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International Concrete Abstracts Portal

Showing 1-5 of 16 Abstracts search results

Document: 

SP225-06

Date: 

May 1, 2005

Author(s):

A. Scanlon

Publication:

Symposium Papers

Volume:

225

Abstract:

Current practice related to design of concrete structures for deflection control is reviewed. The paper discusses the limitations of the current code procedures based on minimum thickness rules and deflection calculations. Results are presented to demonstrate the sensitivity of deflections to span to depth ratio, sustained live load, and extent of cracking.

DOI:

10.14359/14378


Document: 

SP225

Date: 

March 1, 2005

Author(s):

Editors: Florian Barth, Robert Frosch, Hani Nassif, and Andrew Scanlon / Sponsored by: ACI Committee 224 and Joint ACI-ASCE Committee 421 and ACI Committee 435

Publication:

Symposium Papers

Volume:

225

Abstract:

The Edward G. Nawy Symposium was sponsored by ACI Committees 224, Cracking; 421, Design of Reinforced Concrete Slabs; and 435, Deflection of Concrete Building Structures. The symposium and this special publication celebrate and honor the distinguished career of Dr. Nawy as an outstanding educator, committed researcher, influential author, and professional engineer. This special publication offers technical papers on aspects of concrete serviceability, with emphasis on concrete cracking and deflection for prestressed and non-prestressed members. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP225

DOI:

10.14359/14358


Document: 

SP225-01

Date: 

March 1, 2005

Author(s):

R. W. Furlong

Publication:

Symposium Papers

Volume:

225

Abstract:

Building Codes have specified for the purpose of design, that “Theory of Elastic Frames” be used for analyses of indeterminate structures. Sophisticated computer software has been developed based on the condition of elastic response to loading. Designers rely on computed results from such analyses as if those results were perfect and reliable evaluations of structural behavior. The influence of assumptions regarding accepted simplifications, member stiffnesses, load definitions and frame connectivity is addressed. Reliability from elastic analyses is revealed as an illusion, and less sophisticated alternate analytic requirements are suggested.

DOI:

10.14359/14373


Document: 

SP225-04

Date: 

March 1, 2005

Author(s):

V. Ramakrishnan, R. K. Panchalan, and S. S. Bang

Publication:

Symposium Papers

Volume:

225

Abstract:

This paper presents the results of a novel technique in remediating cracks and fissures in concrete by utilizing microbiologically induced calcite (CaCo3). Bacillus Pasteruii, a common soil bacterium was used to induce calcite precipitation. This technique is highly desirable because the mineral precipitation induced as a result of microbial activities, is pollution free and natural. The effectiveness of this technique was evaluated by comparing the compressive strength and stiffness of cracked specimens remediated with bacteria and those of the control specimens (without bacteria). Experimental investigation was also conducted to determine the strength regaining capacity (modulus of rupture) of cracked beams remediated with different concentrations of bacteria. This paper also presents the results of a durability study on cement mortar beams treated with bacteria, exposed to alkaline, sulfate and freeze-thaw environments. Different concentrations of bacteria were used for the investigation. It was found that the use of bacteria improved the stiffness, compressive strength, modulus of rupture and durability of concrete. Scanning electron microscope (SEM) was used to document the role of microbiologically induced mineral precipitation in improving the strength and durability aspects of concrete. Energy Dispersive X-ray (EDX) spectrometer analysis of the precipitated crystals indicated abundance of calcium and the precipitation was confirmed to be calcite.

DOI:

10.14359/14376


Document: 

SP225-03

Date: 

March 1, 2005

Author(s):

S. E. Wallah, D. Hardjito, D. M. J. Sumajouw, and B. V. Rangan

Publication:

Symposium Papers

Volume:

225

Abstract:

As a relatively ‘new’ material, geopolymer concrete offers the benefits as a construction material for sustainable development. It utilises waste materials such as fly ash and has a very low rate of green house gas emission. This paper presents the study of the performance of fly ash based geopolymer concrete to sulfate attack. Test specimens were soaked in sodium sulfate solution and sulfuric acid solution for various periods of time, and the performance of geopolymer concrete is studied by evaluating the effect on the compressive strength, change in length and change in mass. Test results show that exposure to sodium sulfate has no significant effect on geopolymer concrete, whereas exposure to sulfuric acid affects the compressive strength.

DOI:

10.14359/14375


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