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International Concrete Abstracts Portal

Showing 1-5 of 1029 Abstracts search results

Document: 

SP-340-06

Date: 

April 1, 2020

Author(s):

Maria Kaszynska and Adam Zielinski

Publication:

Symposium Papers

Volume:

340

Abstract:

The research paper presents an analysis of autogenous shrinkage development in self-consolidating concrete (SCC). The first stage of the study involved an evaluation of concrete susceptibility to cracking caused by shrinkage of SCC with natural and lightweight aggregate. The shrinkage was tested on concrete rings according to ASTM C 1581/C 1581M- 09a. The influence of aggregate composition, the water content in lightweight aggregate, and SRA admixture on the reduction of concrete susceptibility to cracking, due to the early-age shrinkage deformation was determined. In the second stage of the research, the innovative method measurement of autogenous shrinkage was developed and implemented. The tests were performed on concrete block samples, dimensions 35x150x1150 mm, that had the same concrete volume as ring specimen in the ASTM method. Linear deformation of the concrete samples was measured in constant periods of 500 s using dial gauges with digital data loggers. The investigation allowed evaluating of the influence of water/cement (w/c) ratio of 0.28, 0.34, 0.42, and of aggregate composition on the development of autogenous shrinkage in different stages of curing SCC. The results were compared to existing material models proposed by other researchers. The conducted study indicated a significant influence of the w/c ratio and composition of aggregate on the concrete susceptibility to crack caused by the autogenous shrinkage deformation.


Document: 

SP-339_12

Date: 

March 1, 2020

Author(s):

Burkhart Trost, Harald Schuler, and Bozidar Stojadinovic

Publication:

Symposium Papers

Volume:

339

Abstract:

Sliding failure of reinforced concrete shear walls was observed after the Chilean earthquakes in 1985 and 2010, during shaking table tests, and in many quasi-static cyclic shear walls tests. Sliding may occur along cold joints or flexural cracks that remain open due to permanent deformations induced during cyclic loading. If it occurs, sliding can significantly reduce the horizontal force resistance and change the deformation mechanism of reinforced concrete shear walls, and thereby markedly affect the seismic performance of shear wall buildings. This study provides the interaction diagrams intended to help reinforced concrete shear wall designers exclude the sliding failure mode. Regions where sliding, shear, and flexural failure modes are expected are delineated according to the shear wall shear span to length ratio, the axial force, the horizontal and vertical reinforcement ratios, and the concrete strength. These interaction diagrams are derived using a cyclic reinforced concrete wall response model that considers flexure, shear and sliding load-deformation relationships and the interaction between them. The inter-action diagram is used to develop design recommendations on how to avoid the sliding failure of reinforced concrete shear walls under earthquake loading.


Document: 

SP-337_06

Date: 

January 23, 2020

Author(s):

Edward (Ted) Moffatt, Michael Thomas and Andrew Fahim

Publication:

Symposium Papers

Volume:

337

Abstract:

In 1978, the Canadian Centre of Mineral and Energy Technology (CANMET) initiated a longterm study to determine the performance of concrete in a marine environment. Between 1978 and 1994, over three hundred prisms as part of 14 different experimental phases were placed at the mid-tide level at the Treat Island exposure site. Treat Island is an outdoor exposure site operated by the U.S. Army Corps of Engineers, and lies in the Passamaquoddy Bay, part of the Bay of Fundy, near the town of Eastport in Maine. Following 25 years of exposure, the blocks were retrieved after being exposed to tidal conditions representing approximately 18,250 cycles of wetting and drying, and 2,500 cycles of freezing and thawing. This paper presents the durability performance of concrete from several phases of the CANMET study. This includes concrete incorporating various levels of supplementary cementing materials (up to 80% by mass of cementing material in some cases), with normal density and light-weight aggregate. The paper also compares output from the service-life model Life-365 with experimental chloride profile data. The results indicate the efficacy of SCMs in increasing the concrete resistance to chloride penetration. However, use of very high levels of these materials was found to render the concrete more susceptible to surface scaling. The results also showed that Life-365 model can predict chloride penetration adequately with very simple inputs.


Document: 

SP-337_05

Date: 

January 23, 2020

Author(s):

Kjell Tore Fosså and Widianto

Publication:

Symposium Papers

Volume:

337

Abstract:

This paper describes the development in concrete technology for offshore concrete structures from the 1970’s until now and discusses some potential topics for future research which would result in more cost-effective offshore concrete structures.

Most of the offshore concrete structures constructed in the last 4 decades are still in operation, with no or only minor maintenance required, even though the average age for these structures in the North Sea is more than 25 years. The compressive strength in offshore structures has gradually increased from about 40MPa (5800 psi) in the 1970’s to more than 100MPa (14500 psi) in some of the latest concrete structures. Standards and concrete specifications have been revised several times during these years. In parallel, the knowledge from several research and development programs has been used to further improve the concrete properties and overcome the limitations. Focus has been primarily to improve the compressive strength of the concrete as well as the durability and concrete workability. The cement and admixture industry have been heavily involved in research programs to further adapt and develop these material properties. The result of the product developments in the concrete constituency has also improved cost-effectiveness and durability (including overall life-cycle cost-effectiveness) for offshore concrete structures.

With the new generation technology, the technical limitations we face today will be overcome. With more knowledge and improved technology, the quantity and size of cracks in concrete in service are expected to be reduced, which would also improve durability. In addition, the focus in the future will also be on sustainable and environmentally friendly materials.


Document: 

SP-336_01

Date: 

December 11, 2019

Author(s):

James Lafikes, Rouzbeh Khajehdehi, Muzai Feng, Matthew O’Reilly, David Darwin

Publication:

Symposium Papers

Volume:

336

Abstract:

Supplementary cementitious materials (SCMs) in conjunction with pre-wetted fine lightweight aggregate to provide internal curing are being increasingly used to produce high performance, low-shrinking concrete to mitigate bridge deck cracking, providing more sustainable projects with a longer service life. Additionally, the SCMs aid in concrete sustainability by reducing the amount of cement needed in these projects. This study examines the density of cracks in bridge decks in Indiana and Utah that incorporated internal curing with various combinations of portland cement and SCMs, specifically, slag cement, Class C and Class F fly ash, and silica fume, in concrete mixtures with water-cementitious material ratios ranging from 0.39 to 0.44. When compared with crack densities in low-cracking high-performance concrete (LC-HPC) and control bridge decks in Kansas, concrete mixtures with a paste content higher than 27% exhibited more cracking, regardless of the use of internal curing or SCMs. Bridge decks with paste contents below 26% that incorporate internal curing and SCMs exhibited low cracking at early ages, although additional surveys will be needed before conclusions on long term behavior can be made.


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