Performance of Alternative Binders in Sulfate Environments

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Title: Performance of Alternative Binders in Sulfate Environments

Author(s): L.E. Burris and K.E. Kurtis

Publication: Special Publication

Volume: 317

Issue:

Appears on pages(s): 1-18

Keywords: Alternative cementitious materials; calcium sulfoaluminate cement; calcium aluminate cement; magnesium phosphate cement; alkali activated binders; sustainability; durability

Date: 6/1/2017

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.