Preferred Design Procedure

Pavement recycling is a practical way to conserve the diminishing supply of construction materials and to help reduce the cost of preserving the existing pavement network. When properly designed and constructed, pavements built with recycled materials have been found to perform as well as pavements built with all new materials. Several asphalt pavement recycling techniques, such as hot mix recycling, hot in-place recycling, cold mix recycling, cold in-place recycling, and full depth reclamation, have evolved over the past 35 years. In-place recycling not only reduces the use of new materials but also reduces emissions, traffic, and energy associated with the transport and production of these materials. There are three methods or slab fracturing techniques used to rehabilitate concrete pavements: crack and seat, break and seat, and rubblization.

Even though there are federal standard specifications, each state may have its own methods that are related to specific projects (FHWA 2003).
Table 1 shows typical inputs and outputs for a design analysis of Onsite Use of Recycled Pavement Materials.

Table 1. Typical inputs and outputs for design and analysis procedures.

Performance Criteria/Indicators

Minimum stiffness (anti-fatigue of surface)
Maximum settlement (anti-rutting of flexible
pavement)
Minimum durability
Minimum frost susceptibility
Maximum lateral pressure
Minimum drainage
Maximum leakage (environmental protection)

Subsurface Conditions

Atterberg Limits
Groundwater elevations
Permeability/Hydraulic Conductivity
Organic Content

Loading Conditions

Traffic loads
Embankment pressure
Structure loads

Material Characteristics

Water content
Dielectric value
Particle size distribution
Gravimetric water content
Specific gravity
Stiffness modulus
Shear Strength
Moisture susceptibility rating
Permeability
Permanent strain
Compressibility (WT chips)
Abrasion Resistance
Toughness
Plasticity
Particle shape
Friction angles
Resilient modulus
Unit weight (WT chips)

Construction Techniques

Non-vibratory compaction

Geometry

Asphalt pavements depth
Gravel cushion thickness
Aggregate base course thickness
Granular subbase thickness
Tire chip layer thickness
Soil cover depth