InSight

Seeing what the load cell cannot.

Balanced Mix Design tests such as IDEAL-CT and I-FIT have become popular because they are fast, affordable, and easy to run. But their outputs are still based almost entirely on load and actuator displacement. They tell us how much force a specimen carried, and how quickly the load dropped after peak, but they do not directly show how the asphalt mixture actually deformed, localized, cracked, or failed.

That matters.

Modern asphalt mixtures are no longer simple combinations of aggregate and unmodified binder. They may contain RAP, RAS, polymers, fibers, ground-tire rubber, rejuvenators, and other additives. These materials can change how a mixture absorbs energy, distributes strain, delays cracking, or resists post-peak damage. Conventional BMD indices often compress all of that behaviour into a single number.

InSight adds the missing visual layer.

Using high-resolution cameras, InSight records both sides of the specimen during routine monotonic tests. It measures deformation, movement, crack development, asymmetry, localisation, and failure mode without attaching LVDTs, extensometers, or fragile gauges to the specimen. The test remains simple. The laboratory procedure remains familiar. But the result contains far more information.

The idea has roots in resilient modulus testing. In the late 1970s and 1980s, my father worked with Professor Stephen Brown at the University of Nottingham on what became the Nottingham Asphalt Tester. One of its key advances was the Indirect Tensile Stiffness Modulus test, which measured horizontal diametral deformation under repeated vertical loading. It was developed because older empirical methods, such as Marshall, could miss mix deficiencies that later appeared in the field.

InSight carries that same principle into modern Balanced Mix Design: deformation matters.

Digital Image Correlation has already shown that asphalt specimens reveal far more than a load curve alone can capture. But DIC is expensive, setup-sensitive, difficult to analyze, and usually limited to research environments. InSight takes the useful lesson from DIC — that full-field behaviour is valuable — and makes it practical for routine testing.

The goal is not to make BMD testing more complicated.

The goal is to make the tests laboratories already run more informative, more diagnostic, and more predictive.

InSight turns a standard cracking test into a visual performance test.