11.21.17   Hayder H. Al-Hilal, PE, SMSI, CIP-1, CCI-2, Level 1 Thermographer, ICRI CSMT | More by this Author


Concrete masonry unit (CMU) walls have been widely used as architectural and structural elements in commercial and residential building for decades. Their strength, durability, fire resistance, sound transmission resistance, and energy conservation qualities give them advantages over other wall systems.

CMU walls are often reinforced and partially or fully grouted for resistance to design loads. Grout is used in CMU cells in both vertical and horizontal placements, to tie the wall system together and for structural and other purposes. Hence, proper grout placement is necessary for CMU walls to perform as intended.

The masonry industry has made great progress in developing materials and procedures to achieve proper grout placement. However, for quality assurance purposes, confirmation of proper grouting has always been challenging. Especially when thorough inspection programs during construction have not been available.

With the use of infrared thermography (IR), confirmation of grouting and detection of voids in grouted walls has become relatively quick, inexpensive, and reliable.


Infrared thermography is able to discern the relative differences between thermal mass or thermal capacity (ability of body/mass to absorb and dissipate thermal energy) in grouted and ungrouted (hollow) cells. Grouted cells have more mass than ungrouted cells, therefore they absorb and dissipate heat at a slower rate. IR photographic images of a CMU wall that has vertically grouted cells in between vertically ungrouted cells, show alternating vertical bands, i.e., thermal patterns (see images below).

IR scanning of CMU walls can be performed during daylight or nighttime hours, since grouted cells absorb solar heat during daylight hours and dissipate it at night at slower rate than ungrouted cells.

Photograph and IR image of CMU walls of a stair tower. The IR image (right) shows the alternating thermal patterns of lighter and darker coloration, representing grouted and ungrouted masonry, respectively. In this example, lighter areas represent grouted vertical and horizontal (bond beams), while darker areas represent ungrouted CMU cells.

Photograph and IR image of a partially grouted CMU wall. The IR image (right) shows the alternating thermal patterns of darker and lighter coloration, representing the presence of grouted and ungrouted CMU cells, respectively. This wall was partially grouted to mid-height only

Reinforcing steel bars used in masonry walls are encased in grouted cells. IR does not detect the presence of reinforcing steel within grouted masonry walls. Typically, proper placement of grout is an indicator of placement of reinforcing steel. IR must be supplemented with other nondestructive methods for detecting the presence of reinforcing steel. A high-frequency ground penetrating radar (GPR) can be used to assess the likely presence of reinforcing steel at representative wall locations. The images below show typical two and three-dimensional GPR scans of a reinforced, grouted CMU wall.

Two-dimensional, composite, GPR image of a 4’ x 4’ CMU wall area, showing vertical and horizontal reinforcing steel layout.

Three-dimensional GPR image of reinforcing steel shown in image above.

If you have a need to detect whether voids and reinforcing steel are present in grouted CMU walls or have questions about the use and capabilities of IR, please contact SME. Our qualified engineers, certified thermographers and structural masonry special inspectors can properly assess and identify CMU wall conditions related to grout placement.

For more information, contact Hayder Al-Hilal, PE, SMSI, CIP-1, CCI-2, Level 1 Thermographer.


Subscribe For Updates

Sign up to receive the latest SME insights, news, and project updates.

Leave A Comment