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International Concrete Abstracts Portal

Showing 1-5 of 49 Abstracts search results

Document: 

SP209-32

Date: 

September 26, 2002

Author(s):

G. A. Arenes-Oliva, M. Bergin, and A. M. Zayed

Publication:

Symposium Papers

Volume:

209

Abstract:

The effect of varying cement source fresh and hardened concrete properties is studied under hot weather conditions. For the seven ASTM Type 11 cements studied here, the same mix proportioning was adopted at a mixing temperature of 95 F (35 C) with a constant dosage of water reductiag and air entraining admixtures. Properties of fresh concrete including slump loss over an extended mixing period (EMP) of 90 minutes, air content, and setting times are reported. Also, hardened properties including compressive strength development and rapid chloride permeability test data are reported. Results indicate that the rate of slump loss and setting times are affected by the cement compound composition, calcium sulfate content aad calcium sulfate type. The compressive strength, under hot mixing conditions, is found to be dependent on composition, fineness and morphology of cement compunds.

DOI:

10.14359/12522


Document: 

SP209-22

Date: 

September 26, 2002

Author(s):

H. Akita, H. Koide, M. Tomon, and S. M. Han

Publication:

Symposium Papers

Volume:

209

Abstract:

The best way to investigate the tension softening process is by applying a uniaxial tension force directly on a concrete specimen, because it can measure both tensile strength and the tension softening curve from an identical specimen. However, no standard tests have been adopted to provide a direct measurement of the tension softening curves of concrete. There are three misunderstandings in investigating the tension softening process, concerning the effect of secondary flexure, boundary conditions and notches, Because of these, many inadequate test procedures were proposed until recently. In this paper, the misunderstandings are discussed and clarified in detail with theoretical and experimental considerations. A test procedure for the uniaxial tension test of concrete is proposed with successful test results.

DOI:

10.14359/12512


Document: 

SP209-20

Date: 

September 26, 2002

Author(s):

0. Ple, E. Astudillo de la Vega, G. Bernier and 0. Bayard

Publication:

Symposium Papers

Volume:

209

Abstract:

Numerical and experimental studies or Keactive rowaer doncrete (RPC), reinforced by short steel fibres, under biaxial tensile loading are reported. A semi-analytical model using the Eshelby’s method of inclusion to describe elastic fields perturbation is employed to predict crack nucleation under biaxial tensile strain. A criterion of crack nucleation is investigated theoretically by considering a locally oriented mass of fibres embedded in an homogeneous matrix. An original biaxial crucifonn specimen is designed and fabricated by a systematic testing program guided by the results of a numerical simulation. A prototype machine names ASTREE (developed by SCHENCWLMT) is used in the biaxial test of cruciform specimens. An adaptive control test method was designed, and digital image correlation is employed to obtain the displacement field and the microstructural stress concentration. These preliminary observations support our theoretical analysis based on Eshelby’s inclusion and aims at a better understanding of the mechanisms involved in the RPC damage process.

DOI:

10.14359/12510


Document: 

SP209-09

Date: 

September 26, 2002

Author(s):

L. Arnaud and V. Cerezo

Publication:

Symposium Papers

Volume:

209

Abstract:

This paper deals with the measurement of physical properties (mechanical, thermal, acoustical) of various formulations of concrete containing vegetable particles. Such material is mde up with hemp shives mixed with lime binders. Shives are very porous and so liglitweight. Thus, this concrete presents a high porosity related to the microscopic porosity of the shives and the macroscopic porosity due to the arrangement of particles. Moreover, this material presents a ductile behavior and can bears high strain without been destroyed. Depending on the binder proportion, the mechanical properties of vegetable concrete cover a wide range: maximum stress in between 0.4 and 1.2 MPa, Young madulus in between 20 and 90 MPa, strain at maximum stress in between 4 and 10%. The thermal conductivity ranges from 0.06 to 0.11 W.m-1.K-1, sound absorption between 0.5 and 1. The final aim of this study is to optimize the formulation of vegetable concrete according to its use (wall, floor, roof. . .). A theoretical model made with self-consistent method allows to calculate precisely the coefficient of conductivity l as a function of the mixture proportion and the compactness level. A comparison with experimental measurements shows a good accuracy of the results.

DOI:

10.14359/12499


Document: 

SP209-15

Date: 

September 26, 2002

Author(s):

J. Dimig, E. Rogalla, and J. Duntemann

Publication:

Symposium Papers

Volume:

209

Abstract:

The current ACI Building Code (ACI 318-99) procedure for the shear design of pile caps is the same approach used for two-way slabs. The procedure involves determining a section thickness such that the concrete shear stress (@,) is greater than the applied shear stress (vu) on the critical section. For footings supported on piles, the ACI Code recognizes that these general provisions are not applicable as the depth of the footing increases and some of the pile loads fall within the critical section. In deep pile caps, the critical section may even be located outside the footing, making it impossible to investigate shear at d or dn. For these situations, the ACI Commentary states that the designer should examine shear strength at the face of the column and it refers to procedures outlined in the CRSI Handbook (1996). ACI has recently published proposed revisions for the ACI 318-02 Code, which promotes the use of strut-and-tie models as an alternative to the existing ACI and CRSI procedures. The design methodology involves limiting the concrete stresses in the compression struts and nodal zones to insure that the tension tie (longitudinal reinforcement) yields before significant diagonal cracking develops in the compression struts or crushing in the nodal zones. This paper explains the existing ACI and CRSI procedures and the proposed ACI provisions for strut-and-tie design.

DOI:

10.14359/12505


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