The construction of the dam raise for the Gross Reservoir Expansion (GRE) Project will require placement of approximately 742,600 cubic yards of roller-compacted concrete (RCC). RCC mix trials for the GRE project began in 2017 and continued through design and initial construction stages of the project. The RCC mix trials were conducted to confirm that the RCC could be batched with on-site aggregate and to test local cement and pozzolan suppliers. In 2022, near the start of construction, it was identified that the local cement suppliers would be transitioning their cement production to a Portland Limestone Cement Type 1L and suspending production of the long-time Ordinary Portland Type I/II cement. Portland Limestone Cement has been in use in Europe for two decades and is in the process of transitioning into the US industry. The transition in the US has been gradual in some regions and abrupt in others. The transition in the Rocky Mountain Region resulted in a very rapid change in cement type. For GRE, additional RCC mix trials were required using the Type IL cement.
This paper will compare the performances of the 22 trial mixes using Type I/II cement to the 33 trial mixes using Type IL cement. Properties compared will include compressive strengths (per ASTM C39), trends in water demand, VeBe times (per ASTM C1170), and some associated results from mortar cube testing (per ASTM C109). A comparison will also be presented showing
The results of the additional RCC mix trials for GRE allowed the project to execute the full-scale trial placement and prepare for production RCC placement with confidence in the performance of the Type IL Limestone Cement.
