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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP317

Date: 

September 11, 2017

Publication:

Symposium Papers

Volume:

317

Abstract:

Editors: Mohamed T. Bassuoni, R. Doug Hooton, and Thanos Drimalas

The papers presented in this volume were included in a three-part session sponsored by ACI Committee 201, Durability of Concrete, about sulfate attack on concrete at the ACI Convention in Philadelphia, PA, on October 23-24, 2016. In line with the practice and requirements of the American Concrete Institute, peer review, followed by appropriate response and revision by authors, has been used.

Deterioration of concrete due to sulfate attack is a complex process characterized by multiple damage manifestations including volumetric expansion, cracking, spalling, softening, and in some cases mushiness. Sulfate attack can generally be classified as internal or external to the cementitious matrix, and the underlying damage modes can be chemical or physical. The scope of papers involves a multitude of theoretical and experimental aspects of different forms of sulfate attack. Readers are urged to critically evaluate the work presented herein, in the light of the large body of knowledge and scientific literature on this durability topic.

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-317

DOI:

10.14359/51701103


Document: 

SP317-04

Date: 

June 1, 2017

Author(s):

L.E. Burris and K.E. Kurtis

Publication:

Symposium Papers

Volume:

317

Abstract:

Cement production accounts for 5-7% of annual anthropogenic CO2, making it one of the largest contributors to CO2 emissions. The use of alternative cementitious materials and binders (ACMs) such as calcium sulfoaluminate cement (CSA), calcium aluminate cement (CAC), magnesium phosphate cement (MPC) and alkali-activated binders (AA) are one method of reducing the greenhouse gases associated with the production of concrete. These materials often can be produced at lower temperatures than ordinary portland cements (OPC) and have lower calcium contents, reducing the emissions associated with CO2 released from calcium carbonate during calcination. However, before alternative cements can become viable greener alternatives to ordinary portland cements their chemistry, microstructure, and resulting properties, with respect to durability must first be understood. Using standard mortar bar sulfate testing showed that CSA, AA, and blended CAC systems may be appropriate for use in high sulfate environments, while pure CAC and MPC systems should be avoided. However, additional characterization of the sulfate exposed samples, showing layers of altered microstructures in most samples, suggests that the mechanisms of expansion and degradation due to sulfate ingress, as they are understood for portland cement systems, may not be adequate for determining resistance to sulfate degradation for alternative binder systems. Therefore, additional study is warranted before recommendations on use of ACMs in sulfate-laden environments can be made.

DOI:

10.14359/51700843


Document: 

SP317-08

Date: 

June 1, 2017

Author(s):

Julie Ann Hartell, Andrew J. Boyd, and Patrice Rivard

Publication:

Symposium Papers

Volume:

317

Abstract:

The phenomena involving hydrated cement paste and a source of sulfate anion have been extensively studied over the last four decades. The present publication provides an overview of past external sulfate attack studies along with current views on the accuracy of standard methods to evaluate the performance of a concrete mixture in service; illustrating the need to find other means of laboratory testing based on “real” exposure conditions representative of sulfate reaction kinetics encountered in field structures. This study evaluates the efficacy of stresswave propagation testing to detect concrete microstructural disparities related to sulfate-induced damage. While respecting traditional means of inducing an external sulfate attack in the laboratory (complete immersion in a 5% sodium sulfate solution), the experimental study proposed a different methodology for evaluating the extent of sulfate degraded concrete in the laboratory. Over a 2-year exposure term, the extent of degradation of various specimen types, replicating transport mechanisms reminiscent of those seen in the field, were evaluated using ultrasonic pulse velocity. Through statistical analysis, the results discussed demonstrated that the test procedures conducted were reliable for assessing the changes in behaviour observed.

DOI:

10.14359/51700847


Document: 

SP317-03

Date: 

June 1, 2017

Author(s):

A. Bonakdar, and B. Mobasher

Publication:

Symposium Papers

Volume:

317

Abstract:

External sulfate attack is often described by a diffusion-reaction mechanism which leads to the decomposition of hardened cement paste and cracking of concrete. In most studies, the linear expansion of mortar/concrete prisms is measured according to ASTM C1012. Even though this test can be used to determine the suitability of a mixture for specific sulfate exposure conditions, it does not provide insights on the actual degradation process. This paper presents a series of experiments performed to quantify the damage evolution on cement-based mortars with and without fly ash. Conventional expansion tests were conducted, followed by measuring the chemical and mechanical changes on the cross section of the specimens using EDS and microhardness techniques. The overall damage was further evaluated using a novel flexural fracture test on the specimens. It was observed that partial replacement of cement with class F fly ash reduced the level of mechanical damage in exposure to sulfate attack.

DOI:

10.14359/51700842


Document: 

SP317-10

Date: 

June 1, 2017

Author(s):

Federico M. Aguayo, Thano Drimalas, and Kevin J. Folliard

Publication:

Symposium Papers

Volume:

317

Abstract:

A number of research studies on chemical sulfate attack have been conducted, and considerable disagreement over the mechanisms still exist. They reveal that several factors can influence the severity and type of attack including the concentration of sulfate ions, pH level, temperature, and the nature of the associated cation. However, the biggest challenge that still remains is a performance test method that can determine the sulfate resistance of cement-based systems within a reasonable timeframe. This laboratory experiment – which was part of an extensive doctoral research program – investigated the use of a new vacuum impregnation technique to accelerate the degradation observed during sulfate attack. The mortar bars were immersed in various sulfate solutions and cation types including sodium, magnesium, and calcium sulfate. The results showed an increased rate of linear expansion from the use of the vacuum impregnation technique when compared to the traditional ASTM C1012 method. However, the measured expansion was significantly influenced by the chemical composition of the binders as well the type of sulfate solution used during testing. The microstructural study revealed that the mechanism of expansion seen when using the vacuum impregnation technique was comparable to mechanisms commonly seen in classic cases of external sulfate attack.

DOI:

10.14359/51700849


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