Compaction Delay and Temperature Effects on Early-Age Properties of Roller-Compacted Concrete

The lower water content of roller-compacted concrete (RCC) coupled with climatic conditions (e.g., higher air temperature, increased wind speed, and lower relative humidity) and compaction delay factors (e.g., traffic delay, plant location, and paving speed) can significantly affect the in situ density and hardened properties of RCC pavements. In this study, a control RCC mix was batched and maintained at standard (21°C) and elevated (35°C) temperatures and then compacted at increasing delay times for up to 180 min. The elevated mix temperature and compaction delay times greater than 90 min prevented the RCC mix from achieving 98% of the initial wet density from the modified Proctor test. Two additional RCC mixes were batched to determine if they could maintain a longer compaction window, one containing a rheology-modifying and retarding admixture and the other incorporating saturated fine lightweight aggregates. The RCC with admixture was the most effective at maintaining moisture content, density, compressive strength, and fracture properties at all compaction delay times. For example, at 180 min of delay, the RCC mixture with admixture still maintained 98.2% of the initial wet density, 81% of the compressive strength, and approximately the same fracture toughness and energy. The addition of fine lightweight aggregates did not extend the compaction window relative to standard RCC mix. The gyratory compacted specimens were more sensitive to the effects of temperature and compaction delay on RCC mixes than the vibratory hammer prepared specimens.