Experimental Investigation on Mechanical Properties of Flexible Concrete Blanket Under Freeze–Thaw Cycles

Flexible concrete blankets (FCBs) are emerging as a promising material for slope protection and surface stabilization, offering advantages of light weight, ease of installation, and environmental adaptability. This study investigates the mechanical properties, freeze–thaw resistance, and microstructural evolution of FCBs fabricated with varying cement–sand ratios and high alumina cement dosages. A series of mechanical tests, including compressive, flexural, and tensile strength evaluations, were conducted alongside freeze–thaw cycling tests (up to 125 cycles) to assess mass loss and strength retention. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed to elucidate the hydration mechanisms and damage evolution at the microstructural level. The results demonstrate that FCBs exhibit ductile failure behavior, with peak tensile strengths ranging from 3.1 to 4.5 MPa and tensile strain capacities ranging from 5 to 16%. The optimal mix achieved a compressive strength of 51.2 MPa after 28 days of curing. Freeze–thaw cycling induced a two-stage degradation pattern, with damage initiation occurring at approximately 50 cycles and significant deterioration beyond 75 cycles. After 125 cycles, mass loss ranged from 4.39% to 4.99%, and compressive strength retention varied between 78% and 83%, depending on the mix composition. Mixtures with balanced cement–sand ratios (1:1) and moderate Portland cement content demonstrated superior frost resistance, whereas high alumina cement-rich mixtures exhibited pronounced structural loosening due to phase transformations of unstable hydration products. These findings provide a theoretical and experimental basis for optimizing the composition of FCBs to achieve enhanced mechanical performance and durability in cold-region engineering applications.