Core Testing Principle
Prevent catastrophic winter road cracking before it even starts. The Bending Beam Rheometer (QualiBBR™ 1) uses a standardized 3-point bending creep theory to evaluate exactly how asphalt binders resist low-temperature failure.
By submerging a 127 × 12.7 × 6.35 mm sample in a vibration-free, Peltier-chilled liquid bath, the system isolates pure material performance with zero external interference. Simply apply a constant 980 mN load across the 102 mm span for 240 seconds to track micro-deflections with highly dependable precision.
Flexural Creep Stiffness Equation
The theoretical math behind this process is surprisingly elegant, borrowing some classic engineering logic from structural design.
You do not have to calculate this manually; the QualiBBR-1 software does all the hard math for you while giving a real-time display of deformation, pressure, and temperature curves. Backed by an integrated LVDT calibration system for precise tracking, it runs the numbers to find the resistance to bending over time, which we call S(t), using this classic formula:
S(t) = (P · L³) / (4 · b · h³ · δ(t))
- P: The steady downward push (that 980 mN force).
- L: The 102 mm gap between the two bottom supports holding up our sample.
- b: How wide your little asphalt block is (12.7 mm).
- h: How thick the block is from top to bottom (6.35 mm).
- δ(t): How much the middle of the block sagged at any given second.
Key Parameters: S and m-Values
When pulling up the exported data via the convenient USB port, your laboratory is looking for two absolutely make-or-break theoretical numbers to see if your mix is going to perform as expected:
- Creep Stiffness (the S-value): This tells you how stiff and rigid the material gets when the weather is freezing. You want this number to be satisfyingly low, because if it is too high, the asphalt becomes as brittle as glass and will snap instantly under heavy traffic.
- The m-value: This is a highly descriptive way of measuring how well the asphalt relaxes and stretches out its internal stress as the cold tries to shrink it. We measure this at exactly the 60-second mark. You want this number to be impressively high so the pavement can easily ease off its own tension instead of cracking open.
Basically, a low stiffness coupled with a high relaxation rate is sheer perfection for winter-proof roads.
Standard Compliance & Mixture Testing
Following AASHTO T313, ASTM D6648, and EN 14771 methodologies, the Bending Beam Rheometer (QualiBBR™ 1) executes these theoretical evaluations reliably. While the core theory was originally built for testing the pure, sticky black asphalt binder, clever laboratory teams have adapted the exact same Bending Beam Rheometer method for thin slices of the actual rock-and-asphalt mixture too. Studying how these composite slices bend gives you a wonderfully accurate, real-world preview of how the entire highway will stand up to the freezing winter cold.
