Concrete is the most widely used construction material due to low price, considerable load bearing capacity and the easiness to be formed in different shapes. If all standard procedures are followed and the concrete is made by the designed mix proportions, the possibility that it will not obtain the desired properties is highly unlikely. Therefore, quality characterisation of concrete while it is still fresh is desirable. Concrete performance, including strength and durability, depends on the constituent material proportions. This book presents and discusses research on the quality characterisation of the fresh material, which has been attempted by means of ultrasonic wave propagation.