Coefficient of Thermal Expansion

The thermal expansion characteristics of RCC pavement are governed by the thermal characteristics of the coarse aggregate contained within the mixture. For an RCC pavement structure, the interest in CTE from a design standpoint is blowup potential, since RCC is likely to be under compressive restraint during higher temperature seasons. The low shrinkage typical of RCC mixtures tends to enhance the possibility of high compressive strain conditions. This restraint is reduced at pavement temperatures below the set temperature of the concrete.

In addition to CTE and set temperature, the factors that affect the development of blowup distress include:

• Slab thickness
• Drainage profile
• Slab/subbase interface friction
• Joint load transfer or stiffness

The greater the set temperature (which is likely to be a function of the season of placement), slab thickness, and subbase friction and the lower the CTE, the lower the potential for blowup distress. Essentially, the effects of slab thickness, joint stiffness, and subbase friction can be combined into a single parameter represented by the effective slab thickness.

The drainage profile of a pavement surface becomes important at break lines that facilitate drainage movement. The change in grading potentially creates a weakened location that increases the chances of a blowup. Depending on the season of placement, if a drainage break line follows a longitudinal joint, slab thickening or retrofitting with reinforcing tie bars may add sufficient stiffness to reduce the blowup potential.