Title:
Impact of Under-Sulfated Cement on Concrete Performance: Detection and Mitigation Using Real-Time Slump Monitoring (Prepublished)
Author(s):
Justin Dickey, Kevin J. Folliard, Thanos Drimalas
Publication:
Materials Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
flash set; fly ash; high-range water reducer; incompatibility issues; on-board slump monitoring system (SMS); setting time
DOI:
10.14359/51749036
Date:
7/10/2025
Abstract:
Related References:
This study investigates the impact of under-sulfated cement combined with high calcium fly ash and lignosulfonate-based admixtures in ready-mixed concrete, leading to rapid stiffening and delayed setting. Utilizing an on-board slump monitoring system (SMS) installed on a ready-mixed concrete truck, significant increases in water demand were recorded to maintain target slumps, with mixtures showing minimal slump response to water additions. Laboratory tests, including isothermal calorimetry and mortar trials, confirmed the under-sulfated cement's inadequate sulfate levels as the cause. Optimal sulfate addition was determined through calorimetry, and adjustments with gypsum effectively remedied rapid stiffening and delayed setting. This research demonstrates that an SMS can detect undesirable combinations of cement, fly ash, and admixtures in concrete, allowing real-time corrections. It underscores the importance of optimized sulfate levels in cement, particularly when using high-calcium fly ash combined with some high-range water reducers, to ensure desired concrete performance under varying field conditions.