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International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

Document: 

SP-323_03

Date: 

May 1, 2018

Author(s):

Anna Halicka, Dick A. Hordijk, Eva O.L. Lantsoght

Publication:

Symposium Papers

Volume:

323

Abstract:

Nowadays, finite element analyses provide information about the performance of a structure, but they are more or less simplified. Therefore, load tests are the only way to find the “real” behavior of an existing bridge subjected to the rating process. In this paper, the state-of-the-art concerning load tests of concrete road bridges is presented, and the problems of the execution of such tests are specified. It is pointed out that only load tests accompanied with current finite element analyses may result in a proper assessment of the level of safety of the bridge. The authors’ procedure of complex assessment of such bridges combines in-situ examination of the structure, load testing, and finite element modeling. The paper discusses the following topics: aims and fundamentals of static diagnostic and proof load tests; the load application method according to different codes and specifications; the basis for proper assessment of the target load: reliability index, partial factors approach, global rating factor approach; establishing the load allowable on the bridge, based on the applied proof load; and the proposed procedure of assessment of existing concrete road bridges by load testing.


Document: 

SP288-33

Date: 

September 14, 2012

Author(s):

Ya Peng, Stefan Jacobsen, Klaartje De Weerdt, Bard Pedersen, and Britt Blom Marstrander

Publication:

Symposium Papers

Volume:

288

Abstract:

The improved fluidity of self-consolidating concrete by using chemical admix¬tures sometimes causes stability problems. In this paper some fundamentals of particle settling theory, such as Stokes’ law, are used to investigate particle sedimentation. Some preliminary calculations of stresses from particles (>0.125 mm [4.93E-4 in.]) on matrix (liquid and powder < 0.125 mm) with viscous fluid properties, indicate that yield stress is more important than plastic viscosity for the stability of aggregates when settling in matrix. The Kozeny-Carman equation (KCE) is used to analyse bleeding rate of fresh matrix with three main factors involved: solid fraction, specific surface area and liquid viscosity. Different stabilizing mechanisms of viscosity modifying agents (VMA) and fillers are also reviewed. Finally a settlement model is set up for further investigation.

DOI:

10.14359/51684249


Document: 

SP188-42

Date: 

August 1, 1999

Author(s):

G.P. Terrasi, U. Meier, and B. Burkhardt

Publication:

Symposium Papers

Volume:

188

Abstract:

The aim of this project is the production of a 28 m high CFRP-prestressed spun concrete pylon as a support for electric lines at the 110 kV voltage level (Duralight concept). It is intended to use this pylon as a support mast in a section of the 110 kV line of the Nordostschweizerische Kraftewerke (NOK, Power Company of North East Switzerland) Beznau-Baden. The fundamental advantage of this new design is the low weight in combination with an optimum corrosion resistance. The high corrosion resistance of the CFRP prestressing and shear reinforcement allows minimization of the concrete cover so that a cross-sectional wall thickness in the region of only 4 cm (1.6 inches) can be obtained. This is at present about 10 cm (4 inches) if steel reinforcement is used. The low weight of the CFRP reinforcement (the density of CFRP is only 1.6 g/cm3, which is a fifth of the density of steel) and its high tensile strength (CFRP pretensioning rods have a tensile strength of 3000 MPa, which is twice that of a prestressing steel) are also noteworthy. These two factors permit a weight reduction on the reinforcement side of 90% compared with conventional pre-stressed concrete construction. On the matrix side, high-strength spun concrete of strength class B110 is used. Owing to its high strength, it helps to achieve the stated minimization of the cross-sectional dimensions. The envisaged pylon weight of 4730 kg means a 45% weight reduction compared with the traditional steel reinforced spun concrete pylon. The transport and installation costs are thus lower and the expected life without maintenance is 50 years. This paper describes the technical fundamentals studied in a four year research program at the Swiss Federal Laboratories for Materials Testing and Research EMPA for designing and manufacturing this prototype pylon. The presented pilot project results from a close co-operation of the spun concrete element production plant SACAC with EMPA and the power company NOK.

DOI:

10.14359/5646


Document: 

SP178-57

Date: 

June 1, 1998

Author(s):

J.D. Sota, R. lasi, R. Perez and O.R. Batic

Publication:

Symposium Papers

Volume:

178

Abstract:

Hardened concrete contains interconnected pores if, during its production, the quantity of water used is higher than that required to do away with capillary continuity of the paste. These pores contain ions in solution from the chemical reactions that take place. The major ionic components involved in the reactions may vary in concrete affected by ASR, in contrast with concrete with no ASR. By applying the fundamentals of the Longuet et. al. method, the composition of the liquids contained in the pores of specially proportioned mixtures has been studied. This paper presents the results of the research work carried out up to the age of 180 days in order to know the chemical composition of the liquid contained in the pores of hardened mortars, whether affected or not by the ASR, and that of others to which pozzolans had been added so as to prevent excessive expansion due to ASR.

DOI:

10.14359/6025


Document: 

SP171-15

Date: 

August 1, 1997

Author(s):

Harald Justnes and Erik C. Nygaard

Publication:

Symposium Papers

Volume:

171

Abstract:

The effectiveness of calcium hitrate (CN) as a setting accelerator for cement is dependent on the cement type. The reason for this is explained by the mechanisms for set acceleration, and parametres for predicting the set accelerating efficiency of CN from cement characteristics is pointed out. Performance characteristics such as temperature evolution profile in insulated concrete (i.e. semi-adiabatic) and early compressive strengths (from 8 h) of concretes cured at 20°C for different additiom of different soluble calcium salts are demonstrated. The accelerating effect of CN was compared to additions of both calcium acetate and fortnate on equimolar concentrations of Ca2+ Calcium acetate and formate gave about the same accelerating effect, while CN showed greater acceleration. The difference might be due to an increased content of free Ca2+ (i.e. hot complexed ion) in CN compared with the organic acid salts. The temperature profiles revealed that CN accelerates set and hot the rate of early strength development. However, the 8 h compressive strength was increased when CN was added due to parallel displacement of the temperature evolution curves towards earlier times. Examples are given for field use (e.g. regulating slip forming rates) and potential applications (e.g. element production) of CN in concrete.

DOI:

10.14359/6104


12

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