whole hot concrete surface of 40 to 50 oC in a single operation with a layer thickness of 0.1 to 0.2mm. The results of microscopic analysis, water permeability and compressive strength, on covercrete of those segments, are considerably better than on uncoated segment concrete, which were cured by covering the segments with insulation matting after stripping.

DOI:

10.14359/12681


Document: 

SP212-57

Date: 

June 1, 2003

Author(s):

L. Courard, A. Darimont, R. Degeimbre, and J. Wiertz

Publication:

Symposium Papers

Volume:

212

Abstract:

A research program was set up to analyse the behaviour of more than 20 repair systems, including a wide range of coatings and repair products. Based on PC (Polymer Mortar), PCC (Polymer Modified Cementitious Mortar) and CC (Cementitious Mortar), the repair systems were applied on different concrete substrates in order to analyse the adhesion and its durability. Several ageing factors have been investigated: wet/dry cycles, sun radiation, freeze-thaw cycles, . . . Some ageing factors have a synergistic effect on the properties of materials: a good product may be completely destroyed if supplementary ageing happens. We have developed new test methods in order to simulate as well as possible site conditions and compared them with natural ageing when possible. Wider investigations are devoted to the analysis of the effects of water itself, which is probably the first cause of alteration of adhesion between concrete and repair systems. All these forms of ageing are compared and technical recommendations are proposed.

DOI:

10.14359/12730


Document: 

SP212-38

Date: 

June 1, 2003

Author(s):

J. L. Gallias

Publication:

Symposium Papers

Volume:

212

Abstract:

The deterioration concerns the outside walls of private houses made with hollow concrete blocks and covered with one-layer of white cement based coating. Six years after construction, the walls presented a random local ejection of the coating leaving in the bottom of the hole a rust coloured deteriorated material. Rust-coloured stains on the surface of the wall was also formed. The field study showed that the bottom of the hole reached systematically the concrete block and that the intensity of the deterioration was panially related with the climatic exposure of the walls. Scanning Electron Microscopy, X-Ray Energy Dispersion Spectroscopy and X-Ray Diffraction investigations on sound and deteriorated samples showed that the deterioration results from the oxidation of pyrite nodules of some millimeters of diameter included in the course aggregate of the concrete mixture of the blocks. The oxidation process of the pyrite occurred in wet conditions and in contact with cement compounds producing expansive gypsum and colloidal ferrous hydroxides. The random cracking and the low permeability of the coating were contributing factors to the deterioration process.

DOI:

10.14359/12711


Document: 

SP212-23

Date: 

June 1, 2003

Author(s):

T. Ozturan and M. E. Bastopcu

Publication:

Symposium Papers

Volume:

212

Abstract:

When concrete is properly cured, pozzolanic reaction products of fly ash fill in the spaces between the hydrating cement particles, thus lowering the permeability to water and aggressive chemicals. This paper describes the durability of fly ash concrete subjected to different curing conditions. Sorptivity, chloride-ion penetration, and resistance to deicing-salt scaling were tested for concretes containing 0, 15.30, and 45 percent Class C fly ash by weight of cement. Specimens were tested at 28 and 56 days after being subjected to three different curing conditions. It was seen that increasing the fly ash content decreased the sorptivity, chloride-ion penetration and deicing-salt scaling of concretes with the exception that they were increased for the specimens that were not properly cured. Highest durability performance was observed for concrete specimens subjected to hot water curing. Moist cured specimens came next.

DOI:

10.14359/12696


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