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International Concrete Abstracts Portal

Showing 1-5 of 15 Abstracts search results

Document: 

SP290

Date: 

October 1, 2012

Author(s):

Editors: Anton K. Schindler, Jiri G. Grygar and W. Jason Weiss / Sponsored by: ACI Committee 231 and ACI Committee 213 and ACI Committee 130

Publication:

Symposium Papers

Volume:

290

Abstract:

This CD consists of 14 papers presented at the ACI Fall Convention, Toronto, Canada, October 2012, and sponsored by ACI Committees 130, Sustainability of Concrete; 213, Lightweight Aggregate and Concrete; and 231, Concrete Properties at Early Ages.These papers cover the following general topics: impact on sustainability, mixture proportioning, internal curing methods and their implementation, hydration impacts, volume change effects, mechanical properties, cracking tendency, durability aspects, life-cycle cost analysis, and case studies that document the use of internal curing in full-scale production applications. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-290

DOI:

10.14359/51684134


Document: 

SP290-01

Date: 

September 14, 2012

Author(s):

Benjamin E. Byard and John Ries

Publication:

Symposium Papers

Volume:

290

Abstract:

The internal curing process is often referred to as “curing concrete from the inside out”. This process is accomplished by using materials that absorb water, such as lightweight aggregate, to replace some of the normalweight aggregate in the freshly placed concrete mixture. This absorbed water can then be released from the aggregate into the paste fraction as the paste begins to desiccate. By doing this the hydration reactions of cement and supplementary cementitious materials are enhanced, and capillary stresses are reduced as the water is readily released from the absorbent materials. This paper gives a general overview of internal curing, and will show how internal curing plays a practical and economical role in today’s move toward sustainable concrete. The paper will explain how internal curing works, why internal curing is used, summarize the modern history of internal curing, and how it affects the carbon footprint of a concrete mixture. In addition, how to adjust the concrete mixture to provide appropriate amount of internal curing, and reduce the life-cycle costs of the concrete. Examples of real projects that have used internally cured concrete will then be highlighted.

DOI:

10.14359/51684170


Document: 

SP290-10

Date: 

September 14, 2012

Author(s):

Benjamin E. Byard, Anton K. Schindler, and Robert W. Barnes

Publication:

Symposium Papers

Volume:

290

Abstract:

One strategy for achieving excellent long-term performance of concrete bridge decks is to combine low permeability with minimal early-age cracking. Low permeability can be achieved through the use of concretes with low water-cement ratios; however, topical curing techniques are usually insufficient to maximize hydration and minimize autogenous shrinkage effects. This autogenous shrinkage causes stresses in restrained concrete, which can lead to deleterious early-age cracking. Curing effectiveness can be enhanced through the implementation of prewetted lightweight fine aggregates. Internal curing is provided as the aggregate water gradually desorbs into the surrounding paste. A study of the early-age behavior of internally cured concrete is described in this paper. Internal curing was provided by means of expanded shale, clay, and slate lightweight fine aggregates. Ten mixtures with water-cement ratios of 0.42, 0.36, and 0.30 were investigated. Compressive and tensile strengths of the internally cured concretes were similar to or slightly greater than the strengths of their non-internally cured counterparts, and concrete stiffness decreased as expected in the internally cured mixtures. Autogenous shrinkage strains and stresses were found to increase as the water-cement ratio decreases. However, the autogenous effects were reduced or eliminated in the internally cured concretes.

DOI:

10.14359/51684179


Document: 

SP290-13

Date: 

September 14, 2012

Author(s):

Daniel Cusson and Jim Margeson

Publication:

Symposium Papers

Volume:

290

Abstract:

Highway bridges and parking structures, subject to coupled effects of mechanical loads and corrosion, often show early signs of distress such as concrete cracking and rebar corrosion leading to reduced structural performance and shortened service life. One solution to this problem is to use low-shrinkage low-permeability high-performance concrete (HPC) for bridge decks exposed to de-icing salts and severe loading conditions. A new HPC was formulated to achieve low shrinkage and low permeability, high early-strength, and 28-day compressive strength over 60 MPa (8,700 psi). Its mechanical performance and durability were tested both in the lab and field under severe test conditions, including restrained shrinkage, cycling loading, freezing and thawing cycles, and application of de-icing salts. Models were developed and calibrated to predict structural performance and service life of concrete bridge decks under severe exposure conditions. Prediction models indicate that bridge decks designed with low-shrinkage HPC can achieve a service life up to 100 years. Compared to normal concrete decks, short-t t-to-medium span bridge decks using low-shrinkage HPC could be built at a comparable initial construction cost, but at less than 35% of the life-cycle cost.

DOI:

10.14359/51684182


Document: 

SP290-09

Date: 

September 14, 2012

Author(s):

T. Fu, T. Deboodt and J. H. Ideker

Publication:

Symposium Papers

Volume:

290

Abstract:

In this research, ten different high performance concrete (HPC) mixtures internally cured by pre-wetted lightweight fine aggregate (LWFA) and/or shrinkage reducing admixture (SRA) were cast and their drying shrinkage strain was monitored using the ASTM C157 test. The data collected was used to evaluate six shrinkage prediction models, namely, ACI 209 model, CEB90 model, AASHTO model, B3 model, GL2000 model and ALSN model. The study finds that the GL2000 model shows the best overall performance in predicting shrinkage strain for internally cured HPC. However, more accurate long-term shrinkage prediction can be achieved based on the current ACI 209 model with experimental measurements. This proposed procedure is capable to predict long-term drying shrinkage for concrete using local materials mixture by using short-term experimental measurements.

DOI:

10.14359/51684178


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