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International Concrete Abstracts Portal

Showing 1-5 of 8 Abstracts search results

Document: 

20-192

Date: 

March 1, 2021

Author(s):

A. M. Yasien, M. T. Bassuoni, A. Abayou, and A. Ghazy

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

With aging, concrete structures exhibit deterioration due to multiple reasons. Consequently, repair processes become overwhelmingly essential to extend the service life of structures. This experimental study investigated nano-modified concrete cast and cured under cyclic freezing/low temperatures, including its applicability to partial-depth repair. Seven mixtures, incorporating general-use cement, fly ash (0 to 25%), and nanosilica (0 to 4%) with a cold weather admixture system (antifreeze/accelerator) were tested. The mixtures were evaluated based on fresh, hardened, and durability properties as well as their compatibility with parent/substrate concrete. In addition, mercury intrusion porosimetry and thermogravimetric analysis were conducted to assess the evolution of microstructure under cold temperatures. The incorporation of 4% nanosilica in the cementitious binder, even with the presence of 15% fly ash, markedly enhanced the performance of concrete cast and cured under low temperatures without protection; thus, it may present a viable option for cold weather applications including repair.

DOI:

10.14359/51729331


Document: 

103-M43

Date: 

September 1, 2006

Author(s):

Kenneth C. Hover

Publication:

Materials Journal

Volume:

103

Issue:

5

Abstract:

Surface drying of freshly placed concrete is influenced by the evaporative conditions of the job-site microclimate. The influence of the combined effects of air and concrete temperature, relative humidity, and wind speed are often estimated by use of the equations graphically represented by the evaporation rate nomograph published in multiple ACI documents and elsewhere. This paper further explores the background of the nomograph, from its origins over 200 years ago to its current form, which is based on evaporation rates observed at Lake Hefner in Oklahoma in 1950 to 1951. By understanding the background and the fundamental relationships expressed in the nomograph, one comes to understand its intent, capability, limitations, and instructions for proper use.

DOI:

10.14359/18161


Document: 

91-M09

Date: 

January 1, 1994

Author(s):

ACI Committee 301

Publication:

Materials Journal

Volume:

91

Issue:

1

Abstract:

These specifications are a reference standard which the engineer or architect may make applicable to any building project by citing them in the project specifications. He supplements them as needed by designating or specifying individual project requirements. The document covers materials and proportioning of concrete; reinforcing and prestressing steels; production, placing, and curing of concrete; and formwork design and construction. Methods of treatment of joints and embedded items, repair of surface defects, and finishing of formed surfaces are specified. Separate chapters are devoted to slab construction and finishing, architectural concrete, massive concrete, and materials and methods for constructing post-tensioned concrete. Provisions governing testing, evaluation, and acceptance of concrete as well as for acceptance of the structure are included.

DOI:

10.14359/4452


Document: 

90-M48

Date: 

September 1, 1993

Author(s):

R. L. Day and M. N. Haque

Publication:

Materials Journal

Volume:

90

Issue:

5

Abstract:

This study presents an analysis of the influence of specimen size on the measured compressive strength of plain and fly ash concretes exposed to standard and cold curing. Strength tests were performed on three classes of air-entrained concrete using two sub-bituminous fly ashes at three replacement levels. Analysis of the present experimental results, combined with other results presented in the literature, shows that the compressive strength indicated by 75-mm cylinders is statistically identical to that indicated by 150-mm cylinders. Analysis suggests that this one-to-one relationship between strength of 75- and 150-mm cylinders may be valid for concrete strengths up to 50 MPa (7250 psi). Further analysis of published data leads to the conclusion that the equality of strength among specimen sizes also includes 100-mm- diameter cylinders. The type of mold used to cast test cylinders, whether cardboard, steel, or tin, does not have a significant effect on the trends observed.

DOI:

10.14359/3786


Document: 

88-M13

Date: 

January 1, 1991

Author(s):

ACI Committee 304

Publication:

Materials Journal

Volume:

88

Issue:

1

Abstract:

Includes a short history of, and information on, the basic design and operation of equipment used for the production of concrete by volumetric measurement and continuous mixing (VMCM), frequently called mobile mixers. Definitions, applications, and quality assurance testing are discussed. The use of this equipment is compared to weigh-batch-mix equipment for some of the limited differences.

DOI:

10.14359/3363


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