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International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

Document: 

SP325-07

Date: 

July 25, 2018

Author(s):

John Gajda, Jon Feld, and Christopher C. Ferraro

Publication:

Symposium Papers

Volume:

325

Abstract:

ACI defines mass concrete as:

Any volume of concrete in which a combination of dimensions of the member being cast, the boundary conditions, the characteristics of the concrete mixture, and the ambient conditions can lead to undesirable thermal stresses, cracking, deleterious chemical reactions, or reduction in the long-term strength as a result of elevated concrete temperature due to heat from hydration.

While this definition provides an excellent description of the characteristics of concrete to consider for the purposes of defining mass concrete, it does not provide clear and uncontestable requirements for determining whether a particular placement must be treated as mass concrete. The purpose of this paper is to better define what placements should be treated as mass concrete and to provide the reasoning behind the definition. This paper serves as a guide to provide specification writers, owners, engineers, and contractors a way to better identify the need to treat (or not treat) a particular concrete placement as mass concrete.

DOI:

10.14359/51710948


Document: 

SP325-06

Date: 

July 25, 2018

Author(s):

Christopher C. Ferraro, Mang Tia, and Adrian M. Lawrence

Publication:

Symposium Papers

Volume:

325

Abstract:

Mass concrete mixtures used in transportation-related construction often have large percentages of portland cement replaced by supplementary cementitious materials (SCMs), including slag cement, fly ash, or both. The principle benefit for using SCMs in mass concrete is to create a concrete mixture, which has a low temperature rise. The development of the maturity concept focused primarily on the study of concrete without SCMs. Many of the concrete mixtures being utilized today incorporate considerable amounts of SCMs. This paper investigates the relationship of equivalent age and physical properties of different mass concrete mixtures containing portland cement and SCMs.

DOI:

10.14359/51710947


Document: 

SP325-02

Date: 

July 25, 2018

Author(s):

Stephen B. Tatro and James K. Hinds

Publication:

Symposium Papers

Volume:

325

Abstract:

Shear testing using large concrete or RCC specimens is not commonly done. The equipment and manpower required to produce the required concrete volume and the apparatus required to restrain and apply loads can be quite substantial. All are beyond the market capability of most testing organizations. However, large projects may realize significant benefits if properties of concrete from testing of large specimens can be determined.

This paper will provide general guidelines for when large specimen testing may be advantageous and specific examples of shear testing of large specimens. It will also provide recommendations on practical measures to implement when organizing such testing. The presentation is illustrated with an example of a project where production and testing of large shear specimens has been done. The example is from an RCC project where biaxial shear and direct tensile testing has been done. This is not intended to be a case study but a guidance document that may be applied to future projects.

DOI:

10.14359/51710943


Document: 

SP325-03

Date: 

July 25, 2018

Author(s):

Joseph W. Clendenen and Benn B Stutrud

Publication:

Symposium Papers

Volume:

325

Abstract:

The exothermic reaction of the heat of hydration in concrete can lead to problematic temperature differences between the surface and the core of mass concrete elements, which can lead to thermal cracking. This problem has led many engineers to create maximum temperature differential specifications, as well as maximum temperature specifications in response to concerns over producing conditions which may lead to delayed ettringite formation (DEF). In general, there are two solutions to meet this specification: design a mix that has low or an extended heat of hydration or cool the mass element internally as it cures. Regardless of the method, many engineers require that the mass elements’ temperatures be predicted for the mix design, dimensions of placement, day of placement, placing temperature, and construction methods including the use of insulation. Therefore, mass concrete mix designs are tested experimentally for heat of hydration and thermal properties, and those values are used in a mathematical model. The following is a description of using Isothermal calorimetry to generate information about a mix design, which was used to input into the thermal modeling.

DOI:

10.14359/51710944


Document: 

SP325-05

Date: 

July 25, 2018

Author(s):

Ronald Kozikowski and Bruce Suprenant

Publication:

Symposium Papers

Volume:

325

Abstract:

To minimize thermal cracking, specifications for mass concrete often state a maximum allowable temperature difference, ΔT, between the hottest interior location (usually the center) and surface of the mass concrete section in the days following placement. Section 8 of ACI 301-05, “Specifications for Structural Concrete,” did not set such a limit, but the recent revision, ACI 301-10, sets a default value of 35F for the difference (see box). The 35F difference is based on experience with unreinforced mass concrete dams where the consequences of cracking and subsequent water leakage were critical. For mass concrete in mat foundations, large piers, and thick walls, 35F may be unduly conservative.

DOI:

10.14359/51710946


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