International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 13 Abstracts search results

Document: 

SP218-12

Date: 

February 1, 2004

Author(s):

K. S. Harmon

Publication:

Special Publication

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).

10.14359/13063


Document: 

SP218-11

Date: 

February 1, 2004

Author(s):

M. A. Caldarone and R. G. Burg

Publication:

Special Publication

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.

10.14359/13062


Document: 

SP218-10

Date: 

February 1, 2004

Author(s):

F. de Jesus Cano Barrita, T. W. Bremner, and B. J. Balcom

Publication:

Special Publication

Volume:

218

Abstract:

This work is part of a much larger program to evaluate high performance concrete mixtures that can be used successfully in hot dry climates. In this research magnetic resonance imaging (MRI) was used to measure the effectiveness of extending the moist curing period by incorporating some saturated lightweight aggregates into a concrete mixture being placed in hot dry climatic conditions. A series of concrete mixtures were prepared and moist cured for either 0, 0.5, 1 or 3 days, or by using a curing compound, followed by air drying at 38°C and 40% relative humidity. To accomplish this, 11% by volume of the total aggregate content was replaced with lightweight aggregate. Type I white portland cement and quartz aggregate plus the lightweight aggregate were all selected for their low iron content to minimize adversely affecting the MRI measurements. The concrete mixtures were low strength concrete (W/C=0.60), self-consolidating concrete (W/C=0.33 containing 30% fly ash), and high strength concrete (W/ C=0.30 containing 8% silica fume). Specimens prepared with these mixtures were cast in triplicate. After curing, the specimens were dried in one direction in an environmental chamber at 38°C and 40% relative humidity. As the specimens were drying, magnetic resonance imaging was used to determine the evaporable water distribution. After the drying period, the specimens were conditioned in an oven at 105°C and water absorption tests were undertaken to determine their sorptivity. The profiles obtained during drying indicated a reduced moisture loss with increasing length of moist curing. Also the use of saturated lightweight aggregate does not eliminate the need to provide some external moist curing for a reduced period of time. The results from water uptake experiments indicated that the addition of lightweight aggregate particles substantially increases the sorptivity in low strength concrete while it has only a marginal effect in both self-consolidating and high strength concrete, when compared to the same concrete mixtures containing only normal-weight aggregate.

10.14359/13061


Document: 

SP218-09

Date: 

February 1, 2004

Author(s):

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

Publication:

Special Publication

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.

10.14359/13060


Document: 

SP218-08

Date: 

February 1, 2004

Author(s):

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

Publication:

Special Publication

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.

10.14359/13059


Document: 

SP218-07

Date: 

February 1, 2004

Author(s):

C. L. Tasillo, B. D. Neeley, and A. A. Bombich

Publication:

Special Publication

Volume:

218

Abstract:

In initiating the final phase of modernizing the locks and dams on the Monongahela River, the U.S. Army Corps of Engineers, Pittsburgh District, used float-in and in-the-wet technology to build the new Braddock dam. This is the first use of such technology for an inland navigation project in the United States, and was employed to eliminate the cost and construction time associated with a conventional cofferdam for mass concrete construction. The new Braddock dam design was fabricated as two large, hollow-core segments. Unlike such applications used for offshore structures, the inland application was limited by navigational draft, and lock and bridge clearances. This restricted the overall dimensions and mass of the segments. The use of lightweight concrete in a significant portion of the two large dam segments was central to the success of the design. Good planning, an understanding of the concrete materials, and quality control were critical to project success.

10.14359/13057


Document: 

SP218-06

Date: 

February 1, 2004

Author(s):

G. S. Sylva, N. H. Burns, and J. E. Breen

Publication:

Special Publication

Volume:

218

Abstract:

The Texas Department of Transportation sponsored Project 0-1852 at The University of Texas at Austin to determine the feasibility of using high-performance lightweight concrete in composite bridge girders and precast concrete deck panels. The scope of the research project included lightweight concrete mixture design development; full scale testing of TxDOT Type A (AASHTO Type I) girders with composite decks; an analytical design comparison of normal and lightweight concrete girders with various deck combinations; and an economic analysis. The purpose of this paper is to highlight some of the findings of this research to give engineers and designers a better understanding of high-performance lightweight concrete and its use in composite bridge systems. Some of the potential advantages of using lightweight concrete include lower loads on the substructure and foundation, lower crane capacities, increase in live load capacity, and lower shipping costs. However, lightweight concrete has unique features that must be considered during the design phase to insure a successful project. Some of these considerations include higher material costs and the higher elastic shortening losses that will result due to a lower modulus of elasticity.

10.14359/13056


Document: 

SP218-05

Date: 

February 1, 2004

Author(s):

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

Publication:

Special Publication

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.

10.14359/13055


Document: 

SP218-04

Date: 

February 1, 2004

Author(s):

P. Fidjestol

Publication:

Special Publication

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.

10.14359/13053


Document: 

SP218-03

Date: 

February 1, 2004

Author(s):

M. J. Kowalsky and H. M. Dwairi

Publication:

Special Publication

Volume:

218

Abstract:

This paper discusses four aspects related to the seismic behavior of structures composed of lightweight concrete. Following a brief discussion of the merits of lightweight concrete, the past seismic performance of the material is discussed. The second portion of the paper discusses research that has been conducted on the seismic behavior of lightweight concrete structures and research on parameters that influence the seismic behavior of lightweight concrete. This is followed by a discussion of various existing code-based provisions that have an effect on the seismic design of lightweight concrete structures. Lastly, the paper concludes with a discussion of future research needs.

10.14359/13052


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