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International Concrete Abstracts Portal

Showing 1-5 of 13 Abstracts search results

Document: 

SP218-05

Date: 

February 1, 2004

Author(s):

J. A. Ramirez, J. Olek, and B. J. Malone

Publication:

Symposium Papers

Volume:

218

Abstract:

An experimental investigation was conducted to compare the shear strength of lightweight reinforced concrete beams with that of normal-weight concrete companion specimens. The experimental variables were type of coarse aggregate, concrete compressive strength, and distribution of transverse and longitudinal reinforcement. A total of twelve specimens with shear reinforcement were tested. Seven specimens were made with normal-weight aggregate concrete and five specimens were made with lightweight aggregate concrete. The target concrete strengths were 41 MPa and 69 MPa. Measured shear capacities were compared with calculated values according to the 1998 AASHTO LRFD Bridge Specifications (Interim 2001) and ACI 318-02 Building Code. The experimental findings have shown that both code-based methods produce conservative estimates of shear strength within the range of variables considered in the study.

DOI:

10.14359/13055


Document: 

SP218

Date: 

February 1, 2004

Author(s):

Editors: John Ries and Thomas Holm

Publication:

Symposium Papers

Volume:

218

Abstract:

SP-218 This is a compilation of papers addressing “High-Performance Structural Lightweight Concrete” presented October 30, 2002 at the American Concrete Institute Fall Convention in Phoenix, Arizona. This symposium was sponsored by ACI Committee 213, Lightweight Aggregate and Concrete, to report on a wide range of global construction applications incorporating high-performance lightweight-aggregate concrete. This diverse symposium included papers that covered microstructural issues (autogenous shrinkage, internal curing), material and structural properties (transfer length, shear strength, seismic behavior), and applications in large civil structures (long-span balanced cantilever bridges, offshore platform, float-in navigational locks).

DOI:

10.14359/14032


Document: 

SP218-09

Date: 

February 1, 2004

Author(s):

M. R. Geiker, D. P. Bentz, and O. M. Jensen

Publication:

Symposium Papers

Volume:

218

Abstract:

The use of internal curing is a highly effective means of mitigating autogenous shrinkage in cement mortars (w/cm=0.35, 8 % silica fume). Two different sources of internal water supply are compared: 1) replacement of a portion of the sand by partially saturated lightweight fine aggregate and 2) the addition of superabsorbent polymer particles (SAP). At equal water addition rates, the SAP system is seen to be more efficient in reducing autogenous shrinkage at later ages, most likely due to a more homogeneous distribution of the extra curing water within the three-dimensional mortar microstructure. A comparison of the water distribution in the different systems, based on computer modeling and direct observation of two-dimensional cross sections, is given.

DOI:

10.14359/13060


Document: 

SP218-08

Date: 

February 1, 2004

Author(s):

T. A. Hammer, 0. Bjontegaard, and E. J. Sellevold

Publication:

Symposium Papers

Volume:

218

Abstract:

The 3 main factors determining the efficiency of lightweight aggregate (LWA) as internal curing agents in concrete are discussed with reference to published papers: I) total amount of water in LWA, 2) LWA particle spacing factor and 3) the LWA pore structure. A desorption method is suggested to characterize factor 3) directly as the ability of the LWA to release water. The method is applied to two LWA types and the results demonstrate clear differences. The role of water in ordinary aggregates is discussed with reference to autogenous shrinkage measurements in concrete and the equivalent paste. It is concluded that the aggregate with 0.8% water absorption indeed serves as internal curing agent by reducing and delaying the autogenous shrinkage. Finally, it is shown that sealed curing does reduce and delay both the cement and pozzolanic reactions.

DOI:

10.14359/13059


Document: 

SP218-04

Date: 

February 1, 2004

Author(s):

P. Fidjestol

Publication:

Symposium Papers

Volume:

218

Abstract:

Since more than 70 years ago, lightweight concrete has been used in the marine environment. Prime examples use are the ship Selma, grounded off Galveston; and several other ships of that age, laid up, still able to float. Over the last couple of decades, interest in the actual performance of marine lightweight concrete has grown, and in consequence several studies have been made, covering durability, mechanical properties and design procedures. Since other papers in the session will be concerned with many of the structures that have been placed in or near the sea, these objects are not central to the presentation — the same can be said for general questions like design procedures, long term mechanical properties and the like. The central issues of the paper are specifically related to the marine environment: durability — namely reinforcement corrosion — is briefly touched upon, and water absorption over time and at depth is given more attention. This paper is an opportunity to publish data gathered more than 10 years ago; used, but never made available generally.

DOI:

10.14359/13053


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