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International Concrete Abstracts Portal

Showing 1-5 of 53 Abstracts search results

Document: 

SP172-23

Date: 

December 1, 1999

Author(s):

Shuaib H. Ahmad, Carl V. Jerrett and Paul Zia

Publication:

Symposium Papers

Volume:

172

Abstract:

The expanded use of fiber reinforced polymer (FRP) tendons as prestressing and post-tensioning tendons requires that these tendons be subjected to high axial loads while bent or harped around a curved surface. This paper describes the behavior of one type of CFRP tendon when subjected to combined axial loading and harping. Four test series to study the tendon fiber strain distribution and seven test series to study the tendon ultimate strength were conducted. The tendons were subjected to various combinations of axial loading and harping around a curved surface. Test parameters for the ultimate strength tests included tendon axial load, bend angle, and curvature of harping point. Harping points were set to either 1 in. (25 mm), 5 in. (127 mm), or 20 in. (508 mm) radius. Ultimate strength tests included static strength tests and fatigue tests. Results of the static tests indicate that at failure, the flexural strains at harped point far exceed the average fiber strain recorded in uni-axial tensile strength tests. The flexural strain is defined as the difference between strain readings from a 0.125 inch (3.2 mm) strain gage placed on the tendon bend outside face and the tendon average axial strain. No flexural strains were observed away from the tendon bend beyond about 6 in. (152 mm). Based on the tests, an expression for the tendon flexural strain at harped point as a function of axial load, bend angle, and harping plate curvature was developed. This expression for flexural strain at harped point was used in a maximum strain failure criteria model that accurately predicts the failure of specimens tested in this research. The results of the fatigue testing indicated no degradation of tensile strength due to fatigue loading.

DOI:

10.14359/6145


Document: 

SP172-11

Date: 

December 1, 1999

Author(s):

Salil K. Roy, Poh Kong Beng and Derek 0. Northwood

Publication:

Symposium Papers

Volume:

172

Abstract:

Concrete prisms (40 x 40 x 160 mm) were made with crushed aggregate, non-reactive sand, portland cement with added alkali (NaOH) content (2.5%’ by mass), and water in proportion (by mass) of 1: 1: 1:0.5. The prisms were demolded after 24 hours, cured in water at room temperature for another 24 hours, then boiled under water at a constant pressure (0.15 Mpa) and temperature of 111°C in an autoclave for 2 hours, cooled to room temperature and examined for presence of cracks and changes (before and after boiling) in ultrasonic pulse velocity as well as dynamic Young’s modulus. Conditions for a suspect aggregate to be innocuous could be established from measurements made on aggregates collected from twelve quarries in Singapore, and on a sample of one of these aggregates mixed with an opal from Indonesia. Results obtained by this method are found to agree with those obtained by each of the three ASTM methods (Petrographic Examination (C 229-85) Chemical Method (C 295- 85) and Mortar Bar Expansion Test (C 227-81).

DOI:

10.14359/6133


Document: 

SP172-41

Date: 

December 1, 1999

Author(s):

S. I. Pavlenko and It. P. Myshlyaev

Publication:

Symposium Papers

Volume:

172

Abstract:

Cementless concrete based on high-calcium fly ash and slag sand from thermal power plants and excluding the use of ware aggregate has been developed by the Siberian State Academy for Mining and Metallurgy (SSAMM). The concrete has been patented. It consists of the following components: high-calcium fly ash - 30-40% slag sand with particle size 0 to 5 mm, 30-40% silica fume - 3-4% water (60-80oC ) - as needed, 16-37% Study and optimization of the properties of the created concrete led to a new approach to the problem, that is the methods of simulation modeling. The use of a computing technique in the investigation permitted attainment of more efficient data on the concrete composition and predict its properties.

DOI:

10.14359/6163


Document: 

SP172-35

Date: 

December 1, 1999

Author(s):

Hoom Kim, Yon-Dong Park, Jaeho Noh, Yongsum Song, Chungho Han and Suckhwa Kang

Publication:

Symposium Papers

Volume:

172

Abstract:

To investigate the rheological properties of binders for self-compacting high-performance concrete, six mixtures of self-compacting concrete were initially prepared and tested to estimate their self-compacting property. Then, the binders used in self-compacting concrete were tested for rheological properties using a rotary rheometer. Binders with different water-binder ratios and flow values were also examined to evaluate their rheological characteristics. The binders were composed of normal portland cement, fly ash, two types of ground blast-furnace slag, and limestone powder. The flow curves of binders were obtained by the rotary rheometer with shear rate control. Slump flow, O-funnel time, Box, and L-flow tests were used to estimate self-compacting property of concrete. The flow curves of binders for self-compacting concrete have negligible yield stresses and show an approximately linear behavior at higher shear rates beyond certain limits. Test results also indicate that the binders incorporating fly ash are more appropriate than the other types of binders for quality control of self-compacting concrete.

DOI:

10.14359/6157


Document: 

SP172-14

Date: 

December 1, 1999

Author(s):

Sung-Woo Shin, Suk-Hyung Yoo, Jong-Moon Ahn and Kwang-So0 Lee

Publication:

Symposium Papers

Volume:

172

Abstract:

Fifteen high-strength concrete beams were tested under concentrated load at two-point to investigate their ductile behavior including flexural strength with various compressive stress distribution. And six high strength concrete beams were tested to investigate the minimum reinforcement ratios requirements for high strength concrete. Thus major test variables were the compressive strengthes of concrete and tensile steel ratios. The test results were compared with flexural strength predicted by ACI 318-95. It was found that high strength concrete beams with maximum reinforcement ratio of ACI 318-95 accompany brittle failure and that compressive stress of high strength concrete beams is distributed linearly than that of normal strength concrete beams. New maximum reinforcement ratio is proposed for the ductile behavior of high strength concrete beams.

DOI:

10.14359/6136


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