| The interaction between temperature development within concrete pavement within the first few days after placement and the ambient temperature conditions can influence the long-term quality of the concrete. The thermal behavior of concrete can be characterized from a knowledge of concrete temperature, environmental conditions (air temperature, wind velocity, and solar radiation), and cement hydration in the mixture. To account for those interactions, a computer model is developed for predicting the temperature profile in hardening concrete pavement in terms of material and environmental factors.; A concrete pavement structure is unlike most other structures because it manifests a very large surface to volume ratio causing significant variations in temperature and moisture within the structure. Also, thermal properties such as concrete conductivity and specific heat affect the heat transfer of the concrete pavements at an early age. Since conductivity is an important property, a unique approach is suggested by which concrete conductivity is back-calculated from the best fit value between the computed and measured laboratory process. Concrete conductivity can be represented in terms of the degree of hydration.; Boundary conditions were also considered in the modeling process; such as the use of polyethylene sheets as an insulating material. It was determined, based on historic experiments, heat loss by convection through the polyethylene sheets can be represented in terms of wind velocity. Specially, solar radiation absorptivity can be increased as the polyethylene sheets are covered on the concrete pavement sections.; Also developed is an experimental laboratory procedure which measures the fracture properties of concrete material. Fracture properties are important in characterizing the crack potential of concrete pavements at saw cut notch locations. The procedure suggested provides a method to measure the fracture toughness of concrete in terms of the temperature and curing conditions in the field. Using the maturity concept, temperature-dependent fracture toughness of concrete could be estimated and used to control thermal cracking in the concrete pavement. |
