Sulfate Attack on Concrete-Development of Test Methods to Address Various Mechanisms of Sulfate Attack (PDF)

Development of Test Methods to Address Various Mechanisms of Sulfate Attack (PDF)

Pdf Summary

The document outlines the development of test methods to address various mechanisms of sulfate attack on concrete, emphasizing the challenges in evaluating sulfate resistance. Sulfate attacks are identified in three types: ettringite, physical, and thaumasite, each impacting concrete differently. While there are no standard methods for assessing sulfate resistance, the ACI 318 code provides specifications for limiting C3A content in cement and the use of supplementary cementitious materials (SCMs) or blended cements.<br /><br />The ASTM C452 and C1012 tests are discussed as they assess sulfate expansion in Portland and blended cements, respectively. However, these tests have their limitations. For instance, ASTM C1012 is not designed to mimic real-world conditions, such as different sulfate types or temperatures.<br /><br />Field experiences indicate that severe sulfate attacks often occur due to wetting/drying cycles and evaporative fronts, which are not fully captured by standard immersion tests like ASTM C1012. The document stresses the importance of understanding field conditions and their impacts on concrete durability.<br /><br />The document also highlights the critical role of pore microstructure and transport properties in determining concrete's resistance to sulfate attacks. Mass loss measurement was found to be an efficient method for evaluating physical sulfate salt attack.<br /><br />In conclusion, the document acknowledges the need for improved testing methods to address the various forms of sulfate attacks. It suggests that while ASTM C1012 can evaluate ettringite and thaumasite attacks under controlled conditions, tests are needed that better replicate field conditions, particularly regarding physical sulfate attacks. Consideration is given to developing new tests or mix designs focusing on resistance and curing criteria to enhance sulfate resistance assessment.

Keywords

sulfate attack

concrete durability

ettringite

thaumasite

ACI 318

ASTM C1012

pore microstructure

supplementary cementitious materials

mass loss measurement

transport properties