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International Concrete Abstracts Portal

Showing 1-5 of 22 Abstracts search results

Document: 

SP261-21

Date: 

October 1, 2009

Author(s):

G.Y. Kim, Y.S. Kim, and T.G. Lee

Publication:

Symposium Papers

Volume:

261

Abstract:

In this study, the effects of high temperature on mechanical properties of high strength concrete were experimentally investigated. The effect of elevated temperatures ranging from 20 to 700 °C (68 to 1292 °F) on the material mechanical properties of normal-weight and lightweight aggregate high-strength concrete of 60 MPa grade was evaluated. Tests were conducted on Ø100 × 200 mm (3.94 × 7.87 in.) cylinder specimens. The specimens were tested under both stressed and unstressed conditions. The specimens were preloaded to 20 and 40% of their ultimate compressive strength at room temperature and subjected to temperatures ranging from 100 to 700 °C (212 to 1292 °F), and the compressive strength compared to that observed at 20 °C (68 °F).

DOI:

10.14359/51663218


Document: 

SP261-16

Date: 

October 1, 2009

Author(s):

I. Moundoungou, D. Bulteel, E. Garcia-Diaz, and P. Dégrugilliers

Publication:

Symposium Papers

Volume:

261

Abstract:

Alkali-silica reaction (ASR) concrete expansion tests at 60°C (140°F) and 100 % relative humidity showed that siliceous limestone aggregates could have pessimum behavior similar to that of flint aggregate. For a given content of alkalis, a concrete made with fine and coarse reactive aggregates expands less than concrete made with reactive fine aggregate and no reactive coarse aggregate. The higher the reactivity of the aggregate, the higher is the observed expansion reduction. This expansion reduction effect could be used to make concrete that would have a low level expansion.

DOI:

10.14359/51663213


Document: 

SP261-09

Date: 

October 1, 2009

Author(s):

P. Desnerck, G. De Schutter, and L. Taerwe

Publication:

Symposium Papers

Volume:

261

Abstract:

Aggregate interlock along inclined cracks is one of the basic mechanisms which contributes to the shear resistance of reinforced concrete members. In self-compacting-concrete (SCC) the amount of coarse aggregates is lower than in conventional vibrated concrete (CVC). This different grading could have an influence on the aggregate interlock. To study this effect, push-off tests are carried out. The shear plane of the specimen is crossed by steel bars resulting in reinforcement ratios ranging between 0.45 and 2.68%. It follows that the experimentally determined shear friction of self-compacting concrete is slightly higher than the shear friction of CVC. However, the vertical displacement corresponding with the ultimate shear strength is larger.

DOI:

10.14359/51663206


Document: 

SP261-08

Date: 

October 1, 2009

Author(s):

J. Kwasny, M. Sonebi, and P.A.M. Basheer

Publication:

Symposium Papers

Volume:

261

Abstract:

The performance of self-consolidating pastes was optimized by studying the effect of three mix composition parameters, limestone powder (LSP) content, dosage of superplasticizer (SP), and that of viscosity-modifying admixture (VMA), in a statistically designed experiment. Four properties of the pastes were measured: fluidity (mini-slump flow), Vicat setting times, volume change in the fresh state, and 28-day compressive strength. The optimization was preceded by the evaluation of the response surfaces of all chosen properties in the specified ranges of the three variables. The response surface results emphasized the primary and secondary effects on the properties of cement paste. The optimization indicated that pastes with properties acceptable for self-consolidating applications could be obtained with a moderate LSP content (for example, 19.5% by mass of total powder) and low dosage of the chemical admixtures (for example, 0.64% of SP and 0.01% of VMA by mass of total powder).

DOI:

10.14359/51663205


Document: 

SP261-06

Date: 

October 1, 2009

Author(s):

D. Feys, G. De Schutter, and R. Verhoeven

Publication:

Symposium Papers

Volume:

261

Abstract:

Self-compacting concrete (SCC) is a very flowable cementitious material, which does not need external vibration during casting. On the other hand, somewhat surprisingly, pumping of self-compacting concrete requires higher pumping pressures than traditional concrete. This paradox can be fundamentally explained by studying the rheological properties of self-compacting concrete and linking them to pumping operations. This paper describes full-scale pumping tests on self-compacting concrete. The first part deals with the influence of the rheological properties of the concrete on the pumping process, showing that viscosity and shear thickening have a major importance. The second part discusses the influence of pumping on the rheological properties of the concrete, clearly showing a decrease in viscosity due to pumping. Structural breakdown and air content change the rheological properties of the SCC. If structural breakdown dominates the effects of the air content, the yield stress and plastic viscosity will decrease, and the SCC will show a larger tendency to segregate. If the effects of the air content dominate, the yield stress of the SCC will increase, possibly leading to improper filling of the formwork.

DOI:

10.14359/51663203


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