Effects of Thermal Conductivity of Soil on Temperature Development and Cracking in Mass Concrete Footings

摘要

This paper presents the findings of an investigation on thermal behavior of mass concrete footings placed directly on soil using finite element analysis. A three-dimensional finite element model was developed to predict temperatures in a mass concrete footing-soil system and to assess cracking potential of the concrete at early age. Two bridge pier footings constructed in Florida were monitored for temperature development, and the measured temperatures were compared with the computed temperatures from the finite element model. The results show that the temperatures predicted by the model closely agree with those measured in the field. Several soils with varying thermal resistances were modeled in this study in order to find out which soils can be used as an insulator for mass concrete footings so that an insulation layer would not be needed at the bottom of the footings. The results suggest that dry sand and dry clay provide good insulation at the bottom of mass concrete footings, and soil with an R-value of 0.072 per m or greater (or thermal conductivity of 0.35 W/m-K or lower) would provide adequate insulation at the bottom of concrete footings to prevent early-age cracking in the concrete.