Foaming technologies often use water along with other chemicals to produce expansion of the binder phase. Which statement best describes this process?

• A. It expands the binder phase
• B. It reduces binder volume
• C. It shrinks the binder phase
• D. It has no effect on the binder phase

Answer: (A)

Foaming uses water that turns to steam inside the hot asphalt binder, generating gas bubbles and causing the binder to expand. This gas creation pushes the binder phase outward, forming a foam-like structure with increased volume and entrained air. The expansion lowers viscosity temporarily and improves coating and workability at practical mixing temperatures. Because of the gas generation, the binder volume increases rather than decreases, so the description of expansion is the best fit. It does not shrink, and it certainly isn’t without effect.