An employee was in the mixing room when an asphalt truck arrived to be unloaded. The employee began the procedure for unloading the truck and went outside to the truck to ensure the valve was closed, remove the cap, and attach a hose from the truck to the tanks outside of the mixing room. The cap came off the truck due to pressure behind it and sprayed the employee with the hot asphalt. They sustained burns to the hands, arms, torso, and upper legs.