Internal curing of high strength concrete by using cold bonded aggregates

This study aims at examining experimentally the shrinkage and mechanical properties of High-Strength Concrete (HSC) containing blast furnace slag aggregates (ASA) and artificial fly ash aggregates (AFA) that are employed as water reservoirs to enable internal curing. So as to form fly ash and/or slag aggregates, a dry powder blend of 10% of Portland cement and 90% fly ash or slag was initially pelletized by moisturizing at room temperature in a spinning skewed pan; these were subsequently cured for 28 day. Applying a 0.28 water-to-cement ratio, nine HSCs mixtures were developed with different ASA or AFA replacement levels, i.e. 0%, 5%, 10%, 15%, and 20%. After 28 day, testing of the hardened concretes was conducted for splitting tensile strength, compressive strength, and modulus of elasticity. The concrete was monitored for a 57 day drying period to determine the restrained shrinkage, autogenous shrinkage, and drying shrinkage along with the water loss. The HSCs having 20% ASAs showed the highest mechanical properties. Additionally, HSCs containing ASA showed a longer cracking period of the concretes causing finer cracks that are linked to the lower free shrinkage. Largely in the HSCs containing 20% AFA, there was, however, a noticeable decline in the autogenous shrinkage for all the HSCs with AAs, especially for HSCs with 20% AFA.