2023 Volume 77 Issue 1 Pages 172-180
This study investigated the compressive strength and drying shrinkage of mortar made with recycled fine aggregate carbonated in air or water. Recycled fine aggregate carbonated in air showed a decrease in water absorption and an increase in Oven - dry density. Mortar using recycled fine aggregate carbonated in air showed an increase in compressive strength and a decrease in drying shrinkage. On the other hand, the recycled fine aggregate carbonated in water had the same water absorption and decreased in Oven - dry density. The compressive strength of mortar using recycled fine aggregate carbonated in water decreased and drying shrinkage increased. No clear relationship was found between the water absorption of the recycled fine aggregate and the compressive strength of the mortar, and between the water absorption of the recycled fine aggregate and the drying shrinkage of the mortar.To elucidate the cause, cement paste was carbonated under the same conditions as the recycled fine aggregate and analyzed.The results showed that carbonation in air increased the modulus of elasticity of the cement paste compared to that before carbonation. On the other hand, when carbonated in water, the modulus of elasticity decreased due to leaching of calcium ions. It was estimated that the recycled fine aggregate carbonated in water decreased the modulus of elasticity of the cement paste on the aggregate surface, resulting in a decrease in compressive strength and an increase in drying shrinkage.
