1. Scope

1.1 This guide provides recommendations for the use of passive infrared thermography to detect subsurface defects in concrete structures, such as delamination, voids, honeycombing, or other discontinuities within the concrete. The guide is intended to support the planning, acquisition, processing, and interpretation of passive infrared thermography measurements obtained from exterior concrete structures exposed to environmental conditions.
1.2 This guide describes qualitative and semi-quantitative approaches for evaluating thermal patterns associated with subsurface defects when using passive infrared thermography. The method is inherently sensitive to environmental and material conditions, and its effectiveness may be influenced by factors such as solar incidence, wind speed, moisture, defect depth, and surface conditions, which can limit detectability. This guide does not establish acceptance criteria or quantitative performance thresholds for defect evaluation.

Keywords

Infrared thermography; thermal imaging; delamination; reinforced concrete; nondestructive testing.

Rationale

Existing standards and technical documents relevant to passive infrared thermography (including ASTM D4788, ASTM C1060, ASTM C1153, ISO 18434, ISO 6781, and ACI 228.2R) were developed for applications such as bridge deck overlays, building envelopes, roofs, building insulations, and electrical/mechanical components. Their prescribed procedures, inspection conditions, data acquisition strategies, and interpretation guidance are specific to those materials, geometries, defect types, and thermal mechanisms. The report ACI 228.2R provides guidance on nondestructive testing of concrete; however, its references to infrared thermography primarily defer to ASTM D4788 (bridge decks). The report does not provide specific guidelines for the use of the technique for inspecting a range of concrete components exposed to varying solar incidence.
This guide focuses on the application of passive infrared thermography for detecting subsurface discontinuities in concrete components. Existing standards do not address the broader range of concrete component geometries (such as walls, columns, beams, piers, and slabs) nor the radiometric configuration, inspection timing, data acquisition, and thermal-contrast interpretation practices required for the use of passive infrared thermography on such elements.
This guide expands standardized recommendations for the concrete sector by providing application-specific guidance on inspection planning, instrument selection, radiometric measurement procedures, interpretation, and reporting requirements tailored to a range of concrete components exposed to variable environmental conditions. It is therefore technically distinct from and complementary to the existing ASTM, ISO, and ACI documents listed above and addresses inspection needs not presently covered in current standards or recommendations.

The title and scope are in draft form and are under development within this ASTM Committee.