Engineering Properties of Conventional Concrete Incorporating Different Amounts of Dry Ice

The engineering properties of conventional concrete incorporating dry ice (DI) at 1, 3, and 5% by cement mass were investigated. Four concrete mixtures were evaluated for workability, compressive strength, pH, and surface morphology. Scanning electron microscopy (SEM) was used to qualitatively examine microstructural changes associated with DI incorporation. The results showed that slump decreased progressively as DI content increased, indicating a substantial loss of fresh workability. At 28 days, compressive strength ranged from 37.9 to 48.3 MPa, with the highest value obtained for the 3% DI mixture. Although DI reduced the pH of the hardened concrete, all mixtures remained highly alkaline, with pH values between 12.1 and 13.6. SEM observations showed that the 3% DI mixture had a denser surface morphology with fewer visible voids and more finely distributed crystalline features. In conclusion, 3% DI provided the most favorable balance between strength development and matrix densification among the tested dosages. However, further optimization of workability, phase identification, CO2 uptake measurement, and durability assessment is needed before concrete containing DI can be considered for practical application.