Development of a Mass Concrete Specification for Use in ALDOT Bridge Construction

Abstract

Special precautions must be taken when constructing concrete elements designated as mass concrete. These precautions may be satisfied through the formation of a mass concrete specification. Temperature requirements must be established to mitigate thermal cracking and delayed ettringite formation (DEF), both of which cause premature deterioration of concrete. The temperature difference between the concrete core and outside edge must be limited to prevent excessively wide thermal cracks. To prevent DEF, the maximum concrete temperature must be limited to 160°F or 185°F, depending on the amount and type of supplementary cementing materials (SCMs) used. When designating a member as mass concrete, a minimum element dimension must be established to help ensure that the temperature limits are not exceeded. These temperature and size limits are investigated here in order to develop an ALDOT specification for mass concrete construction. Temperature data from seven ALDOT bridge elements were collected using temperature sensors. Maximum temperatures and temperature differences were used to determine appropriate temperature limits for the ALDOT specification as well as validate the temperature predictions of the ConcreteWorks software used for the same elements. Once ConcreteWorks’ accuracy was determined, 480 theoretical concrete placements were statistically analyzed to determine that the use of low-CTE concrete and SCMs play a major role in limiting maximum temperatures and temperature differences. A mass concrete specification was then developed, which designates mass concrete least dimensions, maximum temperature limits, and maximum temperature difference limits based on SCM use and concrete CTE.