Evaluation and Modification of Commercial Equipment to Evaluate Air Permeability of Concrete

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Abstract

Pyrrhotite in concrete aggregate can lead to severe cracking due to expansion reactions. Most research has focused on screening methods and mix designs that lower the permeability of new structures. However, there is a need to evaluate the feasibility of mitigation techniques for existing structures containing pyrrhotite aggregate but have not yet shown signs of deterioration. Efforts at NIST have focused on evaluating the potential of concrete sealants, which can reduce or entirely eliminate the ingress of water and air into the concrete. Since pyrrhotite needs both oxygen and water to react, one or both components can be slowed to delay pyrrhotite oxidation for some amount of time. One methodology being vetted as a potential test to characterize the performance of mitigating sealants is air permeability. This report details efforts to validate changes made to a commercially available air permeameter to better facilitate NIST's needs. This validation testing was generally conducted in two parts. Part 1 was focused on validating as-received equipment for use with 152.4 mm (6-inch) diameter concrete cores, which is the size the commercially available set-up is made to test. Part 2 was focused on validating retrofitting the equipment to test 101.6 mm (4-inch) diameter cores, which is the common diameter used for laboratory and field-cast concrete specimens.

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Keywords

Metrology, Materials, Infrastructure and Buildings and construction

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