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Showing 1-5 of 46 Abstracts search results

Document: 

SP186-40

Date: 

May 1, 1999

Author(s):

J. Sebe and J. M. Calixto

Publication:

Symposium Papers

Volume:

186

Abstract:

The results of an experimental investigation on the water permeability of high performance concrete are presented. Several aspects were studied including different components for the concrete as well as the load history for the test specimens. The concrete was made with Brazilian Type CP V ARI cement (ASTM Type III), type different aggregates (limestone and gneiss) and silica fume. The concrete compressive strength was above 50 MPa at 28 days. For the water permeability test, the apparatus developed by Ludirdja et al. at the University of Illinois was employed. Permeability test were subjected to different load histories. In series 1, the applied load was equal to 40% of the ultimate compressive strength, while in series 2 this value was increased to 70%. The secant modulus of elasticity and the splitting tensile strength of the concretes at the start of the permeability test were also evaluated. The test results indicate clearly the effects of the load history on the value of the water permeability coefficient. As the load increases, the value of this coefficient also increases. The results also show that for high-performance concrete produced with Brazilian Type CP V ARI cement, the prescribed compressive strength may be reached in a short period of time, but the long-term water permeability coefficient seems to require a longer time to develop.

DOI:

10.14359/5585


Document: 

SP186-44

Date: 

May 1, 1999

Author(s):

B. V. Rangan

Publication:

Symposium Papers

Volume:

186

Abstract:

High Performance High Strength Concrete (HPHSC) has been utilized in columns and in other compression members. The author and his research team at Curtin University have conducted significant research into the behaviour and strength of HPHSC columns for the last eight years. The research comprised extensive experimental work and analytical calculations. Numerous column specimens have been tested in combined axial compression and uniaxial (single and double curvature) bending or biaxial bending. Analytical methods have been developed to predict the response and strength of test columns. Based on the research various proposals for design have been formulated. The paper describes the salient features of this research.

DOI:

10.14359/5589


Document: 

SP186-18

Date: 

May 1, 1999

Author(s):

C. K. Ong, T. W. Bremner, T. A. Holm, and S. R. Boyd

Publication:

Symposium Papers

Volume:

186

Abstract:

Results of an experimental investigation on the performance of cracked fiber reinforced concrete in a simulated marine environment are presented. A total of 111 prismatic specimens (150 by 150 by 510 mm) comprising both lightweight and normal weight concretes were used in this investigation. Cracked specimens with crack sizes of "hairline", .25 mm, 1.0mm, and uncracked specimens were exposed in either simulated seawater for up to a period of 7 years or 5300 alternate wetting and drying cycles. It was found, for both lightweight and normal weight concrete, that the strength development of uncracked specimens is not hampered by alternate wetting and development of uncracked specimens is not hampered by alternate wetting and drying. At the end of 7 years exposure, compressive strength gain of 90% was observed over the seven day moist cured strength for both types of concrete. Corresponding uncracked prismatic specimens showed approximately 25% flexural strength gain; however their post-cracking strength decreased under a prolonged period of alternate wetting and drying. Precracked specimens with cracks of up to .25 mm showed improvement in load carrying capacity up to 1440 wetting and drying cycles. However specimens with cracks of 1.0 mm showed a reduction in load carrying capacity.

DOI:

10.14359/5563


Document: 

SP186-23

Date: 

May 1, 1999

Author(s):

M. N. Soutos, J. H. Bungey, M. J. Brizell, and G. D. Henderson

Publication:

Symposium Papers

Volume:

186

Abstract:

Attempts to study the effect of vibration of fresh concrete have mainly been based on visual observation of, for example the radius of influence of the insertion vibrator, or the rate of flow of concrete down a tube when vibration is applied. The reason for this has been the difficulty of measuring the sinusoidal wave form created by mechanical vibrators. Advances in electronic equipment have made devices for measuring this wave form commercially available, and they have therefore been used in this research project to gain a better understanding of the consolidation process. The amplitude of the sinusoidal signal was calculated from the acceleration measured at distances up to 250mm from the surface of the insertion vibrator. Preliminary tests indicate that the amplitude of the vibratory wave decays exponentially with distance. The damping coefficient is greater for superplasticized high-strength concrete mixtures with low W/C than it is for normal-strength concretes. An attempt was made to relate the damping coefficients to the rheological properties, yield (g) and plastic viscosity (h) values determined from tests carried out with Tattersall's two point test apparatus. Both the yield (g) and plastic viscosity (h) values were found to increase by decreasing the W/C, despite the concrete having an equal slump of 150 mm. This shows that the slump values obtained by the use of high dosages of superplasticizers, as is the case with low W/C, are not directly comparable to those resulting from high water contents, with respect to the rheological behavior of concrete.

DOI:

10.14359/5568


Document: 

SP186-35

Date: 

May 1, 1999

Author(s):

A. P. Almeida and N. de Oliveira Pinto, Jr.

Publication:

Symposium Papers

Volume:

186

Abstract:

Many prediction criteria for evaluating the ultimate strength of high strength concrete deep beams are compared in this research. Added to the theoretical values obtained by the equations, a strut and tie model was developed, using the load path obtained by the Finite Element Method. The values found are also compared with test results in three high strength concrete deep beams with web openings. The test specimens consist of simply supported deep beams with openings located next to one of the supports. It is shown that there is great difference in the values encountered by theoretical analysis, and only ACI's prediction gets close to the test results, in spit of not considering the opening.

DOI:

10.14359/5580


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