Hot-Mix Paving in Marginal Weather

Extension of the construction season for bituminous layers could result in benefits to the public and to the construction industry. Weather conditions in Ohio were studied during the months of March, April, May, October, and November. Application of those weather data to a previously developed thermophysical model yielded the number of days during those months which were acceptable for construction of hot-laid bituminous mats. The criterion of acceptability was an average mat temperature at least 175°F (79°C) 10 minutes after placement. Probabilities of accpetable construction days were calculated by weeks for mat thicknesses between 1.25 in. (32 mm) and 3 in. (76 mm), using the thermophysical model and the current specification of the Ohio Department of Transportation (ODOT). Application of the thermophysical model to mats at least 1.5 in. (38 mm) indicated that construction during March and November could be significantly more frequent under the proposed thermally based specification, as compared to the current ODOT specification. Favorable conditions for 1.25 in. (32-mm) mats were seldom found during the five months studied. Air temperature alone does not adequately characterize the construction environment for thin mats.