Normally, overlays of existing pavements are used to increase the load-carrying capacity of an existing pavement or to correct a defective surface condition on the existing pavement. Of these reasons, the first requires a structural design procedure for determining the thickness of overlay; whereas the second requires only a thickness of overlay sufficient to correct the surface condition, and no increase in load-carrying capacity is considered. The design method for overlays included in this chapter determines the thickness required to increase load-carrying capacity. These methods have been developed from a series of full-scale accelerated traffic tests on various types of overlays and are, therefore, empirical. These methods determine the required thickness of overlay that, when placed on the existing pavement, will be equivalent in performance to the required design thickness of a new pavement placed on subgrade. Course Outline 1. GENERAL 2. DEFINITIONS AND SYMBOLS FOR OVERLAY PAVEMENT DESIGN 3. PREPARATION OF EXISTING PAVEMENT 4. CONDITION OF EXISTING RIGID PAVEMENT 5. RIGID OVERLAY OF EXISTING RIGID PAVEMENT This course will give you professional tools that will help you to understand the technical and design issues in application of flexible and rigid pavement overlays.

Learning Objectives

• Learn the measures necessary to prepare existing pavement for overlay;
• Learn the three co
• nditions of bond when overlaying a rigid pavement with a rigid overlay;
• Learn the condition rating factors (“C”) for existing pavements to be overlaid;
• Learn how to calculate the thickness of rigid overlays for rigid pavements;
• Learn how to design a rigid overlay of an existing flexible pavement;
• Learn how to design overlays for composite pavements;
• Learn how to apply overlays to flexible pavements.