NB_210_22_2 - NB 210-22-2 ENG - Recommendations on How to Prevent Concrete Failure Due to Sulfur
NB 210-22-2 ENG - Recommendations on How to Prevent Concrete Failure Due to Sulfur
National Bulletin: 210-22-2 Date: December 17, 2021 
Subject: Recommendations on How to Prevent Concrete Failure Due to Sulfur 


 
 
Purpose.   To advise States and Technical Centers on how to prevent internal concrete failure caused by iron sulfide (pyrrhotite) in aggregate and external concrete failure caused by other sulfates in soil and water.     
 
Expiration Date.   September 30, 2022  
 
Background.   Certain quarries have been discovered to have pyrrhotites in the aggregate used for concrete. When in the presence of water, pyrrhotite can oxidize and expand, causing the concrete to fracture from internal pressure. See Attachment A – USGS Pyrrhotite in the U.S. Fact Sheet.

Soluble sulfates found regionally in natural environments are sources external to concrete that cause damage by eroding the concrete surface.
         
 
Explanation.   

Internal concrete damage from sulfur.

Concrete cracking occurs when pyrrhotite (iron sulfide, FeS) in aggregate expands in the presence of water. This phenomenon has been documented in at least 10 countries including the United States.

 

NRCS National Material Specification 522 - Aggregates for Portland Cement Concrete (MS 522) specifies using the American Society for Testing and Materials C33 (ASTM C33) Standard Specification for Concrete Aggregates. While ASTM C33 is already in place for aggregates to be used in certified ready-mix concrete plants, it does not cover concerns with pyrrhotite in aggregate.

 

There is currently not an ASTM standard on the acceptable level of sulfur in concrete aggregate.

External concrete damage from sulfur.

Sulfur sources external to concrete causes damage by eroding the concrete surface. External sources can come from soil and water, which include soluble sulfates found regionally in natural environments.

 

Concrete with either a high water to cement ratio (w/cm) and/or a high tricalcium aluminate (C3A) content is more prone to sulfate attack.

 

 

To protect concrete from sulfur, see Attachment B – NDCSMC Sulfate Attack on Concrete Report and Attachment C – Recommendations to Protect Concrete from Sulfur Attack.    

 
Contact.   If you have any questions, contact Arthur Ramthun, National Construction Engineer, at Arthur.Ramthun@usda.gov or (202) 906-0010 for further assistance.     
 
 

 /s/

J. XAVIER MONTOYA   
Acting Deputy Chief for Science and Technology   

 
 

Attachment A - USGS Pyrrhotite in the US Fact Sheet

Attachment B - NDCSMC-Sulfate Attack on Concrete Report

Attachment C - Recommendations to Protect Concrete from Sulfur Attack    

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