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International Concrete Abstracts Portal

Showing 1-5 of 13 Abstracts search results

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: 

SP218-12

Date: 

February 1, 2004

Author(s):

K. S. Harmon

Publication:

Symposium Papers

Volume:

218

Abstract:

This paper outlines the testing program developed for the Raftsundet Bridge, the first bridge in Norway that utilized pumping for placement of lightweight concrete. It reports the results from parallel testing of both normalweight and lightweight concrete performed during construction of this bridge. This paper also presents a discussion of the economics of using high performance lightweight concrete on the Rugsund Bridge. It also describes the Sundoy Bridge, the second bridge in Norway to utilize pumping for lightweight concrete placement. These projects confirm that high strength lightweight concrete is an economical, efficient construction material for long span bridges. While lightweight concrete may cost more per cubic yard than normalweight concrete, the structure may cost less as a result of reduced dead weight and lower foundation costs (1).

DOI:

10.14359/13063

Document: 

SP218-11

Date: 

February 1, 2004

Author(s):

M. A. Caldarone and R. G. Burg

Publication:

Symposium Papers

Volume:

218

Abstract:

Structural lightweight concrete is defined as concrete made with low-density aggregate having an air-dry density of not more than 115 lb/ft3 (1850 kg/m') and a 28-day compressive strength of more than 2500 psi (17.2 MPa). This paper presents the test results of very low-density structural lightweight concrete mixtures developed in the laboratory for the purpose of finding a suitable mixture for use on a historic building rehabilitation project. Mixture parameters included a specified compressive strength of 3000 psi at 28 days and an air-dry density approaching 70 lb/ft3. Various constituent materials, mixture proportions and curing methods were examined. The result of this research exemplifies the feasibility of achieving very low densities with structural concretes.

DOI:

10.14359/13062

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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