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Polysaccharides were extracted from clam (Ruditapes philippinarum) (RPPS) by enzymatic method, and the crude polysaccharides were purified by filtration DEAE-Sepharose Fast Flow chromatography and Sephacryl S-400 size-exclusion chromatography. Two main fractions of RPPS-1a and RPPS-1b were separated. Furthermore, characterizations, such as polysaccharides composition and thermal properties, were analyzed. The results showed that polysaccharides extraction rate was 0.89%, and polysaccharides content was 62.5%. The polysaccharides were comprised of aminosu-gars, uronic acid, fucose and sulfate, which accounted for 0.27%, 59.30%, 0.75% and 1.33%, respectively. According to the infrared spectra, both RPPS-1a and RPPS-1b were polysaccharides containing -CHO and-COOH, and RPPS-1a had an additional sulfate groups. DSC analysis revealed that RPPS-1a might have straight-chain crystals, and RPPS-1b might contain more branch-chain crystals.

Freeze-thaw damage is one of the most representative damages in concrete durability. Commonly, freezing and thawing tests are conducted to investigate the freeze-thaw resistance of concrete, and the loss of dynamic modulus of concrete is regarded as the failure criterion. However, the research on the evolution of concrete strength during the damage process is still not enough when subjected to freezing and thawing. In this study, the concrete freeze-thaw deterioration was considered as isotropic elastic damage, and relative variation functions of dynamic modulus and Poisson’s ratio with freeze-thaw cycles were set up. Based on damage mechanics, the Ottosen failure surface model with four parameters was established to indicate the relationship between the concrete freeze-thaw failure surface and freeze-thaw cycles. Then the four-parameter failure surface model was set into ADINA finite element software program for secondary development to investigate the strength properties of concrete component under freeze-thaw action. The relationship between load and deflection of concrete was analyzed and simulated after 0, 25 and 50 freeze-thaw cycles. The simulated and experimental results are basically identical, which demonstrates that this finite element simulation is a feasible way to analyze and evaluate the performance of concrete structures in cold regions.