Effect of Admixture Types on Durability of High Early Strength Concrete

ABSTRACT High early strength concrete (HESC) has many applications, particularly in the repair and restoration of concrete pavements. These mixtures are designed for rapid strength development using a low water-to-cement ratio (w/cm), specialized cement types (often in higher dosages), and specialized admixtures. Although HESC effectively achieves the required strength, it poses durability challenges. Several studies have explored the effect of these HESC design parameters on strength gain and have provided recommendations to improve it. However, there is limited documentation regarding its durability properties. To better understand HESC’s durability properties, a set of mixtures was analyzed for strength, freeze-thaw durability, and both autogenous and drying shrinkage. These HESC mixtures were composed of low cement content 334.6 kg/m3 (564 lbs./yd3) using ordinary portland cement type III, w/cm of 0.35, three different admixture types, and internal curing (IC) using presaturated lightweight aggregates. It was observed that all HESC mixtures, despite their low cement content, met the criteria established by KDOT Section 833, attaining a minimum compressive strength of 12.41 MPa (1800 psi) and a flexural strength of 2.62 MPa (380 psi) within 6 h of mixing. Furthermore, admixture compatibility and usage of IC for HESC significantly affected their durability properties. HESC with IC demonstrated superior freeze-thaw performance and minimal shrinkage, likely due to their ability to regulate heat during hydration. Although three different admixture types were evaluated for the same mix design and fresh property range, their varying performances emphasize the need to verify admixture compatibility and durability properties before employing them on-field.