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Showing 1-5 of 36 Abstracts search results

Document: 

SP206-33

Date: 

April 1, 2002

Author(s):

S. H. Kosmatka

Publication:

Symposium Papers

Volume:

206

Abstract:

This paper reviews the opportunities that the Portland Cement Association has taken to address part of the education needs of the cement and concrete industries. Addressed are current educational efforts and a review of how research at universities addresses both the educational and technical needs of the industry. A. list of concrete related web sites is included. Through education the concrete industry can meet the need for informed professionals who are necessary to sustain concrete as the building material of choice for this century.

DOI:

10.14359/12274


Document: 

SP206-18

Date: 

April 1, 2002

Author(s):

I. Pane and W. Hansen

Publication:

Symposium Papers

Volume:

206

Abstract:

A current research project on hydration kinetics, mechanical properties and early age stress behavior of blended cement conducted at the University of Michigan is reviewd in this paper. A number of experiments including calorimetry and differential thermal analysis were performed to investigate hydration kinetics. The mechanical properties investigated included the compressive strength, splitting tensile strength, Young's modulus, creep compliance, relaxation modulus, and coefficient of thermal dilation. The early age stress behavior was studied by measuring the stress developed in a uniaxially restrained concrete member. In addition, the deformation due to autogeneous shrinkage was also measured experimentally. The experimental data could be used to quantify degree of hydration,, and temperature effects on hydration, and could be used as imputs for predicting the early age stress development in concrete.

DOI:

10.14359/12259


Document: 

SP206-17

Date: 

April 1, 2002

Author(s):

C. Sujivorakul and A. E. Naaman

Publication:

Symposium Papers

Volume:

206

Abstract:

The bond stress versus slip behavior of steel fibers cut from twisted wire strands (which are made from at least two round steel wires wrapped helically around each other) is investigated and compared to the behavior of a single triangular steel fiber (Torex) twisted along its axis. Single fiber pullout tests simulating fiber pullout in a cracked tensile specimen were used. Parameters investigated are: 1) the embedded length of the fiber in the matrix; 2) the number of individual wires making a strand fiber; 3) the pitch distance of the fgiber; 4) the compressive strength of the mortar matrix (44 and 84 Mpa); and 5) the tensile strength of the fiver. It is observed that, depending on the combination of parameters (embedded length, matrix, strand type and pitch distance) the bond stress-slip response can be elasto-plastic in shape or slip softening after the peak. However, the twisted wire strand fibers are less efficient than the single Torex fiber, in terms of peak pullout load and pullout energy.

DOI:

10.14359/12258


Document: 

SP206-24

Date: 

April 1, 2002

Author(s):

Z. Li, A. C. P. Liu, and C. K. Y. Leung

Publication:

Symposium Papers

Volume:

206

Abstract:

This report presents an experimental investigation on the effect of polyvinyl alcohol (PVA) polymer modified alkali resistance (AR) glass fiber reinforced cementitious composites (GFRC). The performance of the alkali resistance glass fibers in blended cementitious matrix was evaluated by a series of tensile and flexural tests. Specimens with different amounts of PVA polymer were tested. Specimens under dry air and moist curing environment were compared. The results indicate that the addition of 2% (weight)PVA polymer shows improvement in strength, toughness, ductility, and deflection. SEM studies indicated that PVA forms a thin film covering on the glass fiber surface, which inhibits the nucleation of calcium hydroxide crystals on the glass bibres surface and to enhance the formation of C-S-H during the hydration. The presence of PVA shows the ability to reduce the embrittlement of the GFRC and changes the failure mode from brittle to ductile. EDAX results shows that the Ca/Si ratio in the fiber interface of the PVA modified specimens is greatly reduced.

DOI:

10.14359/12265


Document: 

SP206-11

Date: 

April 1, 2002

Author(s):

B. Bissonnette, J. Marchand, C. Martel, and M. Pigeon

Publication:

Symposium Papers

Volume:

206

Abstract:

The influence of superplasticizer on the chemical (total) and autogeneous (external) shrinkage of hydrating cement pastes was investigated. Three different commercial CSA Type 10 cemeents were tested. Test variables also included type of superplasticizer (melamine-based and naphtalene-based) and dosage in admixture (three different dosages). All neat paste mixtures were prepared at a water/cement ratio of 0.35. Chemical shrinkage measurements were carried out using the classical dilatometric method initially developed by Le Chatelier. Autogeneous shrinkage measurements were performed according to the immersion method. All tests were performed in a temperature-controlled bath kept at 20 degrees C. Test results indicate that the dosage in admixture influences the kinetics and magnitude of both chemical shrinkage and autogeneous shrinkage, especially during the first 24 hours. Beyond that period, the overall effects of dosage were observed to be less pronounced. Data also emphasize the potentioal importance of the type of superplasticizer upon early volume changes. Though the investigated cements are known to sometimes exhibit quite different early-age behaviors in the field, no significant differences were observed as far as chemical shrinkage and autogeneous shrinkage are concerned.

DOI:

10.14359/12252


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