Identify the traditional hot-applied waterproofing method used on bridge decks that involves a mixture of graded aggregates and bitumen forming a durable layer.

• A. Mastic asphalt system waterproofing
• B. Sheet system waterproofing
• C. liquid system waterproofing
• D. Bridge expansion joints

Answer: (A)

Hot-applied mastic asphalt waterproofing on bridge decks uses a blend of graded aggregates bound in bitumen, heated and laid as a continuous, cohesive layer. This traditional method creates a dense, seamless film that adheres well to the deck and resists traffic wear, weather, and chemical exposure, providing durable waterproof protection over the life of the bridge. The mixture’s interlocking aggregates plus the bitumen give good impermeability and surface durability, which is why it’s favored for bridge decks.

In contrast, sheet system waterproofing uses pre-formed sheets or membranes, not a hot-mixed asphalt layer; liquid system relies on brush- or spray-applied coatings that cure to a film; and bridge expansion joints are structural features, not a waterproofing layer.