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International Concrete Abstracts Portal

Showing 1-5 of 13 Abstracts search results

Document: 

SP141-12

Date: 

December 1, 1993

Author(s):

V. Novokshchenov and D. Allum

Publication:

Symposium Papers

Volume:

141

Abstract:

Describes the results of inspection of concrete operations and quality control of concrete at the Valley Bridge Project in Bluffs, Illinois, using a computer model, the CQC REPORT. The following variables affecting potential durability and strength of concrete in bridge structures were evaluated: accuracy of measuring of concrete materials, state of control and capability of batching operations, variations in SSD quantities of ingredients per cubic yard of concrete, yield, control over the water-cement ratio, properties of freshly mixed concrete, age of concrete at discharge, compressive strength of concrete cylinders, standards of control over concrete manufacture and concrete testing, amount of rejected concrete, and reason for rejection. Paper is concerned with the 6000 psi (41.4 MPa) concrete mix supplied for bridge spans from one of two batch plants used on the job. Paper also describes the structure of the CQC REPORT and statistical techniques used to analyze test data.

DOI:

10.14359/3995


Document: 

SP141-08

Date: 

December 1, 1993

Author(s):

Koji Sakai

Publication:

Symposium Papers

Volume:

141

Abstract:

Recently, in Japan, application of the roller compacted dam concrete (RCD) method has increased in the construction of concrete gravity dams. The concrete for the RCD method (RCD concrete) features a very stiff consistency with low water content, which enables the use of a vibration roller for compaction. Most of the cement used so far for RCD concrete has used a combination of fly ash with moderate heat portland cement. However, the supply of high-quality fly ash for use in concrete has recently lessened in Japan. One admixture replacing fly ash is granulated blast furnace slag. In this study, properties of RCD concrete made with slag cement featuring blends of moderate heat portland cement and granulated blast furnace slag were examined. The effect of fineness of the individual slag cement components on compressive strength and adiabatic temperature rise were studied. The unit cement content in the concrete was 120 kg/m 3. The maximum size of the coarse aggregate was 150 mm. The results show that concrete with moderate low-heat slag cement can provide the same or better performance as fly ash cement concrete by employing a rational combination of fineness and slag content. Also, the advantages of slag cement at longer ages were confirmed. The results obtained in this study are now being applied to an actual dam construction.

DOI:

10.14359/1196


Document: 

SP141-09

Date: 

December 1, 1993

Author(s):

Sami W. Tabsh and Alex Aswad

Publication:

Symposium Papers

Volume:

141

Abstract:

A reliability-based approach is used to recommend allowable edge loads for precast hollow core slabs. Full-scale test results are used to predict the statistical parameters of the resistance at the edge. The study indicated that the allowable load is a function of dead-to-live load ratio and concrete strength. The analysis is extended to include system reliability of the whole slab due to different failure modes. The failure modes include flexure at midspan and total shear at the ends, in addition to local failure at the edge. The system modeling is composed of a series system made up of three partially correlated elements. A numerical example is also included for illustration. The approach will help engineers make a rational selection of allowable edge loads that occur around large floor openings.

DOI:

10.14359/3965


Document: 

SP141-03

Date: 

December 1, 1993

Author(s):

Nicholas J. Carino

Publication:

Symposium Papers

Volume:

141

Abstract:

In-place testing is used to estimate the compressive strength of concrete in a structure by measuring another related property. A strength relationship is used to convert the in-place test results to an estimate of the compressive strength. Statistical methods are needed for reliable estimates of in-place strength. Such methods should account for the uncertainties in the measured property, the uncertainty of the strength relationship, and the variability of the in-place concrete. Standard statistical procedures for dealing with these uncertainties have not yet been adopted in North American practice. Recommendations are provided for developing the strength relationship, and a reliable, easy-to-use approach is presented to estimate in-place characteristic strength.

DOI:

10.14359/3989


Document: 

SP141-02

Date: 

December 1, 1993

Author(s):

G. M. Idorn

Publication:

Symposium Papers

Volume:

141

Abstract:

The three power centers in the world today must support the tremendous concrete construction and building investments that are needed in the developing regions where 90 percent of the world's population lives. Concurrently, renovations and renewals are required in industrial countries. Profound updating of conventional concrete technology is necessary, recognizing the differences between the behavior of test samples of concrete under laboratory conditions and of field concrete. For example, the historic development of curing concrete is reviewed with emphasis on the methods for monitoring heat development during curing of modern concrete. Proposals for wider transfer of this technology are also presented.

DOI:

10.14359/3988


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