Study on the Mechanical Properties and Dynamic Constitutive Relationship of Ceramsite Concrete Affected by Freeze-Thaw Cycling

Abstract

Abstract In this study, the dynamic and static mechanical properties as well as the internal microstructure (capillary porosity) and constitutive relationship of sulphoaluminate ceramsite concrete with a ceramsite volume fraction of 40% are examined under freeze-thaw cycling. The results reveal that an increase in the number of freeze-thaw cycles or a decrease in the lowest temperature of the freeze-thaw cycle leads to a decline in the compressive strength and performance, causing enlargement of pores in the ceramsite concrete. During the freeze-thaw cycles, the internal pores in the ceramsite concrete expand outward due to water freezing and expansion. In dynamic compression tests, the transition zone between ceramsite and matrix within the ceramsite concrete is the most susceptible to cracking and damage, forming a distinct primary crack. Industrial computed tomography (CT) scanning results demonstrate that both impact compression and freeze-thaw cycling exacerbate the internal damage in concrete. The expansion of internal pores in the concrete during freeze-thaw cycles is closely related to the lowest temperature T*, the number of freeze-thaw cycles N, and the expansion factor k of freeze-thaw pores. In conjunction with experimental analysis, a constitutive relationship is proposed that accounts for the effects of freeze-thaw cycling on the damage behavior of ceramsite concrete.