Study on the damage mechanism of hydraulic concrete under the alternating action of freeze-thaw and abrasion

Abstract

This study investigates the damage mechanism of hydraulic concrete under the alternating action of freeze–thaw (F) and abrasion (W) in cold regions. To this end, three groups of working conditions were established with a constant water-binder ratio. The mass loss and relative dynamic elastic modulus (RDEM) of each cycle were evaluated using the fast-freezing method and underwater method. The phase composition and relative content change of hydration products, pore characteristic parameters and pore size distribution, morphology and microstructure of interfacial transition zone (ITZ) were analyzed by X-ray diffraction (XRD), mercury intrusion porosimeter(MIP), scanning electron microscopyn (SEM) and image recognition technology, respectively. The results indicate that the alternating effect will accelerate the mass loss of concrete and the reduction of the RDEM compared with the single factor. Following four consecutive alternating cycles, the mass loss rates of working conditions W and F group were found to be 4.61 % and 97.66 % lower, respectively, than those of working condition F-W group. The RDEM damage coefficient (γ < 1) was also observed. At the micro level, the freeze-thaw effect will result in the formation of a considerable number of micropores and the expansion of microcracks, with the abrasion effect continuing to promote this process. In the process of alternating action, the dissolution of Ca(OH)2 by external water through microcracks and interconnected pores is accelerated. Concurrently, the pores and microcracks in the ITZ expand, the morphology is roughened, and the microstructure is complicated. The interfacial bonding ability and compactness of different material components decrease. Under the action of external disturbance, cement paste and aggregate fall off, resulting in mass loss and a decreased RDEM.